/* Secret Labs' Regular Expression Engine
 *
 * regular expression matching engine
 *
 * partial history:
 * 1999-10-24 fl   created (based on existing template matcher code)
 * 2000-03-06 fl   first alpha, sort of
 * 2000-08-01 fl   fixes for 1.6b1
 * 2000-08-07 fl   use PyOS_CheckStack() if available
 * 2000-09-20 fl   added expand method
 * 2001-03-20 fl   lots of fixes for 2.1b2
 * 2001-04-15 fl   export copyright as Python attribute, not global
 * 2001-04-28 fl   added __copy__ methods (work in progress)
 * 2001-05-14 fl   fixes for 1.5.2 compatibility
 * 2001-07-01 fl   added BIGCHARSET support (from Martin von Loewis)
 * 2001-10-18 fl   fixed group reset issue (from Matthew Mueller)
 * 2001-10-20 fl   added split primitive; reenable unicode for 1.6/2.0/2.1
 * 2001-10-21 fl   added sub/subn primitive
 * 2001-10-24 fl   added finditer primitive (for 2.2 only)
 * 2001-12-07 fl   fixed memory leak in sub/subn (Guido van Rossum)
 * 2002-11-09 fl   fixed empty sub/subn return type
 * 2003-04-18 mvl  fully support 4-byte codes
 * 2003-10-17 gn   implemented non recursive scheme
 * 2009-07-26 mrab completely re-designed matcher code
 * 2011-11-18 mrab added support for PEP 393 strings
 *
 * Copyright (c) 1997-2001 by Secret Labs AB.  All rights reserved.
 *
 * This version of the SRE library can be redistributed under CNRI's
 * Python 1.6 license.  For any other use, please contact Secret Labs
 * AB (info@pythonware.com).
 *
 * Portions of this engine have been developed in cooperation with
 * CNRI.  Hewlett-Packard provided funding for 1.6 integration and
 * other compatibility work.
 */

/* #define VERBOSE */

#define RE_MEMORY_LIMIT 0x40000000

#if defined(VERBOSE)
#define TRACE(X) printf X;
#else
#define TRACE(X)
#endif

#include "Python.h"
#include "structmember.h" /* offsetof */
#include <ctype.h>
#include "_regex.h"
#include "pyport.h"
#include "pythread.h"

#if PY_VERSION_HEX < 0x03070000
/* Issue 29943: PySlice_GetIndicesEx change broke ABI in 3.5 and 3.6 branches
 */
#if defined(PySlice_GetIndicesEx) && !defined(PYPY_VERSION)
#undef PySlice_GetIndicesEx
#endif
#endif

#if PY_VERSION_HEX < 0x03030000
typedef unsigned char Py_UCS1;
typedef unsigned short Py_UCS2;

#endif
typedef RE_UINT32 RE_CODE;
typedef unsigned char BYTE;

/* Properties in the General Category. */
#define RE_PROP_GC_CN ((RE_PROP_GC << 16) | RE_PROP_CN)
#define RE_PROP_GC_LU ((RE_PROP_GC << 16) | RE_PROP_LU)
#define RE_PROP_GC_LL ((RE_PROP_GC << 16) | RE_PROP_LL)
#define RE_PROP_GC_LT ((RE_PROP_GC << 16) | RE_PROP_LT)
#define RE_PROP_GC_P ((RE_PROP_GC << 16) | RE_PROP_P)

/* Unlimited repeat count. */
#define RE_UNLIMITED (~(RE_CODE)0)

/* The status of a . */
typedef RE_UINT32 RE_STATUS_T;

/* Whether to match concurrently, i.e. release the GIL while matching. */
#define RE_CONC_NO 0
#define RE_CONC_YES 1
#define RE_CONC_DEFAULT 2

/* The result of decoding the timeout. Values are in clock ticks. Non-negative
 * values are valid.
 */
#define RE_NO_TIMEOUT -1
#define RE_BAD_TIMEOUT -2

/* The side that could truncate in a partial match.
 *
 * The values RE_PARTIAL_LEFT and RE_PARTIAL_RIGHT are also used as array
 * indexes, so they need to be 0 and 1.
 */
#define RE_PARTIAL_NONE -1
#define RE_PARTIAL_LEFT 0
#define RE_PARTIAL_RIGHT 1

/* Flags for the kind of 'sub' call: 'sub', 'subn', 'subf', 'subfn'. */
#define RE_SUB 0x0
#define RE_SUBN 0x1
#define RE_SUBF 0x2

/* Error codes. */
#define RE_ERROR_INITIALISING 2 /* Initialising object. */
#define RE_ERROR_SUCCESS 1 /* Successful match. */
#define RE_ERROR_FAILURE 0 /* Unsuccessful match. */
#define RE_ERROR_ILLEGAL -1 /* Illegal code. */
#define RE_ERROR_INTERNAL -2 /* Internal error. */
#define RE_ERROR_CONCURRENT -3 /* "concurrent" invalid. */
#define RE_ERROR_MEMORY -4 /* Out of memory. */
#define RE_ERROR_CANCELLED -5 /* Matching cancelled. */
#define RE_ERROR_REPLACEMENT -6 /* Invalid replacement string. */
#define RE_ERROR_INVALID_GROUP_REF -7 /* Invalid group reference. */
#define RE_ERROR_GROUP_INDEX_TYPE -8 /* Group index type error. */
#define RE_ERROR_NO_SUCH_GROUP -9 /* No such group. */
#define RE_ERROR_INDEX -10 /* String index. */
#define RE_ERROR_NOT_STRING -11 /* Not a string. */
#define RE_ERROR_NOT_UNICODE -12 /* Not a Unicode string. */
#define RE_ERROR_PARTIAL -13 /* Partial match. */
#define RE_ERROR_NOT_BYTES -14 /* Not a bytestring. */
#define RE_ERROR_BAD_TIMEOUT -15 /* "timeout" invalid. */
#define RE_ERROR_TIMED_OUT -16 /* matching has timed out. */

/* Node bitflags. */
#define RE_POSITIVE_OP 0x1
#define RE_ZEROWIDTH_OP 0x2
#define RE_FUZZY_OP 0x4
#define RE_REVERSE_OP 0x8
#define RE_REQUIRED_OP 0x10

/* Guards against further matching can occur at the start of the body and the
 * tail of a repeat containing a repeat.
 */
#define RE_STATUS_BODY 0x1
#define RE_STATUS_TAIL 0x2

/* Whether a guard is added depends on whether there's a repeat in the body of
 * the repeat or a group reference in the body or tail of the repeat.
 */
#define RE_STATUS_NEITHER 0x0
#define RE_STATUS_REPEAT 0x4
#define RE_STATUS_LIMITED 0x8
#define RE_STATUS_REF 0x10
#define RE_STATUS_VISITED_AG 0x20
#define RE_STATUS_VISITED_REP 0x40

/* Whether a string node has been initialised for fast searching. */
#define RE_STATUS_FAST_INIT 0x80

/* Whether a node us being used. (Additional nodes may be created while the
 * pattern is being built.
 */
#define RE_STATUS_USED 0x100

/* Whether a node is a string node. */
#define RE_STATUS_STRING 0x200

/* Whether a repeat node is within another repeat. */
#define RE_STATUS_INNER 0x400

/* Various flags stored in a node status member. */
#define RE_STATUS_SHIFT 11

#define RE_STATUS_FUZZY (RE_FUZZY_OP << RE_STATUS_SHIFT)
#define RE_STATUS_REVERSE (RE_REVERSE_OP << RE_STATUS_SHIFT)
#define RE_STATUS_REQUIRED (RE_REQUIRED_OP << RE_STATUS_SHIFT)
#define RE_STATUS_HAS_GROUPS 0x10000
#define RE_STATUS_HAS_REPEATS 0x20000
#define RE_STATUS_ALL_ATOMIC 0x40000

/* The different error types for fuzzy matching. */
#define RE_FUZZY_SUB 0
#define RE_FUZZY_INS 1
#define RE_FUZZY_DEL 2
#define RE_FUZZY_ERR 3
#define RE_FUZZY_COUNT 3

/* The various values in a FUZZY node. */
#define RE_FUZZY_VAL_MIN_BASE 1
#define RE_FUZZY_VAL_MIN_SUB (RE_FUZZY_VAL_MIN_BASE + RE_FUZZY_SUB)
#define RE_FUZZY_VAL_MIN_INS (RE_FUZZY_VAL_MIN_BASE + RE_FUZZY_INS)
#define RE_FUZZY_VAL_MIN_DEL (RE_FUZZY_VAL_MIN_BASE + RE_FUZZY_DEL)
#define RE_FUZZY_VAL_MIN_ERR (RE_FUZZY_VAL_MIN_BASE + RE_FUZZY_ERR)

#define RE_FUZZY_VAL_MAX_BASE 5
#define RE_FUZZY_VAL_MAX_SUB (RE_FUZZY_VAL_MAX_BASE + RE_FUZZY_SUB)
#define RE_FUZZY_VAL_MAX_INS (RE_FUZZY_VAL_MAX_BASE + RE_FUZZY_INS)
#define RE_FUZZY_VAL_MAX_DEL (RE_FUZZY_VAL_MAX_BASE + RE_FUZZY_DEL)
#define RE_FUZZY_VAL_MAX_ERR (RE_FUZZY_VAL_MAX_BASE + RE_FUZZY_ERR)

#define RE_FUZZY_VAL_COST_BASE 9
#define RE_FUZZY_VAL_SUB_COST (RE_FUZZY_VAL_COST_BASE + RE_FUZZY_SUB)
#define RE_FUZZY_VAL_INS_COST (RE_FUZZY_VAL_COST_BASE + RE_FUZZY_INS)
#define RE_FUZZY_VAL_DEL_COST (RE_FUZZY_VAL_COST_BASE + RE_FUZZY_DEL)
#define RE_FUZZY_VAL_MAX_COST (RE_FUZZY_VAL_COST_BASE + RE_FUZZY_ERR)

/* The maximum number of errors when trying to improve a fuzzy match. */
#define RE_MAX_ERRORS 10

/* The flags which will be set for full Unicode case folding. */
#define RE_FULL_CASE_FOLDING (RE_FLAG_UNICODE | RE_FLAG_FULLCASE | RE_FLAG_IGNORECASE)

/* The shortest string prefix for which we'll use a fast string search. */
#define RE_MIN_FAST_LENGTH 5

static char copyright[] =
    " RE 2.3.0 Copyright (c) 1997-2002 by Secret Labs AB ";

/* The exception to raise on error. */
static PyObject* error_exception;

/* The dictionary of Unicode properties. */
static PyObject* property_dict;

typedef struct RE_State* RE_StatePtr;

/* Bit-flags for the common character properties supported by locale-sensitive
 * matching.
 */
#define RE_LOCALE_ALNUM 0x001
#define RE_LOCALE_ALPHA 0x002
#define RE_LOCALE_CNTRL 0x004
#define RE_LOCALE_DIGIT 0x008
#define RE_LOCALE_GRAPH 0x010
#define RE_LOCALE_LOWER 0x020
#define RE_LOCALE_PRINT 0x040
#define RE_LOCALE_PUNCT 0x080
#define RE_LOCALE_SPACE 0x100
#define RE_LOCALE_UPPER 0x200

/* Info about the current locale.
 *
 * Used by patterns that are locale-sensitive.
 */
typedef struct RE_LocaleInfo {
    unsigned short properties[0x100];
    unsigned char uppercase[0x100];
    unsigned char lowercase[0x100];
} RE_LocaleInfo;

/* Handlers for ASCII, locale and Unicode. */
typedef struct RE_EncodingTable {
    BOOL (*has_property)(RE_LocaleInfo* locale_info, RE_CODE property, Py_UCS4
      ch);
    BOOL (*at_boundary)(RE_StatePtr state, Py_ssize_t text_pos);
    BOOL (*at_word_start)(RE_StatePtr state, Py_ssize_t text_pos);
    BOOL (*at_word_end)(RE_StatePtr state, Py_ssize_t text_pos);
    BOOL (*at_default_boundary)(RE_StatePtr state, Py_ssize_t text_pos);
    BOOL (*at_default_word_start)(RE_StatePtr state, Py_ssize_t text_pos);
    BOOL (*at_default_word_end)(RE_StatePtr state, Py_ssize_t text_pos);
    BOOL (*at_grapheme_boundary)(RE_StatePtr state, Py_ssize_t text_pos);
    BOOL (*is_line_sep)(Py_UCS4 ch);
    BOOL (*at_line_start)(RE_StatePtr state, Py_ssize_t text_pos);
    BOOL (*at_line_end)(RE_StatePtr state, Py_ssize_t text_pos);
    BOOL (*possible_turkic)(RE_LocaleInfo* locale_info, Py_UCS4 ch);
    int (*all_cases)(RE_LocaleInfo* locale_info, Py_UCS4 ch, Py_UCS4*
      codepoints);
    Py_UCS4 (*simple_case_fold)(RE_LocaleInfo* locale_info, Py_UCS4 ch);
    int (*full_case_fold)(RE_LocaleInfo* locale_info, Py_UCS4 ch, Py_UCS4*
      folded);
    int (*all_turkic_i)(RE_LocaleInfo* locale_info, Py_UCS4 ch, Py_UCS4*
      cases);
} RE_EncodingTable;

/* Position within the regex and text. */
typedef struct RE_Position {
    struct RE_Node* node;
    Py_ssize_t text_pos;
} RE_Position;

/* Info about a group's span. */
typedef struct RE_GroupSpan {
    Py_ssize_t start;
    Py_ssize_t end;
} RE_GroupSpan;

/* Storage for the next node. */
typedef struct RE_NextNode {
    struct RE_Node* node;
    struct RE_Node* test;
    struct RE_Node* match_next;
    Py_ssize_t match_step;
} RE_NextNode;

/* A pattern node. */
typedef struct RE_Node {
    RE_NextNode next_1;
    union {
        struct {
            RE_NextNode next_2;
        } nonstring;
        struct {
            /* Used only if (node->status & RE_STATUS_STRING) is true. */
            Py_ssize_t* bad_character_offset;
            Py_ssize_t* good_suffix_offset;
        } string;
    };
    Py_ssize_t step;
    size_t value_count;
    RE_CODE* values;
    RE_STATUS_T status;
    RE_UINT8 op;
    BOOL match;
} RE_Node;

/* Span of a guard (inclusive range). */
typedef struct RE_GuardSpan {
    Py_ssize_t low;
    Py_ssize_t high;
    BOOL protect;
} RE_GuardSpan;

/* Spans guarded against further matching. */
typedef struct RE_GuardList {
    size_t capacity;
    size_t count;
    RE_GuardSpan* spans;
    Py_ssize_t last_text_pos;
    size_t last_low;
} RE_GuardList;

/* Info about a group. */
typedef struct RE_GroupData {
    size_t capacity;
    size_t count;
    Py_ssize_t current;
    RE_GroupSpan* captures;
} RE_GroupData;

/* Info about a repeat. */
typedef struct RE_RepeatData {
    RE_GuardList body_guard_list;
    RE_GuardList tail_guard_list;
    size_t count;
    Py_ssize_t start;
    size_t capture_change;
} RE_RepeatData;

/* Guards for fuzzy sections. */
typedef struct RE_FuzzyGuards {
    RE_GuardList body_guard_list;
    RE_GuardList tail_guard_list;
} RE_FuzzyGuards;

/* Info about a capture group. */
typedef struct RE_GroupInfo {
    Py_ssize_t end_index;
    RE_Node* node;
    BOOL referenced;
    BOOL has_name;
} RE_GroupInfo;

/* Info about a call_ref. */
typedef struct RE_CallRefInfo {
    RE_Node* node;
    BOOL defined;
    BOOL used;
} RE_CallRefInfo;

/* Info about a repeat. */
typedef struct RE_RepeatInfo {
    RE_STATUS_T status;
} RE_RepeatInfo;

/* Info about a string argument. */
typedef struct RE_StringInfo {
    Py_buffer view; /* View of the string if it's a buffer object. */
    void* characters; /* Pointer to the characters of the string. */
    Py_ssize_t length; /* Length of the string. */
    Py_ssize_t charsize; /* Size of the characters in the string. */
    BOOL is_unicode; /* Whether the string is Unicode. */
    BOOL should_release; /* Whether the buffer should be released. */
} RE_StringInfo;

/* Info about where the next match was found, starting from a certain search
 * position. This is used when a pattern starts with a BRANCH.
 */
#define MAX_SEARCH_POSITIONS 7

/* Info about a search position. */
typedef struct {
    Py_ssize_t start_pos;
    Py_ssize_t match_pos;
} RE_SearchPosition;

typedef struct RE_FuzzyChange {
    RE_UINT8 type;
    Py_ssize_t pos;
} RE_FuzzyChange;

typedef struct RE_FuzzyChangesList {
    size_t capacity;
    size_t count;
    RE_FuzzyChange* items;
} RE_FuzzyChangesList;

typedef struct RE_BestChangesList {
    size_t capacity;
    size_t count;
    RE_FuzzyChangesList* lists;
} RE_BestChangesList;

typedef struct RE_LookaroundStateData {
    void* node;
    Py_ssize_t slice_start;
    Py_ssize_t slice_end;
    Py_ssize_t text_pos;
} RE_LookaroundStateData;

typedef struct RE_GroupStateData {
    Py_ssize_t text_pos;
    Py_ssize_t current;
    size_t capture_change;
    RE_CODE private_index;
    RE_CODE public_index;
} RE_GroupStateData;

typedef struct RE_MatchBodyTailStateData {
    RE_Position position;
    size_t count;
    Py_ssize_t start;
    size_t capture_change;
    RE_CODE index;
    Py_ssize_t text_pos;
} RE_MatchBodyTailStateData;

typedef struct RE_BodyEndStateData {
    size_t count;
    Py_ssize_t start;
    size_t capture_change;
    RE_CODE index;
} RE_BodyEndStateData;

typedef struct RE_RepeatStateData {
    size_t count;
    Py_ssize_t start;
    size_t capture_change;
    RE_CODE index;
    Py_ssize_t text_pos;
} RE_RepeatStateData;

typedef struct RE_RepeatOneStateData {
    size_t count;
    Py_ssize_t start;
    void* node;
    RE_CODE index;
} RE_RepeatOneStateData;

/* A stack of bytes. */
typedef struct ByteStack {
    size_t capacity;
    size_t count;
    BYTE* storage;
} ByteStack;

/* The state object used during matching. */
typedef struct RE_State {
    struct PatternObject* pattern; /* Parent PatternObject. */
    /* Info about the string being matched. */
    PyObject* string;
    Py_buffer view; /* View of the string if it's a buffer object. */
    Py_ssize_t charsize;
    void* text;
    Py_ssize_t text_length;
    /* The slice of the string being searched. */
    Py_ssize_t slice_start;
    Py_ssize_t slice_end;
    /* Info about the capture groups. */
    RE_GroupData* groups;
    Py_ssize_t lastindex;
    Py_ssize_t lastgroup;
    /* Info about the repeats. */
    RE_RepeatData* repeats;
    Py_ssize_t search_anchor; /* Where the last match finished. */
    Py_ssize_t match_pos; /* The start position of the match. */
    Py_ssize_t text_pos; /* The current position of the match. */
    Py_ssize_t final_newline; /* The index of newline at end of string, or -1. */
    Py_ssize_t final_line_sep; /* The index of line separator at end of string, or -1. */
    /* Storage for backtrack info. */
    ByteStack sstack; /* The structure stack. */
    ByteStack bstack; /* The backtracking stack. */
    ByteStack pstack; /* The pruning stack. */
    /* Info about the best POSIX match (leftmost longest). */
    Py_ssize_t best_match_pos;
    Py_ssize_t best_text_pos;
    RE_GroupData* best_match_groups;
    /* Miscellaneous. */
    Py_ssize_t min_width; /* The minimum width of the string to match (assuming it's not a fuzzy pattern). */
    RE_EncodingTable* encoding; /* The 'encoding' of the string being searched. */
    RE_LocaleInfo* locale_info; /* Info about the locale, if needed. */
    Py_UCS4 (*char_at)(void* text, Py_ssize_t pos);
    void (*set_char_at)(void* text, Py_ssize_t pos, Py_UCS4 ch);
    void* (*point_to)(void* text, Py_ssize_t pos);
    PyThreadState* thread_state; /* The thread state after releasing the GIL. */
    PyThread_type_lock lock; /* A lock for accessing the state across threads. */
    size_t fuzzy_counts[RE_FUZZY_COUNT]; /* The counts for the current fuzzy matching. */
    RE_Node* fuzzy_node; /* The node of the current fuzzy matching. */
    size_t best_fuzzy_counts[RE_FUZZY_COUNT]; /* Best totals for fuzzy matching. */
    RE_FuzzyGuards* fuzzy_guards; /* The guards for a fuzzy match. */
    size_t total_errors; /* The total number of errors of a fuzzy match. */
    size_t max_errors; /* The maximum permitted number of errors. */
    size_t fewest_errors; /* The fewest errors so far of an enhanced fuzzy match. */
    /* The group call guards. */
    RE_GuardList* group_call_guard_list;
    RE_FuzzyChangesList fuzzy_changes;
    RE_SearchPosition search_positions[MAX_SEARCH_POSITIONS]; /* Where the search matches next. */
    size_t capture_change; /* Incremented every time a captive group changes. */
    Py_ssize_t req_pos; /* The position where the required string matched. */
    Py_ssize_t req_end; /* The end position where the required string matched. */
    Py_ssize_t timeout; /* The timeout in clock ticks. */
    clock_t start_time; /* The clock time when matching started. */
    int partial_side; /* The side that could truncate in a partial match. */
    RE_UINT16 iterations; /* The number of iterations the matching engine has performed since checking for KeyboardInterrupt. */
    BOOL is_unicode; /* Whether the string to be matched is Unicode. */
    BOOL should_release; /* Whether the buffer should be released. */
    BOOL overlapped; /* Whether the matches can be overlapped. */
    BOOL reverse; /* Whether it's a reverse pattern. */
    BOOL visible_captures; /* Whether the 'captures' method will be visible. */
    BOOL version_0; /* Whether to perform version_0 behaviour (same as re module). */
    BOOL must_advance; /* Whether the end of the match must advance past its start. */
    BOOL is_multithreaded; /* Whether to release the GIL while matching. */
    BOOL too_few_errors; /* Whether there were too few fuzzy errors. */
    BOOL match_all; /* Whether to match all of the string ('fullmatch'). */
    BOOL found_match; /* Whether a POSIX match has been found. */
    BOOL is_fuzzy; /* Whether the pattern is fuzzy. */
} RE_State;

/* The PatternObject created from a regular expression. */
typedef struct PatternObject {
    PyObject_HEAD
    PyObject* pattern; /* Pattern source (or None). */
    Py_ssize_t flags; /* Flags used when compiling pattern source. */
    PyObject* packed_code_list;
    PyObject* weakreflist; /* List of weak references */
    /* Nodes into which the regular expression is compiled. */
    RE_Node* start_node;
    RE_Node* start_test;
    size_t true_group_count; /* The true number of capture groups. */
    size_t public_group_count; /* The number of public capture groups. */
    size_t visible_capture_count; /* The number of capture groups that are visible (not hidden in (?(DEFINE)...). */
    size_t repeat_count; /* The number of repeats. */
    Py_ssize_t group_end_index; /* The number of group closures. */
    PyObject* groupindex;
    PyObject* indexgroup;
    PyObject* named_lists;
    size_t named_lists_count;
    PyObject** partial_named_lists[2];
    PyObject* named_list_indexes;
    /* Storage for the pattern nodes. */
    size_t node_capacity;
    size_t node_count;
    RE_Node** node_list;
    /* Info about the capture groups. */
    size_t group_info_capacity;
    RE_GroupInfo* group_info;
    /* Info about the call_refs. */
    size_t call_ref_info_capacity;
    size_t call_ref_info_count;
    RE_CallRefInfo* call_ref_info;
    Py_ssize_t pattern_call_ref;
    /* Info about the repeats. */
    size_t repeat_info_capacity;
    RE_RepeatInfo* repeat_info;
    Py_ssize_t min_width; /* The minimum width of the string to match (assuming it isn't a fuzzy pattern). */
    RE_EncodingTable* encoding; /* Encoding handlers. */
    RE_LocaleInfo* locale_info; /* Info about the locale, if needed. */
    RE_GroupData* groups_storage; /* Cached storage for group data. */
    RE_RepeatData* repeats_storage; /* Cached storage for repeats. */
    BYTE* stack_storage; /* Cached storage for the bstack. */
    size_t stack_capacity; /* The size of the cached storage for bstack. */
    size_t fuzzy_count; /* The number of fuzzy sections. */
    /* Additional info. */
    Py_ssize_t req_offset; /* The offset to the required string. */
    PyObject* required_chars;
    Py_ssize_t req_flags;
    RE_Node* req_string; /* The required string. */
    BOOL is_fuzzy; /* Whether it's a fuzzy pattern. */
    BOOL do_search_start; /* Whether to do an initial search. */
} PatternObject;

/* The MatchObject created when a match is found. */
typedef struct MatchObject {
    PyObject_HEAD
    PyObject* string; /* Link to the target string or NULL if detached. */
    PyObject* substring; /* Link to (a substring of) the target string. */
    Py_ssize_t substring_offset; /* Offset into the target string. */
    PatternObject* pattern; /* Link to the regex (pattern) object. */
    Py_ssize_t pos; /* Start of current slice. */
    Py_ssize_t endpos; /* End of current slice. */
    Py_ssize_t match_start; /* Start of matched slice. */
    Py_ssize_t match_end; /* End of matched slice. */
    Py_ssize_t lastindex; /* Last group seen by the engine (-1 if none). */
    Py_ssize_t lastgroup; /* Last named group seen by the engine (-1 if none). */
    size_t group_count; /* The number of groups. */
    RE_GroupData* groups; /* The capture groups. */
    PyObject* regs;
    size_t fuzzy_counts[RE_FUZZY_COUNT];
    RE_FuzzyChange* fuzzy_changes;
    BOOL partial; /* Whether it's a partial match. */
} MatchObject;

/* The ScannerObject. */
typedef struct ScannerObject {
    PyObject_HEAD
    PatternObject* pattern;
    RE_State state;
    int status;
} ScannerObject;

/* The SplitterObject. */
typedef struct SplitterObject {
    PyObject_HEAD
    PatternObject* pattern;
    RE_State state;
    Py_ssize_t maxsplit;
    Py_ssize_t last_pos;
    Py_ssize_t split_count;
    Py_ssize_t index;
    int status;
} SplitterObject;

/* The CaptureObject. */
typedef struct CaptureObject {
    PyObject_HEAD
    Py_ssize_t group_index;
    MatchObject** match_indirect;
} CaptureObject;

/* Info used when compiling a pattern to nodes. */
typedef struct RE_CompileArgs {
    RE_CODE* code; /* The start of the compiled pattern. */
    RE_CODE* end_code; /* The end of the compiled pattern. */
    PatternObject* pattern; /* The pattern object. */
    Py_ssize_t min_width; /* The minimum width of the string to match (assuming it isn't a fuzzy pattern). */
    RE_Node* start; /* The start node. */
    RE_Node* end; /* The end node. */
    size_t repeat_depth; /* The nesting depth of the repeat. */
    size_t visible_capture_count; /* The number of capture groups that are visible (not hidden in (?(DEFINE)...). */
    BOOL forward; /* Whether it's a forward (not reverse) pattern. */
    BOOL visible_captures; /* Whether all of the captures will be visible. */
    BOOL has_captures; /* Whether the pattern has capture groups. */
    BOOL is_fuzzy; /* Whether the pattern (or some part of it) is fuzzy. */
    BOOL within_fuzzy; /* Whether the subpattern is within a fuzzy section. */
    BOOL has_groups; /* Whether the subpattern contains captures. */
    BOOL has_repeats; /* Whether the subpattern contains repeats. */
    BOOL in_define; /* Whether we're in (?(DEFINE)...). */
    BOOL all_atomic; /* The sequence consists only of atomic items. */
} RE_CompileArgs;

/* The string slices which will be concatenated to make the result string of
 * the 'sub' method.
 *
 * This allows us to avoid creating a list of slices if there of fewer than 2
 * of them. Empty strings aren't recorded, so if 'list' and 'item' are both
 * NULL then the result is an empty string.
 */
typedef struct RE_JoinInfo {
    PyObject* list; /* The list of slices if there are more than 2 of them. */
    PyObject* item; /* The slice if there is only 1 of them. */
    BOOL reversed; /* Whether the slices have been found in reverse order. */
    BOOL is_unicode; /* Whether the string is Unicode. */
} RE_JoinInfo;

/* Info about fuzzy matching. */
typedef struct {
    RE_Node* new_node;
    Py_ssize_t new_text_pos;
    Py_ssize_t limit;
    Py_ssize_t new_string_pos;
    int new_folded_pos;
    int folded_len;
    int new_gfolded_pos;
    int new_group_pos;
    RE_UINT8 fuzzy_type;
    RE_INT8 step;
    BOOL permit_insertion;
} RE_FuzzyData;

typedef struct RE_BestEntry {
     Py_ssize_t match_pos;
     Py_ssize_t text_pos;
} RE_BestEntry;

typedef struct RE_BestList {
    size_t capacity;
    size_t count;
    RE_BestEntry* entries;
} RE_BestList;

/* A stack of guard checks. */
typedef struct RE_Check {
    RE_Node* node;
    RE_STATUS_T result;
} RE_Check;

typedef struct RE_CheckStack {
    size_t capacity;
    size_t count;
    RE_Check* items;
} RE_CheckStack;

/* A stack of nodes. */
typedef struct RE_NodeStack {
    size_t capacity;
    size_t count;
    RE_Node** items;
} RE_NodeStack;

/* Function types for getting info from a MatchObject. */
typedef PyObject* (*RE_GetByIndexFunc)(MatchObject* self, Py_ssize_t index);

/* Returns the magnitude of a 'Py_ssize_t' value. */
Py_LOCAL_INLINE(Py_ssize_t) abs_ssize_t(Py_ssize_t x) {
    return x >= 0 ? x : -x;
}

/* Returns the minimum of 2 'Py_ssize_t' values. */
Py_LOCAL_INLINE(Py_ssize_t) min_ssize_t(Py_ssize_t x, Py_ssize_t y) {
    return x <= y ? x : y;
}

/* Returns the maximum of 2 'Py_ssize_t' values. */
Py_LOCAL_INLINE(Py_ssize_t) max_ssize_t(Py_ssize_t x, Py_ssize_t y) {
    return x >= y ? x : y;
}

/* Returns the minimum of 2 'size_t' values. */
Py_LOCAL_INLINE(size_t) min_size_t(size_t x, size_t y) {
    return x <= y ? x : y;
}

/* Returns the 'maximum' of 2 RE_STATUS_T values. */
Py_LOCAL_INLINE(RE_STATUS_T) max_status_2(RE_STATUS_T x, RE_STATUS_T y) {
    return x >= y ? x : y;
}

/* Returns the 'maximum' of 3 RE_STATUS_T values. */
Py_LOCAL_INLINE(RE_STATUS_T) max_status_3(RE_STATUS_T x, RE_STATUS_T y,
  RE_STATUS_T z) {
    return max_status_2(x, max_status_2(y, z));
}

/* Returns the 'maximum' of 4 RE_STATUS_T values. */
Py_LOCAL_INLINE(RE_STATUS_T) max_status_4(RE_STATUS_T w, RE_STATUS_T x,
  RE_STATUS_T y, RE_STATUS_T z) {
    return max_status_2(max_status_2(w, x), max_status_2(y, z));
}

/* Gets a character at a position assuming 1 byte per character. */
static Py_UCS4 bytes1_char_at(void* text, Py_ssize_t pos) {
    return *((Py_UCS1*)text + pos);
}

/* Sets a character at a position assuming 1 byte per character. */
static void bytes1_set_char_at(void* text, Py_ssize_t pos, Py_UCS4 ch) {
    *((Py_UCS1*)text + pos) = (Py_UCS1)ch;
}

/* Gets a pointer to a position assuming 1 byte per character. */
static void* bytes1_point_to(void* text, Py_ssize_t pos) {
    return (Py_UCS1*)text + pos;
}

/* Gets a character at a position assuming 2 bytes per character. */
static Py_UCS4 bytes2_char_at(void* text, Py_ssize_t pos) {
    return *((Py_UCS2*)text + pos);
}

/* Sets a character at a position assuming 2 bytes per character. */
static void bytes2_set_char_at(void* text, Py_ssize_t pos, Py_UCS4 ch) {
    *((Py_UCS2*)text + pos) = (Py_UCS2)ch;
}

/* Gets a pointer to a position assuming 2 bytes per character. */
static void* bytes2_point_to(void* text, Py_ssize_t pos) {
    return (Py_UCS2*)text + pos;
}

/* Gets a character at a position assuming 4 bytes per character. */
static Py_UCS4 bytes4_char_at(void* text, Py_ssize_t pos) {
    return *((Py_UCS4*)text + pos);
}

/* Sets a character at a position assuming 4 bytes per character. */
static void bytes4_set_char_at(void* text, Py_ssize_t pos, Py_UCS4 ch) {
    *((Py_UCS4*)text + pos) = (Py_UCS4)ch;
}

/* Gets a pointer to a position assuming 4 bytes per character. */
static void* bytes4_point_to(void* text, Py_ssize_t pos) {
    return (Py_UCS4*)text + pos;
}

/* Default for whether a position is on a word boundary. */
static BOOL at_boundary_always(RE_State* state, Py_ssize_t text_pos) {
    return TRUE;
}

/* Converts a BOOL to success/failure. */
Py_LOCAL_INLINE(int) bool_as_status(BOOL value) {
    return value ? RE_ERROR_SUCCESS : RE_ERROR_FAILURE;
}

/* ASCII-specific. */

Py_LOCAL_INLINE(BOOL) unicode_has_property(RE_CODE property, Py_UCS4 ch);

/* Checks whether a character has a property. */
Py_LOCAL_INLINE(BOOL) ascii_has_property(RE_CODE property, Py_UCS4 ch) {
    if (ch > RE_ASCII_MAX) {
        /* Outside the ASCII range. */
        RE_UINT32 value;

        value = property & 0xFFFF;

        return value == 0;
    }

    return unicode_has_property(property, ch);
}

/* Checks whether a character has a property, ignoring case. */
Py_LOCAL_INLINE(BOOL) ascii_has_property_ign(RE_CODE property, Py_UCS4 ch) {
    RE_UINT32 prop;

    prop = property >> 16;

    /* We are working with ASCII. */
    if (property == RE_PROP_GC_LU || property == RE_PROP_GC_LL || property ==
      RE_PROP_GC_LT) {
        RE_UINT32 value;

        value = re_get_general_category(ch);

        return value == RE_PROP_LU || value == RE_PROP_LL || value ==
          RE_PROP_LT;
    } else if (prop == RE_PROP_UPPERCASE || prop == RE_PROP_LOWERCASE)
        return (BOOL)re_get_cased(ch);

    /* The property is case-insensitive. */
    return ascii_has_property(property, ch);
}

/* Wrapper for calling 'ascii_has_property' via a pointer. */
static BOOL ascii_has_property_wrapper(RE_LocaleInfo* locale_info, RE_CODE
  property, Py_UCS4 ch) {
    return ascii_has_property(property, ch);
}

/* Checks whether there's a word character to the left. */
Py_LOCAL_INLINE(BOOL) ascii_word_left(RE_State* state, Py_ssize_t text_pos) {
    return text_pos > 0 && ascii_has_property(RE_PROP_WORD,
      state->char_at(state->text, text_pos - 1));
}

/* Checks whether there's a word character to the right. */
Py_LOCAL_INLINE(BOOL) ascii_word_right(RE_State* state, Py_ssize_t text_pos) {
    return text_pos < state->text_length && ascii_has_property(RE_PROP_WORD,
      state->char_at(state->text, text_pos));
}

/* Checks whether a position is on a word boundary. */
static BOOL ascii_at_boundary(RE_State* state, Py_ssize_t text_pos) {
    BOOL left;
    BOOL right;

    left = ascii_word_left(state, text_pos);
    right = ascii_word_right(state, text_pos);

    return left != right;
}

/* Checks whether a position is at the start of a word. */
static BOOL ascii_at_word_start(RE_State* state, Py_ssize_t text_pos) {
    BOOL left;
    BOOL right;

    left = ascii_word_left(state, text_pos);
    right = ascii_word_right(state, text_pos);

    return !left && right;
}

/* Checks whether a position is at the end of a word. */
static BOOL ascii_at_word_end(RE_State* state, Py_ssize_t text_pos) {
    BOOL left;
    BOOL right;

    left = ascii_word_left(state, text_pos);
    right = ascii_word_right(state, text_pos);

    return left && !right;
}

/* Checks whether a character is a line separator. */
static BOOL ascii_is_line_sep(Py_UCS4 ch) {
    return 0x0A <= ch && ch <= 0x0D;
}

/* Checks whether a position is at the start of a line. */
static BOOL ascii_at_line_start(RE_State* state, Py_ssize_t text_pos) {
    Py_UCS4 ch;

    if (text_pos <= 0)
        return TRUE;

    ch = state->char_at(state->text, text_pos - 1);

    if (ch == 0x0D) {
        if (text_pos >= state->text_length)
            return TRUE;

        /* No line break inside CRLF. */
        return state->char_at(state->text, text_pos) != 0x0A;
    }

    return 0x0A <= ch && ch <= 0x0D;
}

/* Checks whether a position is at the end of a line. */
static BOOL ascii_at_line_end(RE_State* state, Py_ssize_t text_pos) {
    Py_UCS4 ch;

    if (text_pos >= state->text_length)
        return TRUE;

    ch = state->char_at(state->text, text_pos);

    if (ch == 0x0A) {
        if (text_pos <= 0)
            return TRUE;

        /* No line break inside CRLF. */
        return state->char_at(state->text, text_pos - 1) != 0x0D;
    }

    return 0x0A <= ch && ch <= 0x0D;
}

/* Checks whether a character could be Turkic (variants of I/i). For ASCII, it
 * won't be.
 */
static BOOL ascii_possible_turkic(RE_LocaleInfo* locale_info, Py_UCS4 ch) {
    return FALSE;
}

/* Gets all the cases of a character. */
static int ascii_all_cases(RE_LocaleInfo* locale_info, Py_UCS4 ch, Py_UCS4*
  codepoints) {
    int count;

    count = 0;

    codepoints[count++] = ch;

    if (('A' <= ch && ch <= 'Z') || ('a' <= ch && ch <= 'z'))
        /* It's a letter, so add the other case. */
        codepoints[count++] = ch ^ 0x20;

    return count;
}

/* Returns a character with its case folded. */
static Py_UCS4 ascii_simple_case_fold(RE_LocaleInfo* locale_info, Py_UCS4 ch) {
    if ('A' <= ch && ch <= 'Z')
        /* Uppercase folds to lowercase. */
        return ch ^ 0x20;

    return ch;
}

/* Returns a character with its case folded. */
static int ascii_full_case_fold(RE_LocaleInfo* locale_info, Py_UCS4 ch,
  Py_UCS4* folded) {
    if ('A' <= ch && ch <= 'Z')
        /* Uppercase folds to lowercase. */
        folded[0] = ch ^ 0x20;
    else
        folded[0] = ch;

    return 1;
}

/* Gets all the case variants of Turkic 'I'. The given character will be listed
 * first.
 */
static int ascii_all_turkic_i(RE_LocaleInfo* locale_info, Py_UCS4 ch, Py_UCS4*
  cases) {
    int count;

    count = 0;

    cases[count++] = ch;

    if (ch != 'I')
        cases[count++] = 'I';

    if (ch != 'i')
        cases[count++] = 'i';

    return count;
}

/* The handlers for ASCII characters. */
static RE_EncodingTable ascii_encoding = {
    ascii_has_property_wrapper,
    ascii_at_boundary,
    ascii_at_word_start,
    ascii_at_word_end,
    ascii_at_boundary, /* No special "default word boundary" for ASCII. */
    ascii_at_word_start, /* No special "default start of word" for ASCII. */
    ascii_at_word_end, /* No special "default end of a word" for ASCII. */
    at_boundary_always, /* No special "grapheme boundary" for ASCII. */
    ascii_is_line_sep,
    ascii_at_line_start,
    ascii_at_line_end,
    ascii_possible_turkic,
    ascii_all_cases,
    ascii_simple_case_fold,
    ascii_full_case_fold,
    ascii_all_turkic_i,
};

/* Locale-specific. */

/* Checks whether a character has the 'alnum' property in the given locale. */
Py_LOCAL_INLINE(BOOL) locale_isalnum(RE_LocaleInfo* locale_info, Py_UCS4 ch) {
    return ch <= RE_LOCALE_MAX && (locale_info->properties[ch] &
      RE_LOCALE_ALNUM) != 0;
}

/* Checks whether a character has the 'alpha' property in the given locale. */
Py_LOCAL_INLINE(BOOL) locale_isalpha(RE_LocaleInfo* locale_info, Py_UCS4 ch) {
    return ch <= RE_LOCALE_MAX && (locale_info->properties[ch] &
      RE_LOCALE_ALPHA) != 0;
}

/* Checks whether a character has the 'cntrl' property in the given locale. */
Py_LOCAL_INLINE(BOOL) locale_iscntrl(RE_LocaleInfo* locale_info, Py_UCS4 ch) {
    return ch <= RE_LOCALE_MAX && (locale_info->properties[ch] &
      RE_LOCALE_CNTRL) != 0;
}

/* Checks whether a character has the 'digit' property in the given locale. */
Py_LOCAL_INLINE(BOOL) locale_isdigit(RE_LocaleInfo* locale_info, Py_UCS4 ch) {
    return ch <= RE_LOCALE_MAX && (locale_info->properties[ch] &
      RE_LOCALE_DIGIT) != 0;
}

/* Checks whether a character has the 'graph' property in the given locale. */
Py_LOCAL_INLINE(BOOL) locale_isgraph(RE_LocaleInfo* locale_info, Py_UCS4 ch) {
    return ch <= RE_LOCALE_MAX && (locale_info->properties[ch] &
      RE_LOCALE_GRAPH) != 0;
}

/* Checks whether a character has the 'lower' property in the given locale. */
Py_LOCAL_INLINE(BOOL) locale_islower(RE_LocaleInfo* locale_info, Py_UCS4 ch) {
    return ch <= RE_LOCALE_MAX && (locale_info->properties[ch] &
      RE_LOCALE_LOWER) != 0;
}

/* Checks whether a character has the 'print' property in the given locale. */
Py_LOCAL_INLINE(BOOL) locale_isprint(RE_LocaleInfo* locale_info, Py_UCS4 ch) {
    return ch <= RE_LOCALE_MAX && (locale_info->properties[ch] &
      RE_LOCALE_PRINT) != 0;
}

/* Checks whether a character has the 'punct' property in the given locale. */
Py_LOCAL_INLINE(BOOL) locale_ispunct(RE_LocaleInfo* locale_info, Py_UCS4 ch) {
    return ch <= RE_LOCALE_MAX && (locale_info->properties[ch] &
      RE_LOCALE_PUNCT) != 0;
}

/* Checks whether a character has the 'space' property in the given locale. */
Py_LOCAL_INLINE(BOOL) locale_isspace(RE_LocaleInfo* locale_info, Py_UCS4 ch) {
    return ch <= RE_LOCALE_MAX && (locale_info->properties[ch] &
      RE_LOCALE_SPACE) != 0;
}

/* Checks whether a character has the 'upper' property in the given locale. */
Py_LOCAL_INLINE(BOOL) locale_isupper(RE_LocaleInfo* locale_info, Py_UCS4 ch) {
    return ch <= RE_LOCALE_MAX && (locale_info->properties[ch] &
      RE_LOCALE_UPPER) != 0;
}

/* Converts a character to lowercase in the given locale. */
Py_LOCAL_INLINE(Py_UCS4) locale_tolower(RE_LocaleInfo* locale_info, Py_UCS4 ch)
  {
    return ch <= RE_LOCALE_MAX ? locale_info->lowercase[ch] : ch;
}

/* Converts a character to uppercase in the given locale. */
Py_LOCAL_INLINE(Py_UCS4) locale_toupper(RE_LocaleInfo* locale_info, Py_UCS4 ch)
  {
    return ch <= RE_LOCALE_MAX ? locale_info->uppercase[ch] : ch;
}

/* Checks whether a character has a property. */
Py_LOCAL_INLINE(BOOL) locale_has_property(RE_LocaleInfo* locale_info, RE_CODE
  property, Py_UCS4 ch) {
    RE_UINT32 value;
    RE_UINT32 v;

    value = property & 0xFFFF;

    if (ch > RE_LOCALE_MAX)
        /* Outside the locale range. */
        return value == 0;

    switch (property >> 16) {
    case RE_PROP_ALNUM >> 16:
        v = locale_isalnum(locale_info, ch) != 0;
        break;
    case RE_PROP_ALPHA >> 16:
        v = locale_isalpha(locale_info, ch) != 0;
        break;
    case RE_PROP_ANY >> 16:
        v = 1;
        break;
    case RE_PROP_ASCII >> 16:
        v = ch <= RE_ASCII_MAX;
        break;
    case RE_PROP_BLANK >> 16:
        v = ch == '\t' || ch == ' ';
        break;
    case RE_PROP_GC:
        switch (property) {
        case RE_PROP_ASSIGNED:
            v = ch <= RE_LOCALE_MAX;
            break;
        case RE_PROP_CASEDLETTER:
            v = locale_isalpha(locale_info, ch) ? value : 0xFFFF;
            break;
        case RE_PROP_CNTRL:
            v = locale_iscntrl(locale_info, ch) ? value : 0xFFFF;
            break;
        case RE_PROP_DIGIT:
            v = locale_isdigit(locale_info, ch) ? value : 0xFFFF;
            break;
        case RE_PROP_GC_CN:
            v = ch > RE_LOCALE_MAX;
            break;
        case RE_PROP_GC_LL:
            v = locale_islower(locale_info, ch) ? value : 0xFFFF;
            break;
        case RE_PROP_GC_LU:
            v = locale_isupper(locale_info, ch) ? value : 0xFFFF;
            break;
        case RE_PROP_GC_P:
            v = locale_ispunct(locale_info, ch) ? value : 0xFFFF;
            break;
        default:
            v = 0xFFFF;
            break;
        }
        break;
    case RE_PROP_GRAPH >> 16:
        v = locale_isgraph(locale_info, ch) != 0;
        break;
    case RE_PROP_LOWER >> 16:
        v = locale_islower(locale_info, ch) != 0;
        break;
    case RE_PROP_POSIX_ALNUM >> 16:
        v = re_get_posix_alnum(ch) != 0;
        break;
    case RE_PROP_POSIX_DIGIT >> 16:
        v = re_get_posix_digit(ch) != 0;
        break;
    case RE_PROP_POSIX_PUNCT >> 16:
        v = re_get_posix_punct(ch) != 0;
        break;
    case RE_PROP_POSIX_XDIGIT >> 16:
        v = re_get_posix_xdigit(ch) != 0;
        break;
    case RE_PROP_PRINT >> 16:
        v = locale_isprint(locale_info, ch) != 0;
        break;
    case RE_PROP_SPACE >> 16:
        v = locale_isspace(locale_info, ch) != 0;
        break;
    case RE_PROP_UPPER >> 16:
        v = locale_isupper(locale_info, ch) != 0;
        break;
    case RE_PROP_WORD >> 16:
        v = ch == '_' || locale_isalnum(locale_info, ch) != 0;
        break;
    case RE_PROP_XDIGIT >> 16:
        v = re_get_hex_digit(ch) != 0;
        break;
    default:
        v = 0;
        break;
    }

    return v == value;
}

/* Checks whether a character has a property, ignoring case. */
Py_LOCAL_INLINE(BOOL) locale_has_property_ign(RE_LocaleInfo* locale_info,
  RE_CODE property, Py_UCS4 ch) {
    RE_UINT32 prop;

    prop = property >> 16;

    if (property == RE_PROP_GC_LU || property == RE_PROP_GC_LL || property ==
      RE_PROP_GC_LT)
        return locale_isupper(locale_info, ch) || locale_islower(locale_info,
          ch);
    else if (prop == RE_PROP_UPPERCASE || prop == RE_PROP_LOWERCASE)
        return locale_isupper(locale_info, ch) || locale_islower(locale_info,
          ch);

    /* The property is case-insensitive. */
    return locale_has_property(locale_info, property, ch);
}

/* Wrapper for calling 'locale_has_property' via a pointer. */
static BOOL locale_has_property_wrapper(RE_LocaleInfo* locale_info, RE_CODE
  property, Py_UCS4 ch) {
    return locale_has_property(locale_info, property, ch);
}

/* Checks whether there's a word character to the left. */
Py_LOCAL_INLINE(BOOL) locale_word_left(RE_State* state, Py_ssize_t text_pos) {
    return text_pos > 0 && locale_has_property(state->locale_info,
      RE_PROP_WORD, state->char_at(state->text, text_pos - 1));
}

/* Checks whether there's a word character to the right. */
Py_LOCAL_INLINE(BOOL) locale_word_right(RE_State* state, Py_ssize_t text_pos) {
    return text_pos < state->text_length &&
      locale_has_property(state->locale_info, RE_PROP_WORD,
      state->char_at(state->text, text_pos));
}

/* Checks whether a position is on a word boundary. */
static BOOL locale_at_boundary(RE_State* state, Py_ssize_t text_pos) {
    BOOL left;
    BOOL right;

    left = locale_word_left(state, text_pos);
    right = locale_word_right(state, text_pos);

    return left != right;
}

/* Checks whether a position is at the start of a word. */
static BOOL locale_at_word_start(RE_State* state, Py_ssize_t text_pos) {
    BOOL left;
    BOOL right;

    left = locale_word_left(state, text_pos);
    right = locale_word_right(state, text_pos);

    return !left && right;
}

/* Checks whether a position is at the end of a word. */
static BOOL locale_at_word_end(RE_State* state, Py_ssize_t text_pos) {
    BOOL left;
    BOOL right;

    left = locale_word_left(state, text_pos);
    right = locale_word_right(state, text_pos);

    return left && !right;
}

/* Checks whether a character could be Turkic (variants of I/i). */
static BOOL locale_possible_turkic(RE_LocaleInfo* locale_info, Py_UCS4 ch) {
    return locale_toupper(locale_info, ch) == 'I' ||
      locale_tolower(locale_info, ch) == 'i';
}

/* Gets all the cases of a character. */
static int locale_all_cases(RE_LocaleInfo* locale_info, Py_UCS4 ch, Py_UCS4*
  codepoints) {
    int count;
    Py_UCS4 other;

    count = 0;

    codepoints[count++] = ch;

    other = locale_toupper(locale_info, ch);
    if (other != ch)
        codepoints[count++] = other;

    other = locale_tolower(locale_info, ch);
    if (other != ch)
        codepoints[count++] = other;

    return count;
}

/* Returns a character with its case folded. */
static Py_UCS4 locale_simple_case_fold(RE_LocaleInfo* locale_info, Py_UCS4 ch)
  {
    return locale_tolower(locale_info, ch);
}

/* Returns a character with its case folded. */
static int locale_full_case_fold(RE_LocaleInfo* locale_info, Py_UCS4 ch,
  Py_UCS4* folded) {
    folded[0] = locale_tolower(locale_info, ch);

    return 1;
}

/* Gets all the case variants of Turkic 'I'. The given character will be listed
 * first.
 */
static int locale_all_turkic_i(RE_LocaleInfo* locale_info, Py_UCS4 ch, Py_UCS4*
  cases) {
    int count;
    Py_UCS4 other;

    count = 0;

    cases[count++] = ch;

    if (ch != 'I')
        cases[count++] = 'I';

    if (ch != 'i')
        cases[count++] = 'i';

    /* Uppercase 'i' will be either dotted (Turkic) or dotless (non-Turkic). */
    other = locale_toupper(locale_info, 'i');
    if (other != ch && other != 'I')
        cases[count++] = other;

    /* Lowercase 'I' will be either dotless (Turkic) or dotted (non-Turkic). */
    other = locale_tolower(locale_info, 'I');
    if (other != ch && other != 'i')
        cases[count++] = other;

    return count;
}

/* The handlers for locale characters. */
static RE_EncodingTable locale_encoding = {
    locale_has_property_wrapper,
    locale_at_boundary,
    locale_at_word_start,
    locale_at_word_end,
    locale_at_boundary, /* No special "default word boundary" for locale. */
    locale_at_word_start, /* No special "default start of a word" for locale. */
    locale_at_word_end, /* No special "default end of a word" for locale. */
    at_boundary_always, /* No special "grapheme boundary" for locale. */
    ascii_is_line_sep, /* Assume locale line separators are same as ASCII. */
    ascii_at_line_start, /* Assume locale line separators are same as ASCII. */
    ascii_at_line_end, /* Assume locale line separators are same as ASCII. */
    locale_possible_turkic,
    locale_all_cases,
    locale_simple_case_fold,
    locale_full_case_fold,
    locale_all_turkic_i,
};

/* Unicode-specific. */

/* Checks whether a Unicode character has a property. */
Py_LOCAL_INLINE(BOOL) unicode_has_property(RE_CODE property, Py_UCS4 ch) {
    RE_UINT32 prop;
    RE_UINT32 value;
    RE_UINT32 v;

    prop = property >> 16;
    if (prop >= sizeof(re_get_property) / sizeof(re_get_property[0]))
        return FALSE;

    value = property & 0xFFFF;

    if (prop == RE_PROP_SCX) {
        int count;
        RE_UINT8 scripts[RE_MAX_SCX];
        int i;

        count = re_get_script_extensions(ch, scripts);

        for (i = 0; i < count; i++) {
            if (scripts[i] == value)
                return TRUE;
        }

        return FALSE;
    }

    v = re_get_property[prop](ch);

    if (v == value)
        return TRUE;

    if (prop == RE_PROP_GC) {
        switch (value) {
        case RE_PROP_ASSIGNED:
            return v != RE_PROP_CN;
        case RE_PROP_C:
            return (RE_PROP_C_MASK & (1 << v)) != 0;
        case RE_PROP_CASEDLETTER:
            return v == RE_PROP_LU || v == RE_PROP_LL || v == RE_PROP_LT;
        case RE_PROP_L:
            return (RE_PROP_L_MASK & (1 << v)) != 0;
        case RE_PROP_M:
            return (RE_PROP_M_MASK & (1 << v)) != 0;
        case RE_PROP_N:
            return (RE_PROP_N_MASK & (1 << v)) != 0;
        case RE_PROP_P:
            return (RE_PROP_P_MASK & (1 << v)) != 0;
        case RE_PROP_S:
            return (RE_PROP_S_MASK & (1 << v)) != 0;
        case RE_PROP_Z:
            return (RE_PROP_Z_MASK & (1 << v)) != 0;
        }
    }

    return FALSE;
}

/* Checks whether a character has a property, ignoring case. */
Py_LOCAL_INLINE(BOOL) unicode_has_property_ign(RE_CODE property, Py_UCS4 ch) {
    RE_UINT32 prop;

    prop = property >> 16;

    if (property == RE_PROP_GC_LU || property == RE_PROP_GC_LL || property ==
      RE_PROP_GC_LT) {
        RE_UINT32 value;

        value = re_get_general_category(ch);

        return value == RE_PROP_LU || value == RE_PROP_LL || value ==
          RE_PROP_LT;
    } else if (prop == RE_PROP_UPPERCASE || prop == RE_PROP_LOWERCASE)
        return (BOOL)re_get_cased(ch);

    /* The property is case-insensitive. */
    return unicode_has_property(property, ch);
}

/* Wrapper for calling 'unicode_has_property' via a pointer. */
static BOOL unicode_has_property_wrapper(RE_LocaleInfo* locale_info, RE_CODE
  property, Py_UCS4 ch) {
    return unicode_has_property(property, ch);
}

/* Checks whether there's a word character to the left. */
Py_LOCAL_INLINE(BOOL) unicode_word_left(RE_State* state, Py_ssize_t text_pos) {
    return text_pos > 0 && unicode_has_property(RE_PROP_WORD,
      state->char_at(state->text, text_pos - 1));
}

/* Checks whether there's a word character to the right. */
Py_LOCAL_INLINE(BOOL) unicode_word_right(RE_State* state, Py_ssize_t text_pos)
  {
    return text_pos < state->text_length && unicode_has_property(RE_PROP_WORD,
      state->char_at(state->text, text_pos));
}

/* Checks whether a position is on a word boundary. */
static BOOL unicode_at_boundary(RE_State* state, Py_ssize_t text_pos) {
    BOOL left;
    BOOL right;

    left = unicode_word_left(state, text_pos);
    right = unicode_word_right(state, text_pos);

    return left != right;
}

/* Checks whether a position is at the start of a word. */
static BOOL unicode_at_word_start(RE_State* state, Py_ssize_t text_pos) {
    BOOL left;
    BOOL right;

    left = unicode_word_left(state, text_pos);
    right = unicode_word_right(state, text_pos);

    return !left && right;
}

/* Checks whether a position is at the end of a word. */
static BOOL unicode_at_word_end(RE_State* state, Py_ssize_t text_pos) {
    BOOL left;
    BOOL right;

    left = unicode_word_left(state, text_pos);
    right = unicode_word_right(state, text_pos);

    return left && !right;
}

/* Checks whether a character is a Unicode vowel.
 *
 * Only a limited number are treated as vowels.
 */
Py_LOCAL_INLINE(BOOL) is_unicode_vowel(Py_UCS4 ch) {
#if PY_VERSION_HEX >= 0x03030000
    switch (Py_UNICODE_TOLOWER(ch)) {
#else
    switch (Py_UNICODE_TOLOWER((Py_UNICODE)ch)) {
#endif
    case 'a': case 0xE0: case 0xE1: case 0xE2:
    case 'e': case 0xE8: case 0xE9: case 0xEA:
    case 'i': case 0xEC: case 0xED: case 0xEE:
    case 'o': case 0xF2: case 0xF3: case 0xF4:
    case 'u': case 0xF9: case 0xFA: case 0xFB:
        return TRUE;
    default:
        return FALSE;
    }
}

/* Checks whether a character is a Unicode apostrophe.
 *
 * This could be U+0027 (APOSTROPHE) or U+2019 (RIGHT SINGLE QUOTATION MARK /
 * curly apostrophe).
 */
static BOOL is_unicode_apostrophe(Py_UCS4 ch) {
    return ch == 0x27 || ch == 0x2019;
}

Py_LOCAL_INLINE(BOOL) IS_AHLETTER(RE_UINT32 v) {
    return v == RE_WBREAK_ALETTER || v == RE_WBREAK_HEBREWLETTER;
}

Py_LOCAL_INLINE(BOOL) IS_MIDNUMLETQ(RE_UINT32 v) {
    return v == RE_WBREAK_MIDNUMLET || v == RE_WBREAK_SINGLEQUOTE;
}

/* Checks whether a position is on a default word boundary.
 *
 * The rules are defined here:
 * http://www.unicode.org/reports/tr29/#Default_Word_Boundaries
 */
static BOOL unicode_at_default_boundary(RE_State* state, Py_ssize_t text_pos) {
    Py_UCS4 (*char_at)(void* text, Py_ssize_t pos);
    Py_ssize_t left_pos;
    Py_ssize_t right_pos;
    Py_UCS4 left_char;
    Py_UCS4 right_char;
    RE_UINT32 left_prop;
    RE_UINT32 right_prop;
    Py_ssize_t pos;

    /* Break at the start and end of text, unless the text is empty. */
    /* WB1 and WB2 */
    if (text_pos <= 0 || text_pos >= state->text_length)
        return state->text_length > 0;

    /* In this function, left_pos is inclusive, i.e. it's the index of the
     * character.
     */
    char_at = state->char_at;

    left_pos = text_pos - 1;
    right_pos = text_pos;
    left_char = char_at(state->text, left_pos);
    right_char = char_at(state->text, right_pos);

    /* Do not break within CRLF. */
    /* WB3 */
    left_prop = re_get_word_break(left_char);
    right_prop = re_get_word_break(right_char);

    if (left_prop == RE_WBREAK_CR && right_prop == RE_WBREAK_LF)
        return FALSE;

    /* Otherwise break before and after Newlines (including CR and LF) */
    /* WB3a */
    if (left_prop == RE_WBREAK_NEWLINE || left_prop == RE_WBREAK_CR ||
      left_prop == RE_WBREAK_LF)
        return TRUE;

    /* WB3b */
    if (right_prop == RE_WBREAK_NEWLINE || right_prop == RE_WBREAK_CR ||
      right_prop == RE_WBREAK_LF)
        return TRUE;

    /* Do not break within emoji zwj sequences. */
    /* WB3c */
    if (left_prop == RE_WBREAK_ZWJ && re_get_extended_pictographic(right_char)
      != 0)
        return FALSE;

    /* Keep horizontal whitespace together. */
    /* WB3d */
    if (left_prop == RE_WBREAK_WSEGSPACE && right_prop == RE_WBREAK_WSEGSPACE)
        return FALSE;

    /* Ignore Format and Extend characters, except after sot, CR, LF, and
     * Newline. This also has the effect of: Any x (Format || Extend || ZWJ)
     */
    /* WB4 */
    if (right_prop == RE_WBREAK_EXTEND || right_prop == RE_WBREAK_FORMAT ||
      right_prop == RE_WBREAK_ZWJ)
        return FALSE;

    while (left_prop == RE_WBREAK_EXTEND || left_prop == RE_WBREAK_FORMAT ||
      left_prop == RE_WBREAK_ZWJ) {
        if (left_pos <= 0)
            return FALSE;
        --left_pos;
        left_char = char_at(state->text, left_pos);
        left_prop = re_get_word_break(left_char);
    }

    /* Do not break between most letters. */
    /* WB5 */
    if (IS_AHLETTER(left_prop) && IS_AHLETTER(right_prop))
        return FALSE;

    /* Break between apostrophe and vowels (French, Italian). */
    /* WB5a */
    if (is_unicode_apostrophe(left_char) && is_unicode_vowel(right_char))
        return FALSE;

    /* Do not break letters across certain punctuation. */
    /* WB6 */
    if (right_pos + 1 < state->text_length) {
        Py_UCS4 right_right_char;
        RE_UINT32 right_right_prop;

        right_right_char = char_at(state->text, right_pos + 1);
        right_right_prop = re_get_word_break(right_right_char);

        if (IS_AHLETTER(left_prop) && (right_prop == RE_WBREAK_MIDLETTER ||
          IS_MIDNUMLETQ(right_prop)) && IS_AHLETTER(right_right_prop))
            return FALSE;
    }

    /* WB7 */
    if (left_pos - 1 >= 0) {
        Py_UCS4 left_left_char;
        RE_UINT32 left_left_prop;

        left_left_char = char_at(state->text, left_pos - 1);
        left_left_prop = re_get_word_break(left_left_char);

        if (IS_AHLETTER(left_left_prop) && (left_prop == RE_WBREAK_MIDLETTER ||
          IS_MIDNUMLETQ(left_prop)) && IS_AHLETTER(right_prop))
            return FALSE;
    }

    /* WB7a */
    if (left_prop == RE_WBREAK_HEBREWLETTER && right_prop ==
      RE_WBREAK_SINGLEQUOTE)
        return FALSE;

    /* WB7b */
    if (right_pos + 1 < state->text_length) {
        Py_UCS4 right_right_char;
        RE_UINT32 right_right_prop;

        right_right_char = char_at(state->text, right_pos + 1);
        right_right_prop = re_get_word_break(right_right_char);

        if (left_prop == RE_WBREAK_HEBREWLETTER && right_prop ==
          RE_WBREAK_DOUBLEQUOTE && right_right_prop == RE_WBREAK_HEBREWLETTER)
            return FALSE;
    }

    /* WB7c */
    if (left_pos - 1 >= 0) {
        Py_UCS4 left_left_char;
        RE_UINT32 left_left_prop;

        left_left_char = char_at(state->text, left_pos - 1);
        left_left_prop = re_get_word_break(left_left_char);

        if (left_left_prop == RE_WBREAK_HEBREWLETTER && left_prop ==
          RE_WBREAK_DOUBLEQUOTE && right_prop == RE_WBREAK_HEBREWLETTER)
            return FALSE;
    }

    /* Do not break within sequences of digits, or digits adjacent to letters
     * ("3a", or "A3").
     */
    /* WB8 */
    if (left_prop == RE_WBREAK_NUMERIC && right_prop == RE_WBREAK_NUMERIC)
        return FALSE;

    /* WB9 */
    if (IS_AHLETTER(left_prop) && right_prop == RE_WBREAK_NUMERIC)
        return FALSE;

    /* WB10 */
    if (left_prop == RE_WBREAK_NUMERIC && IS_AHLETTER(right_prop))
        return FALSE;

    /* Do not break within sequences, such as "3.2" or "3,456.789". */
    /* WB11 */
    if (left_pos - 1 >= 0) {
        Py_UCS4 left_left_char;
        RE_UINT32 left_left_prop;

        left_left_char = char_at(state->text, left_pos - 1);
        left_left_prop = re_get_word_break(left_left_char);

        if (left_left_prop == RE_WBREAK_NUMERIC && (left_prop ==
          RE_WBREAK_MIDNUM || IS_MIDNUMLETQ(left_prop)) && right_prop ==
          RE_WBREAK_NUMERIC)
            return FALSE;
    }

    /* WB12 */
    if (right_pos + 1 < state->text_length) {
        Py_UCS4 right_right_char;
        RE_UINT32 right_right_prop;

        right_right_char = char_at(state->text, right_pos + 1);
        right_right_prop = re_get_word_break(right_right_char);

        if (left_prop == RE_WBREAK_NUMERIC && (right_prop == RE_WBREAK_MIDNUM
          || IS_MIDNUMLETQ(right_prop)) && right_right_prop ==
          RE_WBREAK_NUMERIC)
            return FALSE;
    }

    /* Do not break between Katakana. */
    /* WB13 */
    if (left_prop == RE_WBREAK_KATAKANA && right_prop == RE_WBREAK_KATAKANA)
        return FALSE;

    /* Do not break from extenders. */
    /* WB13a */
    if ((IS_AHLETTER(left_prop) || left_prop == RE_WBREAK_NUMERIC || left_prop
      == RE_WBREAK_KATAKANA || left_prop == RE_WBREAK_EXTENDNUMLET) &&
      right_prop == RE_WBREAK_EXTENDNUMLET)
        return FALSE;

    /* WB13b */
    if (left_prop == RE_WBREAK_EXTENDNUMLET && (IS_AHLETTER(right_prop) ||
      right_prop == RE_WBREAK_NUMERIC || right_prop == RE_WBREAK_KATAKANA))
        return FALSE;

    /* Do not break within emoji flag sequences. That is, do not break between
     * regional indicator (RI) symbols if there is an odd number of RI
     * characters before the break point.
     */
    /* WB15 and WB16 */
    pos = left_pos;

    while (pos >= 0 && re_get_word_break(char_at(state->text, pos)) ==
      RE_WBREAK_REGIONALINDICATOR)
        --pos;

    if ((left_pos - pos) % 2 == 1)
        return FALSE;

    /* Otherwise, break everywhere (including around ideographs). */
    /* WB999 */
    return TRUE;
}

/* Checks whether a position is at the start/end of a word. */
Py_LOCAL_INLINE(BOOL) unicode_at_default_word_start_or_end(RE_State* state,
  Py_ssize_t text_pos, BOOL at_start) {
    BOOL before;
    BOOL after;

    /* Is it at a boundary? */
    if (!unicode_at_default_boundary(state, text_pos))
        return FALSE;

    /* Look at the 2 characters either side of the boundary. Are they part of a
     * word?
     */
    before = unicode_word_left(state, text_pos);
    after = unicode_word_right(state, text_pos);

    return before != at_start && after == at_start;
}

/* Checks whether a position is at the start of a word. */
static BOOL unicode_at_default_word_start(RE_State* state, Py_ssize_t text_pos)
  {
    return unicode_at_default_word_start_or_end(state, text_pos, TRUE);
}

/* Checks whether a position is at the end of a word. */
static BOOL unicode_at_default_word_end(RE_State* state, Py_ssize_t text_pos) {
    return unicode_at_default_word_start_or_end(state, text_pos, FALSE);
}

/* Checks whether a position is on a grapheme boundary.
 *
 * The rules are defined here:
 * http://www.unicode.org/reports/tr29/#Grapheme_Cluster_Boundaries
 */
static BOOL unicode_at_grapheme_boundary(RE_State* state, Py_ssize_t text_pos)
  {
    Py_UCS4 (*char_at)(void* text, Py_ssize_t pos);
    Py_ssize_t left_pos;
    Py_ssize_t right_pos;
    Py_UCS4 left_char;
    Py_UCS4 right_char;
    RE_UINT32 left_prop;
    RE_UINT32 right_prop;
    Py_ssize_t pos;

    /* Break at the start and end of text, unless the text is empty. */
    /* GB1 and GB2 */
    if (text_pos <= 0 || text_pos >= state->text_length)
        return state->text_length > 0;

    /* In this function, left_pos is inclusive, i.e. it's the index of the
     * character.
     */
    char_at = state->char_at;

    left_pos = text_pos - 1;
    right_pos = text_pos;
    left_char = char_at(state->text, left_pos);
    right_char = char_at(state->text, right_pos);

    /* Do not break between a CR and LF. Otherwise, break before and after
     * controls.
     */
    /* GB3 */
    left_prop = re_get_grapheme_cluster_break(left_char);
    right_prop = re_get_grapheme_cluster_break(right_char);

    if (left_prop == RE_GBREAK_CR && right_prop == RE_GBREAK_LF)
        return FALSE;

    /* GB4 */
    if (left_prop == RE_GBREAK_CONTROL || left_prop == RE_GBREAK_CR ||
      left_prop == RE_GBREAK_LF)
        return TRUE;

    /* GB5 */
    if (right_prop == RE_GBREAK_CONTROL || right_prop == RE_GBREAK_CR ||
      right_prop == RE_GBREAK_LF)
        return TRUE;

    /* Do not break Hangul syllable sequences. */
    /* GB6 */
    if (left_prop == RE_GBREAK_L && (right_prop == RE_GBREAK_L || right_prop ==
      RE_GBREAK_V || right_prop == RE_GBREAK_LV || right_prop ==
      RE_GBREAK_LVT))
        return FALSE;

    /* GB7 */
    if ((left_prop == RE_GBREAK_LV || left_prop == RE_GBREAK_V) && (right_prop
      == RE_GBREAK_V || right_prop == RE_GBREAK_T))
        return FALSE;

    /* GB8 */
    if ((left_prop == RE_GBREAK_LVT || left_prop == RE_GBREAK_T) && left_prop
      == RE_GBREAK_T)
        return FALSE;

    /* Do not break before extending characters or ZWJ. */
    /* GB9 */
    if (right_prop == RE_GBREAK_EXTEND || right_prop == RE_GBREAK_ZWJ)
       return FALSE;

    /* The GB9a and GB9b rules only apply to extended grapheme clusters: Do not
     * break before SpacingMarks, or after Prepend characters.
     */
    /* GB9a */
    if (right_prop == RE_GBREAK_SPACINGMARK)
        return FALSE;

    /* GB9b */
    if (left_prop == RE_GBREAK_PREPEND)
        return FALSE;

    /* Do not break within emoji modifier sequences or emoji zwj sequences. */
    /* GB11 */
    if (left_prop == RE_GBREAK_ZWJ && re_get_extended_pictographic(right_char))
      {
        pos = left_pos - 1;

        while (pos >= 0 && re_get_grapheme_cluster_break(char_at(state->text,
          pos)) == RE_GBREAK_EXTEND)
            --pos;

        if (pos >= 0 && re_get_extended_pictographic(char_at(state->text,
          pos)))
            return FALSE;
    }

    /* The \p{Extended_Pictographic} values are provided as a part of the Emoji
     * data in [UTS51]. Do not break within emoji flag sequences. That is, do
     * not break between regional indicator (RI) symbols if there is an odd
     * number of RI characters before the break point.
     */
    /* GB12 and GB13 */
    pos = left_pos;

    while (pos >= 0 && re_get_grapheme_cluster_break(char_at(state->text, pos))
      == RE_WBREAK_REGIONALINDICATOR)
        --pos;

    if ((left_pos - pos) % 2 == 1)
        return FALSE;

    /* Otherwise, break everywhere. */
    /* GB999 */
    return TRUE;
}

/* Checks whether a character is a line separator. */
static BOOL unicode_is_line_sep(Py_UCS4 ch) {
    return (0x0A <= ch && ch <= 0x0D) || ch == 0x85 || ch == 0x2028 || ch ==
      0x2029;
}

/* Checks whether a position is at the start of a line. */
static BOOL unicode_at_line_start(RE_State* state, Py_ssize_t text_pos) {
    Py_UCS4 ch;

    if (text_pos <= 0)
        return TRUE;

    ch = state->char_at(state->text, text_pos - 1);

    if (ch == 0x0D) {
        if (text_pos >= state->text_length)
            return TRUE;

        /* No line break inside CRLF. */
        return state->char_at(state->text, text_pos) != 0x0A;
    }

    return (0x0A <= ch && ch <= 0x0D) || ch == 0x85 || ch == 0x2028 || ch ==
      0x2029;
}

/* Checks whether a position is at the end of a line. */
static BOOL unicode_at_line_end(RE_State* state, Py_ssize_t text_pos) {
    Py_UCS4 ch;

    if (text_pos >= state->text_length)
        return TRUE;

    ch = state->char_at(state->text, text_pos);

    if (ch == 0x0A) {
        if (text_pos <= 0)
            return TRUE;

        /* No line break inside CRLF. */
        return state->char_at(state->text, text_pos - 1) != 0x0D;
    }

    return (0x0A <= ch && ch <= 0x0D) || ch == 0x85 || ch == 0x2028 || ch ==
      0x2029;
}

/* Checks whether a character could be Turkic (variants of I/i). */
static BOOL unicode_possible_turkic(RE_LocaleInfo* locale_info, Py_UCS4 ch) {
    return ch == 'I' || ch == 'i' || ch == 0x0130 || ch == 0x0131;
}

/* Gets all the cases of a character. */
static int unicode_all_cases(RE_LocaleInfo* locale_info, Py_UCS4 ch, Py_UCS4*
  codepoints) {
    return re_get_all_cases(ch, codepoints);
}

/* Returns a character with its case folded, unless it could be Turkic
 * (variants of I/i).
 */
static Py_UCS4 unicode_simple_case_fold(RE_LocaleInfo* locale_info, Py_UCS4 ch)
  {
    /* Is it a possible Turkic character? If so, pass it through unchanged. */
    if (ch == 'I' || ch == 'i' || ch == 0x0130 || ch == 0x0131)
        return ch;

    return (Py_UCS4)re_get_simple_case_folding(ch);
}

/* Returns a character with its case folded, unless it could be Turkic
 * (variants of I/i).
 */
static int unicode_full_case_fold(RE_LocaleInfo* locale_info, Py_UCS4 ch,
  Py_UCS4* folded) {
    /* Is it a possible Turkic character? If so, pass it through unchanged. */
    if (ch == 'I' || ch == 'i' || ch == 0x0130 || ch == 0x0131) {
        folded[0] = ch;
        return 1;
    }

    return re_get_full_case_folding(ch, folded);
}

/* Gets all the case variants of Turkic 'I'. */
static int unicode_all_turkic_i(RE_LocaleInfo* locale_info, Py_UCS4 ch,
  Py_UCS4* cases) {
    int count;

    count = 0;

    cases[count++] = ch;

    if (ch != 'I')
        cases[count++] = 'I';

    if (ch != 'i')
        cases[count++] = 'i';

    if (ch != 0x130)
        cases[count++] = 0x130;

    if (ch != 0x131)
        cases[count++] = 0x131;

    return count;

}

/* The handlers for Unicode characters. */
static RE_EncodingTable unicode_encoding = {
    unicode_has_property_wrapper,
    unicode_at_boundary,
    unicode_at_word_start,
    unicode_at_word_end,
    unicode_at_default_boundary,
    unicode_at_default_word_start,
    unicode_at_default_word_end,
    unicode_at_grapheme_boundary,
    unicode_is_line_sep,
    unicode_at_line_start,
    unicode_at_line_end,
    unicode_possible_turkic,
    unicode_all_cases,
    unicode_simple_case_fold,
    unicode_full_case_fold,
    unicode_all_turkic_i,
};

Py_LOCAL_INLINE(PyObject*) get_object(char* module_name, char* object_name);

/* Sets the error message. */
Py_LOCAL_INLINE(void) set_error(int status, PyObject* object) {
    TRACE(("<<set_error>>\n"))

    PyErr_Clear();

    switch (status) {
    case RE_ERROR_BAD_TIMEOUT:
        PyErr_SetString(PyExc_ValueError, "timeout not float or None");
        break;
    case RE_ERROR_CANCELLED:
        /* An exception has already been raised, so let it fly. */
        break;
    case RE_ERROR_CONCURRENT:
        PyErr_SetString(PyExc_ValueError, "concurrent not int or None");
        break;
    case RE_ERROR_GROUP_INDEX_TYPE:
        if (object)
            PyErr_Format(PyExc_TypeError,
              "group indices must be integers or strings, not %.200s",
              object->ob_type->tp_name);
        else
            PyErr_Format(PyExc_TypeError,
              "group indices must be integers or strings");
        break;
    case RE_ERROR_ILLEGAL:
        PyErr_SetString(PyExc_RuntimeError, "invalid RE code");
        break;
    case RE_ERROR_INDEX:
        PyErr_SetString(PyExc_TypeError, "string indices must be integers");
        break;
    case RE_ERROR_INVALID_GROUP_REF:
        if (!error_exception)
            error_exception = get_object("regex._regex_core", "error");

        PyErr_SetString(error_exception, "invalid group reference");
        break;
    case RE_ERROR_MEMORY:
        PyErr_NoMemory();
        break;
    case RE_ERROR_NOT_BYTES:
        PyErr_Format(PyExc_TypeError,
          "expected a bytes-like object, %.200s found",
          object->ob_type->tp_name);
        break;
    case RE_ERROR_NOT_STRING:
        PyErr_Format(PyExc_TypeError, "expected string instance, %.200s found",
          object->ob_type->tp_name);
        break;
    case RE_ERROR_NOT_UNICODE:
        PyErr_Format(PyExc_TypeError, "expected str instance, %.200s found",
          object->ob_type->tp_name);
        break;
    case RE_ERROR_NO_SUCH_GROUP:
        PyErr_SetString(PyExc_IndexError, "no such group");
        break;
    case RE_ERROR_REPLACEMENT:
        if (!error_exception)
            error_exception = get_object("regex._regex_core", "error");

        PyErr_SetString(error_exception, "invalid replacement");
        break;
    case RE_ERROR_TIMED_OUT:
        PyErr_SetString(PyExc_TimeoutError, "regex timed out");
        break;
    default:
        /* Other error codes indicate compiler/engine bugs. */
        PyErr_SetString(PyExc_RuntimeError,
          "internal error in regular expression engine");
        break;
    }
}

/* Allocates memory.
 *
 * Sets the Python error handler and returns NULL if the allocation fails.
 */
Py_LOCAL_INLINE(void*) re_alloc(size_t size) {
    void* new_ptr;

    new_ptr = PyMem_Malloc(size);
    if (!new_ptr)
        set_error(RE_ERROR_MEMORY, NULL);

    return new_ptr;
}

/* Reallocates memory.
 *
 * Sets the Python error handler and returns NULL if the reallocation fails.
 */
Py_LOCAL_INLINE(void*) re_realloc(void* ptr, size_t size) {
    void* new_ptr;

    new_ptr = PyMem_Realloc(ptr, size);
    if (!new_ptr)
        set_error(RE_ERROR_MEMORY, NULL);

    return new_ptr;
}

/* Deallocates memory. */
Py_LOCAL_INLINE(void) re_dealloc(void* ptr) {
    PyMem_Free(ptr);
}

/* Releases the GIL if multithreading is enabled. */
Py_LOCAL_INLINE(void) release_GIL(RE_State* state) {
    if (state->is_multithreaded && !state->thread_state)
        state->thread_state = PyEval_SaveThread();
}

/* Acquires the GIL if multithreading is enabled. */
Py_LOCAL_INLINE(void) acquire_GIL(RE_State* state) {
    if (state->is_multithreaded && state->thread_state) {
        PyEval_RestoreThread(state->thread_state);
        state->thread_state = NULL;
    }
}

/* Allocates memory, holding the GIL during the allocation.
 *
 * Sets the Python error handler and returns NULL if the allocation fails.
 */
Py_LOCAL_INLINE(void*) safe_alloc(RE_State* state, size_t size) {
    void* new_ptr;

    acquire_GIL(state);

    new_ptr = re_alloc(size);

    release_GIL(state);

    return new_ptr;
}

/* Reallocates memory, holding the GIL during the reallocation.
 *
 * Sets the Python error handler and returns NULL if the reallocation fails.
 */
Py_LOCAL_INLINE(void*) safe_realloc(RE_State* state, void* ptr, size_t size) {
    void* new_ptr;

    acquire_GIL(state);

    new_ptr = re_realloc(ptr, size);

    release_GIL(state);

    return new_ptr;
}

/* Deallocates memory, holding the GIL during the deallocation. */
Py_LOCAL_INLINE(void) safe_dealloc(RE_State* state, void* ptr) {
    acquire_GIL(state);

    re_dealloc(ptr);

    release_GIL(state);
}

/* Checks whether matching has timed out. */
Py_LOCAL_INLINE(BOOL) check_timed_out(RE_State* state) {
    if (state->timeout < 0)
        /* No timeout. */
        return FALSE;

    if ((Py_ssize_t)(clock() - state->start_time) < state->timeout)
        /* hasn't timed out yet. */
        return FALSE;

    set_error(RE_ERROR_TIMED_OUT, NULL);

    return TRUE;
}

/* Checks whether to cancel due to a KeyboardInterrupt or a timeout. */
Py_LOCAL_INLINE(BOOL) safe_check_cancel(RE_State* state) {
    BOOL result;

    acquire_GIL(state);

    result = (BOOL)PyErr_CheckSignals();

    if (!result)
        /* Has it timed out? */
        result = check_timed_out(state);

    release_GIL(state);

    return result;
}

/* Initialises a stack of bytes. */
Py_LOCAL_INLINE(BOOL) ByteStack_init(RE_State* state, ByteStack* stack) {
    stack->capacity = 0;
    stack->count = 0;
    stack->storage = NULL;

    return TRUE;
}

/* Finalises a stack of bytes. */
Py_LOCAL_INLINE(void) ByteStack_fini(RE_State* state, ByteStack* stack) {
    re_dealloc(stack->storage);
    stack->storage = NULL;
    stack->capacity = 0;
    stack->count = 0;
}

/* Resets a stack of bytes. */
Py_LOCAL_INLINE(void) ByteStack_reset(RE_State* state, ByteStack* stack) {
    stack->count = 0;
}

/* Pushes a byte onto a stack of bytes. */
Py_LOCAL_INLINE(BOOL) ByteStack_push(RE_State* state, ByteStack* stack, BYTE
  item) {
    if (stack->count >= stack->capacity) {
        size_t new_capacity;
        void* new_storage;

        new_capacity = stack->capacity * 2;

        if (new_capacity == 0)
            new_capacity = 64;

        if (new_capacity >= RE_MEMORY_LIMIT) {
            acquire_GIL(state);
            set_error(RE_ERROR_MEMORY, NULL);
            release_GIL(state);
            return FALSE;
        }

        new_storage = safe_realloc(state, stack->storage, new_capacity);
        if (!new_storage)
            return FALSE;

        stack->capacity = new_capacity;
        stack->storage = new_storage;
    }

    stack->storage[stack->count++] = item;

    return TRUE;
}

/* Pushes a block onto a stack of bytes. */
Py_LOCAL_INLINE(BOOL) ByteStack_push_block(RE_State* state, ByteStack* stack,
  void* block, size_t count) {
    size_t new_count;

    new_count = stack->count + count;

    if (new_count > stack->capacity) {
        size_t new_capacity;
        void* new_storage;

        new_capacity = stack->capacity;

        if (new_capacity == 0)
            new_capacity = 256;

        while (new_count > new_capacity)
            new_capacity *= 2;

        if (new_capacity >= RE_MEMORY_LIMIT) {
            acquire_GIL(state);
            set_error(RE_ERROR_MEMORY, NULL);
            release_GIL(state);
            return FALSE;
        }

        new_storage = safe_realloc(state, stack->storage, new_capacity);
        if (!new_storage)
            return FALSE;

        stack->capacity = new_capacity;
        stack->storage = new_storage;
    }

    Py_MEMCPY(stack->storage + stack->count, block, count);
    stack->count = new_count;

    return TRUE;
}

/* Pops a byte off a stack of bytes. */
Py_LOCAL_INLINE(BOOL) ByteStack_pop(RE_State* state, ByteStack* stack, BYTE*
  item) {
    if (stack->count < 1)
        return FALSE;

    *item = stack->storage[--stack->count];

    return TRUE;
}

/* Pops a block off a stack of bytes. */
Py_LOCAL_INLINE(BOOL) ByteStack_pop_block(RE_State* state, ByteStack* stack,
  void* block, size_t count) {
    if (count > stack->count)
        return FALSE;

    stack->count -= count;
    Py_MEMCPY(block, stack->storage + stack->count, count);

    return TRUE;
}

/* Drops a byte off a stack of bytes. */
Py_LOCAL_INLINE(BOOL) ByteStack_drop(RE_State* state, ByteStack* stack) {
    if (stack->count < 1)
        return FALSE;

    --stack->count;

    return TRUE;
}

/* Drops a block off a stack of bytes. */
Py_LOCAL_INLINE(BOOL) ByteStack_drop_block(RE_State* state, ByteStack* stack,
  size_t count) {
    if (count > stack->count)
        return FALSE;

    stack->count -= count;

    return TRUE;
}

/* Gets the top block off a stack of bytes. */
Py_LOCAL_INLINE(BOOL) ByteStack_top_block(RE_State* state, ByteStack* stack,
  void* block, size_t count) {
    if (count > stack->count)
        return FALSE;

    Py_MEMCPY(block, stack->storage + stack->count - count, count);

    return TRUE;
}

/* Pushes a int8 onto a stack of bytes. */
Py_LOCAL_INLINE(BOOL) push_int8(RE_State* state, ByteStack* stack, RE_INT8
  item) {
    return ByteStack_push(state, stack, (BYTE)item);
}

/* Pushes a uint8 onto a stack of bytes. */
Py_LOCAL_INLINE(BOOL) push_uint8(RE_State* state, ByteStack* stack, RE_UINT8
  item) {
    return ByteStack_push(state, stack, (BYTE)item);
}

/* Pushes a bool onto a stack of bytes. */
Py_LOCAL_INLINE(BOOL) push_bool(RE_State* state, ByteStack* stack, BOOL item) {
    return ByteStack_push(state, stack, (BYTE)item);
}

/* Pushes a Py_ssize_t onto a stack of bytes. */
Py_LOCAL_INLINE(BOOL) push_ssize(RE_State* state, ByteStack* stack, Py_ssize_t
  item) {
    return ByteStack_push_block(state, stack, (void*)&item, sizeof(item));
}

/* Pushes a size_t onto a stack of bytes. */
Py_LOCAL_INLINE(BOOL) push_size(RE_State* state, ByteStack* stack, size_t item)
  {
    return ByteStack_push_block(state, stack, (void*)&item, sizeof(item));
}

/* Pushes a code onto a stack of bytes. */
Py_LOCAL_INLINE(BOOL) push_code(RE_State* state, ByteStack* stack, RE_CODE
  item) {
    return ByteStack_push_block(state, stack, (void*)&item, sizeof(item));
}

/* Pushes an int onto a stack of bytes. */
Py_LOCAL_INLINE(BOOL) push_int(RE_State* state, ByteStack* stack, int item) {
    return ByteStack_push_block(state, stack, (void*)&item, sizeof(item));
}

/* Pushes a pointer onto a stack of bytes. */
Py_LOCAL_INLINE(BOOL) push_pointer(RE_State* state, ByteStack* stack, void*
  item) {
    return ByteStack_push_block(state, stack, (void*)&item, sizeof(item));
}

/* Pushes fuzzy counts onto a stack of bytes. */
Py_LOCAL_INLINE(BOOL) push_fuzzy_counts(RE_State* state, ByteStack* stack,
  size_t* fuzzy_counts) {
    if (!state->is_fuzzy)
        return TRUE;

    return ByteStack_push_block(state, stack, (void*)fuzzy_counts,
      RE_FUZZY_COUNT * sizeof(size_t));
}

/* Pushes group spans onto a stack of bytes. */
Py_LOCAL_INLINE(BOOL) push_groups(RE_State* state, ByteStack* stack) {
    Py_ssize_t group_count;
    Py_ssize_t g;

    group_count = (Py_ssize_t)state->pattern->true_group_count;
    if (group_count == 0)
        return TRUE;

    for (g = 0; g < group_count; g++) {
        RE_GroupData* group;

        group = &state->groups[g];

        if (!push_ssize(state, stack, group->current))
            return FALSE;
    }

    /* stack: current#0 current#1 ... */

    return TRUE;
}

/* Pushes group captures and spans onto a stack of bytes. */
Py_LOCAL_INLINE(BOOL) push_captures(RE_State* state, ByteStack* stack) {
    Py_ssize_t group_count;
    Py_ssize_t g;

    group_count = (Py_ssize_t)state->pattern->true_group_count;
    if (group_count == 0)
        return TRUE;

    for (g = 0; g < group_count; g++) {
        RE_GroupData* group;

        group = &state->groups[g];

        if (!push_size(state, stack, group->count))
            return FALSE;
        if (!push_ssize(state, stack, group->current))
            return FALSE;
    }

    /* stack: group[0] group[1] ...
     *
     * group: capture[0] capture[1] ... count current
     */

    return TRUE;
}

/* Pushes the repeat guard data onto the stack. */
Py_LOCAL_INLINE(BOOL) push_guard_data(RE_State* state, ByteStack* stack,
  RE_GuardList* guard_list) {
    if (!ByteStack_push_block(state, stack, (void*)guard_list->spans,
      guard_list->count * sizeof(RE_GuardSpan)))
        return FALSE;
    if (!push_size(state, stack, guard_list->count))
        return FALSE;

    return TRUE;
}

/* Pushes the repeat data onto the stack. */
Py_LOCAL_INLINE(BOOL) push_repeat_data(RE_State* state, ByteStack* stack,
  RE_RepeatData* repeat_data) {
    if (!push_guard_data(state, stack, &repeat_data->body_guard_list))
        return FALSE;
    if (!push_guard_data(state, stack, &repeat_data->tail_guard_list))
        return FALSE;
    if (!push_size(state, stack, repeat_data->count))
        return FALSE;
    if (!push_ssize(state, stack, repeat_data->start))
        return FALSE;
    if (!push_size(state, stack, repeat_data->capture_change))
        return FALSE;

    return TRUE;
}

/* Pushes the repeats onto the stack. */
Py_LOCAL_INLINE(BOOL) push_repeats(RE_State* state, ByteStack* stack) {
    PatternObject* pattern;
    Py_ssize_t repeat_count;
    Py_ssize_t r;

    pattern = state->pattern;

    repeat_count = (Py_ssize_t)pattern->repeat_count;
    if (repeat_count == 0)
        return TRUE;

    for (r = 0; r < repeat_count; r++) {
        if (!push_repeat_data(state, stack, &state->repeats[r]))
            return FALSE;
    }

    return TRUE;
}

/* Pushes the bstack count onto the pstack. */
Py_LOCAL_INLINE(BOOL) push_bstack(RE_State* state) {
    if (!push_size(state, &state->pstack, state->bstack.count))
        return FALSE;

    return TRUE;
}

/* Pushes the sstack count onto the bstack. */
Py_LOCAL_INLINE(BOOL) push_sstack(RE_State* state) {
    if (!push_size(state, &state->bstack, state->sstack.count))
        return FALSE;

    return TRUE;
}

/* Pops a int8 off a stack of bytes. */
Py_LOCAL_INLINE(BOOL) pop_int8(RE_State* state, ByteStack* stack, RE_INT8*
  item) {
    return ByteStack_pop(state, stack, (BYTE*)item);
}

/* Pops a uint8 off a stack of bytes. */
Py_LOCAL_INLINE(BOOL) pop_uint8(RE_State* state, ByteStack* stack, RE_UINT8*
  item) {
    return ByteStack_pop(state, stack, (BYTE*)item);
}

/* Pops a bool off a stack of bytes. */
Py_LOCAL_INLINE(BOOL) pop_bool(RE_State* state, ByteStack* stack, BOOL* item) {
    return ByteStack_pop(state, stack, (BYTE*)item);
}

/* Pops a Py_ssize_t off a stack of bytes. */
Py_LOCAL_INLINE(BOOL) pop_ssize(RE_State* state, ByteStack* stack, Py_ssize_t*
  item) {
    return ByteStack_pop_block(state, stack, (void*)item, sizeof(*item));
}

/* Pops a size_t off a stack of bytes. */
Py_LOCAL_INLINE(BOOL) pop_size(RE_State* state, ByteStack* stack, size_t* item)
  {
    return ByteStack_pop_block(state, stack, (void*)item, sizeof(*item));
}

/* Pops a RE_CODE off a stack of bytes. */
Py_LOCAL_INLINE(BOOL) pop_code(RE_State* state, ByteStack* stack, RE_CODE*
  item) {
    return ByteStack_pop_block(state, stack, (void*)item, sizeof(*item));
}

/* Pops an int off a stack of bytes. */
Py_LOCAL_INLINE(BOOL) pop_int(RE_State* state, ByteStack* stack, int* item) {
    return ByteStack_pop_block(state, stack, (void*)item, sizeof(*item));
}

/* Pops a pointer off a stack of bytes. */
Py_LOCAL_INLINE(BOOL) pop_pointer(RE_State* state, ByteStack* stack, void**
  item) {
    return ByteStack_pop_block(state, stack, (void*)item, sizeof(*item));
}

/* Pops fuzzy counts off a stack of bytes. */
Py_LOCAL_INLINE(BOOL) pop_fuzzy_counts(RE_State* state, ByteStack* stack,
  size_t* fuzzy_counts) {
    if (!state->is_fuzzy)
        return TRUE;

    return ByteStack_pop_block(state, stack, (void*)fuzzy_counts,
      RE_FUZZY_COUNT * sizeof(size_t));
}

/* Pushes group spans off a stack of bytes. */
Py_LOCAL_INLINE(BOOL) pop_groups(RE_State* state, ByteStack* stack) {
    Py_ssize_t group_count;
    Py_ssize_t g;

    /* stack: current#0 current#1 ... */

    group_count = (Py_ssize_t)state->pattern->true_group_count;
    if (group_count == 0)
        return TRUE;

    for (g = group_count - 1; g >= 0; g--) {
        RE_GroupData* group;

        group = &state->groups[g];

        if (!pop_ssize(state, stack, &group->current))
            return FALSE;
    }

    return TRUE;
}

/* Pops group captures and spans off a stack of bytes. */
Py_LOCAL_INLINE(BOOL) pop_captures(RE_State* state, ByteStack* stack) {
    Py_ssize_t group_count;
    Py_ssize_t g;

    /* stack: group[0] group[1] ...
     *
     * group: capture[0] capture[1] ... count current
     */

    group_count = (Py_ssize_t)state->pattern->true_group_count;
    if (group_count == 0)
        return TRUE;

    for (g = group_count - 1; g >= 0; g--) {
        RE_GroupData* group;

        group = &state->groups[g];

        if (!pop_ssize(state, stack, &group->current))
            return FALSE;
        if (!pop_size(state, stack, &group->count))
            return FALSE;
    }

    return TRUE;
}

/* Pops the repeat guard data off the stack. */
Py_LOCAL_INLINE(BOOL) pop_guard_data(RE_State* state, ByteStack* stack,
  RE_GuardList* guard_list) {
    if (!pop_size(state, stack, &guard_list->count))
        return FALSE;
    if (!ByteStack_pop_block(state, stack, (void*)guard_list->spans,
      guard_list->count * sizeof(RE_GuardSpan)))
        return FALSE;

    guard_list->last_text_pos = -1;

    return TRUE;
}

/* Pops the repeat data off the stack. */
Py_LOCAL_INLINE(BOOL) pop_repeat_data(RE_State* state, ByteStack* stack,
  RE_RepeatData* repeat_data) {
    if (!pop_size(state, stack, &repeat_data->capture_change))
        return FALSE;
    if (!pop_ssize(state, stack, &repeat_data->start))
        return FALSE;
    if (!pop_size(state, stack, &repeat_data->count))
        return FALSE;
    if (!pop_guard_data(state, stack, &repeat_data->tail_guard_list))
        return FALSE;
    if (!pop_guard_data(state, stack, &repeat_data->body_guard_list))
        return FALSE;

    return TRUE;
}

/* Pops the repeats off the stack. */
Py_LOCAL_INLINE(BOOL) pop_repeats(RE_State* state, ByteStack* stack) {
    PatternObject* pattern;
    Py_ssize_t repeat_count;
    Py_ssize_t r;

    pattern = state->pattern;

    repeat_count = (Py_ssize_t)pattern->repeat_count;
    if (repeat_count == 0)
        return TRUE;

    for (r = repeat_count - 1; r >= 0; r--) {
        if (!pop_repeat_data(state, stack, &state->repeats[r]))
            return FALSE;
    }

    return TRUE;
}

/* Pops the bstack count off the pstack. */
Py_LOCAL_INLINE(BOOL) pop_bstack(RE_State* state) {

    if (!pop_size(state, &state->pstack, &state->bstack.count))
        return FALSE;

    return TRUE;
}

/* Pops the sstack count off the bstack. */
Py_LOCAL_INLINE(BOOL) pop_sstack(RE_State* state) {

    if (!pop_size(state, &state->bstack, &state->sstack.count))
        return FALSE;

    return TRUE;
}

/* Drops a uint8 off a stack of bytes. */
Py_LOCAL_INLINE(BOOL) drop_uint8(RE_State* state, ByteStack* stack) {
    return ByteStack_drop(state, stack);
}

/* Drops a Py_ssize_t off a stack of bytes. */
Py_LOCAL_INLINE(BOOL) drop_ssize(RE_State* state, ByteStack* stack) {
    return ByteStack_drop_block(state, stack, sizeof(Py_ssize_t));
}

/* Drops a size_t off a stack of bytes. */
Py_LOCAL_INLINE(BOOL) drop_size(RE_State* state, ByteStack* stack) {
    return ByteStack_drop_block(state, stack, sizeof(size_t));
}

/* Drops a pointer off a stack of bytes. */
Py_LOCAL_INLINE(BOOL) drop_pointer(RE_State* state, ByteStack* stack) {
    return ByteStack_drop_block(state, stack, sizeof(void*));
}

/* Drops the repeat guard data off the stack. */
Py_LOCAL_INLINE(BOOL) drop_guard_data(RE_State* state, ByteStack* stack) {
    size_t count;

    if (!pop_size(state, stack, &count))
        return FALSE;
    if (!ByteStack_drop_block(state, stack, count * sizeof(RE_GuardSpan)))
        return FALSE;

    return TRUE;
}

/* Drops the bstack count off the pstack. */
Py_LOCAL_INLINE(BOOL) drop_bstack(RE_State* state) {
    return drop_size(state, &state->pstack);
}

/* Gets the top size_t off a stack of bytes. */
Py_LOCAL_INLINE(BOOL) top_size(RE_State* state, ByteStack* stack, size_t* item)
  {
    return ByteStack_top_block(state, stack, (void*)item, sizeof(*item));
}

/* Returns the top bstack count off the pstack. */
Py_LOCAL_INLINE(BOOL) top_bstack(RE_State* state) {

    return top_size(state, &state->pstack, &state->bstack.count);
}

/* Checks whether a character is in a range. */
Py_LOCAL_INLINE(BOOL) in_range(Py_UCS4 lower, Py_UCS4 upper, Py_UCS4 ch) {
    return lower <= ch && ch <= upper;
}

/* Checks whether a character is in a range, ignoring case. */
Py_LOCAL_INLINE(BOOL) in_range_ign(RE_EncodingTable* encoding, RE_LocaleInfo*
  locale_info, Py_UCS4 lower, Py_UCS4 upper, Py_UCS4 ch) {
    int count;
    Py_UCS4 cases[RE_MAX_CASES];
    int i;

    count = encoding->all_cases(locale_info, ch, cases);

    for (i = 0; i < count; i++) {
        if (in_range(lower, upper, cases[i]))
            return TRUE;
    }

    return FALSE;
}

/* Checks whether 2 characters are the same. */
Py_LOCAL_INLINE(BOOL) same_char(Py_UCS4 ch1, Py_UCS4 ch2) {
    return ch1 == ch2;
}

/* Wrapper for calling 'same_char' via a pointer. */
static BOOL same_char_wrapper(RE_EncodingTable* encoding, RE_LocaleInfo*
  locale_info, Py_UCS4 ch1, Py_UCS4 ch2) {
    return same_char(ch1, ch2);
}

/* Checks whether 2 characters are the same, ignoring case. */
Py_LOCAL_INLINE(BOOL) same_char_ign(RE_EncodingTable* encoding, RE_LocaleInfo*
  locale_info, Py_UCS4 ch1, Py_UCS4 ch2) {
    int count;
    Py_UCS4 cases[RE_MAX_CASES];
    int i;

    if (ch1 == ch2)
        return TRUE;

    count = encoding->all_cases(locale_info, ch1, cases);

    for (i = 1; i < count; i++) {
        if (cases[i] == ch2)
            return TRUE;
    }

    return FALSE;
}

/* Checks whether 2 characters are the same, ignoring case. The first character
 * is already case-folded or is a possible Turkic 'I'.
 */
Py_LOCAL_INLINE(BOOL) same_char_ign_turkic(RE_EncodingTable* encoding,
  RE_LocaleInfo* locale_info, Py_UCS4 ch1, Py_UCS4 ch2) {
    int count;
    Py_UCS4 cases[RE_MAX_CASES];
    int i;

    if (ch1 == ch2)
        return TRUE;

    if (!encoding->possible_turkic(locale_info, ch1))
        return FALSE;

    count = encoding->all_turkic_i(locale_info, ch1, cases);

    for (i = 1; i < count; i++) {
        if (cases[i] == ch2)
            return TRUE;
    }

    return FALSE;
}

/* Wrapper for calling 'same_char' via a pointer. */
static BOOL same_char_ign_wrapper(RE_EncodingTable* encoding, RE_LocaleInfo*
  locale_info, Py_UCS4 ch1, Py_UCS4 ch2) {
    return same_char_ign(encoding, locale_info, ch1, ch2);
}

/* Checks whether a character is anything except a newline. */
Py_LOCAL_INLINE(BOOL) matches_ANY(RE_EncodingTable* encoding, RE_Node* node,
  Py_UCS4 ch) {
    return ch != '\n';
}

/* Checks whether a character is anything except a line separator. */
Py_LOCAL_INLINE(BOOL) matches_ANY_U(RE_EncodingTable* encoding, RE_Node* node,
  Py_UCS4 ch) {
    return !encoding->is_line_sep(ch);
}

/* Checks whether 2 characters are the same. */
Py_LOCAL_INLINE(BOOL) matches_CHARACTER(RE_EncodingTable* encoding,
  RE_LocaleInfo* locale_info, RE_Node* node, Py_UCS4 ch) {
    return same_char(node->values[0], ch);
}

/* Checks whether 2 characters are the same, ignoring case. */
Py_LOCAL_INLINE(BOOL) matches_CHARACTER_IGN(RE_EncodingTable* encoding,
  RE_LocaleInfo* locale_info, RE_Node* node, Py_UCS4 ch) {
    return same_char_ign(encoding, locale_info, node->values[0], ch);
}

/* Checks whether a character has a property. */
Py_LOCAL_INLINE(BOOL) matches_PROPERTY(RE_EncodingTable* encoding,
  RE_LocaleInfo* locale_info, RE_Node* node, Py_UCS4 ch) {
    return encoding->has_property(locale_info, node->values[0], ch);
}

/* Checks whether a character has a property, ignoring case. */
Py_LOCAL_INLINE(BOOL) matches_PROPERTY_IGN(RE_EncodingTable* encoding,
  RE_LocaleInfo* locale_info, RE_Node* node, Py_UCS4 ch) {
    RE_UINT32 property;
    RE_UINT32 prop;

    property = node->values[0];
    prop = property >> 16;

    /* We need to do special handling of case-sensitive properties according to
     * the 'encoding'.
     */
    if (encoding == &unicode_encoding) {
        /* We are working with Unicode. */
        if (property == RE_PROP_GC_LU || property == RE_PROP_GC_LL || property
          == RE_PROP_GC_LT) {
            RE_UINT32 value;

            value = re_get_general_category(ch);

            return value == RE_PROP_LU || value == RE_PROP_LL || value ==
              RE_PROP_LT;
        } else if (prop == RE_PROP_UPPERCASE || prop == RE_PROP_LOWERCASE)
            return (BOOL)re_get_cased(ch);

        /* The property is case-insensitive. */
        return unicode_has_property(property, ch);
    } else if (encoding == &ascii_encoding) {
        /* We are working with ASCII. */
        if (property == RE_PROP_GC_LU || property == RE_PROP_GC_LL || property
          == RE_PROP_GC_LT) {
            RE_UINT32 value;

            value = re_get_general_category(ch);

            return value == RE_PROP_LU || value == RE_PROP_LL || value ==
              RE_PROP_LT;
        } else if (prop == RE_PROP_UPPERCASE || prop == RE_PROP_LOWERCASE)
            return (BOOL)re_get_cased(ch);

        /* The property is case-insensitive. */
        return ascii_has_property(property, ch);
    } else {
        /* We are working with Locale. */
        if (property == RE_PROP_GC_LU || property == RE_PROP_GC_LL || property
          == RE_PROP_GC_LT)
            return locale_isupper(locale_info, ch) ||
              locale_islower(locale_info, ch);
        else if (prop == RE_PROP_UPPERCASE || prop == RE_PROP_LOWERCASE)
            return locale_isupper(locale_info, ch) ||
              locale_islower(locale_info, ch);

        /* The property is case-insensitive. */
        return locale_has_property(locale_info, property, ch);
    }
}

/* Checks whether a character is in a range. */
Py_LOCAL_INLINE(BOOL) matches_RANGE(RE_EncodingTable* encoding, RE_LocaleInfo*
  locale_info, RE_Node* node, Py_UCS4 ch) {
    return in_range(node->values[0], node->values[1], ch);
}

/* Checks whether a character is in a range, ignoring case. */
Py_LOCAL_INLINE(BOOL) matches_RANGE_IGN(RE_EncodingTable* encoding,
  RE_LocaleInfo* locale_info, RE_Node* node, Py_UCS4 ch) {
    return in_range_ign(encoding, locale_info, node->values[0],
      node->values[1], ch);
}

Py_LOCAL_INLINE(BOOL) in_set_diff(RE_EncodingTable* encoding, RE_LocaleInfo*
  locale_info, RE_Node* node, Py_UCS4 ch);
Py_LOCAL_INLINE(BOOL) in_set_inter(RE_EncodingTable* encoding, RE_LocaleInfo*
  locale_info, RE_Node* node, Py_UCS4 ch);
Py_LOCAL_INLINE(BOOL) in_set_sym_diff(RE_EncodingTable* encoding,
  RE_LocaleInfo* locale_info, RE_Node* node, Py_UCS4 ch);
Py_LOCAL_INLINE(BOOL) in_set_union(RE_EncodingTable* encoding, RE_LocaleInfo*
  locale_info, RE_Node* node, Py_UCS4 ch);

/* Checks whether a character matches a set member. */
Py_LOCAL_INLINE(BOOL) matches_member(RE_EncodingTable* encoding, RE_LocaleInfo*
  locale_info, RE_Node* member, Py_UCS4 ch) {
    switch (member->op) {
    case RE_OP_CHARACTER:
        /* values are: char_code */
        TRACE(("%s %d %d\n", re_op_text[member->op], member->match,
          member->values[0]))
        return ch == member->values[0];
    case RE_OP_PROPERTY:
        /* values are: property */
        TRACE(("%s %d %d\n", re_op_text[member->op], member->match,
          member->values[0]))
        return encoding->has_property(locale_info, member->values[0], ch);
    case RE_OP_RANGE:
        /* values are: lower, upper */
        TRACE(("%s %d %d %d\n", re_op_text[member->op], member->match,
          member->values[0], member->values[1]))
        return in_range(member->values[0], member->values[1], ch);
    case RE_OP_SET_DIFF:
        TRACE(("%s\n", re_op_text[member->op]))
        return in_set_diff(encoding, locale_info, member, ch);
    case RE_OP_SET_INTER:
        TRACE(("%s\n", re_op_text[member->op]))
        return in_set_inter(encoding, locale_info, member, ch);
    case RE_OP_SET_SYM_DIFF:
        TRACE(("%s\n", re_op_text[member->op]))
        return in_set_sym_diff(encoding, locale_info, member, ch);
    case RE_OP_SET_UNION:
        TRACE(("%s\n", re_op_text[member->op]))
        return in_set_union(encoding, locale_info, member, ch);
    case RE_OP_STRING:
    {
        /* values are: char_code, char_code, ... */
        size_t i;
        TRACE(("%s %d %" PY_FORMAT_SIZE_T "d\n", re_op_text[member->op],
          member->match, member->value_count))

        for (i = 0; i < member->value_count; i++) {
            if (ch == member->values[i])
                return TRUE;
        }
        return FALSE;
    }
    default:
        return FALSE;
    }
}

/* Checks whether a character matches a set member, ignoring case. */
Py_LOCAL_INLINE(BOOL) matches_member_ign(RE_EncodingTable* encoding,
  RE_LocaleInfo* locale_info, RE_Node* member, int case_count, Py_UCS4* cases)
  {
    int i;

    for (i = 0; i < case_count; i++) {
        switch (member->op) {
        case RE_OP_CHARACTER:
            /* values are: char_code */
            TRACE(("%s %d %d\n", re_op_text[member->op], member->match,
              member->values[0]))
            if (cases[i] == member->values[0])
                return TRUE;
            break;
        case RE_OP_PROPERTY:
            /* values are: property */
            TRACE(("%s %d %d\n", re_op_text[member->op], member->match,
              member->values[0]))
            if (encoding->has_property(locale_info, member->values[0],
              cases[i]))
                return TRUE;
            break;
        case RE_OP_RANGE:
            /* values are: lower, upper */
            TRACE(("%s %d %d %d\n", re_op_text[member->op], member->match,
              member->values[0], member->values[1]))
            if (in_range(member->values[0], member->values[1], cases[i]))
                return TRUE;
            break;
        case RE_OP_SET_DIFF:
            TRACE(("%s\n", re_op_text[member->op]))
            if (in_set_diff(encoding, locale_info, member, cases[i]))
                return TRUE;
            break;
        case RE_OP_SET_INTER:
            TRACE(("%s\n", re_op_text[member->op]))
            if (in_set_inter(encoding, locale_info, member, cases[i]))
                return TRUE;
            break;
        case RE_OP_SET_SYM_DIFF:
            TRACE(("%s\n", re_op_text[member->op]))
            if (in_set_sym_diff(encoding, locale_info, member, cases[i]))
                return TRUE;
            break;
        case RE_OP_SET_UNION:
            TRACE(("%s\n", re_op_text[member->op]))
            if (in_set_union(encoding, locale_info, member, cases[i]))
                return TRUE;
            break;
        case RE_OP_STRING:
        {
            size_t j;
            TRACE(("%s %d %d\n", re_op_text[member->op], member->match,
              member->value_count))

            for (j = 0; j < member->value_count; j++) {
                if (cases[i] == member->values[j])
                    return TRUE;
            }
            break;
        }
        default:
            return TRUE;
        }
    }

    return FALSE;
}

/* Checks whether a character is in a set difference. */
Py_LOCAL_INLINE(BOOL) in_set_diff(RE_EncodingTable* encoding, RE_LocaleInfo*
  locale_info, RE_Node* node, Py_UCS4 ch) {
    RE_Node* member;

    member = node->nonstring.next_2.node;

    if (matches_member(encoding, locale_info, member, ch) != member->match)
        return FALSE;

    member = member->next_1.node;

    while (member) {
        if (matches_member(encoding, locale_info, member, ch) == member->match)
            return FALSE;

        member = member->next_1.node;
    }

    return TRUE;
}

/* Checks whether a character is in a set difference, ignoring case. */
Py_LOCAL_INLINE(BOOL) in_set_diff_ign(RE_EncodingTable* encoding,
  RE_LocaleInfo* locale_info, RE_Node* node, int case_count, Py_UCS4* cases) {
    RE_Node* member;

    member = node->nonstring.next_2.node;

    if (matches_member_ign(encoding, locale_info, member, case_count, cases) !=
      member->match)
        return FALSE;

    member = member->next_1.node;

    while (member) {
        if (matches_member_ign(encoding, locale_info, member, case_count,
          cases) == member->match)
            return FALSE;

        member = member->next_1.node;
    }

    return TRUE;
}

/* Checks whether a character is in a set intersection. */
Py_LOCAL_INLINE(BOOL) in_set_inter(RE_EncodingTable* encoding, RE_LocaleInfo*
  locale_info, RE_Node* node, Py_UCS4 ch) {
    RE_Node* member;

    member = node->nonstring.next_2.node;

    while (member) {
        if (matches_member(encoding, locale_info, member, ch) != member->match)
            return FALSE;

        member = member->next_1.node;
    }

    return TRUE;
}

/* Checks whether a character is in a set intersection, ignoring case. */
Py_LOCAL_INLINE(BOOL) in_set_inter_ign(RE_EncodingTable* encoding,
  RE_LocaleInfo* locale_info, RE_Node* node, int case_count, Py_UCS4* cases) {
    RE_Node* member;

    member = node->nonstring.next_2.node;

    while (member) {
        if (matches_member_ign(encoding, locale_info, member, case_count,
          cases) != member->match)
            return FALSE;

        member = member->next_1.node;
    }

    return TRUE;
}

/* Checks whether a character is in a set symmetric difference. */
Py_LOCAL_INLINE(BOOL) in_set_sym_diff(RE_EncodingTable* encoding,
  RE_LocaleInfo* locale_info, RE_Node* node, Py_UCS4 ch) {
    RE_Node* member;
    BOOL result;

    member = node->nonstring.next_2.node;

    result = FALSE;

    while (member) {
        if (matches_member(encoding, locale_info, member, ch) == member->match)
            result = !result;

        member = member->next_1.node;
    }

    return result;
}

/* Checks whether a character is in a set symmetric difference, ignoring case.
 */
Py_LOCAL_INLINE(BOOL) in_set_sym_diff_ign(RE_EncodingTable* encoding,
  RE_LocaleInfo* locale_info, RE_Node* node, int case_count, Py_UCS4* cases) {
    RE_Node* member;
    BOOL result;

    member = node->nonstring.next_2.node;

    result = FALSE;

    while (member) {
        if (matches_member_ign(encoding, locale_info, member, case_count,
          cases) == member->match)
            result = !result;

        member = member->next_1.node;
    }

    return result;
}

/* Checks whether a character is in a set union. */
Py_LOCAL_INLINE(BOOL) in_set_union(RE_EncodingTable* encoding, RE_LocaleInfo*
  locale_info, RE_Node* node, Py_UCS4 ch) {
    RE_Node* member;

    member = node->nonstring.next_2.node;

    while (member) {
        if (matches_member(encoding, locale_info, member, ch) == member->match)
            return TRUE;

        member = member->next_1.node;
    }

    return FALSE;
}

/* Checks whether a character is in a set union, ignoring case. */
Py_LOCAL_INLINE(BOOL) in_set_union_ign(RE_EncodingTable* encoding,
  RE_LocaleInfo* locale_info, RE_Node* node, int case_count, Py_UCS4* cases) {
    RE_Node* member;

    member = node->nonstring.next_2.node;

    while (member) {
        if (matches_member_ign(encoding, locale_info, member, case_count,
          cases) == member->match)
            return TRUE;

        member = member->next_1.node;
    }

    return FALSE;
}

/* Checks whether a character is in a set. */
Py_LOCAL_INLINE(BOOL) matches_SET(RE_EncodingTable* encoding,
RE_LocaleInfo* locale_info, RE_Node* node, Py_UCS4 ch) {
    switch (node->op) {
    case RE_OP_SET_DIFF:
    case RE_OP_SET_DIFF_REV:
        return in_set_diff(encoding, locale_info, node, ch);
    case RE_OP_SET_INTER:
    case RE_OP_SET_INTER_REV:
        return in_set_inter(encoding, locale_info, node, ch);
    case RE_OP_SET_SYM_DIFF:
    case RE_OP_SET_SYM_DIFF_REV:
        return in_set_sym_diff(encoding, locale_info, node, ch);
    case RE_OP_SET_UNION:
    case RE_OP_SET_UNION_REV:
        return in_set_union(encoding, locale_info, node, ch);
    }

    return FALSE;
}

/* Checks whether a character is in a set, ignoring case. */
Py_LOCAL_INLINE(BOOL) matches_SET_IGN(RE_EncodingTable* encoding,
RE_LocaleInfo* locale_info, RE_Node* node, Py_UCS4 ch) {
    Py_UCS4 cases[RE_MAX_CASES];
    int case_count;

    case_count = encoding->all_cases(locale_info, ch, cases);

    switch (node->op) {
    case RE_OP_SET_DIFF_IGN:
    case RE_OP_SET_DIFF_IGN_REV:
        return in_set_diff_ign(encoding, locale_info, node, case_count, cases);
    case RE_OP_SET_INTER_IGN:
    case RE_OP_SET_INTER_IGN_REV:
        return in_set_inter_ign(encoding, locale_info, node, case_count,
          cases);
    case RE_OP_SET_SYM_DIFF_IGN:
    case RE_OP_SET_SYM_DIFF_IGN_REV:
        return in_set_sym_diff_ign(encoding, locale_info, node, case_count,
          cases);
    case RE_OP_SET_UNION_IGN:
    case RE_OP_SET_UNION_IGN_REV:
        return in_set_union_ign(encoding, locale_info, node, case_count,
          cases);
    }

    return FALSE;
}

/* Resets a guard list. */
Py_LOCAL_INLINE(void) reset_guard_list(RE_GuardList* guard_list) {
    guard_list->count = 0;
    guard_list->last_text_pos = -1;
}

/* Clears the groups. */
Py_LOCAL_INLINE(void) clear_groups(RE_State* state) {
    size_t i;

    for (i = 0; i < state->pattern->true_group_count; i++) {
        RE_GroupData* group;

        group = &state->groups[i];
        group->count = 0;

        group->current = -1;
    }
}

/* Resets the various guards. */
Py_LOCAL_INLINE(void) reset_guards(RE_State* state) {
    size_t i;

    /* Reset the guards for the repeats. */
    for (i = 0; i < state->pattern->repeat_count; i++) {
        reset_guard_list(&state->repeats[i].body_guard_list);
        reset_guard_list(&state->repeats[i].tail_guard_list);
    }

    /* Reset the guards for the fuzzy sections. */
    for (i = 0; i < state->pattern->fuzzy_count; i++) {
        reset_guard_list(&state->fuzzy_guards[i].body_guard_list);
        reset_guard_list(&state->fuzzy_guards[i].tail_guard_list);
    }

    /* Reset the guards for the group calls. */
    for (i = 0; i < state->pattern->call_ref_info_count; i++)
        reset_guard_list(&state->group_call_guard_list[i]);
}

/* Initialises the state for a match. */
Py_LOCAL_INLINE(void) init_match(RE_State* state) {
    /* Reset the stacks. */
    ByteStack_reset(state, &state->sstack);
    ByteStack_reset(state, &state->bstack);
    ByteStack_reset(state, &state->pstack);

    state->search_anchor = state->text_pos;
    state->match_pos = state->text_pos;

    /* Clear the groups. */
    clear_groups(state);

    /* Reset the guards. */
    reset_guards(state);

    /* Clear the counts and cost for matching. */
    if (state->is_fuzzy) {
        memset(state->fuzzy_counts, 0, sizeof(state->fuzzy_counts));
        state->fuzzy_node = NULL;
        state->fuzzy_changes.count = 0;
    }

    state->total_errors = 0;
    state->found_match = FALSE;
    state->capture_change = 0;
    state->iterations = 0;
}

/* Checks whether a node matches only 1 character. */
Py_LOCAL_INLINE(BOOL) node_matches_one_character(RE_Node* node) {
    switch (node->op) {
    case RE_OP_ANY:
    case RE_OP_ANY_ALL:
    case RE_OP_ANY_ALL_REV:
    case RE_OP_ANY_REV:
    case RE_OP_ANY_U:
    case RE_OP_ANY_U_REV:
    case RE_OP_CHARACTER:
    case RE_OP_CHARACTER_IGN:
    case RE_OP_CHARACTER_IGN_REV:
    case RE_OP_CHARACTER_REV:
    case RE_OP_PROPERTY:
    case RE_OP_PROPERTY_IGN:
    case RE_OP_PROPERTY_IGN_REV:
    case RE_OP_PROPERTY_REV:
    case RE_OP_RANGE:
    case RE_OP_RANGE_IGN:
    case RE_OP_RANGE_IGN_REV:
    case RE_OP_RANGE_REV:
    case RE_OP_SET_DIFF:
    case RE_OP_SET_DIFF_IGN:
    case RE_OP_SET_DIFF_IGN_REV:
    case RE_OP_SET_DIFF_REV:
    case RE_OP_SET_INTER:
    case RE_OP_SET_INTER_IGN:
    case RE_OP_SET_INTER_IGN_REV:
    case RE_OP_SET_INTER_REV:
    case RE_OP_SET_SYM_DIFF:
    case RE_OP_SET_SYM_DIFF_IGN:
    case RE_OP_SET_SYM_DIFF_IGN_REV:
    case RE_OP_SET_SYM_DIFF_REV:
    case RE_OP_SET_UNION:
    case RE_OP_SET_UNION_IGN:
    case RE_OP_SET_UNION_IGN_REV:
    case RE_OP_SET_UNION_REV:
        return TRUE;
    default:
        return FALSE;
    }
}

/* Locates the start node for testing ahead. */
Py_LOCAL_INLINE(RE_Node*) locate_test_start(RE_Node* node) {
    for (;;) {
        switch (node->op) {
        case RE_OP_BOUNDARY:
            switch (node->next_1.node->op) {
            case RE_OP_STRING:
            case RE_OP_STRING_FLD:
            case RE_OP_STRING_FLD_REV:
            case RE_OP_STRING_IGN:
            case RE_OP_STRING_IGN_REV:
            case RE_OP_STRING_REV:
                return node->next_1.node;
            default:
                return node;
            }
        case RE_OP_CALL_REF:
        case RE_OP_END_GROUP:
        case RE_OP_START_GROUP:
            node = node->next_1.node;
            break;
        case RE_OP_GREEDY_REPEAT:
        case RE_OP_LAZY_REPEAT:
            if (node->values[1] == 0)
                return node;
            node = node->next_1.node;
            break;
        case RE_OP_GREEDY_REPEAT_ONE:
        case RE_OP_LAZY_REPEAT_ONE:
            if (node->values[1] == 0)
                return node;
            return node->nonstring.next_2.node;
        case RE_OP_LOOKAROUND:
            node = node->nonstring.next_2.node;
            break;
        default:
            if (node->step == 0 && node_matches_one_character(node)) {
                switch (node->next_1.node->op) {
                case RE_OP_END_OF_STRING:
                case RE_OP_START_OF_STRING:
                    return node->next_1.node;
                }
            }

            return node;
        }
    }
}

/* Checks whether a character matches any of a set of case characters. */
Py_LOCAL_INLINE(BOOL) any_case(Py_UCS4 ch, int case_count, Py_UCS4* cases) {
    int i;

    for (i = 0; i < case_count; i++) {
        if (ch == cases[i])
            return TRUE;
    }

    return FALSE;
}

/* Matches many ANYs, up to a limit. */
Py_LOCAL_INLINE(Py_ssize_t) match_many_ANY(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos, Py_ssize_t limit, BOOL match) {
    void* text;

    text = state->text;

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        while (text_ptr < limit_ptr && (text_ptr[0] != '\n') == match)
            ++text_ptr;

        text_pos = text_ptr - (Py_UCS1*)text;
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        while (text_ptr < limit_ptr && (text_ptr[0] != '\n') == match)
            ++text_ptr;

        text_pos = text_ptr - (Py_UCS2*)text;
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        while (text_ptr < limit_ptr && (text_ptr[0] != '\n') == match)
            ++text_ptr;

        text_pos = text_ptr - (Py_UCS4*)text;
        break;
    }
    }

    return text_pos;
}

/* Matches many ANYs, up to a limit, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) match_many_ANY_REV(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos, Py_ssize_t limit, BOOL match) {
    void* text;

    text = state->text;

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        while (text_ptr > limit_ptr && (text_ptr[-1] != '\n') == match)
            --text_ptr;

        text_pos = text_ptr - (Py_UCS1*)text;
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        while (text_ptr > limit_ptr && (text_ptr[-1] != '\n') == match)
            --text_ptr;

        text_pos = text_ptr - (Py_UCS2*)text;
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        while (text_ptr > limit_ptr && (text_ptr[-1] != '\n') == match)
            --text_ptr;

        text_pos = text_ptr - (Py_UCS4*)text;
        break;
    }
    }

    return text_pos;
}

/* Matches many ANY_Us, up to a limit. */
Py_LOCAL_INLINE(Py_ssize_t) match_many_ANY_U(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos, Py_ssize_t limit, BOOL match) {
    void* text;
    RE_EncodingTable* encoding;

    text = state->text;
    encoding = state->encoding;

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        if (encoding == &unicode_encoding) {
            while (text_ptr < limit_ptr && unicode_is_line_sep(text_ptr[0]) !=
              match)
                ++text_ptr;
        } else {
            while (text_ptr < limit_ptr && ascii_is_line_sep(text_ptr[0]) !=
              match)
                ++text_ptr;
        }

        text_pos = text_ptr - (Py_UCS1*)text;
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        if (encoding == &unicode_encoding) {
            while (text_ptr < limit_ptr && unicode_is_line_sep(text_ptr[0]) !=
              match)
                ++text_ptr;
        } else {
            while (text_ptr < limit_ptr && ascii_is_line_sep(text_ptr[0]) !=
              match)
                ++text_ptr;
        }

        text_pos = text_ptr - (Py_UCS2*)text;
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        if (encoding == &unicode_encoding) {
            while (text_ptr < limit_ptr && unicode_is_line_sep(text_ptr[0]) !=
              match)
                ++text_ptr;
        } else {
            while (text_ptr < limit_ptr && ascii_is_line_sep(text_ptr[0]) !=
              match)
                ++text_ptr;
        }

        text_pos = text_ptr - (Py_UCS4*)text;
        break;
    }
    }

    return text_pos;
}

/* Matches many ANY_Us, up to a limit, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) match_many_ANY_U_REV(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, Py_ssize_t limit, BOOL match) {
    void* text;
    RE_EncodingTable* encoding;

    text = state->text;
    encoding = state->encoding;

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        if (encoding == &unicode_encoding) {
            while (text_ptr > limit_ptr && unicode_is_line_sep(text_ptr[-1]) !=
              match)
                --text_ptr;
        } else {
            while (text_ptr > limit_ptr && ascii_is_line_sep(text_ptr[-1]) !=
              match)
                --text_ptr;
        }

        text_pos = text_ptr - (Py_UCS1*)text;
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        if (encoding == &unicode_encoding) {
            while (text_ptr > limit_ptr && unicode_is_line_sep(text_ptr[-1]) !=
              match)
                --text_ptr;
        } else {
            while (text_ptr > limit_ptr && ascii_is_line_sep(text_ptr[-1]) !=
              match)
                --text_ptr;
        }

        text_pos = text_ptr - (Py_UCS2*)text;
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        if (encoding == &unicode_encoding) {
            while (text_ptr > limit_ptr && unicode_is_line_sep(text_ptr[-1]) !=
              match)
                --text_ptr;
        } else {
            while (text_ptr > limit_ptr && ascii_is_line_sep(text_ptr[-1]) !=
              match)
                --text_ptr;
        }

        text_pos = text_ptr - (Py_UCS4*)text;
        break;
    }
    }

    return text_pos;
}

/* Matches many CHARACTERs, up to a limit. */
Py_LOCAL_INLINE(Py_ssize_t) match_many_CHARACTER(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, Py_ssize_t limit, BOOL match) {
    void* text;
    Py_UCS4 ch;

    text = state->text;
    match = node->match == match;
    ch = node->values[0];

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        while (text_ptr < limit_ptr && (text_ptr[0] == ch) == match)
            ++text_ptr;

        text_pos = text_ptr - (Py_UCS1*)text;
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        while (text_ptr < limit_ptr && (text_ptr[0] == ch) == match)
            ++text_ptr;

        text_pos = text_ptr - (Py_UCS2*)text;
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        while (text_ptr < limit_ptr && (text_ptr[0] == ch) == match)
            ++text_ptr;

        text_pos = text_ptr - (Py_UCS4*)text;
        break;
    }
    }

    return text_pos;
}

/* Matches many CHARACTERs, up to a limit, ignoring case. */
Py_LOCAL_INLINE(Py_ssize_t) match_many_CHARACTER_IGN(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, Py_ssize_t limit, BOOL match) {
    void* text;
    Py_UCS4 cases[RE_MAX_CASES];
    int case_count;

    text = state->text;
    match = node->match == match;
    case_count = state->encoding->all_cases(state->locale_info,
      node->values[0], cases);

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        while (text_ptr < limit_ptr && any_case(text_ptr[0], case_count, cases)
          == match)
            ++text_ptr;

        text_pos = text_ptr - (Py_UCS1*)text;
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        while (text_ptr < limit_ptr && any_case(text_ptr[0], case_count, cases)
          == match)
            ++text_ptr;

        text_pos = text_ptr - (Py_UCS2*)text;
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        while (text_ptr < limit_ptr && any_case(text_ptr[0], case_count, cases)
          == match)
            ++text_ptr;

        text_pos = text_ptr - (Py_UCS4*)text;
        break;
    }
    }

    return text_pos;
}

/* Matches many CHARACTERs, up to a limit, backwards, ignoring case. */
Py_LOCAL_INLINE(Py_ssize_t) match_many_CHARACTER_IGN_REV(RE_State* state,
  RE_Node* node, Py_ssize_t text_pos, Py_ssize_t limit, BOOL match) {
    void* text;
    Py_UCS4 cases[RE_MAX_CASES];
    int case_count;

    text = state->text;
    match = node->match == match;
    case_count = state->encoding->all_cases(state->locale_info,
      node->values[0], cases);

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        while (text_ptr > limit_ptr && any_case(text_ptr[-1], case_count,
          cases) == match)
            --text_ptr;

        text_pos = text_ptr - (Py_UCS1*)text;
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        while (text_ptr > limit_ptr && any_case(text_ptr[-1], case_count,
          cases) == match)
            --text_ptr;

        text_pos = text_ptr - (Py_UCS2*)text;
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        while (text_ptr > limit_ptr && any_case(text_ptr[-1], case_count,
          cases) == match)
            --text_ptr;

        text_pos = text_ptr - (Py_UCS4*)text;
        break;
    }
    }

    return text_pos;
}

/* Matches many CHARACTERs, up to a limit, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) match_many_CHARACTER_REV(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, Py_ssize_t limit, BOOL match) {
    void* text;
    Py_UCS4 ch;

    text = state->text;
    match = node->match == match;
    ch = node->values[0];

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        while (text_ptr > limit_ptr && (text_ptr[-1] == ch) == match)
            --text_ptr;

        text_pos = text_ptr - (Py_UCS1*)text;
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        while (text_ptr > limit_ptr && (text_ptr[-1] == ch) == match)
            --text_ptr;

        text_pos = text_ptr - (Py_UCS2*)text;
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        while (text_ptr > limit_ptr && (text_ptr[-1] == ch) == match)
            --text_ptr;

        text_pos = text_ptr - (Py_UCS4*)text;
        break;
    }
    }

    return text_pos;
}

/* Matches many PROPERTYs, up to a limit. */
Py_LOCAL_INLINE(Py_ssize_t) match_many_PROPERTY(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos, Py_ssize_t limit, BOOL match) {
    void* text;
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;
    RE_CODE property;

    text = state->text;
    match = node->match == match;
    encoding = state->encoding;
    locale_info = state->locale_info;
    property = node->values[0];

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        if (encoding == &unicode_encoding) {
            while (text_ptr < limit_ptr && unicode_has_property(property,
              text_ptr[0]) == match)
                ++text_ptr;
        } else if (encoding == &ascii_encoding) {
            while (text_ptr < limit_ptr && ascii_has_property(property,
              text_ptr[0]) == match)
                ++text_ptr;
        } else {
            while (text_ptr < limit_ptr && locale_has_property(locale_info,
              property,
                text_ptr[0]) == match)
                ++text_ptr;
        }

        text_pos = text_ptr - (Py_UCS1*)text;
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        if (encoding == &unicode_encoding) {
            while (text_ptr < limit_ptr && unicode_has_property(property,
              text_ptr[0]) == match)
                ++text_ptr;
        } else if (encoding == &ascii_encoding) {
            while (text_ptr < limit_ptr && ascii_has_property(property,
              text_ptr[0]) == match)
                ++text_ptr;
        } else {
            while (text_ptr < limit_ptr && locale_has_property(locale_info,
              property,
                text_ptr[0]) == match)
                ++text_ptr;
        }

        text_pos = text_ptr - (Py_UCS2*)text;
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        if (encoding == &unicode_encoding) {
            while (text_ptr < limit_ptr && unicode_has_property(property,
              text_ptr[0]) == match)
                ++text_ptr;
        } else if (encoding == &ascii_encoding) {
            while (text_ptr < limit_ptr && ascii_has_property(property,
              text_ptr[0]) == match)
                ++text_ptr;
        } else {
            while (text_ptr < limit_ptr && locale_has_property(locale_info,
              property,
                text_ptr[0]) == match)
                ++text_ptr;
        }

        text_pos = text_ptr - (Py_UCS4*)text;
        break;
    }
    }

    return text_pos;
}

/* Matches many PROPERTYs, up to a limit, ignoring case. */
Py_LOCAL_INLINE(Py_ssize_t) match_many_PROPERTY_IGN(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, Py_ssize_t limit, BOOL match) {
    void* text;
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;
    RE_CODE property;

    text = state->text;
    match = node->match == match;
    encoding = state->encoding;
    locale_info = state->locale_info;
    property = node->values[0];

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        if (encoding == &unicode_encoding) {
            while (text_ptr < limit_ptr && unicode_has_property_ign(property,
              text_ptr[0]) == match)
                ++text_ptr;
        } else if (encoding == &ascii_encoding) {
            while (text_ptr < limit_ptr && ascii_has_property_ign(property,
              text_ptr[0]) == match)
                ++text_ptr;
        } else {
            while (text_ptr < limit_ptr && locale_has_property_ign(locale_info,
              property,
                text_ptr[0]) == match)
                ++text_ptr;
        }

        text_pos = text_ptr - (Py_UCS1*)text;
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        if (encoding == &unicode_encoding) {
            while (text_ptr < limit_ptr && unicode_has_property_ign(property,
              text_ptr[0]) == match)
                ++text_ptr;
        } else if (encoding == &ascii_encoding) {
            while (text_ptr < limit_ptr && ascii_has_property_ign(property,
              text_ptr[0]) == match)
                ++text_ptr;
        } else {
            while (text_ptr < limit_ptr && locale_has_property_ign(locale_info,
              property,
                text_ptr[0]) == match)
                ++text_ptr;
        }

        text_pos = text_ptr - (Py_UCS2*)text;
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        if (encoding == &unicode_encoding) {
            while (text_ptr < limit_ptr && unicode_has_property_ign(property,
              text_ptr[0]) == match)
                ++text_ptr;
        } else if (encoding == &ascii_encoding) {
            while (text_ptr < limit_ptr && ascii_has_property_ign(property,
              text_ptr[0]) == match)
                ++text_ptr;
        } else {
            while (text_ptr < limit_ptr && locale_has_property_ign(locale_info,
              property,
                text_ptr[0]) == match)
                ++text_ptr;
        }

        text_pos = text_ptr - (Py_UCS4*)text;
        break;
    }
    }

    return text_pos;
}

/* Matches many PROPERTYs, up to a limit, backwards, ignoring case. */
Py_LOCAL_INLINE(Py_ssize_t) match_many_PROPERTY_IGN_REV(RE_State* state,
  RE_Node* node, Py_ssize_t text_pos, Py_ssize_t limit, BOOL match) {
    void* text;
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;
    RE_CODE property;

    text = state->text;
    match = node->match == match;
    encoding = state->encoding;
    locale_info = state->locale_info;
    property = node->values[0];

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        if (encoding == &unicode_encoding) {
            while (text_ptr > limit_ptr && unicode_has_property_ign(property,
              text_ptr[-1]) == match)
                --text_ptr;
        } else if (encoding == &ascii_encoding) {
            while (text_ptr > limit_ptr && ascii_has_property_ign(property,
              text_ptr[-1]) == match)
                --text_ptr;
        } else {
            while (text_ptr > limit_ptr && locale_has_property_ign(locale_info,
              property,
                text_ptr[-1]) == match)
                --text_ptr;
        }

        text_pos = text_ptr - (Py_UCS1*)text;
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        if (encoding == &unicode_encoding) {
            while (text_ptr > limit_ptr && unicode_has_property_ign(property,
              text_ptr[-1]) == match)
                --text_ptr;
        } else if (encoding == &ascii_encoding) {
            while (text_ptr > limit_ptr && ascii_has_property_ign(property,
              text_ptr[-1]) == match)
                --text_ptr;
        } else {
            while (text_ptr > limit_ptr && locale_has_property_ign(locale_info,
              property,
                text_ptr[-1]) == match)
                --text_ptr;
        }

        text_pos = text_ptr - (Py_UCS2*)text;
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        if (encoding == &unicode_encoding) {
            while (text_ptr > limit_ptr && unicode_has_property_ign(property,
              text_ptr[-1]) == match)
                --text_ptr;
        } else if (encoding == &ascii_encoding) {
            while (text_ptr > limit_ptr && ascii_has_property_ign(property,
              text_ptr[-1]) == match)
                --text_ptr;
        } else {
            while (text_ptr > limit_ptr && locale_has_property_ign(locale_info,
              property,
                text_ptr[-1]) == match)
                --text_ptr;
        }

        text_pos = text_ptr - (Py_UCS4*)text;
        break;
    }
    }

    return text_pos;
}

/* Matches many PROPERTYs, up to a limit, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) match_many_PROPERTY_REV(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, Py_ssize_t limit, BOOL match) {
    void* text;
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;
    RE_CODE property;

    text = state->text;
    match = node->match == match;
    encoding = state->encoding;
    locale_info = state->locale_info;
    property = node->values[0];

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        if (encoding == &unicode_encoding) {
            while (text_ptr > limit_ptr && unicode_has_property(property,
              text_ptr[-1]) == match)
                --text_ptr;
        } else if (encoding == &ascii_encoding) {
            while (text_ptr > limit_ptr && ascii_has_property(property,
              text_ptr[-1]) == match)
                --text_ptr;
        } else {
            while (text_ptr > limit_ptr && locale_has_property(locale_info,
              property,
                text_ptr[-1]) == match)
                --text_ptr;
        }

        text_pos = text_ptr - (Py_UCS1*)text;
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        if (encoding == &unicode_encoding) {
            while (text_ptr > limit_ptr && unicode_has_property(property,
              text_ptr[-1]) == match)
                --text_ptr;
        } else if (encoding == &ascii_encoding) {
            while (text_ptr > limit_ptr && ascii_has_property(property,
              text_ptr[-1]) == match)
                --text_ptr;
        } else {
            while (text_ptr > limit_ptr && locale_has_property(locale_info,
              property,
                text_ptr[-1]) == match)
                --text_ptr;
        }

        text_pos = text_ptr - (Py_UCS2*)text;
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        if (encoding == &unicode_encoding) {
            while (text_ptr > limit_ptr && unicode_has_property(property,
              text_ptr[-1]) == match)
                --text_ptr;
        } else if (encoding == &ascii_encoding) {
            while (text_ptr > limit_ptr && ascii_has_property(property,
              text_ptr[-1]) == match)
                --text_ptr;
        } else {
            while (text_ptr > limit_ptr && locale_has_property(locale_info,
              property,
                text_ptr[-1]) == match)
                --text_ptr;
        }

        text_pos = text_ptr - (Py_UCS4*)text;
        break;
    }
    }

    return text_pos;
}

/* Matches many RANGEs, up to a limit. */
Py_LOCAL_INLINE(Py_ssize_t) match_many_RANGE(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos, Py_ssize_t limit, BOOL match) {
    void* text;
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;

    text = state->text;
    match = node->match == match;
    encoding = state->encoding;
    locale_info = state->locale_info;

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        while (text_ptr < limit_ptr && matches_RANGE(encoding, locale_info,
          node, text_ptr[0]) == match)
            ++text_ptr;

        text_pos = text_ptr - (Py_UCS1*)text;
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        while (text_ptr < limit_ptr && matches_RANGE(encoding, locale_info,
          node, text_ptr[0]) == match)
            ++text_ptr;

        text_pos = text_ptr - (Py_UCS2*)text;
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        while (text_ptr < limit_ptr && matches_RANGE(encoding, locale_info,
          node, text_ptr[0]) == match)
            ++text_ptr;

        text_pos = text_ptr - (Py_UCS4*)text;
        break;
    }
    }

    return text_pos;
}

/* Matches many RANGEs, up to a limit, ignoring case. */
Py_LOCAL_INLINE(Py_ssize_t) match_many_RANGE_IGN(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, Py_ssize_t limit, BOOL match) {
    void* text;
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;

    text = state->text;
    match = node->match == match;
    encoding = state->encoding;
    locale_info = state->locale_info;

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        while (text_ptr < limit_ptr && matches_RANGE_IGN(encoding, locale_info,
          node, text_ptr[0]) == match)
            ++text_ptr;

        text_pos = text_ptr - (Py_UCS1*)text;
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        while (text_ptr < limit_ptr && matches_RANGE_IGN(encoding, locale_info,
          node, text_ptr[0]) == match)
            ++text_ptr;

        text_pos = text_ptr - (Py_UCS2*)text;
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        while (text_ptr < limit_ptr && matches_RANGE_IGN(encoding, locale_info,
          node, text_ptr[0]) == match)
            ++text_ptr;

        text_pos = text_ptr - (Py_UCS4*)text;
        break;
    }
    }

    return text_pos;
}

/* Matches many RANGEs, up to a limit, backwards, ignoring case. */
Py_LOCAL_INLINE(Py_ssize_t) match_many_RANGE_IGN_REV(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, Py_ssize_t limit, BOOL match) {
    void* text;
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;

    text = state->text;
    match = node->match == match;
    encoding = state->encoding;
    locale_info = state->locale_info;

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        while (text_ptr > limit_ptr && matches_RANGE_IGN(encoding, locale_info,
          node, text_ptr[-1]) == match)
            --text_ptr;

        text_pos = text_ptr - (Py_UCS1*)text;
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        while (text_ptr > limit_ptr && matches_RANGE_IGN(encoding, locale_info,
          node, text_ptr[-1]) == match)
            --text_ptr;

        text_pos = text_ptr - (Py_UCS2*)text;
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        while (text_ptr > limit_ptr && matches_RANGE_IGN(encoding, locale_info,
          node, text_ptr[-1]) == match)
            --text_ptr;

        text_pos = text_ptr - (Py_UCS4*)text;
        break;
    }
    }

    return text_pos;
}

/* Matches many RANGEs, up to a limit, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) match_many_RANGE_REV(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, Py_ssize_t limit, BOOL match) {
    void* text;
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;

    text = state->text;
    match = node->match == match;
    encoding = state->encoding;
    locale_info = state->locale_info;

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        while (text_ptr > limit_ptr && matches_RANGE(encoding, locale_info,
          node, text_ptr[-1]) == match)
            --text_ptr;

        text_pos = text_ptr - (Py_UCS1*)text;
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        while (text_ptr > limit_ptr && matches_RANGE(encoding, locale_info,
          node, text_ptr[-1]) == match)
            --text_ptr;

        text_pos = text_ptr - (Py_UCS2*)text;
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        while (text_ptr > limit_ptr && matches_RANGE(encoding, locale_info,
          node, text_ptr[-1]) == match)
            --text_ptr;

        text_pos = text_ptr - (Py_UCS4*)text;
        break;
    }
    }

    return text_pos;
}

/* Matches many SETs, up to a limit. */
Py_LOCAL_INLINE(Py_ssize_t) match_many_SET(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos, Py_ssize_t limit, BOOL match) {
    void* text;
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;

    text = state->text;
    match = node->match == match;
    encoding = state->encoding;
    locale_info = state->locale_info;

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        while (text_ptr < limit_ptr && matches_SET(encoding, locale_info, node,
          text_ptr[0]) == match)
            ++text_ptr;

        text_pos = text_ptr - (Py_UCS1*)text;
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        while (text_ptr < limit_ptr && matches_SET(encoding, locale_info, node,
          text_ptr[0]) == match)
            ++text_ptr;

        text_pos = text_ptr - (Py_UCS2*)text;
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        while (text_ptr < limit_ptr && matches_SET(encoding, locale_info, node,
          text_ptr[0]) == match)
            ++text_ptr;

        text_pos = text_ptr - (Py_UCS4*)text;
        break;
    }
    }

    return text_pos;
}

/* Matches many SETs, up to a limit, ignoring case. */
Py_LOCAL_INLINE(Py_ssize_t) match_many_SET_IGN(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos, Py_ssize_t limit, BOOL match) {
    void* text;
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;

    text = state->text;
    match = node->match == match;
    encoding = state->encoding;
    locale_info = state->locale_info;

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        while (text_ptr < limit_ptr && matches_SET_IGN(encoding, locale_info,
          node, text_ptr[0]) == match)
            ++text_ptr;

        text_pos = text_ptr - (Py_UCS1*)text;
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        while (text_ptr < limit_ptr && matches_SET_IGN(encoding, locale_info,
          node, text_ptr[0]) == match)
            ++text_ptr;

        text_pos = text_ptr - (Py_UCS2*)text;
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        while (text_ptr < limit_ptr && matches_SET_IGN(encoding, locale_info,
          node, text_ptr[0]) == match)
            ++text_ptr;

        text_pos = text_ptr - (Py_UCS4*)text;
        break;
    }
    }

    return text_pos;
}

/* Matches many SETs, up to a limit, backwards, ignoring case. */
Py_LOCAL_INLINE(Py_ssize_t) match_many_SET_IGN_REV(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, Py_ssize_t limit, BOOL match) {
    void* text;
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;

    text = state->text;
    match = node->match == match;
    encoding = state->encoding;
    locale_info = state->locale_info;

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        while (text_ptr > limit_ptr && matches_SET_IGN(encoding, locale_info,
          node, text_ptr[-1]) == match)
            --text_ptr;

        text_pos = text_ptr - (Py_UCS1*)text;
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        while (text_ptr > limit_ptr && matches_SET_IGN(encoding, locale_info,
          node, text_ptr[-1]) == match)
            --text_ptr;

        text_pos = text_ptr - (Py_UCS2*)text;
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        while (text_ptr > limit_ptr && matches_SET_IGN(encoding, locale_info,
          node, text_ptr[-1]) == match)
            --text_ptr;

        text_pos = text_ptr - (Py_UCS4*)text;
        break;
    }
    }

    return text_pos;
}

/* Matches many SETs, up to a limit, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) match_many_SET_REV(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos, Py_ssize_t limit, BOOL match) {
    void* text;
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;

    text = state->text;
    match = node->match == match;
    encoding = state->encoding;
    locale_info = state->locale_info;

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        while (text_ptr > limit_ptr && matches_SET(encoding, locale_info, node,
          text_ptr[-1]) == match)
            --text_ptr;

        text_pos = text_ptr - (Py_UCS1*)text;
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        while (text_ptr > limit_ptr && matches_SET(encoding, locale_info, node,
          text_ptr[-1]) == match)
            --text_ptr;

        text_pos = text_ptr - (Py_UCS2*)text;
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        while (text_ptr > limit_ptr && matches_SET(encoding, locale_info, node,
          text_ptr[-1]) == match)
            --text_ptr;

        text_pos = text_ptr - (Py_UCS4*)text;
        break;
    }
    }

    return text_pos;
}

/* Counts a repeated character pattern. */
Py_LOCAL_INLINE(size_t) count_one(RE_State* state, RE_Node* node, Py_ssize_t
  text_pos, size_t max_count, BOOL* is_partial) {
    size_t count;

    *is_partial = FALSE;

    if (max_count < 1)
        return 0;

    switch (node->op) {
    case RE_OP_ANY:
        count = min_size_t((size_t)(state->slice_end - text_pos), max_count);

        count = (size_t)(match_many_ANY(state, node, text_pos, text_pos +
          (Py_ssize_t)count, TRUE) - text_pos);

        *is_partial = count == (size_t)(state->text_length - text_pos) && count
          < max_count && state->partial_side == RE_PARTIAL_RIGHT;

        return count;
    case RE_OP_ANY_ALL:
        count = min_size_t((size_t)(state->slice_end - text_pos), max_count);

        *is_partial = count == (size_t)(state->text_length - text_pos) && count
          < max_count && state->partial_side == RE_PARTIAL_RIGHT;

        return count;
    case RE_OP_ANY_ALL_REV:
        count = min_size_t((size_t)(text_pos - state->slice_start), max_count);

        *is_partial = count == (size_t)(text_pos) && count < max_count &&
          state->partial_side == RE_PARTIAL_LEFT;

        return count;
    case RE_OP_ANY_REV:
        count = min_size_t((size_t)(text_pos - state->slice_start), max_count);

        count = (size_t)(text_pos - match_many_ANY_REV(state, node, text_pos,
          text_pos - (Py_ssize_t)count, TRUE));

        *is_partial = count == (size_t)(text_pos) && count < max_count &&
          state->partial_side == RE_PARTIAL_LEFT;

        return count;
    case RE_OP_ANY_U:
        count = min_size_t((size_t)(state->slice_end - text_pos), max_count);

        count = (size_t)(match_many_ANY_U(state, node, text_pos, text_pos +
          (Py_ssize_t)count, TRUE) - text_pos);

        *is_partial = count == (size_t)(state->text_length - text_pos) && count
          < max_count && state->partial_side == RE_PARTIAL_RIGHT;

        return count;
    case RE_OP_ANY_U_REV:
        count = min_size_t((size_t)(text_pos - state->slice_start), max_count);

        count = (size_t)(text_pos - match_many_ANY_U_REV(state, node, text_pos,
          text_pos - (Py_ssize_t)count, TRUE));

        *is_partial = count == (size_t)(text_pos) && count < max_count &&
          state->partial_side == RE_PARTIAL_LEFT;

        return count;
    case RE_OP_CHARACTER:
        count = min_size_t((size_t)(state->slice_end - text_pos), max_count);

        count = (size_t)(match_many_CHARACTER(state, node, text_pos, text_pos +
          (Py_ssize_t)count, TRUE) - text_pos);

        *is_partial = count == (size_t)(state->text_length - text_pos) && count
          < max_count && state->partial_side == RE_PARTIAL_RIGHT;

        return count;
    case RE_OP_CHARACTER_IGN:
        count = min_size_t((size_t)(state->slice_end - text_pos), max_count);

        count = (size_t)(match_many_CHARACTER_IGN(state, node, text_pos,
          text_pos + (Py_ssize_t)count, TRUE) - text_pos);

        *is_partial = count == (size_t)(state->text_length - text_pos) && count
          < max_count && state->partial_side == RE_PARTIAL_RIGHT;

        return count;
    case RE_OP_CHARACTER_IGN_REV:
        count = min_size_t((size_t)(text_pos - state->slice_start), max_count);

        count = (size_t)(text_pos - match_many_CHARACTER_IGN_REV(state, node,
          text_pos, text_pos - (Py_ssize_t)count, TRUE));

        *is_partial = count == (size_t)(text_pos) && count < max_count &&
          state->partial_side == RE_PARTIAL_LEFT;

        return count;
    case RE_OP_CHARACTER_REV:
        count = min_size_t((size_t)(text_pos - state->slice_start), max_count);

        count = (size_t)(text_pos - match_many_CHARACTER_REV(state, node,
          text_pos, text_pos - (Py_ssize_t)count, TRUE));

        *is_partial = count == (size_t)(text_pos) && count < max_count &&
          state->partial_side == RE_PARTIAL_LEFT;

        return count;
    case RE_OP_PROPERTY:
        count = min_size_t((size_t)(state->slice_end - text_pos), max_count);

        count = (size_t)(match_many_PROPERTY(state, node, text_pos, text_pos +
          (Py_ssize_t)count, TRUE) - text_pos);

        *is_partial = count == (size_t)(state->text_length - text_pos) && count
          < max_count && state->partial_side == RE_PARTIAL_RIGHT;

        return count;
    case RE_OP_PROPERTY_IGN:
        count = min_size_t((size_t)(state->slice_end - text_pos), max_count);

        count = (size_t)(match_many_PROPERTY_IGN(state, node, text_pos,
          text_pos + (Py_ssize_t)count, TRUE) - text_pos);

        *is_partial = count == (size_t)(state->text_length - text_pos) && count
          < max_count && state->partial_side == RE_PARTIAL_RIGHT;

        return count;
    case RE_OP_PROPERTY_IGN_REV:
        count = min_size_t((size_t)(text_pos - state->slice_start), max_count);

        count = (size_t)(text_pos - match_many_PROPERTY_IGN_REV(state, node,
          text_pos, text_pos - (Py_ssize_t)count, TRUE));

        *is_partial = count == (size_t)(text_pos) && count < max_count &&
          state->partial_side == RE_PARTIAL_LEFT;

        return count;
    case RE_OP_PROPERTY_REV:
        count = min_size_t((size_t)(text_pos - state->slice_start), max_count);

        count = (size_t)(text_pos - match_many_PROPERTY_REV(state, node,
          text_pos, text_pos - (Py_ssize_t)count, TRUE));

        *is_partial = count == (size_t)(text_pos) && count < max_count &&
          state->partial_side == RE_PARTIAL_LEFT;

        return count;
    case RE_OP_RANGE:
        count = min_size_t((size_t)(state->slice_end - text_pos), max_count);

        count = (size_t)(match_many_RANGE(state, node, text_pos, text_pos +
          (Py_ssize_t)count, TRUE) - text_pos);

        *is_partial = count == (size_t)(state->text_length - text_pos) && count
          < max_count && state->partial_side == RE_PARTIAL_RIGHT;

        return count;
    case RE_OP_RANGE_IGN:
        count = min_size_t((size_t)(state->slice_end - text_pos), max_count);

        count = (size_t)(match_many_RANGE_IGN(state, node, text_pos, text_pos +
          (Py_ssize_t)count, TRUE) - text_pos);

        *is_partial = count == (size_t)(state->text_length - text_pos) && count
          < max_count && state->partial_side == RE_PARTIAL_RIGHT;

        return count;
    case RE_OP_RANGE_IGN_REV:
        count = min_size_t((size_t)(text_pos - state->slice_start), max_count);

        count = (size_t)(text_pos - match_many_RANGE_IGN_REV(state, node,
          text_pos, text_pos - (Py_ssize_t)count, TRUE));

        *is_partial = count == (size_t)(text_pos) && count < max_count &&
          state->partial_side == RE_PARTIAL_LEFT;

        return count;
    case RE_OP_RANGE_REV:
        count = min_size_t((size_t)(text_pos - state->slice_start), max_count);

        count = (size_t)(text_pos - match_many_RANGE_REV(state, node, text_pos,
          text_pos - (Py_ssize_t)count, TRUE));

        *is_partial = count == (size_t)(text_pos) && count < max_count &&
          state->partial_side == RE_PARTIAL_LEFT;

        return count;
    case RE_OP_SET_DIFF:
    case RE_OP_SET_INTER:
    case RE_OP_SET_SYM_DIFF:
    case RE_OP_SET_UNION:
        count = min_size_t((size_t)(state->slice_end - text_pos), max_count);

        count = (size_t)(match_many_SET(state, node, text_pos, text_pos +
          (Py_ssize_t)count, TRUE) - text_pos);

        *is_partial = count == (size_t)(state->text_length - text_pos) && count
          < max_count && state->partial_side == RE_PARTIAL_RIGHT;

        return count;
    case RE_OP_SET_DIFF_IGN:
    case RE_OP_SET_INTER_IGN:
    case RE_OP_SET_SYM_DIFF_IGN:
    case RE_OP_SET_UNION_IGN:
        count = min_size_t((size_t)(state->slice_end - text_pos), max_count);

        count = (size_t)(match_many_SET_IGN(state, node, text_pos, text_pos +
          (Py_ssize_t)count, TRUE) - text_pos);

        *is_partial = count == (size_t)(state->text_length - text_pos) && count
          < max_count && state->partial_side == RE_PARTIAL_RIGHT;

        return count;
    case RE_OP_SET_DIFF_IGN_REV:
    case RE_OP_SET_INTER_IGN_REV:
    case RE_OP_SET_SYM_DIFF_IGN_REV:
    case RE_OP_SET_UNION_IGN_REV:
        count = min_size_t((size_t)(text_pos - state->slice_start), max_count);

        count = (size_t)(text_pos - match_many_SET_IGN_REV(state, node,
          text_pos, text_pos - (Py_ssize_t)count, TRUE));

        *is_partial = count == (size_t)(text_pos) && count < max_count &&
          state->partial_side == RE_PARTIAL_LEFT;

        return count;
    case RE_OP_SET_DIFF_REV:
    case RE_OP_SET_INTER_REV:
    case RE_OP_SET_SYM_DIFF_REV:
    case RE_OP_SET_UNION_REV:
        count = min_size_t((size_t)(text_pos - state->slice_start), max_count);

        count = (size_t)(text_pos - match_many_SET_REV(state, node, text_pos,
          text_pos - (Py_ssize_t)count, TRUE));

        *is_partial = count == (size_t)(text_pos) && count < max_count &&
          state->partial_side == RE_PARTIAL_LEFT;

        return count;
    }

    return 0;
}

/* Performs a simple string search. */
Py_LOCAL_INLINE(Py_ssize_t) simple_string_search(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, Py_ssize_t limit, BOOL* is_partial) {
    Py_ssize_t length;
    RE_CODE* values;
    Py_UCS4 check_char;

    length = (Py_ssize_t)node->value_count;
    values = node->values;
    check_char = values[0];

    *is_partial = FALSE;

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text = (Py_UCS1*)state->text;
        Py_UCS1* text_ptr = text + text_pos;
        Py_UCS1* limit_ptr = text + limit;

        while (text_ptr < limit_ptr) {
            if (text_ptr[0] == check_char) {
                Py_ssize_t s_pos;

                s_pos = 1;

                for (;;) {
                    if (s_pos >= length)
                        /* End of search string. */
                        return text_ptr - text;

                    if (text_ptr + s_pos >= limit_ptr) {
                        /* Off the end of the text. */
                        if (state->partial_side == RE_PARTIAL_RIGHT) {
                            /* Partial match. */
                            *is_partial = TRUE;
                            return text_ptr - text;
                        }

                        return -1;

                    }

                    if (!same_char(text_ptr[s_pos], values[s_pos]))
                        break;

                    ++s_pos;
                }
            }

            ++text_ptr;
        }
        text_pos = text_ptr - text;
        break;
    }
    case 2:
    {
        Py_UCS2* text = (Py_UCS2*)state->text;
        Py_UCS2* text_ptr = text + text_pos;
        Py_UCS2* limit_ptr = text + limit;

        while (text_ptr < limit_ptr) {
            if (text_ptr[0] == check_char) {
                Py_ssize_t s_pos;

                s_pos = 1;

                for (;;) {
                    if (s_pos >= length)
                        /* End of search string. */
                        return text_ptr - text;

                    if (text_ptr + s_pos >= limit_ptr) {
                        /* Off the end of the text. */
                        if (state->partial_side == RE_PARTIAL_RIGHT) {
                            /* Partial match. */
                            *is_partial = TRUE;
                            return text_ptr - text;
                        }

                        return -1;

                    }

                    if (!same_char(text_ptr[s_pos], values[s_pos]))
                        break;

                    ++s_pos;
                }
            }

            ++text_ptr;
        }
        text_pos = text_ptr - text;
        break;
    }
    case 4:
    {
        Py_UCS4* text = (Py_UCS4*)state->text;
        Py_UCS4* text_ptr = text + text_pos;
        Py_UCS4* limit_ptr = text + limit;

        while (text_ptr < limit_ptr) {
            if (text_ptr[0] == check_char) {
                Py_ssize_t s_pos;

                s_pos = 1;

                for (;;) {
                    if (s_pos >= length)
                        /* End of search string. */
                        return text_ptr - text;

                    if (text_ptr + s_pos >= limit_ptr) {
                        /* Off the end of the text. */
                        if (state->partial_side == RE_PARTIAL_RIGHT) {
                            /* Partial match. */
                            *is_partial = TRUE;
                            return text_ptr - text;
                        }

                        return -1;

                    }

                    if (!same_char(text_ptr[s_pos], values[s_pos]))
                        break;

                    ++s_pos;
                }
            }

            ++text_ptr;
        }
        text_pos = text_ptr - text;
        break;
    }
    }

    /* Off the end of the text. */
    if (state->partial_side == RE_PARTIAL_RIGHT) {
        /* Partial match. */
        *is_partial = TRUE;
        return text_pos;
    }

    return -1;
}

/* Performs a simple string search, ignoring case. */
Py_LOCAL_INLINE(Py_ssize_t) simple_string_search_ign(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, Py_ssize_t limit, BOOL* is_partial) {
    Py_ssize_t length;
    RE_CODE* values;
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;
    Py_UCS4 cases[RE_MAX_CASES];
    int case_count;

    length = (Py_ssize_t)node->value_count;
    values = node->values;
    encoding = state->encoding;
    locale_info = state->locale_info;
    case_count = encoding->all_cases(locale_info, values[0], cases);

    *is_partial = FALSE;

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text = (Py_UCS1*)state->text;
        Py_UCS1* text_ptr = text + text_pos;
        Py_UCS1* limit_ptr = text + limit;

        while (text_ptr < limit_ptr) {
            if (any_case(text_ptr[0], case_count, cases)) {
                Py_ssize_t s_pos;

                s_pos = 1;

                for (;;) {
                    if (s_pos >= length)
                        /* End of search string. */
                        return text_ptr - text;

                    if (text_ptr + s_pos >= limit_ptr) {
                        /* Off the end of the text. */
                        if (state->partial_side == RE_PARTIAL_RIGHT) {
                            /* Partial match. */
                            *is_partial = TRUE;
                            return text_ptr - text;
                        }

                        return -1;

                    }

                    if (!same_char_ign(encoding, locale_info, text_ptr[s_pos],
                      values[s_pos]))
                        break;

                    ++s_pos;
                }
            }

            ++text_ptr;
        }
        text_pos = text_ptr - text;
        break;
    }
    case 2:
    {
        Py_UCS2* text = (Py_UCS2*)state->text;
        Py_UCS2* text_ptr = text + text_pos;
        Py_UCS2* limit_ptr = text + limit;

        while (text_ptr < limit_ptr) {
            if (any_case(text_ptr[0], case_count, cases)) {
                Py_ssize_t s_pos;

                s_pos = 1;

                for (;;) {
                    if (s_pos >= length)
                        /* End of search string. */
                        return text_ptr - text;

                    if (text_ptr + s_pos >= limit_ptr) {
                        /* Off the end of the text. */
                        if (state->partial_side == RE_PARTIAL_RIGHT) {
                            /* Partial match. */
                            *is_partial = TRUE;
                            return text_ptr - text;
                        }

                        return -1;

                    }

                    if (!same_char_ign(encoding, locale_info, text_ptr[s_pos],
                      values[s_pos]))
                        break;

                    ++s_pos;
                }
            }

            ++text_ptr;
        }
        text_pos = text_ptr - text;
        break;
    }
    case 4:
    {
        Py_UCS4* text = (Py_UCS4*)state->text;
        Py_UCS4* text_ptr = text + text_pos;
        Py_UCS4* limit_ptr = text + limit;

        while (text_ptr < limit_ptr) {
            if (any_case(text_ptr[0], case_count, cases)) {
                Py_ssize_t s_pos;

                s_pos = 1;

                for (;;) {
                    if (s_pos >= length)
                        /* End of search string. */
                        return text_ptr - text;

                    if (text_ptr + s_pos >= limit_ptr) {
                        /* Off the end of the text. */
                        if (state->partial_side == RE_PARTIAL_RIGHT) {
                            /* Partial match. */
                            *is_partial = TRUE;
                            return text_ptr - text;
                        }

                        return -1;

                    }

                    if (!same_char_ign(encoding, locale_info, text_ptr[s_pos],
                      values[s_pos]))
                        break;

                    ++s_pos;
                }
            }

            ++text_ptr;
        }
        text_pos = text_ptr - text;
        break;
    }
    }

    /* Off the end of the text. */
    if (state->partial_side == RE_PARTIAL_RIGHT) {
        /* Partial match. */
        *is_partial = TRUE;
        return text_pos;
    }

    return -1;
}

/* Performs a simple string search, backwards, ignoring case. */
Py_LOCAL_INLINE(Py_ssize_t) simple_string_search_ign_rev(RE_State* state,
  RE_Node* node, Py_ssize_t text_pos, Py_ssize_t limit, BOOL* is_partial) {
    Py_ssize_t length;
    RE_CODE* values;
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;
    Py_UCS4 cases[RE_MAX_CASES];
    int case_count;

    length = (Py_ssize_t)node->value_count;
    values = node->values;
    encoding = state->encoding;
    locale_info = state->locale_info;
    case_count = encoding->all_cases(locale_info, values[length - 1], cases);

    *is_partial = FALSE;

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text = (Py_UCS1*)state->text;
        Py_UCS1* text_ptr = text + text_pos;
        Py_UCS1* limit_ptr = text + limit;

        while (text_ptr > limit_ptr) {
            if (any_case(text_ptr[-1], case_count, cases)) {
                Py_ssize_t s_pos;

                s_pos = 1;

                for (;;) {
                    if (s_pos >= length)
                        /* End of search string. */
                        return text_ptr - text;

                    if (text_ptr - s_pos <= limit_ptr) {
                        /* Off the end of the text. */
                        if (state->partial_side == RE_PARTIAL_LEFT) {
                            /* Partial match. */
                            *is_partial = TRUE;
                            return text_ptr - text;
                        }

                        return -1;

                    }

                    if (!same_char_ign(encoding, locale_info, text_ptr[- s_pos
                      - 1], values[length - s_pos - 1]))
                        break;

                    ++s_pos;
                }
            }

            --text_ptr;
        }
        text_pos = text_ptr - text;
        break;
    }
    case 2:
    {
        Py_UCS2* text = (Py_UCS2*)state->text;
        Py_UCS2* text_ptr = text + text_pos;
        Py_UCS2* limit_ptr = text + limit;

        while (text_ptr > limit_ptr) {
            if (any_case(text_ptr[-1], case_count, cases)) {
                Py_ssize_t s_pos;

                s_pos = 1;

                for (;;) {
                    if (s_pos >= length)
                        /* End of search string. */
                        return text_ptr - text;

                    if (text_ptr - s_pos <= limit_ptr) {
                        /* Off the end of the text. */
                        if (state->partial_side == RE_PARTIAL_LEFT) {
                            /* Partial match. */
                            *is_partial = TRUE;
                            return text_ptr - text;
                        }

                        return -1;

                    }

                    if (!same_char_ign(encoding, locale_info, text_ptr[- s_pos
                      - 1], values[length - s_pos - 1]))
                        break;

                    ++s_pos;
                }
            }

            --text_ptr;
        }
        text_pos = text_ptr - text;
        break;
    }
    case 4:
    {
        Py_UCS4* text = (Py_UCS4*)state->text;
        Py_UCS4* text_ptr = text + text_pos;
        Py_UCS4* limit_ptr = text + limit;

        while (text_ptr > limit_ptr) {
            if (any_case(text_ptr[-1], case_count, cases)) {
                Py_ssize_t s_pos;

                s_pos = 1;

                for (;;) {
                    if (s_pos >= length)
                        /* End of search string. */
                        return text_ptr - text;

                    if (text_ptr - s_pos <= limit_ptr) {
                        /* Off the end of the text. */
                        if (state->partial_side == RE_PARTIAL_LEFT) {
                            /* Partial match. */
                            *is_partial = TRUE;
                            return text_ptr - text;
                        }

                        return -1;

                    }

                    if (!same_char_ign(encoding, locale_info, text_ptr[- s_pos
                      - 1], values[length - s_pos - 1]))
                        break;

                    ++s_pos;
                }
            }

            --text_ptr;
        }
        text_pos = text_ptr - text;
        break;
    }
    }

    /* Off the end of the text. */
    if (state->partial_side == RE_PARTIAL_LEFT) {
        /* Partial match. */
        *is_partial = TRUE;
        return text_pos;
    }

    return -1;
}

/* Performs a simple string search, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) simple_string_search_rev(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, Py_ssize_t limit, BOOL* is_partial) {
    Py_ssize_t length;
    RE_CODE* values;
    Py_UCS4 check_char;

    length = (Py_ssize_t)node->value_count;
    values = node->values;
    check_char = values[length - 1];

    *is_partial = FALSE;

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text = (Py_UCS1*)state->text;
        Py_UCS1* text_ptr = text + text_pos;
        Py_UCS1* limit_ptr = text + limit;

        while (text_ptr > limit_ptr) {
            if (text_ptr[-1] == check_char) {
                Py_ssize_t s_pos;

                s_pos = 1;

                for (;;) {
                    if (s_pos >= length)
                        /* End of search string. */
                        return text_ptr - text;

                    if (text_ptr - s_pos <= limit_ptr) {
                        /* Off the end of the text. */
                        if (state->partial_side == RE_PARTIAL_LEFT) {
                            /* Partial match. */
                            *is_partial = TRUE;
                            return text_ptr - text;
                        }

                        return -1;

                    }

                    if (!same_char(text_ptr[- s_pos - 1], values[length - s_pos
                      - 1]))
                        break;

                    ++s_pos;
                }
            }

            --text_ptr;
        }
        text_pos = text_ptr - text;
        break;
    }
    case 2:
    {
        Py_UCS2* text = (Py_UCS2*)state->text;
        Py_UCS2* text_ptr = text + text_pos;
        Py_UCS2* limit_ptr = text + limit;

        while (text_ptr > limit_ptr) {
            if (text_ptr[-1] == check_char) {
                Py_ssize_t s_pos;

                s_pos = 1;

                for (;;) {
                    if (s_pos >= length)
                        /* End of search string. */
                        return text_ptr - text;

                    if (text_ptr - s_pos <= limit_ptr) {
                        /* Off the end of the text. */
                        if (state->partial_side == RE_PARTIAL_LEFT) {
                            /* Partial match. */
                            *is_partial = TRUE;
                            return text_ptr - text;
                        }

                        return -1;

                    }

                    if (!same_char(text_ptr[- s_pos - 1], values[length - s_pos
                      - 1]))
                        break;

                    ++s_pos;
                }
            }

            --text_ptr;
        }
        text_pos = text_ptr - text;
        break;
    }
    case 4:
    {
        Py_UCS4* text = (Py_UCS4*)state->text;
        Py_UCS4* text_ptr = text + text_pos;
        Py_UCS4* limit_ptr = text + limit;

        while (text_ptr > limit_ptr) {
            if (text_ptr[-1] == check_char) {
                Py_ssize_t s_pos;

                s_pos = 1;

                for (;;) {
                    if (s_pos >= length)
                        /* End of search string. */
                        return text_ptr - text;

                    if (text_ptr - s_pos <= limit_ptr) {
                        /* Off the end of the text. */
                        if (state->partial_side == RE_PARTIAL_LEFT) {
                            /* Partial match. */
                            *is_partial = TRUE;
                            return text_ptr - text;
                        }

                        return -1;

                    }

                    if (!same_char(text_ptr[- s_pos - 1], values[length - s_pos
                      - 1]))
                        break;

                    ++s_pos;
                }
            }

            --text_ptr;
        }
        text_pos = text_ptr - text;
        break;
    }
    }

    /* Off the end of the text. */
    if (state->partial_side == RE_PARTIAL_LEFT) {
        /* Partial match. */
        *is_partial = TRUE;
        return text_pos;
    }

    return -1;
}

/* Performs a Boyer-Moore fast string search. */
Py_LOCAL_INLINE(Py_ssize_t) fast_string_search(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos, Py_ssize_t limit) {
    void* text;
    Py_ssize_t length;
    RE_CODE* values;
    Py_ssize_t* bad_character_offset;
    Py_ssize_t* good_suffix_offset;
    Py_ssize_t last_pos;
    Py_UCS4 check_char;

    text = state->text;
    length = (Py_ssize_t)node->value_count;
    values = node->values;
    good_suffix_offset = node->string.good_suffix_offset;
    bad_character_offset = node->string.bad_character_offset;
    last_pos = length - 1;
    check_char = values[last_pos];
    limit -= length;

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        while (text_ptr <= limit_ptr) {
            Py_UCS4 ch;

            ch = text_ptr[last_pos];
            if (ch == check_char) {
                Py_ssize_t pos;

                pos = last_pos - 1;
                while (pos >= 0 && same_char(text_ptr[pos], values[pos]))
                    --pos;

                if (pos < 0)
                    return text_ptr - (Py_UCS1*)text;

                text_ptr += good_suffix_offset[pos];
            } else
                text_ptr += bad_character_offset[ch & 0xFF];
        }
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        while (text_ptr <= limit_ptr) {
            Py_UCS4 ch;

            ch = text_ptr[last_pos];
            if (ch == check_char) {
                Py_ssize_t pos;

                pos = last_pos - 1;
                while (pos >= 0 && same_char(text_ptr[pos], values[pos]))
                    --pos;

                if (pos < 0)
                    return text_ptr - (Py_UCS2*)text;

                text_ptr += good_suffix_offset[pos];
            } else
                text_ptr += bad_character_offset[ch & 0xFF];
        }
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        while (text_ptr <= limit_ptr) {
            Py_UCS4 ch;

            ch = text_ptr[last_pos];
            if (ch == check_char) {
                Py_ssize_t pos;

                pos = last_pos - 1;
                while (pos >= 0 && same_char(text_ptr[pos], values[pos]))
                    --pos;

                if (pos < 0)
                    return text_ptr - (Py_UCS4*)text;

                text_ptr += good_suffix_offset[pos];
            } else
                text_ptr += bad_character_offset[ch & 0xFF];
        }
        break;
    }
    }

    return -1;
}

/* Performs a Boyer-Moore fast string search, ignoring case. */
Py_LOCAL_INLINE(Py_ssize_t) fast_string_search_ign(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, Py_ssize_t limit) {
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;
    void* text;
    Py_ssize_t length;
    RE_CODE* values;
    Py_ssize_t* bad_character_offset;
    Py_ssize_t* good_suffix_offset;
    Py_ssize_t last_pos;
    Py_UCS4 cases[RE_MAX_CASES];
    int case_count;

    encoding = state->encoding;
    locale_info = state->locale_info;
    text = state->text;
    length = (Py_ssize_t)node->value_count;
    values = node->values;
    good_suffix_offset = node->string.good_suffix_offset;
    bad_character_offset = node->string.bad_character_offset;
    last_pos = length - 1;
    case_count = encoding->all_cases(locale_info, values[last_pos], cases);
    limit -= length;

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        while (text_ptr <= limit_ptr) {
            Py_UCS4 ch;

            ch = text_ptr[last_pos];
            if (any_case(ch, case_count, cases)) {
                Py_ssize_t pos;

                pos = last_pos - 1;
                while (pos >= 0 && same_char_ign(encoding, locale_info,
                  text_ptr[pos], values[pos]))
                    --pos;

                if (pos < 0)
                    return text_ptr - (Py_UCS1*)text;

                text_ptr += good_suffix_offset[pos];
            } else
                text_ptr += bad_character_offset[ch & 0xFF];
        }
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        while (text_ptr <= limit_ptr) {
            Py_UCS4 ch;

            ch = text_ptr[last_pos];
            if (any_case(ch, case_count, cases)) {
                Py_ssize_t pos;

                pos = last_pos - 1;
                while (pos >= 0 && same_char_ign(encoding, locale_info,
                  text_ptr[pos], values[pos]))
                    --pos;

                if (pos < 0)
                    return text_ptr - (Py_UCS2*)text;

                text_ptr += good_suffix_offset[pos];
            } else
                text_ptr += bad_character_offset[ch & 0xFF];
        }
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        while (text_ptr <= limit_ptr) {
            Py_UCS4 ch;

            ch = text_ptr[last_pos];
            if (any_case(ch, case_count, cases)) {
                Py_ssize_t pos;

                pos = last_pos - 1;
                while (pos >= 0 && same_char_ign(encoding, locale_info,
                  text_ptr[pos], values[pos]))
                    --pos;

                if (pos < 0)
                    return text_ptr - (Py_UCS4*)text;

                text_ptr += good_suffix_offset[pos];
            } else
                text_ptr += bad_character_offset[ch & 0xFF];
        }
        break;
    }
    }

    return -1;
}

/* Performs a Boyer-Moore fast string search, backwards, ignoring case. */
Py_LOCAL_INLINE(Py_ssize_t) fast_string_search_ign_rev(RE_State* state,
  RE_Node* node, Py_ssize_t text_pos, Py_ssize_t limit) {
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;
    void* text;
    Py_ssize_t length;
    RE_CODE* values;
    Py_ssize_t* bad_character_offset;
    Py_ssize_t* good_suffix_offset;
    Py_UCS4 cases[RE_MAX_CASES];
    int case_count;

    encoding = state->encoding;
    locale_info = state->locale_info;
    text = state->text;
    length = (Py_ssize_t)node->value_count;
    values = node->values;
    good_suffix_offset = node->string.good_suffix_offset;
    bad_character_offset = node->string.bad_character_offset;
    case_count = encoding->all_cases(locale_info, values[0], cases);
    text_pos -= length;

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        while (text_ptr >= limit_ptr) {
            Py_UCS4 ch;

            ch = text_ptr[0];
            if (any_case(ch, case_count, cases)) {
                Py_ssize_t pos;

                pos = 1;
                while (pos < length && same_char_ign(encoding, locale_info,
                  text_ptr[pos], values[pos]))
                    ++pos;

                if (pos >= length)
                    return text_ptr - (Py_UCS1*)text + length;

                text_ptr += good_suffix_offset[pos];
            } else
                text_ptr += bad_character_offset[ch & 0xFF];
        }
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        while (text_ptr >= limit_ptr) {
            Py_UCS4 ch;

            ch = text_ptr[0];
            if (any_case(ch, case_count, cases)) {
                Py_ssize_t pos;

                pos = 1;
                while (pos < length && same_char_ign(encoding, locale_info,
                  text_ptr[pos], values[pos]))
                    ++pos;

                if (pos >= length)
                    return text_ptr - (Py_UCS2*)text + length;

                text_ptr += good_suffix_offset[pos];
            } else
                text_ptr += bad_character_offset[ch & 0xFF];
        }
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        while (text_ptr >= limit_ptr) {
            Py_UCS4 ch;

            ch = text_ptr[0];
            if (any_case(ch, case_count, cases)) {
                Py_ssize_t pos;

                pos = 1;
                while (pos < length && same_char_ign(encoding, locale_info,
                  text_ptr[pos], values[pos]))
                    ++pos;

                if (pos >= length)
                    return text_ptr - (Py_UCS4*)text + length;

                text_ptr += good_suffix_offset[pos];
            } else
                text_ptr += bad_character_offset[ch & 0xFF];
        }
        break;
    }
    }

    return -1;
}

/* Performs a Boyer-Moore fast string search, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) fast_string_search_rev(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, Py_ssize_t limit) {
    void* text;
    Py_ssize_t length;
    RE_CODE* values;
    Py_ssize_t* bad_character_offset;
    Py_ssize_t* good_suffix_offset;
    Py_UCS4 check_char;

    text = state->text;
    length = (Py_ssize_t)node->value_count;
    values = node->values;
    good_suffix_offset = node->string.good_suffix_offset;
    bad_character_offset = node->string.bad_character_offset;
    check_char = values[0];
    text_pos -= length;

    switch (state->charsize) {
    case 1:
    {
        Py_UCS1* text_ptr;
        Py_UCS1* limit_ptr;

        text_ptr = (Py_UCS1*)text + text_pos;
        limit_ptr = (Py_UCS1*)text + limit;

        while (text_ptr >= limit_ptr) {
            Py_UCS4 ch;

            ch = text_ptr[0];
            if (ch == check_char) {
                Py_ssize_t pos;

                pos = 1;
                while (pos < length && same_char(text_ptr[pos], values[pos]))
                    ++pos;

                if (pos >= length)
                    return text_ptr - (Py_UCS1*)text + length;

                text_ptr += good_suffix_offset[pos];
            } else
                text_ptr += bad_character_offset[ch & 0xFF];
        }
        break;
    }
    case 2:
    {
        Py_UCS2* text_ptr;
        Py_UCS2* limit_ptr;

        text_ptr = (Py_UCS2*)text + text_pos;
        limit_ptr = (Py_UCS2*)text + limit;

        while (text_ptr >= limit_ptr) {
            Py_UCS4 ch;

            ch = text_ptr[0];
            if (ch == check_char) {
                Py_ssize_t pos;

                pos = 1;
                while (pos < length && same_char(text_ptr[pos], values[pos]))
                    ++pos;

                if (pos >= length)
                    return text_ptr - (Py_UCS2*)text + length;

                text_ptr += good_suffix_offset[pos];
            } else
                text_ptr += bad_character_offset[ch & 0xFF];
        }
        break;
    }
    case 4:
    {
        Py_UCS4* text_ptr;
        Py_UCS4* limit_ptr;

        text_ptr = (Py_UCS4*)text + text_pos;
        limit_ptr = (Py_UCS4*)text + limit;

        while (text_ptr >= limit_ptr) {
            Py_UCS4 ch;

            ch = text_ptr[0];
            if (ch == check_char) {
                Py_ssize_t pos;

                pos = 1;
                while (pos < length && same_char(text_ptr[pos], values[pos]))
                    ++pos;

                if (pos >= length)
                    return text_ptr - (Py_UCS4*)text + length;

                text_ptr += good_suffix_offset[pos];
            } else
                text_ptr += bad_character_offset[ch & 0xFF];
        }
        break;
    }
    }

    return -1;
}

/* Builds the tables for a Boyer-Moore fast string search. */
Py_LOCAL_INLINE(BOOL) build_fast_tables(RE_State* state, RE_Node* node, BOOL
  ignore) {
    Py_ssize_t length;
    RE_CODE* values;
    Py_ssize_t* bad;
    Py_ssize_t* good;
    Py_UCS4 ch;
    Py_ssize_t last_pos;
    Py_ssize_t pos;
    BOOL (*is_same_char)(RE_EncodingTable* encoding, RE_LocaleInfo*
      locale_info, Py_UCS4 ch1, Py_UCS4 ch2);
    Py_ssize_t suffix_len;
    BOOL saved_start;
    Py_ssize_t s;
    Py_ssize_t i;
    Py_ssize_t s_start;
    Py_UCS4 codepoints[RE_MAX_CASES];

    length = (Py_ssize_t)node->value_count;

    if (length < RE_MIN_FAST_LENGTH)
        return TRUE;

    values = node->values;
    bad = (Py_ssize_t*)re_alloc(256 * sizeof(bad[0]));
    good = (Py_ssize_t*)re_alloc((size_t)length * sizeof(good[0]));

    if (!bad || !good) {
        re_dealloc(bad);
        re_dealloc(good);

        return FALSE;
    }

    for (ch = 0; ch < 0x100; ch++)
        bad[ch] = length;

    last_pos = length - 1;

    for (pos = 0; pos < last_pos; pos++) {
        Py_ssize_t offset;

        offset = last_pos - pos;
        ch = values[pos];
        if (ignore) {
            int count;
            int c;

            count = state->encoding->all_cases(state->locale_info, ch,
              codepoints);

            for (c = 0; c < count; c++)
                bad[codepoints[c] & 0xFF] = offset;
        } else
            bad[ch & 0xFF] = offset;
    }

    is_same_char = ignore ? same_char_ign_wrapper : same_char_wrapper;

    suffix_len = 2;
    pos = length - suffix_len;
    saved_start = FALSE;
    s = pos - 1;
    i = suffix_len - 1;
    s_start = s;

    while (pos >= 0) {
        /* Look for another occurrence of the suffix. */
        while (i > 0) {
            /* Have we dropped off the end of the string? */
            if (s + i < 0)
                break;

            if (is_same_char(state->encoding, state->locale_info, values[s +
              i], values[pos + i]))
                /* It still matches. */
                --i;
            else {
                /* Start again further along. */
                --s;
                i = suffix_len - 1;
            }
        }

        if (s >= 0 && is_same_char(state->encoding, state->locale_info,
          values[s], values[pos])) {
            /* We haven't dropped off the end of the string, and the suffix has
             * matched this far, so this is a good starting point for the next
             * iteration.
             */
            --s;
            if (!saved_start) {
                s_start = s;
                saved_start = TRUE;
            }
        } else {
            /* Calculate the suffix offset. */
            good[pos] = pos - s;

            /* Extend the suffix and start searching for _this_ one. */
            --pos;
            ++suffix_len;

            /* Where's a good place to start searching? */
            if (saved_start) {
                s = s_start;
                saved_start = FALSE;
            } else
                --s;

            /* Can we short-circuit the searching? */
            if (s < 0)
                break;
        }

        i = suffix_len - 1;
    }

    /* Fill-in any remaining entries. */
    while (pos >= 0) {
        good[pos] = pos - s;
        --pos;
        --s;
    }

    node->string.bad_character_offset = bad;
    node->string.good_suffix_offset = good;

    return TRUE;
}

/* Builds the tables for a Boyer-Moore fast string search, backwards. */
Py_LOCAL_INLINE(BOOL) build_fast_tables_rev(RE_State* state, RE_Node* node,
  BOOL ignore) {
    Py_ssize_t length;
    RE_CODE* values;
    Py_ssize_t* bad;
    Py_ssize_t* good;
    Py_UCS4 ch;
    Py_ssize_t last_pos;
    Py_ssize_t pos;
    BOOL (*is_same_char)(RE_EncodingTable* encoding, RE_LocaleInfo*
      locale_info, Py_UCS4 ch1, Py_UCS4 ch2);
    Py_ssize_t suffix_len;
    BOOL saved_start;
    Py_ssize_t s;
    Py_ssize_t i;
    Py_ssize_t s_start;
    Py_UCS4 codepoints[RE_MAX_CASES];

    length = (Py_ssize_t)node->value_count;

    if (length < RE_MIN_FAST_LENGTH)
        return TRUE;

    values = node->values;
    bad = (Py_ssize_t*)re_alloc(256 * sizeof(bad[0]));
    good = (Py_ssize_t*)re_alloc((size_t)length * sizeof(good[0]));

    if (!bad || !good) {
        re_dealloc(bad);
        re_dealloc(good);

        return FALSE;
    }

    for (ch = 0; ch < 0x100; ch++)
        bad[ch] = -length;

    last_pos = length - 1;

    for (pos = last_pos; pos > 0; pos--) {
        Py_ssize_t offset;

        offset = -pos;
        ch = values[pos];
        if (ignore) {
            int count;
            int c;

            count = state->encoding->all_cases(state->locale_info, ch,
              codepoints);

            for (c = 0; c < count; c++)
                bad[codepoints[c] & 0xFF] = offset;
        } else
            bad[ch & 0xFF] = offset;
    }

    is_same_char = ignore ? same_char_ign_wrapper : same_char_wrapper;

    suffix_len = 2;
    pos = suffix_len - 1;
    saved_start = FALSE;
    s = pos + 1;
    i = suffix_len - 1;
    s_start = s;

    while (pos < length) {
        /* Look for another occurrence of the suffix. */
        while (i > 0) {
            /* Have we dropped off the end of the string? */
            if (s - i >= length)
                break;

            if (is_same_char(state->encoding, state->locale_info, values[s -
              i], values[pos - i]))
                /* It still matches. */
                --i;
            else {
                /* Start again further along. */
                ++s;
                i = suffix_len - 1;
            }
        }

        if (s < length && is_same_char(state->encoding, state->locale_info,
          values[s], values[pos])) {
            /* We haven't dropped off the end of the string, and the suffix has
             * matched this far, so this is a good starting point for the next
             * iteration.
             */
            ++s;
            if (!saved_start) {
                s_start = s;
                saved_start = TRUE;
            }
        } else {
            /* Calculate the suffix offset. */
            good[pos] = pos - s;

            /* Extend the suffix and start searching for _this_ one. */
            ++pos;
            ++suffix_len;

            /* Where's a good place to start searching? */
            if (saved_start) {
                s = s_start;
                saved_start = FALSE;
            } else
                ++s;

            /* Can we short-circuit the searching? */
            if (s >= length)
                break;
        }

        i = suffix_len - 1;
    }

    /* Fill-in any remaining entries. */
    while (pos < length) {
        good[pos] = pos - s;
        ++pos;
        ++s;
    }

    node->string.bad_character_offset = bad;
    node->string.good_suffix_offset = good;

    return TRUE;
}

/* Performs a string search. */
Py_LOCAL_INLINE(Py_ssize_t) string_search(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos, Py_ssize_t limit, BOOL* is_partial) {
    Py_ssize_t found_pos;

    *is_partial = FALSE;

    /* Has the node been initialised for fast searching, if necessary? */
    if (!(node->status & RE_STATUS_FAST_INIT)) {
        /* Ideally the pattern should immutable and shareable across threads.
         * Internally, however, it isn't. For safety we need to hold the GIL.
         */
        acquire_GIL(state);

        /* Double-check because of multithreading. */
        if (!(node->status & RE_STATUS_FAST_INIT)) {
            build_fast_tables(state, node, FALSE);
            node->status |= RE_STATUS_FAST_INIT;
        }

        release_GIL(state);
    }

    if (node->string.bad_character_offset) {
        /* Start with a fast search. This will find the string if it's complete
         * (i.e. not truncated).
         */
        found_pos = fast_string_search(state, node, text_pos, limit);
        if (found_pos < 0 && state->partial_side == RE_PARTIAL_RIGHT)
            /* We didn't find the string, but it could've been truncated, so
             * try again, starting close to the end.
             */
            found_pos = simple_string_search(state, node, limit -
              (Py_ssize_t)(node->value_count - 1), limit, is_partial);
    } else
        found_pos = simple_string_search(state, node, text_pos, limit,
          is_partial);

    return found_pos;
}

/* Performs a string search, ignoring case. */
Py_LOCAL_INLINE(Py_ssize_t) string_search_fld(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos, Py_ssize_t limit, Py_ssize_t* new_pos, BOOL* is_partial)
  {
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;
    int (*full_case_fold)(RE_LocaleInfo* locale_info, Py_UCS4 ch, Py_UCS4*
      folded);
    Py_UCS4 (*char_at)(void* text, Py_ssize_t pos);
    void* text;
    RE_CODE* values;
    Py_ssize_t start_pos;
    int f_pos;
    int folded_len;
    Py_ssize_t length;
    Py_ssize_t s_pos;
    Py_UCS4 folded[RE_MAX_FOLDED];

    encoding = state->encoding;
    locale_info = state->locale_info;
    full_case_fold = encoding->full_case_fold;
    char_at = state->char_at;
    text = state->text;

    values = node->values;
    start_pos = text_pos;
    f_pos = 0;
    folded_len = 0;
    length = (Py_ssize_t)node->value_count;
    s_pos = 0;

    *is_partial = FALSE;

    while (s_pos < length || f_pos < folded_len) {
        if (f_pos >= folded_len) {
            /* Fetch and casefold another character. */
            if (text_pos >= limit) {
                if (text_pos >= state->text_length && state->partial_side ==
                  RE_PARTIAL_RIGHT) {
                    *is_partial = TRUE;
                    return start_pos;
                }

                return -1;
            }

            folded_len = full_case_fold(locale_info, char_at(text, text_pos),
              folded);
            f_pos = 0;
        }

        if (s_pos < length && same_char_ign_turkic(encoding, locale_info,
          values[s_pos], folded[f_pos])) {
            ++s_pos;
            ++f_pos;

            if (f_pos >= folded_len)
                ++text_pos;
        } else {
            ++start_pos;
            text_pos = start_pos;
            f_pos = 0;
            folded_len = 0;
            s_pos = 0;
        }
    }

    /* We found the string. */
    if (new_pos)
        *new_pos = text_pos;

    return start_pos;
}

/* Performs a string search, backwards, ignoring case. */
Py_LOCAL_INLINE(Py_ssize_t) string_search_fld_rev(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, Py_ssize_t limit, Py_ssize_t* new_pos, BOOL*
  is_partial) {
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;
    int (*full_case_fold)(RE_LocaleInfo* locale_info, Py_UCS4 ch, Py_UCS4*
      folded);
    Py_UCS4 (*char_at)(void* text, Py_ssize_t pos);
    void* text;
    RE_CODE* values;
    Py_ssize_t start_pos;
    int f_pos;
    int folded_len;
    Py_ssize_t length;
    Py_ssize_t s_pos;
    Py_UCS4 folded[RE_MAX_FOLDED];

    encoding = state->encoding;
    locale_info = state->locale_info;
    full_case_fold = encoding->full_case_fold;
    char_at = state->char_at;
    text = state->text;

    values = node->values;
    start_pos = text_pos;
    f_pos = 0;
    folded_len = 0;
    length = (Py_ssize_t)node->value_count;
    s_pos = 0;

    *is_partial = FALSE;

    while (s_pos < length || f_pos < folded_len) {
        if (f_pos >= folded_len) {
            /* Fetch and casefold another character. */
            if (text_pos <= limit) {
                if (text_pos <= 0 && state->partial_side == RE_PARTIAL_LEFT) {
                    *is_partial = TRUE;
                    return start_pos;
                }

                return -1;
            }

            folded_len = full_case_fold(locale_info, char_at(text, text_pos -
              1), folded);
            f_pos = 0;
        }

        if (s_pos < length && same_char_ign_turkic(encoding, locale_info,
          values[length - s_pos - 1], folded[folded_len - f_pos - 1])) {
            ++s_pos;
            ++f_pos;

            if (f_pos >= folded_len)
                --text_pos;
        } else {
            --start_pos;
            text_pos = start_pos;
            f_pos = 0;
            folded_len = 0;
            s_pos = 0;
        }
    }

    /* We found the string. */
    if (new_pos)
        *new_pos = text_pos;

    return start_pos;
}

/* Performs a string search, ignoring case. */
Py_LOCAL_INLINE(Py_ssize_t) string_search_ign(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos, Py_ssize_t limit, BOOL* is_partial) {
    Py_ssize_t found_pos;

    *is_partial = FALSE;

    /* Has the node been initialised for fast searching, if necessary? */
    if (!(node->status & RE_STATUS_FAST_INIT)) {
        /* Ideally the pattern should immutable and shareable across threads.
         * Internally, however, it isn't. For safety we need to hold the GIL.
         */
        acquire_GIL(state);

        /* Double-check because of multithreading. */
        if (!(node->status & RE_STATUS_FAST_INIT)) {
            build_fast_tables(state, node, TRUE);
            node->status |= RE_STATUS_FAST_INIT;
        }

        release_GIL(state);
    }

    if (node->string.bad_character_offset) {
        /* Start with a fast search. This will find the string if it's complete
         * (i.e. not truncated).
         */
        found_pos = fast_string_search_ign(state, node, text_pos, limit);
        if (found_pos < 0 && state->partial_side == RE_PARTIAL_RIGHT)
            /* We didn't find the string, but it could've been truncated, so
             * try again, starting close to the end.
             */
            found_pos = simple_string_search_ign(state, node, limit -
              (Py_ssize_t)(node->value_count - 1), limit, is_partial);
    } else
        found_pos = simple_string_search_ign(state, node, text_pos, limit,
          is_partial);

    return found_pos;
}

/* Performs a string search, backwards, ignoring case. */
Py_LOCAL_INLINE(Py_ssize_t) string_search_ign_rev(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, Py_ssize_t limit, BOOL* is_partial) {
    Py_ssize_t found_pos;

    *is_partial = FALSE;

    /* Has the node been initialised for fast searching, if necessary? */
    if (!(node->status & RE_STATUS_FAST_INIT)) {
        /* Ideally the pattern should immutable and shareable across threads.
         * Internally, however, it isn't. For safety we need to hold the GIL.
         */
        acquire_GIL(state);

        /* Double-check because of multithreading. */
        if (!(node->status & RE_STATUS_FAST_INIT)) {
            build_fast_tables_rev(state, node, TRUE);
            node->status |= RE_STATUS_FAST_INIT;
        }

        release_GIL(state);
    }

    if (node->string.bad_character_offset) {
        /* Start with a fast search. This will find the string if it's complete
         * (i.e. not truncated).
         */
        found_pos = fast_string_search_ign_rev(state, node, text_pos, limit);
        if (found_pos < 0 && state->partial_side == RE_PARTIAL_LEFT)
            /* We didn't find the string, but it could've been truncated, so
             * try again, starting close to the end.
             */
            found_pos = simple_string_search_ign_rev(state, node, limit +
              (Py_ssize_t)(node->value_count - 1), limit, is_partial);
    } else
        found_pos = simple_string_search_ign_rev(state, node, text_pos, limit,
          is_partial);

    return found_pos;
}

/* Performs a string search, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) string_search_rev(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos, Py_ssize_t limit, BOOL* is_partial) {
    Py_ssize_t found_pos;

    *is_partial = FALSE;

    /* Has the node been initialised for fast searching, if necessary? */
    if (!(node->status & RE_STATUS_FAST_INIT)) {
        /* Ideally the pattern should immutable and shareable across threads.
         * Internally, however, it isn't. For safety we need to hold the GIL.
         */
        acquire_GIL(state);

        /* Double-check because of multithreading. */
        if (!(node->status & RE_STATUS_FAST_INIT)) {
            build_fast_tables_rev(state, node, FALSE);
            node->status |= RE_STATUS_FAST_INIT;
        }

        release_GIL(state);
    }

    if (node->string.bad_character_offset) {
        /* Start with a fast search. This will find the string if it's complete
         * (i.e. not truncated).
         */
        found_pos = fast_string_search_rev(state, node, text_pos, limit);
        if (found_pos < 0 && state->partial_side == RE_PARTIAL_LEFT)
            /* We didn't find the string, but it could've been truncated, so
             * try again, starting close to the end.
             */
            found_pos = simple_string_search_rev(state, node, limit +
              (Py_ssize_t)(node->value_count - 1), limit, is_partial);
    } else
        found_pos = simple_string_search_rev(state, node, text_pos, limit,
          is_partial);

    return found_pos;
}

/* Returns how many characters there could be before full case-folding. */
Py_LOCAL_INLINE(Py_ssize_t) possible_unfolded_length(Py_ssize_t length) {
    if (length == 0)
        return 0;

    if (length < RE_MAX_FOLDED)
        return 1;

    return length / RE_MAX_FOLDED;
}

/* Checks whether there's any character except a newline at a position. */
Py_LOCAL_INLINE(int) try_match_ANY(RE_State* state, RE_Node* node, Py_ssize_t
  text_pos) {
    if (text_pos >= state->text_length) {
        if (state->partial_side == RE_PARTIAL_RIGHT)
            return RE_ERROR_PARTIAL;

        return RE_ERROR_FAILURE;
    }

    return bool_as_status(text_pos < state->slice_end &&
      matches_ANY(state->encoding, node, state->char_at(state->text,
      text_pos)));
}

/* Checks whether there's any character at all at a position. */
Py_LOCAL_INLINE(int) try_match_ANY_ALL(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    if (text_pos >= state->text_length) {
        if (state->partial_side == RE_PARTIAL_RIGHT)
            return RE_ERROR_PARTIAL;

        return RE_ERROR_FAILURE;
    }

    return bool_as_status(text_pos < state->slice_end);
}

/* Checks whether there's any character at all at a position, backwards. */
Py_LOCAL_INLINE(int) try_match_ANY_ALL_REV(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    if (text_pos <= 0) {
        if (state->partial_side == RE_PARTIAL_LEFT)
            return RE_ERROR_PARTIAL;

        return RE_ERROR_FAILURE;
    }

    return bool_as_status(text_pos > state->slice_start);
}

/* Checks whether there's any character except a newline at a position,
 * backwards.
 */
Py_LOCAL_INLINE(int) try_match_ANY_REV(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    if (text_pos <= 0) {
        if (state->partial_side == RE_PARTIAL_LEFT)
            return RE_ERROR_PARTIAL;

        return RE_ERROR_FAILURE;
    }

    return bool_as_status(text_pos > state->slice_start &&
      matches_ANY(state->encoding, node, state->char_at(state->text, text_pos -
      1)));
}

/* Checks whether there's any character except a line separator at a position.
 */
Py_LOCAL_INLINE(int) try_match_ANY_U(RE_State* state, RE_Node* node, Py_ssize_t
  text_pos) {
    if (text_pos >= state->text_length) {
        if (state->partial_side == RE_PARTIAL_RIGHT)
            return RE_ERROR_PARTIAL;

        return RE_ERROR_FAILURE;
    }

    return bool_as_status(text_pos < state->slice_end &&
      matches_ANY_U(state->encoding, node, state->char_at(state->text,
      text_pos)));
}

/* Checks whether there's any character except a line separator at a position,
 * backwards.
 */
Py_LOCAL_INLINE(int) try_match_ANY_U_REV(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    if (text_pos <= 0) {
        if (state->partial_side == RE_PARTIAL_LEFT)
            return RE_ERROR_PARTIAL;

        return RE_ERROR_FAILURE;
    }

    return bool_as_status(text_pos > state->slice_start &&
      matches_ANY_U(state->encoding, node, state->char_at(state->text, text_pos
      - 1)));
}

/* Checks whether a position is on a word boundary. */
Py_LOCAL_INLINE(int) try_match_BOUNDARY(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    return bool_as_status(state->encoding->at_boundary(state, text_pos) ==
      node->match);
}

/* Checks whether there's a character at a position. */
Py_LOCAL_INLINE(int) try_match_CHARACTER(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    if (text_pos >= state->text_length) {
        if (state->partial_side == RE_PARTIAL_RIGHT)
            return RE_ERROR_PARTIAL;

        return RE_ERROR_FAILURE;
    }

    return bool_as_status(text_pos < state->slice_end &&
      matches_CHARACTER(state->encoding, state->locale_info, node,
      state->char_at(state->text, text_pos)) == node->match);
}

/* Checks whether there's a character at a position, ignoring case. */
Py_LOCAL_INLINE(int) try_match_CHARACTER_IGN(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    if (text_pos >= state->text_length) {
        if (state->partial_side == RE_PARTIAL_RIGHT)
            return RE_ERROR_PARTIAL;

        return RE_ERROR_FAILURE;
    }

    return bool_as_status(text_pos < state->slice_end &&
      matches_CHARACTER_IGN(state->encoding, state->locale_info, node,
      state->char_at(state->text, text_pos)) == node->match);
}

/* Checks whether there's a character at a position, ignoring case, backwards.
 */
Py_LOCAL_INLINE(int) try_match_CHARACTER_IGN_REV(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos) {
    if (text_pos <= 0) {
        if (state->partial_side == RE_PARTIAL_LEFT)
            return RE_ERROR_PARTIAL;

        return RE_ERROR_FAILURE;
    }

    return bool_as_status(text_pos > state->slice_start &&
      matches_CHARACTER_IGN(state->encoding, state->locale_info, node,
      state->char_at(state->text, text_pos - 1)) == node->match);
}

/* Checks whether there's a character at a position, backwards. */
Py_LOCAL_INLINE(int) try_match_CHARACTER_REV(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    if (text_pos <= 0) {
        if (state->partial_side == RE_PARTIAL_LEFT)
            return RE_ERROR_PARTIAL;

        return RE_ERROR_FAILURE;
    }

    return bool_as_status(text_pos > state->slice_start &&
      matches_CHARACTER(state->encoding, state->locale_info, node,
      state->char_at(state->text, text_pos - 1)) == node->match);
}

/* Checks whether a position is on a default word boundary. */
Py_LOCAL_INLINE(int) try_match_DEFAULT_BOUNDARY(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    return bool_as_status(state->encoding->at_default_boundary(state, text_pos)
      == node->match);
}

/* Checks whether a position is at the default end of a word. */
Py_LOCAL_INLINE(int) try_match_DEFAULT_END_OF_WORD(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos) {
    return bool_as_status(state->encoding->at_default_word_end(state,
      text_pos));
}

/* Checks whether a position is at the default start of a word. */
Py_LOCAL_INLINE(int) try_match_DEFAULT_START_OF_WORD(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos) {
    return bool_as_status(state->encoding->at_default_word_start(state,
      text_pos));
}

/* Checks whether a position is at the end of a line. */
Py_LOCAL_INLINE(int) try_match_END_OF_LINE(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    return bool_as_status(text_pos >= state->slice_end ||
      state->char_at(state->text, text_pos) == '\n');
}

/* Checks whether a position is at the end of a line. */
Py_LOCAL_INLINE(int) try_match_END_OF_LINE_U(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    return bool_as_status(state->encoding->at_line_end(state, text_pos));
}

/* Checks whether a position is at the end of the string. */
Py_LOCAL_INLINE(int) try_match_END_OF_STRING(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    return bool_as_status(text_pos >= state->text_length);
}

/* Checks whether a position is at the end of a line or the string. */
Py_LOCAL_INLINE(int) try_match_END_OF_STRING_LINE(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos) {
    return bool_as_status(text_pos >= state->text_length || text_pos ==
      state->final_newline);
}

/* Checks whether a position is at the end of the string. */
Py_LOCAL_INLINE(int) try_match_END_OF_STRING_LINE_U(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos) {
    return bool_as_status(text_pos >= state->text_length || text_pos ==
      state->final_line_sep);
}

/* Checks whether a position is at the end of a word. */
Py_LOCAL_INLINE(int) try_match_END_OF_WORD(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    return bool_as_status(state->encoding->at_word_end(state, text_pos));
}

/* Checks whether a position is on a grapheme boundary. */
Py_LOCAL_INLINE(int) try_match_GRAPHEME_BOUNDARY(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos) {
    return bool_as_status(state->encoding->at_grapheme_boundary(state,
      text_pos));
}

/* Checks whether there's a character with a certain property at a position. */
Py_LOCAL_INLINE(int) try_match_PROPERTY(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    if (text_pos >= state->text_length) {
        if (state->partial_side == RE_PARTIAL_RIGHT)
            return RE_ERROR_PARTIAL;

        return RE_ERROR_FAILURE;
    }

    return bool_as_status(text_pos < state->slice_end &&
      matches_PROPERTY(state->encoding, state->locale_info, node,
      state->char_at(state->text, text_pos)) == node->match);
}

/* Checks whether there's a character with a certain property at a position,
 * ignoring case.
 */
Py_LOCAL_INLINE(int) try_match_PROPERTY_IGN(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    if (text_pos >= state->text_length) {
        if (state->partial_side == RE_PARTIAL_RIGHT)
            return RE_ERROR_PARTIAL;

        return RE_ERROR_FAILURE;
    }

    return bool_as_status(text_pos < state->slice_end &&
      matches_PROPERTY_IGN(state->encoding, state->locale_info, node,
      state->char_at(state->text, text_pos)) == node->match);
}

/* Checks whether there's a character with a certain property at a position,
 * ignoring case, backwards.
 */
Py_LOCAL_INLINE(int) try_match_PROPERTY_IGN_REV(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    if (text_pos <= 0) {
        if (state->partial_side == RE_PARTIAL_LEFT)
            return RE_ERROR_PARTIAL;

        return RE_ERROR_FAILURE;
    }

    return bool_as_status(text_pos > state->slice_start &&
      matches_PROPERTY_IGN(state->encoding, state->locale_info, node,
      state->char_at(state->text, text_pos - 1)) == node->match);
}

/* Checks whether there's a character with a certain property at a position,
 * backwards.
 */
Py_LOCAL_INLINE(int) try_match_PROPERTY_REV(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    if (text_pos <= 0) {
        if (state->partial_side == RE_PARTIAL_LEFT)
            return RE_ERROR_PARTIAL;

        return RE_ERROR_FAILURE;
    }

    return bool_as_status(text_pos > state->slice_start &&
      matches_PROPERTY(state->encoding, state->locale_info, node,
      state->char_at(state->text, text_pos - 1)) == node->match);
}

/* Checks whether there's a character in a certain range at a position. */
Py_LOCAL_INLINE(int) try_match_RANGE(RE_State* state, RE_Node* node, Py_ssize_t
  text_pos) {
    if (text_pos >= state->text_length) {
        if (state->partial_side == RE_PARTIAL_RIGHT)
            return RE_ERROR_PARTIAL;

        return RE_ERROR_FAILURE;
    }

    return bool_as_status(text_pos < state->slice_end &&
      matches_RANGE(state->encoding, state->locale_info, node,
      state->char_at(state->text, text_pos)) == node->match);
}

/* Checks whether there's a character in a certain range at a position,
 * ignoring case.
 */
Py_LOCAL_INLINE(int) try_match_RANGE_IGN(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    if (text_pos >= state->text_length) {
        if (state->partial_side == RE_PARTIAL_RIGHT)
            return RE_ERROR_PARTIAL;

        return RE_ERROR_FAILURE;
    }

    return bool_as_status(text_pos < state->slice_end &&
      matches_RANGE_IGN(state->encoding, state->locale_info, node,
      state->char_at(state->text, text_pos)) == node->match);
}

/* Checks whether there's a character in a certain range at a position,
 * ignoring case, backwards.
 */
Py_LOCAL_INLINE(int) try_match_RANGE_IGN_REV(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    if (text_pos <= 0) {
        if (state->partial_side == RE_PARTIAL_LEFT)
            return RE_ERROR_PARTIAL;

        return RE_ERROR_FAILURE;
    }

    return bool_as_status(text_pos > state->slice_start &&
      matches_RANGE_IGN(state->encoding, state->locale_info, node,
      state->char_at(state->text, text_pos - 1)) == node->match);
}

/* Checks whether there's a character in a certain range at a position,
 * backwards.
 */
Py_LOCAL_INLINE(int) try_match_RANGE_REV(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    if (text_pos <= 0) {
        if (state->partial_side == RE_PARTIAL_LEFT)
            return RE_ERROR_PARTIAL;

        return RE_ERROR_FAILURE;
    }

    return bool_as_status(text_pos > state->slice_start &&
      matches_RANGE(state->encoding, state->locale_info, node,
      state->char_at(state->text, text_pos - 1)) == node->match);
}

/* Checks whether a position is at the search anchor. */
Py_LOCAL_INLINE(int) try_match_SEARCH_ANCHOR(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    return bool_as_status(text_pos == state->search_anchor);
}

/* Checks whether there's a character in a certain set at a position. */
Py_LOCAL_INLINE(int) try_match_SET(RE_State* state, RE_Node* node, Py_ssize_t
  text_pos) {
    if (text_pos >= state->text_length) {
        if (state->partial_side == RE_PARTIAL_RIGHT)
            return RE_ERROR_PARTIAL;

        return RE_ERROR_FAILURE;
    }

    return bool_as_status(text_pos < state->slice_end &&
      matches_SET(state->encoding, state->locale_info, node,
      state->char_at(state->text, text_pos)) == node->match);
}

/* Checks whether there's a character in a certain set at a position, ignoring
 * case.
 */
Py_LOCAL_INLINE(int) try_match_SET_IGN(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    if (text_pos >= state->text_length) {
        if (state->partial_side == RE_PARTIAL_RIGHT)
            return RE_ERROR_PARTIAL;

        return RE_ERROR_FAILURE;
    }

    return bool_as_status(text_pos < state->slice_end &&
      matches_SET_IGN(state->encoding, state->locale_info, node,
      state->char_at(state->text, text_pos)) == node->match);
}

/* Checks whether there's a character in a certain set at a position, ignoring
 * case, backwards.
 */
Py_LOCAL_INLINE(int) try_match_SET_IGN_REV(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    if (text_pos <= 0) {
        if (state->partial_side == RE_PARTIAL_LEFT)
            return RE_ERROR_PARTIAL;

        return RE_ERROR_FAILURE;
    }

    return bool_as_status(text_pos > state->slice_start &&
      matches_SET_IGN(state->encoding, state->locale_info, node,
      state->char_at(state->text, text_pos - 1)) == node->match);
}

/* Checks whether there's a character in a certain set at a position,
 * backwards.
 */
Py_LOCAL_INLINE(int) try_match_SET_REV(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    if (text_pos <= 0) {
        if (state->partial_side == RE_PARTIAL_LEFT)
            return RE_ERROR_PARTIAL;

        return RE_ERROR_FAILURE;
    }

    return bool_as_status(text_pos > state->slice_start &&
      matches_SET(state->encoding, state->locale_info, node,
      state->char_at(state->text, text_pos - 1)) == node->match);
}

/* Checks whether a position is at the start of a line. */
Py_LOCAL_INLINE(int) try_match_START_OF_LINE(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    return bool_as_status(text_pos <= 0 || state->char_at(state->text, text_pos
      - 1) == '\n');
}

/* Checks whether a position is at the start of a line. */
Py_LOCAL_INLINE(int) try_match_START_OF_LINE_U(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    return bool_as_status(state->encoding->at_line_start(state, text_pos));
}

/* Checks whether a position is at the start of the string. */
Py_LOCAL_INLINE(int) try_match_START_OF_STRING(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    return bool_as_status(text_pos <= 0);
}

/* Checks whether a position is at the start of a word. */
Py_LOCAL_INLINE(int) try_match_START_OF_WORD(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos) {
    return bool_as_status(state->encoding->at_word_start(state, text_pos));
}

/* Checks whether there's a certain string at a position. */
Py_LOCAL_INLINE(int) try_match_STRING(RE_State* state, RE_NextNode* next,
  RE_Node* node, Py_ssize_t text_pos, RE_Position* next_position) {
    Py_ssize_t length;
    Py_UCS4 (*char_at)(void* text, Py_ssize_t pos);
    RE_CODE* values;
    Py_ssize_t s_pos;

    length = (Py_ssize_t)node->value_count;
    char_at = state->char_at;
    values = node->values;

    for (s_pos = 0; s_pos < length; s_pos++) {
        if (text_pos + s_pos >= state->slice_end) {
            if (state->partial_side == RE_PARTIAL_RIGHT) {
                next_position->text_pos = text_pos;
                return RE_ERROR_PARTIAL;
            }

            return RE_ERROR_FAILURE;
        }

        if (!same_char(char_at(state->text, text_pos + s_pos), values[s_pos]))
            return RE_ERROR_FAILURE;
    }

    next_position->node = next->match_next;
    next_position->text_pos = text_pos + next->match_step;

    return RE_ERROR_SUCCESS;
}

/* Checks whether there's a certain string at a position, ignoring case. */
Py_LOCAL_INLINE(int) try_match_STRING_FLD(RE_State* state, RE_NextNode* next,
  RE_Node* node, Py_ssize_t text_pos, RE_Position* next_position) {
    Py_ssize_t length;
    Py_UCS4 (*char_at)(void* text, Py_ssize_t pos);
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;
    int (*full_case_fold)(RE_LocaleInfo* locale_info, Py_UCS4 ch, Py_UCS4*
      folded);
    Py_ssize_t s_pos;
    RE_CODE* values;
    int folded_len;
    int f_pos;
    Py_ssize_t start_pos;
    Py_UCS4 folded[RE_MAX_FOLDED];

    length = (Py_ssize_t)node->value_count;
    char_at = state->char_at;
    encoding = state->encoding;
    locale_info = state->locale_info;
    full_case_fold = encoding->full_case_fold;

    s_pos = 0;
    values = node->values;
    folded_len = 0;
    f_pos = 0;
    start_pos = text_pos;

    while (s_pos < length) {
        if (f_pos >= folded_len) {
            /* Fetch and casefold another character. */
            if (text_pos >= state->slice_end) {
                if (state->partial_side == RE_PARTIAL_RIGHT) {
                    if (next->match_step == 0)
                        next_position->text_pos = start_pos;
                    else
                        next_position->text_pos = text_pos;
                    return RE_ERROR_PARTIAL;
                }

                return RE_ERROR_FAILURE;
            }

            folded_len = full_case_fold(locale_info, char_at(state->text,
              text_pos), folded);
            f_pos = 0;
        }

        if (!same_char_ign(encoding, locale_info, values[s_pos],
          folded[f_pos]))
            return RE_ERROR_FAILURE;

        ++s_pos;
        ++f_pos;

        if (f_pos >= folded_len)
            ++text_pos;
    }

    if (f_pos < folded_len)
        return RE_ERROR_FAILURE;

    next_position->node = next->match_next;
    if (next->match_step == 0)
        next_position->text_pos = start_pos;
    else
        next_position->text_pos = text_pos;

    return RE_ERROR_SUCCESS;
}

/* Checks whether there's a certain string at a position, ignoring case,
 * backwards.
 */
Py_LOCAL_INLINE(int) try_match_STRING_FLD_REV(RE_State* state, RE_NextNode*
  next, RE_Node* node, Py_ssize_t text_pos, RE_Position* next_position) {
    Py_ssize_t length;
    Py_UCS4 (*char_at)(void* text, Py_ssize_t pos);
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;
    int (*full_case_fold)(RE_LocaleInfo* locale_info, Py_UCS4 ch, Py_UCS4*
      folded);
    Py_ssize_t s_pos;
    RE_CODE* values;
    int folded_len;
    int f_pos;
    Py_ssize_t start_pos;
    Py_UCS4 folded[RE_MAX_FOLDED];

    length = (Py_ssize_t)node->value_count;
    char_at = state->char_at;
    encoding = state->encoding;
    locale_info = state->locale_info;
    full_case_fold = encoding->full_case_fold;

    s_pos = 0;
    values = node->values;
    folded_len = 0;
    f_pos = 0;
    start_pos = text_pos;

    while (s_pos < length) {
        if (f_pos >= folded_len) {
            /* Fetch and casefold another character. */
            if (text_pos <= state->slice_start) {
                if (state->partial_side == RE_PARTIAL_LEFT) {
                    if (next->match_step == 0)
                        next_position->text_pos = start_pos;
                    else
                        next_position->text_pos = text_pos;
                    return RE_ERROR_PARTIAL;
                }

                return RE_ERROR_FAILURE;
            }

            folded_len = full_case_fold(locale_info, char_at(state->text,
              text_pos - 1), folded);
            f_pos = 0;
        }

        if (!same_char_ign(encoding, locale_info, values[length - s_pos - 1],
          folded[folded_len - f_pos - 1]))
            return RE_ERROR_FAILURE;

        ++s_pos;
        ++f_pos;

        if (f_pos >= folded_len)
            --text_pos;
    }

    if (f_pos < folded_len)
        return RE_ERROR_FAILURE;

    next_position->node = next->match_next;
    if (next->match_step == 0)
        next_position->text_pos = start_pos;
    else
        next_position->text_pos = text_pos;

    return RE_ERROR_SUCCESS;
}

/* Checks whether there's a certain string at a position, ignoring case. */
Py_LOCAL_INLINE(int) try_match_STRING_IGN(RE_State* state, RE_NextNode* next,
  RE_Node* node, Py_ssize_t text_pos, RE_Position* next_position) {
    Py_ssize_t length;
    Py_UCS4 (*char_at)(void* text, Py_ssize_t pos);
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;
    RE_CODE* values;
    Py_ssize_t s_pos;

    length = (Py_ssize_t)node->value_count;
    char_at = state->char_at;
    encoding = state->encoding;
    locale_info = state->locale_info;
    values = node->values;

    for (s_pos = 0; s_pos < length; s_pos++) {
        if (text_pos + s_pos >= state->slice_end) {
            if (state->partial_side == RE_PARTIAL_RIGHT) {
                next_position->text_pos = text_pos;
                return RE_ERROR_PARTIAL;
            }

            return RE_ERROR_FAILURE;
        }

        if (!same_char_ign(encoding, locale_info, char_at(state->text, text_pos
          + s_pos), values[s_pos]))
            return RE_ERROR_FAILURE;
    }

    next_position->node = next->match_next;
    next_position->text_pos = text_pos + next->match_step;

    return RE_ERROR_SUCCESS;
}

/* Checks whether there's a certain string at a position, ignoring case,
 * backwards.
 */
Py_LOCAL_INLINE(int) try_match_STRING_IGN_REV(RE_State* state, RE_NextNode*
  next, RE_Node* node, Py_ssize_t text_pos, RE_Position* next_position) {
    Py_ssize_t length;
    Py_UCS4 (*char_at)(void* text, Py_ssize_t pos);
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;
    RE_CODE* values;
    Py_ssize_t s_pos;

    length = (Py_ssize_t)node->value_count;
    char_at = state->char_at;
    encoding = state->encoding;
    locale_info = state->locale_info;
    values = node->values;

    for (s_pos = 0; s_pos < length; s_pos++) {
        if (text_pos - s_pos <= state->slice_start) {
            if (state->partial_side == RE_PARTIAL_LEFT) {
                next_position->text_pos = text_pos;
                return RE_ERROR_PARTIAL;
            }

            return RE_ERROR_FAILURE;
        }

        if (!same_char_ign(encoding, locale_info, char_at(state->text, text_pos
          - s_pos - 1), values[length - s_pos - 1]))
            return RE_ERROR_FAILURE;
    }

    next_position->node = next->match_next;
    next_position->text_pos = text_pos + next->match_step;

    return RE_ERROR_SUCCESS;
}

/* Checks whether there's a certain string at a position, backwards. */
Py_LOCAL_INLINE(int) try_match_STRING_REV(RE_State* state, RE_NextNode* next,
  RE_Node* node, Py_ssize_t text_pos, RE_Position* next_position) {
    Py_ssize_t length;
    Py_UCS4 (*char_at)(void* text, Py_ssize_t pos);
    RE_CODE* values;
    Py_ssize_t s_pos;

    length = (Py_ssize_t)node->value_count;
    char_at = state->char_at;
    values = node->values;

    for (s_pos = 0; s_pos < length; s_pos++) {
        if (text_pos - s_pos <= state->slice_start) {
            if (state->partial_side == RE_PARTIAL_LEFT) {
                next_position->text_pos = text_pos;
                return RE_ERROR_PARTIAL;
            }

            return RE_ERROR_FAILURE;
        }

        if (!same_char(char_at(state->text, text_pos - s_pos - 1),
          values[length - s_pos - 1]))
            return RE_ERROR_FAILURE;
    }

    next_position->node = next->match_next;
    next_position->text_pos = text_pos + next->match_step;

    return RE_ERROR_SUCCESS;
}

/* Tries a match at the current text position.
 *
 * Returns the next node and text position if the match succeeds.
 */
Py_LOCAL_INLINE(int) try_match(RE_State* state, RE_NextNode* next, Py_ssize_t
  text_pos, RE_Position* next_position) {
    RE_Node* test;
    int status;

    test = next->test;

    if (test->status & RE_STATUS_FUZZY) {
        next_position->node = next->node;
        next_position->text_pos = text_pos;
        return RE_ERROR_SUCCESS;
    }

    switch (test->op) {
    case RE_OP_ANY:
        status = try_match_ANY(state, test, text_pos);
        break;
    case RE_OP_ANY_ALL:
        status = try_match_ANY_ALL(state, test, text_pos);
        break;
    case RE_OP_ANY_ALL_REV:
        status = try_match_ANY_ALL_REV(state, test, text_pos);
        break;
    case RE_OP_ANY_REV:
        status = try_match_ANY_REV(state, test, text_pos);
        break;
    case RE_OP_ANY_U:
        status = try_match_ANY_U(state, test, text_pos);
        break;
    case RE_OP_ANY_U_REV:
        status = try_match_ANY_U_REV(state, test, text_pos);
        break;
    case RE_OP_BOUNDARY:
        status = try_match_BOUNDARY(state, test, text_pos);
        break;
    case RE_OP_CHARACTER:
        status = try_match_CHARACTER(state, test, text_pos);
        break;
    case RE_OP_CHARACTER_IGN:
        status = try_match_CHARACTER_IGN(state, test, text_pos);
        break;
    case RE_OP_CHARACTER_IGN_REV:
        status = try_match_CHARACTER_IGN_REV(state, test, text_pos);
        break;
    case RE_OP_CHARACTER_REV:
        status = try_match_CHARACTER_REV(state, test, text_pos);
        break;
    case RE_OP_DEFAULT_BOUNDARY:
        status = try_match_DEFAULT_BOUNDARY(state, test, text_pos);
        break;
    case RE_OP_DEFAULT_END_OF_WORD:
        status = try_match_DEFAULT_END_OF_WORD(state, test, text_pos);
        break;
    case RE_OP_DEFAULT_START_OF_WORD:
        status = try_match_DEFAULT_START_OF_WORD(state, test, text_pos);
        break;
    case RE_OP_END_OF_LINE:
        status = try_match_END_OF_LINE(state, test, text_pos);
        break;
    case RE_OP_END_OF_LINE_U:
        status = try_match_END_OF_LINE_U(state, test, text_pos);
        break;
    case RE_OP_END_OF_STRING:
        status = try_match_END_OF_STRING(state, test, text_pos);
        break;
    case RE_OP_END_OF_STRING_LINE:
        status = try_match_END_OF_STRING_LINE(state, test, text_pos);
        break;
    case RE_OP_END_OF_STRING_LINE_U:
        status = try_match_END_OF_STRING_LINE_U(state, test, text_pos);
        break;
    case RE_OP_END_OF_WORD:
        status = try_match_END_OF_WORD(state, test, text_pos);
        break;
    case RE_OP_GRAPHEME_BOUNDARY:
        status = try_match_GRAPHEME_BOUNDARY(state, test, text_pos);
        break;
    case RE_OP_PROPERTY:
        status = try_match_PROPERTY(state, test, text_pos);
        break;
    case RE_OP_PROPERTY_IGN:
        status = try_match_PROPERTY_IGN(state, test, text_pos);
        break;
    case RE_OP_PROPERTY_IGN_REV:
        status = try_match_PROPERTY_IGN_REV(state, test, text_pos);
        break;
    case RE_OP_PROPERTY_REV:
        status = try_match_PROPERTY_REV(state, test, text_pos);
        break;
    case RE_OP_RANGE:
        status = try_match_RANGE(state, test, text_pos);
        break;
    case RE_OP_RANGE_IGN:
        status = try_match_RANGE_IGN(state, test, text_pos);
        break;
    case RE_OP_RANGE_IGN_REV:
        status = try_match_RANGE_IGN_REV(state, test, text_pos);
        break;
    case RE_OP_RANGE_REV:
        status = try_match_RANGE_REV(state, test, text_pos);
        break;
    case RE_OP_SEARCH_ANCHOR:
        status = try_match_SEARCH_ANCHOR(state, test, text_pos);
        break;
    case RE_OP_SET_DIFF:
    case RE_OP_SET_INTER:
    case RE_OP_SET_SYM_DIFF:
    case RE_OP_SET_UNION:
        status = try_match_SET(state, test, text_pos);
        break;
    case RE_OP_SET_DIFF_IGN:
    case RE_OP_SET_INTER_IGN:
    case RE_OP_SET_SYM_DIFF_IGN:
    case RE_OP_SET_UNION_IGN:
        status = try_match_SET_IGN(state, test, text_pos);
        break;
    case RE_OP_SET_DIFF_IGN_REV:
    case RE_OP_SET_INTER_IGN_REV:
    case RE_OP_SET_SYM_DIFF_IGN_REV:
    case RE_OP_SET_UNION_IGN_REV:
        status = try_match_SET_IGN_REV(state, test, text_pos);
        break;
    case RE_OP_SET_DIFF_REV:
    case RE_OP_SET_INTER_REV:
    case RE_OP_SET_SYM_DIFF_REV:
    case RE_OP_SET_UNION_REV:
        status = try_match_SET_REV(state, test, text_pos);
        break;
    case RE_OP_START_OF_LINE:
        status = try_match_START_OF_LINE(state, test, text_pos);
        break;
    case RE_OP_START_OF_LINE_U:
        status = try_match_START_OF_LINE_U(state, test, text_pos);
        break;
    case RE_OP_START_OF_STRING:
        status = try_match_START_OF_STRING(state, test, text_pos);
        break;
    case RE_OP_START_OF_WORD:
        status = try_match_START_OF_WORD(state, test, text_pos);
        break;
    case RE_OP_STRING:
        return try_match_STRING(state, next, test, text_pos, next_position);
    case RE_OP_STRING_FLD:
        return try_match_STRING_FLD(state, next, test, text_pos,
          next_position);
    case RE_OP_STRING_FLD_REV:
        return try_match_STRING_FLD_REV(state, next, test, text_pos,
          next_position);
    case RE_OP_STRING_IGN:
        return try_match_STRING_IGN(state, next, test, text_pos,
          next_position);
    case RE_OP_STRING_IGN_REV:
        return try_match_STRING_IGN_REV(state, next, test, text_pos,
          next_position);
    case RE_OP_STRING_REV:
        return try_match_STRING_REV(state, next, test, text_pos,
          next_position);
    case RE_OP_SUCCESS:
        if (state->match_all) {
            /* We want to match all of the slice. */
            if (state->reverse) {
                if (text_pos > 0)
                    return RE_ERROR_FAILURE;
            } else {
                if (text_pos < state->text_length)
                    return RE_ERROR_FAILURE;
            }
        }

        next_position->node = next->node;
        next_position->text_pos = text_pos;
        return RE_ERROR_SUCCESS;
    default:
        next_position->node = next->node;
        next_position->text_pos = text_pos;
        return RE_ERROR_SUCCESS;
    }

    if (status != RE_ERROR_SUCCESS)
        return status;

    next_position->node = next->match_next;
    next_position->text_pos = text_pos + next->match_step;

    return RE_ERROR_SUCCESS;
}

/* Searches for a word boundary. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_BOUNDARY(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, BOOL* is_partial) {
    BOOL (*at_boundary)(RE_State* state, Py_ssize_t text_pos);

    at_boundary = state->encoding->at_boundary;

    *is_partial = FALSE;

    for (;;) {
        if (at_boundary(state, text_pos) == node->match)
            return text_pos;

        if (text_pos >= state->slice_end)
            return -1;

        ++text_pos;
    }
}

/* Searches for a word boundary, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_BOUNDARY_rev(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, BOOL* is_partial) {
    BOOL (*at_boundary)(RE_State* state, Py_ssize_t text_pos);

    at_boundary = state->encoding->at_boundary;

    *is_partial = FALSE;

    for (;;) {
        if (at_boundary(state, text_pos) == node->match)
            return text_pos;

        if (text_pos <= state->slice_start)
            return -1;

        --text_pos;
    }
}

/* Searches for a default word boundary. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_DEFAULT_BOUNDARY(RE_State* state,
  RE_Node* node, Py_ssize_t text_pos, BOOL* is_partial) {
    BOOL (*at_default_boundary)(RE_State* state, Py_ssize_t text_pos);

    at_default_boundary = state->encoding->at_default_boundary;

    *is_partial = FALSE;

    for (;;) {
        if (at_default_boundary(state, text_pos) == node->match)
            return text_pos;

        if (text_pos >= state->slice_end)
            return -1;

        ++text_pos;
    }
}

/* Searches for a default word boundary, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_DEFAULT_BOUNDARY_rev(RE_State* state,
  RE_Node* node, Py_ssize_t text_pos, BOOL* is_partial) {
    BOOL (*at_default_boundary)(RE_State* state, Py_ssize_t text_pos);

    at_default_boundary = state->encoding->at_default_boundary;

    *is_partial = FALSE;

    for (;;) {
        if (at_default_boundary(state, text_pos) == node->match)
            return text_pos;

        if (text_pos <= state->slice_start)
            return -1;

        --text_pos;
    }
}

/* Searches for the default end of a word. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_DEFAULT_END_OF_WORD(RE_State* state,
  RE_Node* node, Py_ssize_t text_pos, BOOL* is_partial) {
    BOOL (*at_default_word_end)(RE_State* state, Py_ssize_t text_pos);

    at_default_word_end = state->encoding->at_default_word_end;

    *is_partial = FALSE;

    for (;;) {
        if (at_default_word_end(state, text_pos) == node->match)
            return text_pos;

        if (text_pos >= state->slice_end)
            return -1;

        ++text_pos;
    }
}

/* Searches for the default end of a word, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_DEFAULT_END_OF_WORD_rev(RE_State*
  state, RE_Node* node, Py_ssize_t text_pos, BOOL* is_partial) {
    BOOL (*at_default_word_end)(RE_State* state, Py_ssize_t text_pos);

    at_default_word_end = state->encoding->at_default_word_end;

    *is_partial = FALSE;

    for (;;) {
        if (at_default_word_end(state, text_pos) == node->match)
            return text_pos;

        if (text_pos <= state->slice_start)
            return -1;

        --text_pos;
    }
}

/* Searches for the default start of a word. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_DEFAULT_START_OF_WORD(RE_State* state,
  RE_Node* node, Py_ssize_t text_pos, BOOL* is_partial) {
    BOOL (*at_default_word_start)(RE_State* state, Py_ssize_t text_pos);

    at_default_word_start = state->encoding->at_default_word_start;

    *is_partial = FALSE;

    for (;;) {
        if (at_default_word_start(state, text_pos) == node->match)
            return text_pos;

        if (text_pos >= state->slice_end)
            return -1;

        ++text_pos;
    }
}

/* Searches for the default start of a word, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_DEFAULT_START_OF_WORD_rev(RE_State*
  state, RE_Node* node, Py_ssize_t text_pos, BOOL* is_partial) {
    BOOL (*at_default_word_start)(RE_State* state, Py_ssize_t text_pos);

    at_default_word_start = state->encoding->at_default_word_start;

    *is_partial = FALSE;

    for (;;) {
        if (at_default_word_start(state, text_pos) == node->match)
            return text_pos;

        if (text_pos <= state->slice_start)
            return -1;

        --text_pos;
    }
}

/* Searches for the end of line. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_END_OF_LINE(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, BOOL* is_partial) {
    *is_partial = FALSE;

    for (;;) {
        if (text_pos >= state->text_length || state->char_at(state->text,
          text_pos) == '\n')
            return text_pos;

        if (text_pos >= state->slice_end)
            return -1;

        ++text_pos;
    }
}

/* Searches for the end of line, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_END_OF_LINE_rev(RE_State* state,
  RE_Node* node, Py_ssize_t text_pos, BOOL* is_partial) {
    *is_partial = FALSE;

    for (;;) {
        if (text_pos >= state->text_length || state->char_at(state->text,
          text_pos) == '\n')
            return text_pos;

        if (text_pos <= state->slice_start)
            return -1;

        --text_pos;
    }
}

/* Searches for the end of the string. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_END_OF_STRING(RE_State* state,
  RE_Node* node, Py_ssize_t text_pos, BOOL* is_partial) {
    *is_partial = FALSE;

    if (state->slice_end >= state->text_length)
        return state->text_length;

    return -1;
}

/* Searches for the end of the string, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_END_OF_STRING_rev(RE_State* state,
  RE_Node* node, Py_ssize_t text_pos, BOOL* is_partial) {
    *is_partial = FALSE;

    if (text_pos >= state->text_length)
        return text_pos;

    return -1;
}

/* Searches for the end of the string or line. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_END_OF_STRING_LINE(RE_State* state,
  RE_Node* node, Py_ssize_t text_pos, BOOL* is_partial) {
    *is_partial = FALSE;

    if (text_pos <= state->final_newline)
        text_pos = state->final_newline;
    else if (text_pos <= state->text_length)
        text_pos = state->text_length;

    if (text_pos > state->slice_end)
        return -1;

    if (text_pos >= state->text_length)
        return text_pos;

    return text_pos;
}

/* Searches for the end of the string or line, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_END_OF_STRING_LINE_rev(RE_State*
  state, RE_Node* node, Py_ssize_t text_pos, BOOL* is_partial) {
    *is_partial = FALSE;

    if (text_pos >= state->text_length)
        text_pos = state->text_length;
    else if (text_pos >= state->final_newline)
        text_pos = state->final_newline;
    else
        return -1;

    if (text_pos < state->slice_start)
        return -1;

    if (text_pos <= 0)
        return text_pos;

    return text_pos;
}

/* Searches for the end of a word. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_END_OF_WORD(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, BOOL* is_partial) {
    BOOL (*at_word_end)(RE_State* state, Py_ssize_t text_pos);

    at_word_end = state->encoding->at_word_end;

    *is_partial = FALSE;

    for (;;) {
        if (at_word_end(state, text_pos) == node->match)
            return text_pos;

        if (text_pos >= state->slice_end)
            return -1;

        ++text_pos;
    }
}

/* Searches for the end of a word, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_END_OF_WORD_rev(RE_State* state,
  RE_Node* node, Py_ssize_t text_pos, BOOL* is_partial) {
    BOOL (*at_word_end)(RE_State* state, Py_ssize_t text_pos);

    at_word_end = state->encoding->at_word_end;

    *is_partial = FALSE;

    for (;;) {
        if (at_word_end(state, text_pos) == node->match)
            return text_pos;

        if (text_pos <= state->slice_start)
            return -1;

        --text_pos;
    }
}

/* Searches for a grapheme boundary. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_GRAPHEME_BOUNDARY(RE_State* state,
  RE_Node* node, Py_ssize_t text_pos, BOOL* is_partial) {
    BOOL (*at_grapheme_boundary)(RE_State* state, Py_ssize_t text_pos);

    at_grapheme_boundary = state->encoding->at_grapheme_boundary;

    *is_partial = FALSE;

    for (;;) {
        if (at_grapheme_boundary(state, text_pos) == node->match)
            return text_pos;

        if (text_pos >= state->slice_end)
            return -1;

        ++text_pos;
    }
}

/* Searches for a grapheme boundary, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_GRAPHEME_BOUNDARY_rev(RE_State* state,
  RE_Node* node, Py_ssize_t text_pos, BOOL* is_partial) {
    BOOL (*at_grapheme_boundary)(RE_State* state, Py_ssize_t text_pos);

    at_grapheme_boundary = state->encoding->at_grapheme_boundary;

    *is_partial = FALSE;

    for (;;) {
        if (at_grapheme_boundary(state, text_pos) == node->match)
            return text_pos;

        if (text_pos <= state->slice_start)
            return -1;

        --text_pos;
    }
}

/* Searches for the start of line. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_START_OF_LINE(RE_State* state,
  RE_Node* node, Py_ssize_t text_pos, BOOL* is_partial) {
    *is_partial = FALSE;

    for (;;) {
        if (text_pos <= 0 || state->char_at(state->text, text_pos - 1) == '\n')
            return text_pos;

        if (text_pos >= state->slice_end)
            return -1;

        ++text_pos;
    }
}

/* Searches for the start of line, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_START_OF_LINE_rev(RE_State* state,
  RE_Node* node, Py_ssize_t text_pos, BOOL* is_partial) {
    *is_partial = FALSE;

    for (;;) {
        if (text_pos <= 0 || state->char_at(state->text, text_pos - 1) == '\n')
            return text_pos;

        if (text_pos <= state->slice_start)
            return -1;

        --text_pos;
    }
}

/* Searches for the start of the string. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_START_OF_STRING(RE_State* state,
  RE_Node* node, Py_ssize_t text_pos, BOOL* is_partial) {
    *is_partial = FALSE;

    if (text_pos <= 0)
        return text_pos;

    return -1;
}

/* Searches for the start of the string, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_START_OF_STRING_rev(RE_State* state,
  RE_Node* node, Py_ssize_t text_pos, BOOL* is_partial) {
    *is_partial = FALSE;

    if (state->slice_start <= 0)
        return 0;

    return -1;
}

/* Searches for the start of a word. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_START_OF_WORD(RE_State* state,
  RE_Node* node, Py_ssize_t text_pos, BOOL* is_partial) {
    BOOL (*at_word_start)(RE_State* state, Py_ssize_t text_pos);

    at_word_start = state->encoding->at_word_start;

    *is_partial = FALSE;

    for (;;) {
        if (at_word_start(state, text_pos) == node->match)
            return text_pos;

        if (text_pos >= state->slice_end)
            return -1;

        ++text_pos;
    }
}

/* Searches for the start of a word, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_START_OF_WORD_rev(RE_State* state,
  RE_Node* node, Py_ssize_t text_pos, BOOL* is_partial) {
    BOOL (*at_word_start)(RE_State* state, Py_ssize_t text_pos);

    at_word_start = state->encoding->at_word_start;

    *is_partial = FALSE;

    for (;;) {
        if (at_word_start(state, text_pos) == node->match)
            return text_pos;

        if (text_pos <= state->slice_start)
            return -1;

        --text_pos;
    }
}

/* Searches for a string. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_STRING(RE_State* state, RE_Node* node,
  Py_ssize_t text_pos, BOOL* is_partial) {
    *is_partial = FALSE;

    if ((node->status & RE_STATUS_REQUIRED) && text_pos == state->req_pos)
        return text_pos;

    return string_search(state, node, text_pos, state->slice_end, is_partial);
}

/* Searches for a string, ignoring case. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_STRING_FLD(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, Py_ssize_t* new_pos, BOOL* is_partial) {
    *is_partial = FALSE;

    if ((node->status & RE_STATUS_REQUIRED) && text_pos == state->req_pos) {
        *new_pos = state->req_end;
        return text_pos;
    }

    return string_search_fld(state, node, text_pos, state->slice_end, new_pos,
      is_partial);
}

/* Searches for a string, ignoring case, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_STRING_FLD_REV(RE_State* state,
  RE_Node* node, Py_ssize_t text_pos, Py_ssize_t* new_pos, BOOL* is_partial) {
    *is_partial = FALSE;

    if ((node->status & RE_STATUS_REQUIRED) && text_pos == state->req_pos) {
        *new_pos = state->req_end;
        return text_pos;
    }

    return string_search_fld_rev(state, node, text_pos, state->slice_start,
      new_pos, is_partial);
}

/* Searches for a string, ignoring case. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_STRING_IGN(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, BOOL* is_partial) {
    *is_partial = FALSE;

    if ((node->status & RE_STATUS_REQUIRED) && text_pos == state->req_pos)
        return text_pos;

    return string_search_ign(state, node, text_pos, state->slice_end,
      is_partial);
}

/* Searches for a string, ignoring case, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_STRING_IGN_REV(RE_State* state,
  RE_Node* node, Py_ssize_t text_pos, BOOL* is_partial) {
    *is_partial = FALSE;

    if ((node->status & RE_STATUS_REQUIRED) && text_pos == state->req_pos)
        return text_pos;

    return string_search_ign_rev(state, node, text_pos, state->slice_start,
      is_partial);
}

/* Searches for a string, backwards. */
Py_LOCAL_INLINE(Py_ssize_t) search_start_STRING_REV(RE_State* state, RE_Node*
  node, Py_ssize_t text_pos, BOOL* is_partial) {
    *is_partial = FALSE;

    if ((node->status & RE_STATUS_REQUIRED) && text_pos == state->req_pos)
        return text_pos;

    return string_search_rev(state, node, text_pos, state->slice_start,
      is_partial);
}

/* Searches for the start of a match. */
Py_LOCAL_INLINE(int) search_start(RE_State* state, RE_NextNode* next,
  RE_Position* new_position, int search_index) {
    Py_ssize_t start_pos;
    RE_Node* test;
    RE_Node* node;
    RE_SearchPosition* info;
    Py_ssize_t text_pos;

    start_pos = state->text_pos;
    TRACE(("<<search_start>> at %" PY_FORMAT_SIZE_T "d\n", start_pos))

    test = next->test;
    node = next->node;

    if (state->reverse) {
        if (start_pos < state->slice_start) {
            if (state->partial_side == RE_PARTIAL_LEFT) {
                new_position->text_pos = state->slice_start;
                return RE_ERROR_PARTIAL;
            }

            return RE_ERROR_FAILURE;
        }
    } else {
        if (start_pos > state->slice_end) {
            if (state->partial_side == RE_PARTIAL_RIGHT) {
                new_position->text_pos = state->slice_end;
                return RE_ERROR_PARTIAL;
            }
        }
    }

    if (test->status & RE_STATUS_FUZZY) {
        /* Don't call 'search_start' again. */
        state->pattern->do_search_start = FALSE;

        state->match_pos = start_pos;
        new_position->node = node;
        new_position->text_pos = start_pos;

        return RE_ERROR_SUCCESS;
    }

again:
    if (!state->is_fuzzy && state->partial_side == RE_PARTIAL_NONE) {
        if (state->reverse) {
            if (start_pos - state->min_width < state->slice_start)
                return RE_ERROR_FAILURE;
        } else {
            if (start_pos + state->min_width > state->slice_end)
                return RE_ERROR_FAILURE;
        }
    }

    if (search_index < MAX_SEARCH_POSITIONS) {
        info = &state->search_positions[search_index];
        if (state->reverse) {
            if (info->start_pos >= 0 && info->start_pos >= start_pos &&
              start_pos >= info->match_pos) {
                state->match_pos = info->match_pos;

                new_position->text_pos = state->match_pos;
                new_position->node = node;

                return RE_ERROR_SUCCESS;
            }
        } else {
            if (info->start_pos >= 0 && info->start_pos <= start_pos &&
              start_pos <= info->match_pos) {
                state->match_pos = info->match_pos;

                new_position->text_pos = state->match_pos;
                new_position->node = node;

                return RE_ERROR_SUCCESS;
            }
        }
    } else
        info = NULL;

    switch (test->op) {
    case RE_OP_ANY:
        start_pos = match_many_ANY(state, test, start_pos, state->slice_end,
          FALSE);

        if (start_pos >= state->text_length) {
            if (state->partial_side == RE_PARTIAL_RIGHT) {
                new_position->text_pos = start_pos;
                return RE_ERROR_PARTIAL;
            }
        }

        if (start_pos >= state->slice_end)
            return RE_ERROR_FAILURE;
        break;
    case RE_OP_ANY_ALL:
    case RE_OP_ANY_ALL_REV:
        break;
    case RE_OP_ANY_REV:
        start_pos = match_many_ANY_REV(state, test, start_pos,
          state->slice_start, FALSE);

        if (start_pos <= 0) {
            if (state->partial_side == RE_PARTIAL_LEFT) {
                new_position->text_pos = start_pos;
                return RE_ERROR_PARTIAL;
            }
        }

        if (start_pos <= state->slice_start)
            return RE_ERROR_FAILURE;
        break;
    case RE_OP_ANY_U:
        start_pos = match_many_ANY_U(state, test, start_pos, state->slice_end,
          FALSE);

        if (start_pos >= state->text_length) {
            if (state->partial_side == RE_PARTIAL_RIGHT) {
                new_position->text_pos = start_pos;
                return RE_ERROR_PARTIAL;
            }
        }

        if (start_pos >= state->slice_end)
            return RE_ERROR_FAILURE;
        break;
    case RE_OP_ANY_U_REV:
        start_pos = match_many_ANY_U_REV(state, test, start_pos,
          state->slice_start, FALSE);

        if (start_pos <= 0) {
            if (state->partial_side == RE_PARTIAL_LEFT) {
                new_position->text_pos = start_pos;
                return RE_ERROR_PARTIAL;
            }
        }

        if (start_pos <= state->slice_start)
            return RE_ERROR_FAILURE;
        break;
    case RE_OP_BOUNDARY:
    {
        BOOL is_partial;

        if (state->reverse)
            start_pos = search_start_BOUNDARY_rev(state, test, start_pos,
              &is_partial);
        else
            start_pos = search_start_BOUNDARY(state, test, start_pos,
              &is_partial);

        if (start_pos < 0)
            return RE_ERROR_FAILURE;

        if (is_partial) {
            new_position->text_pos = start_pos;
            return RE_ERROR_PARTIAL;
        }
        break;
    }
    case RE_OP_CHARACTER:
        start_pos = match_many_CHARACTER(state, test, start_pos,
          state->slice_end, FALSE);

        if (start_pos >= state->text_length) {
            if (state->partial_side == RE_PARTIAL_RIGHT) {
                new_position->text_pos = start_pos;
                return RE_ERROR_PARTIAL;
            }
        }

        if (start_pos >= state->slice_end)
            return RE_ERROR_FAILURE;
        break;
    case RE_OP_CHARACTER_IGN:
        start_pos = match_many_CHARACTER_IGN(state, test, start_pos,
          state->slice_end, FALSE);

        if (start_pos >= state->text_length) {
            if (state->partial_side == RE_PARTIAL_RIGHT) {
                new_position->text_pos = start_pos;
                return RE_ERROR_PARTIAL;
            }
        }

        if (start_pos >= state->slice_end)
            return RE_ERROR_FAILURE;
        break;
    case RE_OP_CHARACTER_IGN_REV:
        start_pos = match_many_CHARACTER_IGN_REV(state, test, start_pos,
          state->slice_start, FALSE);

        if (start_pos <= 0) {
            if (state->partial_side == RE_PARTIAL_LEFT) {
                new_position->text_pos = start_pos;
                return RE_ERROR_PARTIAL;
            }
        }

        if (start_pos <= state->slice_start)
            return RE_ERROR_FAILURE;
        break;
    case RE_OP_CHARACTER_REV:
        start_pos = match_many_CHARACTER_REV(state, test, start_pos,
          state->slice_start, FALSE);

        if (start_pos <= 0) {
            if (state->partial_side == RE_PARTIAL_LEFT) {
                new_position->text_pos = start_pos;
                return RE_ERROR_PARTIAL;
            }
        }

        if (start_pos <= state->slice_start)
            return RE_ERROR_FAILURE;
        break;
    case RE_OP_DEFAULT_BOUNDARY:
    {
        BOOL is_partial;

        if (state->reverse)
            start_pos = search_start_DEFAULT_BOUNDARY_rev(state, test,
              start_pos, &is_partial);
        else
            start_pos = search_start_DEFAULT_BOUNDARY(state, test, start_pos,
              &is_partial);

        if (start_pos < 0)
            return RE_ERROR_FAILURE;

        if (is_partial) {
            new_position->text_pos = start_pos;
            return RE_ERROR_PARTIAL;
        }
        break;
    }
    case RE_OP_DEFAULT_END_OF_WORD:
    {
        BOOL is_partial;

        if (state->reverse)
            start_pos = search_start_DEFAULT_END_OF_WORD_rev(state, test,
              start_pos, &is_partial);
        else
            start_pos = search_start_DEFAULT_END_OF_WORD(state, test,
              start_pos, &is_partial);

        if (start_pos < 0)
            return RE_ERROR_FAILURE;

        if (is_partial) {
            new_position->text_pos = start_pos;
            return RE_ERROR_PARTIAL;
        }
        break;
    }
    case RE_OP_DEFAULT_START_OF_WORD:
    {
        BOOL is_partial;

        if (state->reverse)
            start_pos = search_start_DEFAULT_START_OF_WORD_rev(state, test,
              start_pos, &is_partial);
        else
            start_pos = search_start_DEFAULT_START_OF_WORD(state, test,
              start_pos, &is_partial);

        if (start_pos < 0)
            return RE_ERROR_FAILURE;

        if (is_partial) {
            new_position->text_pos = start_pos;
            return RE_ERROR_PARTIAL;
        }
        break;
    }
    case RE_OP_END_OF_LINE:
    {
        BOOL is_partial;

        if (state->reverse)
            start_pos = search_start_END_OF_LINE_rev(state, test, start_pos,
              &is_partial);
        else
            start_pos = search_start_END_OF_LINE(state, test, start_pos,
              &is_partial);

        if (start_pos < 0)
            return RE_ERROR_FAILURE;

        if (is_partial) {
            new_position->text_pos = start_pos;
            return RE_ERROR_PARTIAL;
        }
        break;
    }
    case RE_OP_END_OF_STRING:
    {
        BOOL is_partial;

        if (state->reverse)
            start_pos = search_start_END_OF_STRING_rev(state, test, start_pos,
              &is_partial);
        else
            start_pos = search_start_END_OF_STRING(state, test, start_pos,
              &is_partial);

        if (start_pos < 0)
            return RE_ERROR_FAILURE;

        if (is_partial) {
            new_position->text_pos = start_pos;
            return RE_ERROR_PARTIAL;
        }
        break;
    }
    case RE_OP_END_OF_STRING_LINE:
    {
        BOOL is_partial;

        if (state->reverse)
            start_pos = search_start_END_OF_STRING_LINE_rev(state, test,
              start_pos, &is_partial);
        else
            start_pos = search_start_END_OF_STRING_LINE(state, test, start_pos,
              &is_partial);

        if (start_pos < 0)
            return RE_ERROR_FAILURE;

        if (is_partial) {
            new_position->text_pos = start_pos;
            return RE_ERROR_PARTIAL;
        }
        break;
    }
    case RE_OP_END_OF_WORD:
    {
        BOOL is_partial;

        if (state->reverse)
            start_pos = search_start_END_OF_WORD_rev(state, test, start_pos,
              &is_partial);
        else
            start_pos = search_start_END_OF_WORD(state, test, start_pos,
              &is_partial);

        if (start_pos < 0)
            return RE_ERROR_FAILURE;

        if (is_partial) {
            new_position->text_pos = start_pos;
            return RE_ERROR_PARTIAL;
        }
        break;
    }
    case RE_OP_GRAPHEME_BOUNDARY:
    {
        BOOL is_partial;

        if (state->reverse)
            start_pos = search_start_GRAPHEME_BOUNDARY_rev(state, test,
              start_pos, &is_partial);
        else
            start_pos = search_start_GRAPHEME_BOUNDARY(state, test, start_pos,
              &is_partial);

        if (start_pos < 0)
            return RE_ERROR_FAILURE;

        if (is_partial) {
            new_position->text_pos = start_pos;
            return RE_ERROR_PARTIAL;
        }
        break;
    }
    case RE_OP_PROPERTY:
        start_pos = match_many_PROPERTY(state, test, start_pos,
          state->slice_end, FALSE);

        if (start_pos >= state->text_length) {
            if (state->partial_side == RE_PARTIAL_RIGHT) {
                new_position->text_pos = start_pos;
                return RE_ERROR_PARTIAL;
            }
        }

        if (start_pos >= state->slice_end)
            return RE_ERROR_FAILURE;
        break;
    case RE_OP_PROPERTY_IGN:
        start_pos = match_many_PROPERTY_IGN(state, test, start_pos,
          state->slice_end, FALSE);

        if (start_pos >= state->text_length) {
            if (state->partial_side == RE_PARTIAL_RIGHT) {
                new_position->text_pos = start_pos;
                return RE_ERROR_PARTIAL;
            }
        }

        if (start_pos >= state->slice_end)
            return RE_ERROR_FAILURE;
        break;
    case RE_OP_PROPERTY_IGN_REV:
        start_pos = match_many_PROPERTY_IGN_REV(state, test, start_pos,
          state->slice_start, FALSE);

        if (start_pos <= 0) {
            if (state->partial_side == RE_PARTIAL_LEFT) {
                new_position->text_pos = start_pos;
                return RE_ERROR_PARTIAL;
            }
        }

        if (start_pos <= state->slice_start)
            return RE_ERROR_FAILURE;
        break;
    case RE_OP_PROPERTY_REV:
        start_pos = match_many_PROPERTY_REV(state, test, start_pos,
          state->slice_start, FALSE);

        if (start_pos <= 0) {
            if (state->partial_side == RE_PARTIAL_LEFT) {
                new_position->text_pos = start_pos;
                return RE_ERROR_PARTIAL;
            }
        }

        if (start_pos <= state->slice_start)
            return RE_ERROR_FAILURE;
        break;
    case RE_OP_RANGE:
        start_pos = match_many_RANGE(state, test, start_pos, state->slice_end,
          FALSE);

        if (start_pos >= state->text_length) {
            if (state->partial_side == RE_PARTIAL_RIGHT) {
                new_position->text_pos = start_pos;
                return RE_ERROR_PARTIAL;
            }
        }

        if (start_pos >= state->slice_end)
            return RE_ERROR_FAILURE;
        break;
    case RE_OP_RANGE_IGN:
        start_pos = match_many_RANGE_IGN(state, test, start_pos,
          state->slice_end, FALSE);

        if (start_pos >= state->text_length) {
            if (state->partial_side == RE_PARTIAL_RIGHT) {
                new_position->text_pos = start_pos;
                return RE_ERROR_PARTIAL;
            }
        }

        if (start_pos >= state->slice_end)
            return RE_ERROR_FAILURE;
        break;
    case RE_OP_RANGE_IGN_REV:
        start_pos = match_many_RANGE_IGN_REV(state, test, start_pos,
          state->slice_start, FALSE);

        if (start_pos <= 0) {
            if (state->partial_side == RE_PARTIAL_LEFT) {
                new_position->text_pos = start_pos;
                return RE_ERROR_PARTIAL;
            }
        }

        if (start_pos <= state->slice_start)
            return RE_ERROR_FAILURE;
        break;
    case RE_OP_RANGE_REV:
        start_pos = match_many_RANGE_REV(state, test, start_pos,
          state->slice_start, FALSE);

        if (start_pos <= 0) {
            if (state->partial_side == RE_PARTIAL_LEFT) {
                new_position->text_pos = start_pos;
                return RE_ERROR_PARTIAL;
            }
        }

        if (start_pos <= state->slice_start)
            return RE_ERROR_FAILURE;
        break;
    case RE_OP_SEARCH_ANCHOR:
        if (state->reverse) {
            if (start_pos < state->search_anchor)
                return RE_ERROR_FAILURE;
        } else {
            if (start_pos > state->search_anchor)
                return RE_ERROR_FAILURE;
        }

        start_pos = state->search_anchor;
        break;
    case RE_OP_SET_DIFF:
    case RE_OP_SET_INTER:
    case RE_OP_SET_SYM_DIFF:
    case RE_OP_SET_UNION:
        start_pos = match_many_SET(state, test, start_pos, state->slice_end,
          FALSE);

        if (start_pos >= state->text_length) {
            if (state->partial_side == RE_PARTIAL_RIGHT) {
                new_position->text_pos = start_pos;
                return RE_ERROR_PARTIAL;
            }
        }

        if (start_pos >= state->slice_end)
            return FALSE;
        break;
    case RE_OP_SET_DIFF_IGN:
    case RE_OP_SET_INTER_IGN:
    case RE_OP_SET_SYM_DIFF_IGN:
    case RE_OP_SET_UNION_IGN:
        start_pos = match_many_SET_IGN(state, test, start_pos,
          state->slice_end, FALSE);

        if (start_pos >= state->text_length) {
            if (state->partial_side == RE_PARTIAL_RIGHT) {
                new_position->text_pos = start_pos;
                return RE_ERROR_PARTIAL;
            }
        }

        if (start_pos >= state->slice_end)
            return FALSE;
        break;
    case RE_OP_SET_DIFF_IGN_REV:
    case RE_OP_SET_INTER_IGN_REV:
    case RE_OP_SET_SYM_DIFF_IGN_REV:
    case RE_OP_SET_UNION_IGN_REV:
        start_pos = match_many_SET_IGN_REV(state, test, start_pos,
          state->slice_start, FALSE);

        if (start_pos <= 0) {
            if (state->partial_side == RE_PARTIAL_LEFT) {
                new_position->text_pos = start_pos;
                return RE_ERROR_PARTIAL;
            }
        }

        if (start_pos <= state->slice_start)
            return FALSE;
        break;
    case RE_OP_SET_DIFF_REV:
    case RE_OP_SET_INTER_REV:
    case RE_OP_SET_SYM_DIFF_REV:
    case RE_OP_SET_UNION_REV:
        start_pos = match_many_SET_REV(state, test, start_pos,
          state->slice_start, FALSE);

        if (start_pos <= 0) {
            if (state->partial_side == RE_PARTIAL_LEFT) {
                new_position->text_pos = start_pos;
                return RE_ERROR_PARTIAL;
            }
        }

        if (start_pos <= state->slice_start)
            return FALSE;
        break;
    case RE_OP_START_OF_LINE:
    {
        BOOL is_partial;

        if (state->reverse)
            start_pos = search_start_START_OF_LINE_rev(state, test, start_pos,
              &is_partial);
        else
            start_pos = search_start_START_OF_LINE(state, test, start_pos,
              &is_partial);

        if (start_pos < 0)
            return RE_ERROR_FAILURE;

        if (is_partial) {
            new_position->text_pos = start_pos;
            return RE_ERROR_PARTIAL;
        }
        break;
    }
    case RE_OP_START_OF_STRING:
    {
        BOOL is_partial;

        if (state->reverse)
            start_pos = search_start_START_OF_STRING_rev(state, test,
              start_pos, &is_partial);
        else
            start_pos = search_start_START_OF_STRING(state, test, start_pos,
              &is_partial);

        if (start_pos < 0)
            return RE_ERROR_FAILURE;

        if (is_partial) {
            new_position->text_pos = start_pos;
            return RE_ERROR_PARTIAL;
        }
        break;
    }
    case RE_OP_START_OF_WORD:
    {
        BOOL is_partial;

        if (state->reverse)
            start_pos = search_start_START_OF_WORD_rev(state, test, start_pos,
              &is_partial);
        else
            start_pos = search_start_START_OF_WORD(state, test, start_pos,
              &is_partial);

        if (start_pos < 0)
            return RE_ERROR_FAILURE;

        if (is_partial) {
            new_position->text_pos = start_pos;
            return RE_ERROR_PARTIAL;
        }
        break;
    }
    case RE_OP_STRING:
    {
        BOOL is_partial;

        start_pos = search_start_STRING(state, test, start_pos, &is_partial);
        if (start_pos < 0)
            return RE_ERROR_FAILURE;

        if (is_partial) {
            new_position->text_pos = start_pos;
            return RE_ERROR_PARTIAL;
        }
        break;
    }
    case RE_OP_STRING_FLD:
    {
        Py_ssize_t new_pos;
        BOOL is_partial;

        start_pos = search_start_STRING_FLD(state, test, start_pos, &new_pos,
          &is_partial);
        if (start_pos < 0)
            return RE_ERROR_FAILURE;

        if (is_partial) {
            new_position->text_pos = start_pos;
            return RE_ERROR_PARTIAL;
        }

        /* Can we look further ahead? */
        if (test == node) {
            if (test->next_1.node) {
                int status;

                status = try_match(state, &test->next_1, new_pos,
                  new_position);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE) {
                    ++start_pos;

                    if (start_pos >= state->slice_end) {
                        if (state->partial_side == RE_PARTIAL_RIGHT) {
                            new_position->text_pos = state->slice_start;
                            return RE_ERROR_PARTIAL;
                        }

                        return RE_ERROR_FAILURE;
                    }

                    goto again;
                }
            }

            /* It's a possible match. */
            state->match_pos = start_pos;

            if (info) {
                info->start_pos = state->text_pos;
                info->match_pos = state->match_pos;
            }

            return RE_ERROR_SUCCESS;
        }
        break;
    }
    case RE_OP_STRING_FLD_REV:
    {
        Py_ssize_t new_pos;
        BOOL is_partial;

        start_pos = search_start_STRING_FLD_REV(state, test, start_pos,
          &new_pos, &is_partial);
        if (start_pos < 0)
            return RE_ERROR_FAILURE;

        if (is_partial) {
            new_position->text_pos = start_pos;
            return RE_ERROR_PARTIAL;
        }

        /* Can we look further ahead? */
        if (test == node) {
            if (test->next_1.node) {
                int status;

                status = try_match(state, &test->next_1, new_pos,
                  new_position);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE) {
                    --start_pos;

                    if (start_pos <= state->slice_start) {
                        if (state->partial_side == RE_PARTIAL_LEFT) {
                            new_position->text_pos = state->slice_start;
                            return RE_ERROR_PARTIAL;
                        }

                        return RE_ERROR_FAILURE;
                    }

                    goto again;
                }
            }

            /* It's a possible match. */
            state->match_pos = start_pos;

            if (info) {
                info->start_pos = state->text_pos;
                info->match_pos = state->match_pos;
            }

            return RE_ERROR_SUCCESS;
        }
        break;
    }
    case RE_OP_STRING_IGN:
    {
        BOOL is_partial;

        start_pos = search_start_STRING_IGN(state, test, start_pos,
          &is_partial);
        if (start_pos < 0)
            return RE_ERROR_FAILURE;

        if (is_partial) {
            new_position->text_pos = start_pos;
            return RE_ERROR_PARTIAL;
        }
        break;
    }
    case RE_OP_STRING_IGN_REV:
    {
        BOOL is_partial;

        start_pos = search_start_STRING_IGN_REV(state, test, start_pos,
          &is_partial);
        if (start_pos < 0)
            return RE_ERROR_FAILURE;

        if (is_partial) {
            new_position->text_pos = start_pos;
            return RE_ERROR_PARTIAL;
        }
        break;
    }
    case RE_OP_STRING_REV:
    {
        BOOL is_partial;

        start_pos = search_start_STRING_REV(state, test, start_pos,
          &is_partial);
        if (start_pos < 0)
            return RE_ERROR_FAILURE;

        if (is_partial) {
            new_position->text_pos = start_pos;
            return RE_ERROR_PARTIAL;
        }
        break;
    }
    default:
        /* Don't call 'search_start' again. */
        state->pattern->do_search_start = FALSE;

        state->match_pos = start_pos;
        new_position->node = node;
        new_position->text_pos = start_pos;
        return RE_ERROR_SUCCESS;
    }

    /* Can we look further ahead? */
    if (test == node) {
        text_pos = start_pos + test->step;

        if (test->next_1.node) {
            int status;

            status = try_match(state, &test->next_1, text_pos, new_position);
            if (status == RE_ERROR_PARTIAL) {
                new_position->node = node;
                new_position->text_pos = start_pos;
                return status;
            }
            if (status < 0)
                return status;

            if (status == RE_ERROR_FAILURE) {
                if (state->reverse) {
                    --start_pos;

                    if (start_pos < state->slice_start) {
                        if (state->partial_side == RE_PARTIAL_LEFT) {
                            new_position->text_pos = state->slice_start;
                            return RE_ERROR_PARTIAL;
                        }

                        return RE_ERROR_FAILURE;
                    }
                } else {
                    ++start_pos;

                    if (start_pos > state->slice_end) {
                        if (state->partial_side == RE_PARTIAL_RIGHT) {
                            new_position->text_pos = state->slice_end;
                            return RE_ERROR_PARTIAL;
                        }

                        return RE_ERROR_FAILURE;
                    }
                }

                goto again;
            }
        }
    } else {
        new_position->node = node;
        new_position->text_pos = start_pos;
    }

    /* It's a possible match. */
    state->match_pos = start_pos;

    if (info) {
        info->start_pos = state->text_pos;
        info->match_pos = state->match_pos;
    }

    return RE_ERROR_SUCCESS;
}

/* Saves a capture group. */
Py_LOCAL_INLINE(BOOL) save_capture(RE_State* state, size_t private_index,
  size_t public_index, RE_GroupSpan span) {
    RE_GroupData* group;

    /* Capture group indexes are 1-based (excluding group 0, which is the
     * entire matched string).
     */
    group = &state->groups[public_index - 1];

    if (group->count >= group->capacity) {
        size_t new_capacity;
        RE_GroupSpan* new_captures;

        new_capacity = group->capacity * 2;

        if (new_capacity == 0)
            new_capacity = 16;

        new_captures = (RE_GroupSpan*)safe_realloc(state, group->captures,
          new_capacity * sizeof(RE_GroupSpan));
        if (!new_captures)
            return FALSE;

        group->captures = new_captures;
        group->capacity = new_capacity;
    }

    group->captures[group->count++] = span;

    return TRUE;
}

/* Unsaves a capture group. */
Py_LOCAL_INLINE(void) unsave_capture(RE_State* state, size_t private_index,
  size_t public_index) {
    RE_GroupData* group;

    /* Capture group indexes are 1-based (excluding group 0, which is the
     * entire matched string).
     */
    group = &state->groups[public_index - 1];

    if (group->count > 0)
        --group->count;
}

/* Inserts a new span in a guard list. */
Py_LOCAL_INLINE(BOOL) insert_guard_span(RE_State* state, RE_GuardList*
  guard_list, size_t index) {
    size_t n;

    if (guard_list->count >= guard_list->capacity) {
        size_t new_capacity;
        RE_GuardSpan* new_spans;

        new_capacity = guard_list->capacity * 2;

        if (new_capacity == 0)
            new_capacity = 16;

        new_spans = (RE_GuardSpan*)safe_realloc(state, guard_list->spans,
          new_capacity * sizeof(RE_GuardSpan));
        if (!new_spans)
            return FALSE;

        guard_list->capacity = new_capacity;
        guard_list->spans = new_spans;
    }

    n = guard_list->count - index;
    if (n > 0)
        memmove(guard_list->spans + index + 1, guard_list->spans + index, n *
          sizeof(RE_GuardSpan));
    ++guard_list->count;

    return TRUE;
}

/* Deletes a span in a guard list. */
Py_LOCAL_INLINE(void) delete_guard_span(RE_GuardList* guard_list, size_t index)
  {
    size_t n;

    n = guard_list->count - index - 1;
    if (n > 0)
        memmove(guard_list->spans + index, guard_list->spans + index + 1, n *
          sizeof(RE_GuardSpan));
    --guard_list->count;
}

/* Checks whether a position is guarded against further matching. */
Py_LOCAL_INLINE(BOOL) is_guarded(RE_GuardList* guard_list, Py_ssize_t text_pos)
  {
    Py_ssize_t below;
    Py_ssize_t above;
    RE_GuardSpan* spans;
    Py_ssize_t count;

    guard_list->last_text_pos = -1;

    spans = guard_list->spans;
    count = (Py_ssize_t)guard_list->count;

    if (count == 0 || text_pos < spans[0].low || text_pos > spans[count -
      1].high)
        return FALSE;

    below = -1;
    above = count;

    while (above - below > 1) {
        Py_ssize_t mid;
        RE_GuardSpan* span;

        mid = (below + above) / 2;
        span = &spans[mid];

        if (text_pos < span->low)
            above = mid;
        else if (text_pos > span->high)
            below = mid;
        else
            return span->protect;
    }

    return FALSE;
}

/* Guards a position against further matching. */
Py_LOCAL_INLINE(BOOL) guard(RE_State* state, RE_GuardList* guard_list,
  Py_ssize_t text_pos, BOOL protect) {
    Py_ssize_t below;
    Py_ssize_t above;
    RE_GuardSpan* spans;
    Py_ssize_t count;

    guard_list->last_text_pos = -1;

    spans = guard_list->spans;
    count = (Py_ssize_t)guard_list->count;

    if (count > 0 && text_pos > spans[count - 1].high) {
        below = count - 1;
        above = count;
    } else if (count > 0 && text_pos < spans[0].low) {
        below = -1;
        above = 0;
    } else {
        below = -1;
        above = count;

        while (above - below > 1) {
            Py_ssize_t mid;
            RE_GuardSpan* span;

            mid = (below + above) / 2;
            span = &spans[mid];

            if (text_pos < span->low)
                above = mid;
            else if (text_pos > span->high)
                below = mid;
            else
                return TRUE;
        }
    }

    /* Add the position to the guard list. */
    if (below >= 0 && text_pos - spans[below].high == 1 && spans[below].protect
      == protect) {
        if (above < count && spans[above].low - text_pos == 1 &&
          spans[above].protect == protect) {
            /* The new position joins 2 spans */
            spans[below].high = spans[above].high;
            delete_guard_span(guard_list, (size_t)above);
        } else {
            /* The new position is just above the 'below' span. */
            spans[below].high = text_pos;
        }
    } else if (above < count && spans[above].low - text_pos == 1 &&
      spans[above].protect == protect) {
        /* The new position is just below the 'above' span. */
        spans[above].low = text_pos;
    } else {
        /* Insert a new span. */
        if (!insert_guard_span(state, guard_list, (size_t)above))
            return FALSE;
        spans = guard_list->spans;
        spans[above].low = text_pos;
        spans[above].high = text_pos;
        spans[above].protect = protect;
    }

    return TRUE;
}

/* Guards a position against further matching for a repeat. */
Py_LOCAL_INLINE(BOOL) guard_repeat(RE_State* state, size_t index, Py_ssize_t
  text_pos, RE_STATUS_T guard_type, BOOL protect) {
    RE_GuardList* guard_list;

    /* Is a guard active here? */
    if (!(state->pattern->repeat_info[index].status & guard_type))
        return TRUE;

    /* Which guard list? */
    if (guard_type & RE_STATUS_BODY)
        guard_list = &state->repeats[index].body_guard_list;
    else
        guard_list = &state->repeats[index].tail_guard_list;

    return guard(state, guard_list, text_pos, protect);
}

/* Guards a range of positions against further matching. */
Py_LOCAL_INLINE(Py_ssize_t) guard_range(RE_State* state, RE_GuardList*
  guard_list, Py_ssize_t lo_pos, Py_ssize_t hi_pos, BOOL protect) {
    Py_ssize_t below;
    Py_ssize_t above;
    RE_GuardSpan* spans;
    Py_ssize_t count;

    guard_list->last_text_pos = -1;

    spans = guard_list->spans;
    count = (Py_ssize_t)guard_list->count;

    below = -1;
    above = count;

    while (above - below > 1) {
        Py_ssize_t mid;
        RE_GuardSpan* span;

        mid = (below + above) / 2;
        span = &spans[mid];

        if (lo_pos < span->low)
            above = mid;
        else if (lo_pos > span->high)
            below = mid;
        else
            return span->high + 1;
    }

    /* Add the range to the guard list. */
    if (below >= 0 && lo_pos - spans[below].high == 1 && spans[below].protect
      == protect) {
        if (above < count && spans[above].low - hi_pos <= 1 &&
          spans[above].protect == protect) {
            /* The new range joins the spans */
            spans[below].high = spans[above].high;
            delete_guard_span(guard_list, (size_t)above);
            spans = guard_list->spans;
        } else {
            if (above < count)
                hi_pos = min_ssize_t(hi_pos, spans[above].low - 1);

            spans[below].high = hi_pos;
        }

        lo_pos = spans[below].high + 1;
    } else if (above < count && spans[above].low - hi_pos <= 1 &&
      spans[above].protect == protect) {
        spans[above].low = lo_pos;
        lo_pos = spans[above].high + 1;
    } else {
        /* Insert a new span. */
        if (!insert_guard_span(state, guard_list, (size_t)above))
            return -1;
        spans = guard_list->spans;

        if (above < count)
            hi_pos = min_ssize_t(hi_pos, spans[above].low - 1);

        spans[above].low = lo_pos;
        spans[above].high = hi_pos;
        spans[above].protect = protect;
        lo_pos = spans[above].high + 1;
    }

    return lo_pos;
}

/* Guards a range of positions against further matching for a repeat. */
Py_LOCAL_INLINE(BOOL) guard_repeat_range(RE_State* state, size_t index,
  Py_ssize_t lo_pos, Py_ssize_t hi_pos, RE_STATUS_T guard_type, BOOL protect) {
    RE_GuardList* guard_list;

    /* Is a guard active here? */
    if (!(state->pattern->repeat_info[index].status & guard_type))
        return TRUE;

    /* Which guard list? */
    if (guard_type & RE_STATUS_BODY)
        guard_list = &state->repeats[index].body_guard_list;
    else
        guard_list = &state->repeats[index].tail_guard_list;

    while (lo_pos <= hi_pos) {
        lo_pos = guard_range(state, guard_list, lo_pos, hi_pos, protect);
        if (lo_pos < 0)
            return FALSE;
    }

    return TRUE;
}

/* Checks whether a position is guarded against further matching for a repeat.
 */
Py_LOCAL_INLINE(BOOL) is_repeat_guarded(RE_State* state, size_t index,
  Py_ssize_t text_pos, RE_STATUS_T guard_type) {
    RE_GuardList* guard_list;

    /* Is a guard active here? */
    if (!(state->pattern->repeat_info[index].status & guard_type))
        return FALSE;

    /* Which guard list? */
    if (guard_type == RE_STATUS_BODY)
        guard_list = &state->repeats[index].body_guard_list;
    else
        guard_list = &state->repeats[index].tail_guard_list;

    return is_guarded(guard_list, text_pos);
}

/* Builds a Unicode string. */
Py_LOCAL_INLINE(PyObject*) build_unicode_value(void* buffer, Py_ssize_t start,
  Py_ssize_t end, Py_ssize_t buffer_charsize) {
#if defined(PYPY_VERSION) && PY_VERSION_HEX < 0x05090000
    Py_ssize_t len;
    Py_UNICODE* codepoints;
    PyObject* result;

    len = end - start;
    codepoints = (Py_UNICODE*)re_alloc(len * Py_UNICODE_SIZE);
    if (!codepoints)
        return NULL;

    switch (buffer_charsize) {
    case 1:
    {
        Py_UCS1* from_ptr;
        Py_UCS1* end_ptr;
        Py_UCS4* to_ptr;

        from_ptr = (Py_UCS1*)buffer + start;
        end_ptr = (Py_UCS1*)buffer + end;
        to_ptr = codepoints;

        while (from_ptr < end_ptr)
            *to_ptr++ = *from_ptr++;

        break;
    }
    case 2:
    {
        Py_UCS2* from_ptr;
        Py_UCS2* end_ptr;
        Py_UCS4* to_ptr;

        from_ptr = (Py_UCS2*)buffer + start;
        end_ptr = (Py_UCS2*)buffer + end;
        to_ptr = codepoints;

        while (from_ptr < end_ptr)
            *to_ptr++ = *from_ptr++;

        break;
    }
#if Py_UNICODE_SIZE == 4
    case 4:
    {
        Py_UCS4* from_ptr;
        Py_UCS4* end_ptr;
        Py_UCS4* to_ptr;

        from_ptr = (Py_UCS4*)buffer + start;
        end_ptr = (Py_UCS4*)buffer + end;
        to_ptr = codepoints;

        while (from_ptr < end_ptr)
            *to_ptr++ = *from_ptr++;

        break;
    }
#endif
    default:
    {
        Py_UCS1* from_ptr;
        Py_UCS1* end_ptr;
        Py_UCS4* to_ptr;

        from_ptr = (Py_UCS1*)buffer + start;
        end_ptr = (Py_UCS1*)buffer + end;
        to_ptr = codepoints;

        while (from_ptr < end_ptr)
            *to_ptr++ = *from_ptr++;

        break;
    }
    }

    result = PyUnicode_FromUnicode(codepoints, len);
    re_dealloc(codepoints);

    return result;
#else
#if PY_VERSION_HEX >= 0x03030000
    Py_ssize_t len;
    int kind;

    buffer = (void*)((RE_UINT8*)buffer + start * buffer_charsize);
    len = end - start;

    switch (buffer_charsize) {
    case 1:
        kind = PyUnicode_1BYTE_KIND;
        break;
    case 2:
        kind = PyUnicode_2BYTE_KIND;
        break;
    case 4:
        kind = PyUnicode_4BYTE_KIND;
        break;
    default:
        kind = PyUnicode_1BYTE_KIND;
        break;
    }

    return PyUnicode_FromKindAndData(kind, buffer, len);
#else
    Py_ssize_t len;

    buffer = (void*)((RE_UINT8*)buffer + start * buffer_charsize);
    len = end - start;

    return PyUnicode_FromUnicode(buffer, len);
#endif
#endif
}

/* Builds a bytestring. Returns NULL if any member is too wide. */
Py_LOCAL_INLINE(PyObject*) build_bytes_value(void* buffer, Py_ssize_t start,
  Py_ssize_t end, Py_ssize_t buffer_charsize) {
    Py_ssize_t len;
    Py_UCS1* byte_buffer;
    Py_ssize_t i;
    PyObject* result;

    buffer = (void*)((RE_UINT8*)buffer + start * buffer_charsize);
    len = end - start;

    if (buffer_charsize == 1)
        return Py_BuildValue("y#", buffer, len);

    byte_buffer = re_alloc((size_t)len);
    if (!byte_buffer)
        return NULL;

    for (i = 0; i < len; i++) {
        Py_UCS2 c = ((Py_UCS2*)buffer)[i];
        if (c > 0xFF)
            goto too_wide;

        byte_buffer[i] = (Py_UCS1)c;
    }

    result = Py_BuildValue("y#", byte_buffer, len);

    re_dealloc(byte_buffer);

    return result;

too_wide:
    re_dealloc(byte_buffer);

    return NULL;
}

/* Looks for a string in a string set. */
Py_LOCAL_INLINE(int) string_set_contains(RE_State* state, PyObject* string_set,
  Py_ssize_t first, Py_ssize_t last) {
    PyObject* string;
    int status;

    if (state->is_unicode)
        string = build_unicode_value(state->text, first, last,
          state->charsize);
    else
        string = build_bytes_value(state->text, first, last, state->charsize);
    if (!string)
        return RE_ERROR_INTERNAL;

    status = PySet_Contains(string_set, string);
    Py_DECREF(string);

    return status;
}

/* Looks for a string in a string set, ignoring case. */
Py_LOCAL_INLINE(int) string_set_contains_ign(RE_State* state, PyObject*
  string_set, void* buffer, Py_ssize_t first, Py_ssize_t last, Py_ssize_t
   index, Py_ssize_t buffer_charsize) {
    Py_UCS4 (*char_at)(void* text, Py_ssize_t pos);
    void (*set_char_at)(void* text, Py_ssize_t pos, Py_UCS4 ch);
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;
    BOOL (*possible_turkic)(RE_LocaleInfo* locale_info, Py_UCS4 ch);
    Py_UCS4 codepoints[4];

    switch (buffer_charsize) {
    case 1:
        char_at = bytes1_char_at;
        set_char_at = bytes1_set_char_at;
        break;
    case 2:
        char_at = bytes2_char_at;
        set_char_at = bytes2_set_char_at;
        break;
    case 4:
        char_at = bytes4_char_at;
        set_char_at = bytes4_set_char_at;
        break;
    default:
        char_at = bytes1_char_at;
        set_char_at = bytes1_set_char_at;
        break;
    }

    encoding = state->encoding;
    locale_info = state->locale_info;
    possible_turkic = encoding->possible_turkic;

    /* Look for a possible Turkic 'I'. */
    while (index < last && !possible_turkic(locale_info, char_at(buffer,
      index)))
        ++index;

    if (index < last) {
        /* Possible Turkic 'I'. */
        int count;
        int i;

        /* Try all the alternatives to the 'I'. */
        count = encoding->all_turkic_i(locale_info, char_at(buffer, index),
          codepoints);

        for (i = 0; i < count; i++) {
            int status;

            set_char_at(buffer, index, codepoints[i]);

            /* Recurse for the remainder of the string. */
            status = string_set_contains_ign(state, string_set, buffer, first,
              last, index + 1, buffer_charsize);
            if (status != 0)
                return status;
        }

        return 0;
    } else {
        /* No Turkic 'I'. */
        PyObject* string;
        int status;

        if (state->is_unicode)
            string = build_unicode_value(buffer, first, last, buffer_charsize);
        else
            string = build_bytes_value(buffer, first, last, buffer_charsize);
        if (!string)
            return RE_ERROR_MEMORY;

        status = PySet_Contains(string_set, string);
        Py_DECREF(string);

        return status;
    }
}

/* Creates a partial string set for truncation at the left or right side. */
Py_LOCAL_INLINE(int) make_partial_string_set(RE_State* state, RE_Node* node) {
    PatternObject* pattern;
    int partial_side;
    PyObject* string_set;
    PyObject* partial_set;
    PyObject* iter = NULL;
    PyObject* item = NULL;
    PyObject* slice = NULL;

    pattern = state->pattern;
    partial_side = state->partial_side;
    if (partial_side != RE_PARTIAL_LEFT && partial_side != RE_PARTIAL_RIGHT)
        return RE_ERROR_INTERNAL;

    /* Fetch the full string set. PyList_GET_ITEM borrows a reference. */
    string_set = PyList_GET_ITEM(pattern->named_list_indexes, node->values[0]);
    if (!string_set)
        return RE_ERROR_INTERNAL;

    /* Gets the list of partial string sets. */
    if (!pattern->partial_named_lists[partial_side]) {
        size_t size;

        size = pattern->named_lists_count * sizeof(PyObject*);
        pattern->partial_named_lists[partial_side] = re_alloc(size);
        if (!pattern->partial_named_lists[partial_side])
            return RE_ERROR_INTERNAL;

        memset(pattern->partial_named_lists[partial_side], 0, size);
    }

    /* Get the partial string set. */
    partial_set = pattern->partial_named_lists[partial_side][node->values[0]];
    if (partial_set)
        return 1;

    /* Build the partial string set. */
    partial_set = PySet_New(NULL);
    if (!partial_set)
        return RE_ERROR_INTERNAL;

    iter = PyObject_GetIter(string_set);
    if (!iter)
        goto error;

    item = PyIter_Next(iter);

    while (item) {
        Py_ssize_t len;
        Py_ssize_t first;
        Py_ssize_t last;

        len = PySequence_Length(item);
        if (len == -1)
            goto error;

        first = 0;
        last = len;

        while (last - first > 1) {
            int status;

            /* Shorten the entry. */
            if (partial_side == RE_PARTIAL_LEFT)
                ++first;
            else
                --last;

            slice = PySequence_GetSlice(item, first, last);
            if (!slice)
                goto error;

            status = PySet_Add(partial_set, slice);
            Py_DECREF(slice);
            if (status < 0)
                goto error;
        }

        Py_DECREF(item);
        item = PyIter_Next(iter);
    }

    if (PyErr_Occurred())
        goto error;

    Py_DECREF(iter);

    pattern->partial_named_lists[partial_side][node->values[0]] = partial_set;

    return 1;

error:
    Py_XDECREF(item);
    Py_XDECREF(iter);
    Py_DECREF(partial_set);

    return RE_ERROR_INTERNAL;
}

/* Tries to match a string at the current position with a member of a string
 * set, forwards or backwards.
 */
Py_LOCAL_INLINE(int) string_set_match_fwdrev(RE_State* state, RE_Node* node,
  BOOL reverse) {
    Py_ssize_t min_len;
    Py_ssize_t max_len;
    Py_ssize_t text_available;
    Py_ssize_t slice_available;
    int partial_side;
    Py_ssize_t len;
    Py_ssize_t first;
    Py_ssize_t last;
    int status;
    PyObject* string_set;

    min_len = (Py_ssize_t)node->values[1];
    max_len = (Py_ssize_t)node->values[2];

    acquire_GIL(state);

    if (reverse) {
        text_available = state->text_pos;
        slice_available = state->text_pos - state->slice_start;
        partial_side = RE_PARTIAL_LEFT;
    } else {
        text_available = state->text_length - state->text_pos;
        slice_available = state->slice_end - state->text_pos;
        partial_side = RE_PARTIAL_RIGHT;
    }

    /* Get as many characters as we need for the longest possible match. */
    len = min_ssize_t(max_len, slice_available);

    if (reverse) {
        first = state->text_pos - len;
        last = state->text_pos;
    } else {
        first = state->text_pos;
        last = state->text_pos + len;
    }

    /* If we didn't get all of the characters we need, is a partial match
     * allowed?
     */
    if (len < max_len && len == text_available && state->partial_side ==
      partial_side) {
        if (len == 0) {
            /* An empty string is always a possible partial match. */
            status = RE_ERROR_PARTIAL;
            goto finished;
        }

        /* Make a set of the possible partial matches. */
        status = make_partial_string_set(state, node);
        if (status < 0)
            goto finished;

        /* Fetch the partial string set. */
        string_set =
          state->pattern->partial_named_lists[partial_side][node->values[0]];

        /* Is the text we have a partial match? */
        status = string_set_contains(state, string_set, first, last);
        if (status < 0)
            goto finished;

        if (status == 1) {
            /* Advance past the match. */
            if (reverse)
                state->text_pos -= len;
            else
                state->text_pos += len;

            status = RE_ERROR_PARTIAL;
            goto finished;
        }
    }

    /* Fetch the string set. PyList_GET_ITEM borrows a reference. */
    string_set = PyList_GET_ITEM(state->pattern->named_list_indexes,
      node->values[0]);
    if (!string_set) {
        status = RE_ERROR_INTERNAL;
        goto finished;
    }

    /* We've already looked for a partial match (if allowed), but what about a
     * complete match?
     */
    while (len >= min_len) {
        status = string_set_contains(state, string_set, first, last);

        if (status == 1) {
            /* Advance past the match. */
            if (reverse)
                state->text_pos -= len;
            else
                state->text_pos += len;

            status = 1;
            goto finished;
        }

        /* Look for a shorter match. */
        --len;
        if (reverse)
            ++first;
        else
            --last;
    }

    /* No match. */
    status = 0;

finished:
    release_GIL(state);

    return status;
}

/* Tries to match a string at the current position with a member of a string
 * set, ignoring case, forwards or backwards.
 */
Py_LOCAL_INLINE(int) string_set_match_fld_fwdrev(RE_State* state, RE_Node*
  node, BOOL reverse) {
    int (*full_case_fold)(RE_LocaleInfo* locale_info, Py_UCS4 ch, Py_UCS4*
      folded);
    Py_UCS4 (*char_at)(void* text, Py_ssize_t pos);
    Py_ssize_t folded_charsize;
    void (*set_char_at)(void* text, Py_ssize_t pos, Py_UCS4 ch);
    Py_ssize_t min_len;
    Py_ssize_t max_len;
    Py_ssize_t buf_len;
    void* folded;
    int status;
    BOOL* end_of_fold = NULL;
    Py_ssize_t text_available;
    Py_ssize_t slice_available;
    Py_ssize_t t_pos;
    Py_ssize_t f_pos;
    int step;
    int partial_side;
    Py_ssize_t len;
    Py_ssize_t consumed;
    Py_UCS4 codepoints[RE_MAX_FOLDED];
    Py_ssize_t first;
    Py_ssize_t last;
    PyObject* string_set;

    full_case_fold = state->encoding->full_case_fold;
    char_at = state->char_at;

#if PY_VERSION_HEX >= 0x03030000
    /* The folded string needs to be at least 2 bytes per character. */
    folded_charsize = max_ssize_t(state->charsize, sizeof(Py_UCS2));
#else
    /* The folded string will have the same width as the original string. */
    folded_charsize = state->charsize;
#endif

    switch (folded_charsize) {
    case 1:
        set_char_at = bytes1_set_char_at;
        break;
    case 2:
        set_char_at = bytes2_set_char_at;
        break;
    case 4:
        set_char_at = bytes4_set_char_at;
        break;
    default:
        return RE_ERROR_INTERNAL;
    }

    min_len = (Py_ssize_t)node->values[1];
    max_len = (Py_ssize_t)node->values[2];

    acquire_GIL(state);

    /* Allocate a buffer for the folded string. */
    buf_len = max_len + RE_MAX_FOLDED;
    folded = re_alloc((size_t)(buf_len * folded_charsize));
    if (!folded) {
        status = RE_ERROR_MEMORY;
        goto finished;
    }

    end_of_fold = re_alloc((size_t)buf_len * sizeof(BOOL));
    if (!end_of_fold) {
        status = RE_ERROR_MEMORY;
        goto finished;
    }

    memset(end_of_fold, 0, (size_t)buf_len * sizeof(BOOL));

    if (reverse) {
        text_available = state->text_pos;
        slice_available = state->text_pos - state->slice_start;
        t_pos = state->text_pos - 1;
        f_pos = buf_len;
        step = -1;
        partial_side = RE_PARTIAL_LEFT;
    } else {
        text_available = state->text_length - state->text_pos;
        slice_available = state->slice_end - state->text_pos;
        t_pos = state->text_pos;
        f_pos = 0;
        step = 1;
        partial_side = RE_PARTIAL_RIGHT;
    }

    /* We can stop getting characters as soon as the case-folded string is long
     * enough (each codepoint from the text can expand to more than one folded
     * codepoint).
     */
    len = 0;
    end_of_fold[len] = TRUE;

    consumed = 0;
    while (len < max_len && consumed < slice_available) {
        int count;
        int j;

        count = full_case_fold(state->locale_info, char_at(state->text, t_pos),
          codepoints);

        if (reverse)
            f_pos -= count;

        for (j = 0; j < count; j++)
            set_char_at(folded, f_pos + j, codepoints[j]);

        if (!reverse)
            f_pos += count;

        len += count;
        end_of_fold[len] = TRUE;
        ++consumed;
        t_pos += step;
    }

    if (reverse) {
        first = f_pos;
        last = buf_len;
    } else {
        first = 0;
        last = f_pos;
    }

    /* If we didn't get all of the characters we need, is a partial match
     * allowed?
     */
    if (len < max_len && len == text_available && state->partial_side ==
      partial_side) {
        if (len == 0) {
            /* An empty string is always a possible partial match. */
            status = RE_ERROR_PARTIAL;
            goto finished;
        }

        /* Make a set of the possible partial matches. */
        status = make_partial_string_set(state, node);
        if (status < 0)
            goto finished;

        /* Fetch the partial string set. */
        string_set =
          state->pattern->partial_named_lists[partial_side][node->values[0]];

        /* Is the text we have a partial match? */
        status = string_set_contains_ign(state, string_set, folded, first,
          last, first, folded_charsize);
        if (status < 0)
            goto finished;

        if (status == 1) {
            /* Advance past the match. */
            if (reverse)
                state->text_pos -= consumed;
            else
                state->text_pos += consumed;

            status = RE_ERROR_PARTIAL;
            goto finished;
        }
    }

    /* Fetch the string set. PyList_GET_ITEM borrows a reference. */
    string_set = PyList_GET_ITEM(state->pattern->named_list_indexes,
      node->values[0]);
    if (!string_set) {
        status = RE_ERROR_INTERNAL;
        goto finished;
    }

    /* We've already looked for a partial match (if allowed), but what about a
     * complete match?
     */
    while (len >= min_len) {
        if (end_of_fold[len]) {
            status = string_set_contains_ign(state, string_set, folded, first,
              last, first, folded_charsize);

            if (status == 1) {
                /* Advance past the match. */
                if (reverse)
                    state->text_pos -= consumed;
                else
                    state->text_pos += consumed;

                status = 1;
                goto finished;
            }

            --consumed;
        }

        /* Look for a shorter match. */
        --len;
        if (reverse)
            ++first;
        else
            --last;
    }

    /* No match. */
    status = 0;

finished:
    re_dealloc(end_of_fold);
    re_dealloc(folded);

    release_GIL(state);

    return status;
}

/* Tries to match a string at the current position with a member of a string
 * set, ignoring case, forwards or backwards.
 */
Py_LOCAL_INLINE(int) string_set_match_ign_fwdrev(RE_State* state, RE_Node*
  node, BOOL reverse) {
    Py_UCS4 (*simple_case_fold)(RE_LocaleInfo* locale_info, Py_UCS4 ch);
    Py_UCS4 (*char_at)(void* text, Py_ssize_t pos);
    Py_ssize_t folded_charsize;
    void (*set_char_at)(void* text, Py_ssize_t pos, Py_UCS4 ch);
    Py_ssize_t min_len;
    Py_ssize_t max_len;
    void* folded;
    int status;
    Py_ssize_t text_available;
    Py_ssize_t slice_available;
    Py_ssize_t t_pos;
    Py_ssize_t f_pos;
    int step;
    int partial_side;
    Py_ssize_t len;
    Py_ssize_t i;
    Py_ssize_t first;
    Py_ssize_t last;
    PyObject* string_set;

    simple_case_fold = state->encoding->simple_case_fold;
    char_at = state->char_at;

#if PY_VERSION_HEX >= 0x03030000
    /* The folded string needs to be at least 2 bytes per character. */
    folded_charsize = max_ssize_t(state->charsize, sizeof(Py_UCS2));
#else
    /* The folded string will have the same width as the original string. */
    folded_charsize = state->charsize;
#endif

    switch (folded_charsize) {
    case 1:
        set_char_at = bytes1_set_char_at;
        break;
    case 2:
        set_char_at = bytes2_set_char_at;
        break;
    case 4:
        set_char_at = bytes4_set_char_at;
        break;
    default:
        return RE_ERROR_INTERNAL;
    }

    min_len = (Py_ssize_t)node->values[1];
    max_len = (Py_ssize_t)node->values[2];

    acquire_GIL(state);

    /* Allocate a buffer for the folded string. */
    folded = re_alloc((size_t)(max_len * folded_charsize));
    if (!folded) {
        status = RE_ERROR_MEMORY;
        goto finished;
    }

    if (reverse) {
        text_available = state->text_pos;
        slice_available = state->text_pos - state->slice_start;
        t_pos = state->text_pos - 1;
        f_pos = max_len - 1;
        step = -1;
        partial_side = RE_PARTIAL_LEFT;
    } else {
        text_available = state->text_length - state->text_pos;
        slice_available = state->slice_end - state->text_pos;
        t_pos = state->text_pos;
        f_pos = 0;
        step = 1;
        partial_side = RE_PARTIAL_RIGHT;
    }

    /* Get as many characters as we need for the longest possible match. */
    len = min_ssize_t(max_len, slice_available);

    for (i = 0; i < len; i ++) {
        Py_UCS4 ch;

        ch = simple_case_fold(state->locale_info, char_at(state->text, t_pos));
        set_char_at(folded, f_pos, ch);
        t_pos += step;
        f_pos += step;
    }

    if (reverse) {
        first = f_pos + 1;
        last = max_len;
    } else {
        first = 0;
        last = f_pos;
    }

    /* If we didn't get all of the characters we need, is a partial match
     * allowed?
     */
    if (len < max_len && len == text_available && state->partial_side ==
      partial_side) {
        if (len == 0) {
            /* An empty string is always a possible partial match. */
            status = RE_ERROR_PARTIAL;
            goto finished;
        }

        /* Make a set of the possible partial matches. */
        status = make_partial_string_set(state, node);
        if (status < 0)
            goto finished;

        /* Fetch the partial string set. */
        string_set =
          state->pattern->partial_named_lists[partial_side][node->values[0]];

        /* Is the text we have a partial match? */
        status = string_set_contains_ign(state, string_set, folded, first,
          last, first, folded_charsize);
        if (status < 0)
            goto finished;

        if (status == 1) {
            /* Advance past the match. */
            if (reverse)
                state->text_pos -= len;
            else
                state->text_pos += len;

            status = RE_ERROR_PARTIAL;
            goto finished;
        }
    }

    /* Fetch the string set. PyList_GET_ITEM borrows a reference. */
    string_set = PyList_GET_ITEM(state->pattern->named_list_indexes,
      node->values[0]);
    if (!string_set) {
        status = RE_ERROR_INTERNAL;
        goto finished;
    }

    /* We've already looked for a partial match (if allowed), but what about a
     * complete match?
     */
    while (len >= min_len) {
        status = string_set_contains_ign(state, string_set, folded, first,
          last, first, folded_charsize);

        if (status == 1) {
            /* Advance past the match. */
            if (reverse)
                state->text_pos -= len;
            else
                state->text_pos += len;

            status = 1;
            goto finished;
        }

        /* Look for a shorter match. */
        --len;
        if (reverse)
            ++first;
        else
            --last;
    }

    /* No match. */
    status = 0;

finished:
    re_dealloc(folded);

    release_GIL(state);

    return status;
}

Py_LOCAL_INLINE(size_t) total_errors(size_t* fuzzy_counts) {
    return fuzzy_counts[RE_FUZZY_DEL] + fuzzy_counts[RE_FUZZY_INS] +
      fuzzy_counts[RE_FUZZY_SUB];
}

Py_LOCAL_INLINE(size_t) total_cost(size_t* fuzzy_counts, RE_Node* fuzzy_node) {
    RE_CODE* values;

    values = fuzzy_node->values;

    return fuzzy_counts[RE_FUZZY_DEL] * values[RE_FUZZY_VAL_DEL_COST] +
      fuzzy_counts[RE_FUZZY_INS] * values[RE_FUZZY_VAL_INS_COST] +
      fuzzy_counts[RE_FUZZY_SUB] * values[RE_FUZZY_VAL_SUB_COST];
}

/* Checks whether any additional fuzzy error is permitted. */
Py_LOCAL_INLINE(BOOL) any_error_permitted(RE_State* state) {
    size_t* fuzzy_counts;
    RE_CODE* values;
    size_t error_count;
    size_t cost;

    fuzzy_counts = state->fuzzy_counts;
    values = state->fuzzy_node->values;
    error_count = total_errors(fuzzy_counts);
    cost = total_cost(fuzzy_counts, state->fuzzy_node);

    return cost <= values[RE_FUZZY_VAL_MAX_COST] && error_count <
      state->max_errors;
}

/* Checks whether this additional fuzzy error is permitted. */
Py_LOCAL_INLINE(BOOL) this_error_permitted(RE_State* state, RE_UINT8
  fuzzy_type) {
    size_t* fuzzy_counts;
    RE_CODE* values;
    size_t error_count;
    size_t cost;

    fuzzy_counts = state->fuzzy_counts;
    values = state->fuzzy_node->values;
    error_count = total_errors(fuzzy_counts);
    cost = total_cost(fuzzy_counts, state->fuzzy_node);

    return fuzzy_counts[fuzzy_type] < values[RE_FUZZY_VAL_MAX_BASE +
      fuzzy_type] && error_count < values[RE_FUZZY_VAL_MAX_ERR] && error_count
      < state->max_errors && cost + values[RE_FUZZY_VAL_COST_BASE + fuzzy_type]
      <= values[RE_FUZZY_VAL_MAX_COST];
}

/* Checks whether an insertion is permitted. */
Py_LOCAL_INLINE(BOOL) insertion_permitted(RE_State* state, RE_Node* fuzzy_node,
  size_t* fuzzy_counts) {

    RE_CODE* values;
    size_t error_count;
    size_t cost;

    values = fuzzy_node->values;
    error_count = total_errors(fuzzy_counts);
    cost = total_cost(fuzzy_counts, fuzzy_node);

    return fuzzy_counts[RE_FUZZY_INS] < values[RE_FUZZY_VAL_MAX_INS] &&
      error_count < values[RE_FUZZY_VAL_MAX_ERR] && cost +
      values[RE_FUZZY_VAL_INS_COST] <= values[RE_FUZZY_VAL_MAX_COST] &&
      error_count < state->max_errors;
}

/* Checks whether the errors are within the fuzzy constraints. */
Py_LOCAL_INLINE(BOOL) fuzzy_within_constraints(size_t* fuzzy_counts, RE_Node*
  fuzzy_node, size_t max_errors) {
    RE_CODE* values;
    size_t del_count;
    size_t ins_count;
    size_t sub_count;
    size_t err_count;

    values = fuzzy_node->values;
    del_count = fuzzy_counts[RE_FUZZY_DEL];
    ins_count = fuzzy_counts[RE_FUZZY_INS];
    sub_count = fuzzy_counts[RE_FUZZY_SUB];

    if (del_count < values[RE_FUZZY_VAL_MIN_DEL] || del_count >
      values[RE_FUZZY_VAL_MAX_DEL])
        return FALSE;
    if (ins_count < values[RE_FUZZY_VAL_MIN_INS] || ins_count >
      values[RE_FUZZY_VAL_MAX_INS])
        return FALSE;
    if (sub_count < values[RE_FUZZY_VAL_MIN_SUB] || sub_count >
      values[RE_FUZZY_VAL_MAX_SUB])
        return FALSE;

    err_count = del_count + ins_count + sub_count;

    if (err_count < values[RE_FUZZY_VAL_MIN_ERR] || err_count >
      values[RE_FUZZY_VAL_MAX_ERR])
        return FALSE;

    if (err_count > max_errors)
        return FALSE;

    return total_cost(fuzzy_counts, fuzzy_node) <=
      values[RE_FUZZY_VAL_MAX_COST];
}

/* Checks whether we've reached the end of the text during a fuzzy partial
 * match.
 */
Py_LOCAL_INLINE(int) check_fuzzy_partial(RE_State* state, Py_ssize_t text_pos)
  {
    switch (state->partial_side) {
    case RE_PARTIAL_LEFT:
        if (text_pos < 0)
            return RE_ERROR_PARTIAL;
        break;
    case RE_PARTIAL_RIGHT:
        if (text_pos > state->text_length)
            return RE_ERROR_PARTIAL;
        break;
    }

    return RE_ERROR_FAILURE;
}

/* Records a change in a fuzzy change. */
Py_LOCAL_INLINE(BOOL) record_fuzzy(RE_State* state, RE_UINT8 fuzzy_type,
  Py_ssize_t text_pos) {
    RE_FuzzyChangesList* change_list;
    RE_FuzzyChange* change;

    change_list = &state->fuzzy_changes;

    if (change_list->count >= change_list->capacity) {
        size_t new_capacity;
        RE_FuzzyChange* new_items;

        new_capacity = change_list->capacity * 2;

        if (new_capacity == 0)
            new_capacity = 64;

        new_items = (RE_FuzzyChange*)safe_realloc(state, change_list->items,
          new_capacity * sizeof(RE_FuzzyChange));
        if (!new_items)
            return FALSE;

        change_list->items = new_items;
        change_list->capacity = new_capacity;
    }

    change = &change_list->items[change_list->count++];
    change->type = fuzzy_type;
    change->pos = text_pos;

    return TRUE;
}

/* "Unrecords" a change in a fuzzy change. */
Py_LOCAL_INLINE(void) unrecord_fuzzy(RE_State* state) {
    --state->fuzzy_changes.count;
}

/* Makes a list of lists of fuzzy changes. */
Py_LOCAL_INLINE(void) make_fuzzy_changes_list(RE_FuzzyChangesList*
  changes_list) {
    changes_list->capacity = 0;
    changes_list->count = 0;
    changes_list->items = NULL;
}

/* Makes a list of lists of fuzzy changes. */
Py_LOCAL_INLINE(void) make_best_changes_list(RE_BestChangesList*
  best_changes_list) {
    best_changes_list->capacity = 0;
    best_changes_list->count = 0;
    best_changes_list->lists = NULL;
}

/* Clears a list of lists of fuzzy changes. */
Py_LOCAL_INLINE(void) clear_best_fuzzy_changes(RE_State* state,
  RE_BestChangesList* best_changes_list) {
    size_t i;

    for (i = 0; i < best_changes_list->count; i++) {
        RE_FuzzyChangesList* list;

        list = &best_changes_list->lists[i];
        list->capacity = 0;
        list->count = 0;
        safe_dealloc(state, list->items);
        list->items = NULL;
    }

    best_changes_list->count = 0;
}

/* Destroys a list of lists of fuzzy changes. */
Py_LOCAL_INLINE(void) destroy_best_changes_list(RE_State* state,
  RE_BestChangesList* best_changes_list) {
    clear_best_fuzzy_changes(state, best_changes_list);
    safe_dealloc(state, best_changes_list->lists);
}

/* Adds a list of fuzzy changes to a list of best fuzzy changes. */
Py_LOCAL_INLINE(BOOL) add_best_fuzzy_changes(RE_State* state,
  RE_BestChangesList* best_changes_list) {
    size_t size;
    RE_FuzzyChange* items;
    RE_FuzzyChangesList* changes;

    if (best_changes_list->count >= best_changes_list->capacity) {
        size_t new_capacity;
        RE_FuzzyChangesList* new_lists;

        new_capacity = best_changes_list->capacity * 2;

        if (new_capacity == 0)
            new_capacity = 64;

        new_lists = (RE_FuzzyChangesList*)safe_realloc(state,
          best_changes_list->lists, new_capacity *
          sizeof(RE_FuzzyChangesList));
        if (!new_lists)
            return FALSE;

        best_changes_list->lists = new_lists;
        best_changes_list->capacity = new_capacity;
    }

    size = (size_t)state->fuzzy_changes.count * sizeof(RE_FuzzyChange);
    items = (RE_FuzzyChange*)safe_alloc(state, size);
    if (!items)
        return FALSE;
    Py_MEMCPY(items, state->fuzzy_changes.items, size);

    changes = &best_changes_list->lists[best_changes_list->count++];
    changes->capacity = state->fuzzy_changes.count;
    changes->count = state->fuzzy_changes.count;
    changes->items = items;

    return TRUE;
}

/* Initialises a list of fuzzy changes. */
Py_LOCAL_INLINE(void) make_changes_list(RE_State* state, RE_FuzzyChangesList*
  best_changes_list) {
    best_changes_list->capacity = 0;
    best_changes_list->count = 0;
    best_changes_list->items = NULL;
}

/* Finitialises a list of fuzzy changes. */
Py_LOCAL_INLINE(void) destroy_changes_list(RE_State* state,
  RE_FuzzyChangesList* best_changes_list) {
    safe_dealloc(state, best_changes_list->items);
}

/* Saves a list of fuzzy changes. */
Py_LOCAL_INLINE(BOOL) save_fuzzy_changes(RE_State* state, RE_FuzzyChangesList*
  best_changes_list) {
    if (state->fuzzy_changes.count > best_changes_list->capacity) {
        size_t new_capacity;
        RE_FuzzyChange* new_items;

        new_capacity = best_changes_list->capacity;

        if (new_capacity == 0)
            new_capacity = 64;

        while (state->fuzzy_changes.count > new_capacity)
            new_capacity *= 2;

        new_items = (RE_FuzzyChange*)safe_realloc(state,
          best_changes_list->items, new_capacity * sizeof(RE_FuzzyChange));
        if (!new_items)
            return FALSE;

        best_changes_list->items = new_items;
        best_changes_list->capacity = new_capacity;
    }

    Py_MEMCPY(best_changes_list->items, state->fuzzy_changes.items,
      (size_t)state->fuzzy_changes.count * sizeof(RE_FuzzyChange));
    best_changes_list->count = state->fuzzy_changes.count;

    return TRUE;
}

/* Restores a list of fuzzy changes. */
Py_LOCAL_INLINE(void) restore_fuzzy_changes(RE_State* state,
  RE_FuzzyChangesList* best_changes_list) {
    Py_MEMCPY(state->fuzzy_changes.items, best_changes_list->items,
      (size_t)best_changes_list->count * sizeof(RE_FuzzyChange));
    state->fuzzy_changes.count = best_changes_list->count;
}

/* Checks a fuzzy match of an item. */
Py_LOCAL_INLINE(int) next_fuzzy_match_item(RE_State* state, RE_FuzzyData* data,
  BOOL is_string, RE_INT8 step) {
    Py_ssize_t new_pos;

    if (this_error_permitted(state, data->fuzzy_type)) {
        switch (data->fuzzy_type) {
        case RE_FUZZY_DEL:
            /* Could a character at text_pos have been deleted? */
            if (step == 0)
                return RE_ERROR_FAILURE;

            if (is_string)
                data->new_string_pos += step;
            else
                data->new_node = data->new_node->next_1.node;
            return RE_ERROR_SUCCESS;
        case RE_FUZZY_INS:
            /* Could the character at text_pos have been inserted? */
            if (!data->permit_insertion)
                return RE_ERROR_FAILURE;

            if (step == 0)
                new_pos = data->new_text_pos + data->step;
            else
                new_pos = data->new_text_pos + step;
            if (state->slice_start <= new_pos && new_pos <= state->slice_end) {
                data->new_text_pos = new_pos;
                return RE_ERROR_SUCCESS;
            }

            return check_fuzzy_partial(state, new_pos);
        case RE_FUZZY_SUB:
            /* Could the character at text_pos have been substituted? */
            if (step == 0)
                return RE_ERROR_FAILURE;

            new_pos = data->new_text_pos + step;
            if (state->slice_start <= new_pos && new_pos <= state->slice_end) {
                data->new_text_pos = new_pos;
                if (is_string)
                    data->new_string_pos += step;
                else
                    data->new_node = data->new_node->next_1.node;
                return RE_ERROR_SUCCESS;
            }

            return check_fuzzy_partial(state, new_pos);
        }
    }

    return RE_ERROR_FAILURE;
}

/* Tries a fuzzy match of an item of width 0 or 1. */
Py_LOCAL_INLINE(int) fuzzy_match_item(RE_State* state, BOOL search, Py_ssize_t*
  text_pos, RE_Node** node, RE_INT8 step) {
    size_t* fuzzy_counts;
    RE_FuzzyData data;

    fuzzy_counts = state->fuzzy_counts;

    if (!any_error_permitted(state))
        return RE_ERROR_FAILURE;

    data.new_text_pos = *text_pos;
    data.new_node = *node;

    if (step == 0) {
        if (data.new_node->status & RE_STATUS_REVERSE) {
            data.step = -1;
            data.limit = state->slice_start;
        } else {
            data.step = 1;
            data.limit = state->slice_end;
        }
    } else
        data.step = step;

    /* Permit insertion except initially when searching (it's better just to
     * start searching one character later).
     */
    data.permit_insertion = !search || data.new_text_pos !=
      state->search_anchor;

    for (data.fuzzy_type = 0; data.fuzzy_type < RE_FUZZY_COUNT;
      data.fuzzy_type++) {
        int status;

        status = next_fuzzy_match_item(state, &data, FALSE, step);
        if (status < 0)
            return status;

        if (status == RE_ERROR_SUCCESS)
            goto found;
    }

    return RE_ERROR_FAILURE;

found:
    if (!push_pointer(state, &state->bstack, *node))
        return RE_ERROR_MEMORY;
    if (!push_int8(state, &state->bstack, step))
        return RE_ERROR_MEMORY;
    if (!push_ssize(state, &state->bstack, *text_pos))
        return RE_ERROR_MEMORY;
    if (!push_uint8(state, &state->bstack, data.fuzzy_type))
        return RE_ERROR_MEMORY;
    if (!push_uint8(state, &state->bstack, (*node)->op))
        return RE_ERROR_MEMORY;

    /* bstack: node step text_pos fuzzy_type op */

    if (!record_fuzzy(state, data.fuzzy_type, data.new_text_pos - data.step))
        return RE_ERROR_MEMORY;

    ++fuzzy_counts[data.fuzzy_type];
    ++state->capture_change;

    *text_pos = data.new_text_pos;
    *node = data.new_node;

    return RE_ERROR_SUCCESS;
}

/* Retries a fuzzy match of a item of width 0 or 1. */
Py_LOCAL_INLINE(int) retry_fuzzy_match_item(RE_State* state, RE_UINT8 op, BOOL
  search, Py_ssize_t* text_pos, RE_Node** node, BOOL advance) {
    size_t* fuzzy_counts;
    Py_ssize_t curr_text_pos;
    RE_FuzzyData data;
    RE_INT8 step;
    RE_Node* curr_node;

    fuzzy_counts = state->fuzzy_counts;

    unrecord_fuzzy(state);

    /* bstack: node step text_pos fuzzy_type */

    if (!pop_uint8(state, &state->bstack, &data.fuzzy_type))
        return RE_ERROR_MEMORY;
    if (!pop_ssize(state, &state->bstack, &curr_text_pos))
        return RE_ERROR_MEMORY;
    if (!pop_int8(state, &state->bstack, &step))
        return RE_ERROR_MEMORY;
    if (!pop_pointer(state, &state->bstack, (void*)&curr_node))
        return RE_ERROR_MEMORY;

    data.new_text_pos = curr_text_pos;
    data.new_node = curr_node;
    data.step = step;

    /* bstack: - */

    if (data.fuzzy_type >= 0)
        --fuzzy_counts[data.fuzzy_type];

    /* Permit insertion except initially when searching (it's better just to
     * start searching one character later).
     */
    data.permit_insertion = !search || data.new_text_pos !=
      state->search_anchor;

    step = advance ? data.step : 0;

    for (++data.fuzzy_type; data.fuzzy_type < RE_FUZZY_COUNT;
      data.fuzzy_type++) {
        int status;

        status = next_fuzzy_match_item(state, &data, FALSE, step);
        if (status < 0)
            return status;

        if (status == RE_ERROR_SUCCESS)
            goto found;
    }

    return RE_ERROR_FAILURE;

found:
    if (!push_pointer(state, &state->bstack, curr_node))
        return RE_ERROR_MEMORY;
    if (!push_int8(state, &state->bstack, step))
        return RE_ERROR_MEMORY;
    if (!push_ssize(state, &state->bstack, curr_text_pos))
        return RE_ERROR_MEMORY;
    if (!push_uint8(state, &state->bstack, data.fuzzy_type))
        return RE_ERROR_MEMORY;
    if (!push_uint8(state, &state->bstack, op))
        return RE_ERROR_MEMORY;

    /* bstack: node step text_pos fuzzy_type op */

    if (!record_fuzzy(state, data.fuzzy_type, data.new_text_pos - data.step))
        return RE_ERROR_MEMORY;

    ++fuzzy_counts[data.fuzzy_type];
    ++state->capture_change;

    *text_pos = data.new_text_pos;
    *node = data.new_node;

    return RE_ERROR_SUCCESS;
}

/* Tries a fuzzy insertion of characters, initially 0, after a string. */
Py_LOCAL_INLINE(int) fuzzy_insert(RE_State* state, Py_ssize_t text_pos, int
  step, RE_Node* node) {
    Py_ssize_t limit;

    limit = step > 0 ? state->slice_end : state->slice_start;

    if (text_pos == limit || !insertion_permitted(state, state->fuzzy_node,
      state->fuzzy_counts))
        return RE_ERROR_SUCCESS;

    if (!push_int8(state, &state->bstack, (RE_INT8)step))
        return RE_ERROR_MEMORY;
    if (!push_ssize(state, &state->bstack, text_pos))
        return RE_ERROR_MEMORY;
    if (!push_ssize(state, &state->bstack, 0))
        return RE_ERROR_MEMORY;
    if (!push_pointer(state, &state->bstack, node))
        return RE_ERROR_MEMORY;
    if (!push_uint8(state, &state->bstack, RE_OP_FUZZY_INSERT))
        return RE_ERROR_MEMORY;

    /* bstack: step text_pos count node FUZZY_INSERT */

    return RE_ERROR_SUCCESS;
}

/* Retries a fuzzy insertion of characters after a string. */
Py_LOCAL_INLINE(int) retry_fuzzy_insert(RE_State* state, Py_ssize_t *text_pos,
  RE_Node** node) {
    RE_Node* curr_node;
    Py_ssize_t count;
    Py_ssize_t curr_text_pos;
    RE_INT8 step;
    Py_ssize_t limit;

    /* bstack: step text_pos count node */

    if (!pop_pointer(state, &state->bstack, (void*)&curr_node))
        return RE_ERROR_MEMORY;
    if (!pop_ssize(state, &state->bstack, &count))
        return RE_ERROR_MEMORY;
    if (!pop_ssize(state, &state->bstack, &curr_text_pos))
        return RE_ERROR_MEMORY;
    if (!pop_int8(state, &state->bstack, &step))
        return RE_ERROR_MEMORY;

    limit = step > 0 ? state->slice_end : state->slice_start;

    if (curr_text_pos == limit || !insertion_permitted(state,
      state->fuzzy_node, state->fuzzy_counts)) {
        while (count > 0) {
            unrecord_fuzzy(state);
            --state->fuzzy_counts[RE_FUZZY_INS];
            --count;
        }

        return RE_ERROR_FAILURE;
    }

    curr_text_pos += step;
    ++count;

    if (!push_int8(state, &state->bstack, step))
        return RE_ERROR_MEMORY;
    if (!push_ssize(state, &state->bstack, curr_text_pos))
        return RE_ERROR_MEMORY;
    if (!push_ssize(state, &state->bstack, count))
        return RE_ERROR_MEMORY;
    if (!push_pointer(state, &state->bstack, curr_node))
        return RE_ERROR_MEMORY;
    if (!push_uint8(state, &state->bstack, RE_OP_FUZZY_INSERT))
        return RE_ERROR_MEMORY;

    /* bstack: step text_pos count node FUZZY_INSERT */

    if (!record_fuzzy(state, RE_FUZZY_INS, curr_text_pos - step))
        return RE_ERROR_MEMORY;

    ++state->fuzzy_counts[RE_FUZZY_INS];
    ++state->capture_change;

    *text_pos = curr_text_pos;
    *node = curr_node;

    return RE_ERROR_SUCCESS;
}

/* Tries a fuzzy match of a string. */
Py_LOCAL_INLINE(int) fuzzy_match_string(RE_State* state, BOOL search,
  Py_ssize_t* text_pos, RE_Node* node, Py_ssize_t* string_pos, RE_INT8 step) {
    size_t* fuzzy_counts;
    RE_FuzzyData data;

    fuzzy_counts = state->fuzzy_counts;

    if (!any_error_permitted(state))
        return RE_ERROR_FAILURE;

    data.new_text_pos = *text_pos;
    data.new_string_pos = *string_pos;
    data.step = step;

    /* Permit insertion except initially when searching (it's better just to
     * start searching one character later).
     */
    data.permit_insertion = !search || data.new_text_pos !=
      state->search_anchor;

    for (data.fuzzy_type = 0; data.fuzzy_type < RE_FUZZY_COUNT;
      data.fuzzy_type++) {
        int status;

        status = next_fuzzy_match_item(state, &data, TRUE, data.step);
        if (status < 0)
            return status;

        if (status == RE_ERROR_SUCCESS)
            goto found;
    }

    return RE_ERROR_FAILURE;

found:
    if (!push_pointer(state, &state->bstack, node))
        return RE_ERROR_MEMORY;
    if (!push_int8(state, &state->bstack, step))
        return RE_ERROR_MEMORY;
    if (!push_ssize(state, &state->bstack, *string_pos))
        return RE_ERROR_MEMORY;
    if (!push_ssize(state, &state->bstack, *text_pos))
        return RE_ERROR_MEMORY;
    if (!push_uint8(state, &state->bstack, data.fuzzy_type))
        return RE_ERROR_MEMORY;
    if (!push_uint8(state, &state->bstack, node->op))
        return RE_ERROR_MEMORY;

    /* bstack: node step string_pos text_pos fuzzy_type op */

    if (!record_fuzzy(state, data.fuzzy_type, data.new_text_pos - data.step))
        return RE_ERROR_MEMORY;

    ++fuzzy_counts[data.fuzzy_type];
    ++state->capture_change;

    *text_pos = data.new_text_pos;
    *string_pos = data.new_string_pos;

    return RE_ERROR_SUCCESS;
}

/* Retries a fuzzy match of a string. */
Py_LOCAL_INLINE(int) retry_fuzzy_match_string(RE_State* state, RE_UINT8 op,
  BOOL search, Py_ssize_t* text_pos, RE_Node** node, Py_ssize_t* string_pos) {
    size_t* fuzzy_counts;
    RE_FuzzyData data;
    Py_ssize_t curr_text_pos;
    Py_ssize_t curr_string_pos;
    RE_Node* new_node;

    fuzzy_counts = state->fuzzy_counts;

    unrecord_fuzzy(state);

    /* bstack: node step string_pos text_pos fuzzy_type */

    if (!pop_uint8(state, &state->bstack, &data.fuzzy_type))
        return RE_ERROR_MEMORY;
    if (!pop_ssize(state, &state->bstack, &curr_text_pos))
        return RE_ERROR_MEMORY;
    if (!pop_ssize(state, &state->bstack, &curr_string_pos))
        return RE_ERROR_MEMORY;
    if (!pop_int8(state, &state->bstack, &data.step))
        return RE_ERROR_MEMORY;
    if (!pop_pointer(state, &state->bstack, (void*)&new_node))
        return RE_ERROR_MEMORY;

    data.new_text_pos = curr_text_pos;
    data.new_string_pos = curr_string_pos;

    --fuzzy_counts[data.fuzzy_type];

    /* Permit insertion except initially when searching (it's better just to
     * start searching one character later).
     */
    data.permit_insertion = !search || data.new_text_pos !=
      state->search_anchor;

    for (++data.fuzzy_type; data.fuzzy_type < RE_FUZZY_COUNT;
      data.fuzzy_type++) {
        int status;

        status = next_fuzzy_match_item(state, &data, TRUE, data.step);
        if (status < 0)
            return status;

        if (status == RE_ERROR_SUCCESS)
            goto found;
    }

    return RE_ERROR_FAILURE;

found:
    if (!push_pointer(state, &state->bstack, new_node))
        return RE_ERROR_MEMORY;
    if (!push_int8(state, &state->bstack, data.step))
        return RE_ERROR_MEMORY;
    if (!push_ssize(state, &state->bstack, curr_string_pos))
        return RE_ERROR_MEMORY;
    if (!push_ssize(state, &state->bstack, curr_text_pos))
        return RE_ERROR_MEMORY;
    if (!push_uint8(state, &state->bstack, data.fuzzy_type))
        return RE_ERROR_MEMORY;
    if (!push_uint8(state, &state->bstack, op))
        return RE_ERROR_MEMORY;

    if (!record_fuzzy(state, data.fuzzy_type, data.new_text_pos - data.step))
        return RE_ERROR_MEMORY;

    /* bstack: node step string_pos text_pos fuzzy_type op */

    ++fuzzy_counts[data.fuzzy_type];
    ++state->capture_change;

    *text_pos = data.new_text_pos;
    *node = new_node;
    *string_pos = data.new_string_pos;

    return RE_ERROR_SUCCESS;
}

/* Checks a fuzzy match of a atring. */
Py_LOCAL_INLINE(int) next_fuzzy_match_string_fld(RE_State* state, RE_FuzzyData*
  data) {
    int new_pos;

    if (this_error_permitted(state, data->fuzzy_type)) {
        switch (data->fuzzy_type) {
        case RE_FUZZY_DEL:
            /* Could a character at text_pos have been deleted? */
            data->new_string_pos += data->step;
            return RE_ERROR_SUCCESS;
        case RE_FUZZY_INS:
            /* Could the character at text_pos have been inserted? */
            if (!data->permit_insertion)
                return RE_ERROR_FAILURE;

            new_pos = data->new_folded_pos + data->step;
            if (0 <= new_pos && new_pos <= data->folded_len) {
                data->new_folded_pos = new_pos;
                return RE_ERROR_SUCCESS;
            }

            return check_fuzzy_partial(state, new_pos);
        case RE_FUZZY_SUB:
            /* Could the character at text_pos have been substituted? */
            new_pos = data->new_folded_pos + data->step;
            if (0 <= new_pos && new_pos <= data->folded_len) {
                data->new_folded_pos = new_pos;
                data->new_string_pos += data->step;
                return RE_ERROR_SUCCESS;
            }

            return check_fuzzy_partial(state, new_pos);
        }
    }

    return RE_ERROR_FAILURE;
}

/* Tries a fuzzy match of a string, ignoring case. */
Py_LOCAL_INLINE(int) fuzzy_match_string_fld(RE_State* state, BOOL search,
  Py_ssize_t* text_pos, RE_Node* node, Py_ssize_t* string_pos, int* folded_pos,
  int folded_len, RE_INT8 step) {
    size_t* fuzzy_counts;
    Py_ssize_t new_text_pos;
    RE_FuzzyData data;

    fuzzy_counts = state->fuzzy_counts;

    if (!any_error_permitted(state))
        return RE_ERROR_FAILURE;

    new_text_pos = *text_pos;
    data.new_string_pos = *string_pos;
    data.new_folded_pos = *folded_pos;
    data.folded_len = folded_len;
    data.step = step;

    /* Permit insertion except initially when searching (it's better just to
     * start searching one character later).
     */
    data.permit_insertion = !search || new_text_pos != state->search_anchor;
    if (step > 0) {
        if (data.new_folded_pos != 0)
            data.permit_insertion = RE_ERROR_SUCCESS;
    } else {
        if (data.new_folded_pos != folded_len)
            data.permit_insertion = RE_ERROR_SUCCESS;
    }

    for (data.fuzzy_type = 0; data.fuzzy_type < RE_FUZZY_COUNT;
      data.fuzzy_type++) {
        int status;

        status = next_fuzzy_match_string_fld(state, &data);
        if (status < 0)
            return status;

        if (status == RE_ERROR_SUCCESS)
            goto found;
    }

    return RE_ERROR_FAILURE;

found:
    if (!push_pointer(state, &state->bstack, node))
        return RE_ERROR_MEMORY;
    if (!push_int8(state, &state->bstack, step))
        return RE_ERROR_MEMORY;
    if (!push_ssize(state, &state->bstack, *string_pos))
        return RE_ERROR_MEMORY;
    if (!push_int(state, &state->bstack, *folded_pos))
        return RE_ERROR_MEMORY;
    if (!push_int(state, &state->bstack, folded_len))
        return RE_ERROR_MEMORY;
    if (!push_ssize(state, &state->bstack, new_text_pos))
        return RE_ERROR_MEMORY;
    if (!push_uint8(state, &state->bstack, data.fuzzy_type))
        return RE_ERROR_MEMORY;
    if (!push_uint8(state, &state->bstack, node->op))
        return RE_ERROR_MEMORY;

    /* bstack: node step string_pos folded_pos folded_len text_pos fuzzy_type
     * op
     */

    if (!record_fuzzy(state, data.fuzzy_type, data.new_text_pos - data.step))
        return RE_ERROR_MEMORY;

    ++fuzzy_counts[data.fuzzy_type];
    ++state->capture_change;

    *text_pos = new_text_pos;
    *string_pos = data.new_string_pos;
    *folded_pos = data.new_folded_pos;

    return RE_ERROR_SUCCESS;
}

/* Retries a fuzzy match of a string, ignoring case. */
Py_LOCAL_INLINE(int) retry_fuzzy_match_string_fld(RE_State* state, RE_UINT8 op,
  BOOL search, Py_ssize_t* text_pos, RE_Node** node, Py_ssize_t* string_pos,
  int* folded_pos) {
    size_t* fuzzy_counts;
    RE_FuzzyData data;
    Py_ssize_t new_text_pos;
    int curr_folded_pos;
    Py_ssize_t curr_string_pos;
    RE_Node* new_node;

    fuzzy_counts = state->fuzzy_counts;

    unrecord_fuzzy(state);

    /* bstack: node step string_pos folded_pos folded_len text_pos fuzzy_type
     */

    if (!pop_uint8(state, &state->bstack, &data.fuzzy_type))
        return RE_ERROR_MEMORY;
    if (!pop_ssize(state, &state->bstack, &new_text_pos))
        return RE_ERROR_MEMORY;
    if (!pop_int(state, &state->bstack, &data.folded_len))
        return RE_ERROR_MEMORY;
    if (!pop_int(state, &state->bstack, &curr_folded_pos))
        return RE_ERROR_MEMORY;
    if (!pop_ssize(state, &state->bstack, &curr_string_pos))
        return RE_ERROR_MEMORY;
    if (!pop_int8(state, &state->bstack, &data.step))
        return RE_ERROR_MEMORY;
    if (!pop_pointer(state, &state->bstack, (void*)&new_node))
        return RE_ERROR_MEMORY;

    data.new_string_pos = curr_string_pos;
    data.new_folded_pos = curr_folded_pos;

    --fuzzy_counts[data.fuzzy_type];

    /* Permit insertion except initially when searching (it's better just to
     * start searching one character later).
     */
    data.permit_insertion = !search || new_text_pos != state->search_anchor;
    if (data.step > 0) {
        if (data.new_folded_pos != 0)
            data.permit_insertion = RE_ERROR_SUCCESS;
    } else {
        if (data.new_folded_pos != data.folded_len)
            data.permit_insertion = RE_ERROR_SUCCESS;
    }

    for (++data.fuzzy_type; data.fuzzy_type < RE_FUZZY_COUNT;
      data.fuzzy_type++) {
        int status;

        status = next_fuzzy_match_string_fld(state, &data);
        if (status < 0)
            return status;

        if (status == RE_ERROR_SUCCESS)
            goto found;
    }

    return RE_ERROR_FAILURE;

found:
    if (!push_pointer(state, &state->bstack, new_node))
        return RE_ERROR_MEMORY;
    if (!push_int8(state, &state->bstack, data.step))
        return RE_ERROR_MEMORY;
    if (!push_ssize(state, &state->bstack, curr_string_pos))
        return RE_ERROR_MEMORY;
    if (!push_int(state, &state->bstack, curr_folded_pos))
        return RE_ERROR_MEMORY;
    if (!push_int(state, &state->bstack, data.folded_len))
        return RE_ERROR_MEMORY;
    if (!push_ssize(state, &state->bstack, new_text_pos))
        return RE_ERROR_MEMORY;
    if (!push_uint8(state, &state->bstack, data.fuzzy_type))
        return RE_ERROR_MEMORY;
    if (!push_uint8(state, &state->bstack, op))
        return RE_ERROR_MEMORY;

    /* bstack: node step string_pos folded_pos folded_len text_pos fuzzy_type
     * op
     */

    if (!record_fuzzy(state, data.fuzzy_type, data.new_text_pos - data.step))
        return RE_ERROR_MEMORY;

    ++fuzzy_counts[data.fuzzy_type];
    ++state->capture_change;

    *text_pos = new_text_pos;
    *node = new_node;
    *string_pos = data.new_string_pos;
    *folded_pos = data.new_folded_pos;

    return RE_ERROR_SUCCESS;
}

/* Checks a fuzzy match of a atring. */
Py_LOCAL_INLINE(int) next_fuzzy_match_group_fld(RE_State* state, RE_FuzzyData*
  data) {
    int new_pos;

    if (this_error_permitted(state, data->fuzzy_type)) {
        switch (data->fuzzy_type) {
        case RE_FUZZY_DEL:
            /* Could a character at text_pos have been deleted? */
            data->new_gfolded_pos += data->step;
            return RE_ERROR_SUCCESS;
        case RE_FUZZY_INS:
            /* Could the character at text_pos have been inserted? */
            if (!data->permit_insertion)
                return RE_ERROR_FAILURE;

            new_pos = data->new_folded_pos + data->step;
            if (0 <= new_pos && new_pos <= data->folded_len) {
                data->new_folded_pos = new_pos;
                return RE_ERROR_SUCCESS;
            }

            return check_fuzzy_partial(state, new_pos);
        case RE_FUZZY_SUB:
            /* Could the character at text_pos have been substituted? */
            new_pos = data->new_folded_pos + data->step;
            if (0 <= new_pos && new_pos <= data->folded_len) {
                data->new_folded_pos = new_pos;
                data->new_gfolded_pos += data->step;
                return RE_ERROR_SUCCESS;
            }

            return check_fuzzy_partial(state, new_pos);
        }
    }

    return RE_ERROR_FAILURE;
}

/* Tries a fuzzy match of a group reference, ignoring case. */
Py_LOCAL_INLINE(int) fuzzy_match_group_fld(RE_State* state, BOOL search,
  Py_ssize_t* text_pos, RE_Node* node, int* folded_pos, int folded_len,
  Py_ssize_t* group_pos, int* gfolded_pos, int gfolded_len, RE_INT8 step) {
    size_t* fuzzy_counts;
    Py_ssize_t new_text_pos;
    RE_FuzzyData data;
    Py_ssize_t new_group_pos;

    fuzzy_counts = state->fuzzy_counts;

    if (!any_error_permitted(state))
        return RE_ERROR_FAILURE;

    new_text_pos = *text_pos;
    data.new_folded_pos = *folded_pos;
    data.folded_len = folded_len;
    new_group_pos = *group_pos;
    data.new_gfolded_pos = *gfolded_pos;
    data.step = step;

    /* Permit insertion except initially when searching (it's better just to
     * start searching one character later).
     */
    data.permit_insertion = !search || new_text_pos != state->search_anchor;
    if (data.step > 0) {
        if (data.new_folded_pos != 0)
            data.permit_insertion = RE_ERROR_SUCCESS;
    } else {
        if (data.new_folded_pos != folded_len)
            data.permit_insertion = RE_ERROR_SUCCESS;
    }

    for (data.fuzzy_type = 0; data.fuzzy_type < RE_FUZZY_COUNT;
      data.fuzzy_type++) {
        int status;

        status = next_fuzzy_match_group_fld(state, &data);
        if (status < 0)
            return status;

        if (status == RE_ERROR_SUCCESS)
            goto found;
    }

    return RE_ERROR_FAILURE;

found:
    if (!push_pointer(state, &state->bstack, node))
        return RE_ERROR_MEMORY;
    if (!push_int8(state, &state->bstack, step))
        return RE_ERROR_MEMORY;
    if (!push_int(state, &state->bstack, *gfolded_pos))
        return RE_ERROR_MEMORY;
    if (!push_int(state, &state->bstack, gfolded_len))
        return RE_ERROR_MEMORY;
    if (!push_ssize(state, &state->bstack, *group_pos))
        return RE_ERROR_MEMORY;
    if (!push_int(state, &state->bstack, *folded_pos))
        return RE_ERROR_MEMORY;
    if (!push_int(state, &state->bstack, folded_len))
        return RE_ERROR_MEMORY;
    if (!push_ssize(state, &state->bstack, new_text_pos))
        return RE_ERROR_MEMORY;
    if (!push_uint8(state, &state->bstack, data.fuzzy_type))
        return RE_ERROR_MEMORY;
    if (!push_uint8(state, &state->bstack, node->op))
        return RE_ERROR_MEMORY;

    /* bstack: node step gfolded_pos gfolded_len group_pos folded_pos
     * folded_len text_pos fuzzy_type op
     */

    if (!record_fuzzy(state, data.fuzzy_type, data.new_text_pos - data.step))
        return RE_ERROR_MEMORY;

    ++fuzzy_counts[data.fuzzy_type];
    ++state->capture_change;

    *text_pos = new_text_pos;
    *group_pos = new_group_pos;
    *folded_pos = data.new_folded_pos;
    *gfolded_pos = data.new_gfolded_pos;

    return RE_ERROR_SUCCESS;
}

/* Retries a fuzzy match of a group reference, ignoring case. */
Py_LOCAL_INLINE(int) retry_fuzzy_match_group_fld(RE_State* state, RE_UINT8 op,
  BOOL search, Py_ssize_t* text_pos, RE_Node** node, int* folded_pos,
  Py_ssize_t* group_pos, int* gfolded_pos) {
    size_t* fuzzy_counts;
    RE_FuzzyData data;
    Py_ssize_t new_text_pos;
    int new_folded_pos;
    Py_ssize_t new_group_pos;
    int gfolded_len;
    int new_gfolded_pos;
    RE_Node* new_node;

    fuzzy_counts = state->fuzzy_counts;

    unrecord_fuzzy(state);

    /* bstack: node step gfolded_pos gfolded_len group_pos folded_pos
     * folded_len text_pos fuzzy_type
     */

    if (!pop_uint8(state, &state->bstack, &data.fuzzy_type))
        return RE_ERROR_MEMORY;
    if (!pop_ssize(state, &state->bstack, &new_text_pos))
        return RE_ERROR_MEMORY;
    if (!pop_int(state, &state->bstack, &data.folded_len))
        return RE_ERROR_MEMORY;
    if (!pop_int(state, &state->bstack, &new_folded_pos))
        return RE_ERROR_MEMORY;
    if (!pop_ssize(state, &state->bstack, &new_group_pos))
        return RE_ERROR_MEMORY;
    if (!pop_int(state, &state->bstack, &gfolded_len))
        return RE_ERROR_MEMORY;
    if (!pop_int(state, &state->bstack, &new_gfolded_pos))
        return RE_ERROR_MEMORY;
    if (!pop_int8(state, &state->bstack, &data.step))
        return RE_ERROR_MEMORY;
    if (!pop_pointer(state, &state->bstack, (void*)&new_node))
        return RE_ERROR_MEMORY;

    data.new_folded_pos = new_folded_pos;
    data.new_gfolded_pos = new_gfolded_pos;

    --fuzzy_counts[data.fuzzy_type];

    /* Permit insertion except initially when searching (it's better just to
     * start searching one character later).
     */
    data.permit_insertion = !search || new_text_pos != state->search_anchor ||
      data.new_folded_pos != data.folded_len;

    for (++data.fuzzy_type; data.fuzzy_type < RE_FUZZY_COUNT;
      data.fuzzy_type++) {
        int status;

        status = next_fuzzy_match_group_fld(state, &data);
        if (status < 0)
            return status;

        if (status == RE_ERROR_SUCCESS)
            goto found;
    }

    return RE_ERROR_FAILURE;

found:
    if (!push_pointer(state, &state->bstack, new_node))
        return RE_ERROR_MEMORY;
    if (!push_int8(state, &state->bstack, data.step))
        return RE_ERROR_MEMORY;
    if (!push_int(state, &state->bstack, new_gfolded_pos))
        return RE_ERROR_MEMORY;
    if (!push_int(state, &state->bstack, gfolded_len))
        return RE_ERROR_MEMORY;
    if (!push_ssize(state, &state->bstack, new_group_pos))
        return RE_ERROR_MEMORY;
    if (!push_int(state, &state->bstack, new_folded_pos))
        return RE_ERROR_MEMORY;
    if (!push_int(state, &state->bstack, data.folded_len))
        return RE_ERROR_MEMORY;
    if (!push_ssize(state, &state->bstack, new_text_pos))
        return RE_ERROR_MEMORY;
    if (!push_uint8(state, &state->bstack, data.fuzzy_type))
        return RE_ERROR_MEMORY;
    if (!push_uint8(state, &state->bstack, op))
        return RE_ERROR_MEMORY;

    /* bstack: node step gfolded_pos gfolded_len group_pos folded_pos
     * folded_len text_pos fuzzy_type op
     */

    if (!record_fuzzy(state, data.fuzzy_type, data.new_text_pos - data.step))
        return RE_ERROR_MEMORY;

    ++fuzzy_counts[data.fuzzy_type];
    ++state->capture_change;

    *text_pos = new_text_pos;
    *node = new_node;
    *group_pos = new_group_pos;
    *folded_pos = data.new_folded_pos;
    *gfolded_pos = data.new_gfolded_pos;

    return RE_ERROR_SUCCESS;
}

/* Locates the required string, if there's one. */
Py_LOCAL_INLINE(Py_ssize_t) locate_required_string(RE_State* state, BOOL
  search) {
    PatternObject* pattern;
    Py_ssize_t found_pos;
    Py_ssize_t end_pos;

    pattern = state->pattern;

    if (!pattern->req_string)
        /* There isn't a required string, so start matching from the current
         * position.
         */
        return state->text_pos;

    /* Search for the required string and calculate where to start matching. */
    switch (pattern->req_string->op) {
    case RE_OP_STRING:
    {
        BOOL is_partial;
        Py_ssize_t limit;

        if (search || pattern->req_offset < 0)
            limit = state->slice_end;
        else {
            limit = state->slice_start + pattern->req_offset +
              (Py_ssize_t)pattern->req_string->value_count;
            if (limit > state->slice_end || limit < 0)
                limit = state->slice_end;
        }

        if (state->req_pos < 0 || state->text_pos > state->req_pos)
            /* First time or already passed it. */
            found_pos = string_search(state, pattern->req_string,
              state->text_pos, limit, &is_partial);
        else {
            found_pos = state->req_pos;
            end_pos = state->req_end;
            is_partial = FALSE;
        }

        if (found_pos < 0)
            /* The required string wasn't found. */
            return -1;

        if (!is_partial) {
            /* Record where the required string matched. */
            state->req_pos = found_pos;
            state->req_end = found_pos +
              (Py_ssize_t)pattern->req_string->value_count;
        }

        if (pattern->req_offset >= 0) {
            /* Step back from the required string to where we should start
             * matching.
             */
            found_pos -= pattern->req_offset;
            if (found_pos >= state->text_pos)
                return found_pos;
        }
        break;
    }
    case RE_OP_STRING_FLD:
    {
        BOOL is_partial;
        Py_ssize_t limit;

        if (search || pattern->req_offset < 0)
            limit = state->slice_end;
        else {
            limit = state->slice_start + pattern->req_offset +
              (Py_ssize_t)pattern->req_string->value_count;
            if (limit > state->slice_end || limit < 0)
                limit = state->slice_end;
        }

        if (state->req_pos < 0 || state->text_pos > state->req_pos)
            /* First time or already passed it. */
            found_pos = string_search_fld(state, pattern->req_string,
              state->text_pos, limit, &end_pos, &is_partial);
        else {
            found_pos = state->req_pos;
            end_pos = state->req_end;
            is_partial = FALSE;
        }

        if (found_pos < 0)
            /* The required string wasn't found. */
            return -1;

        if (!is_partial) {
            /* Record where the required string matched. */
            state->req_pos = found_pos;
            state->req_end = end_pos;
        }

        if (pattern->req_offset >= 0) {
            /* Step back from the required string to where we should start
             * matching.
             */
            found_pos -= pattern->req_offset;
            if (found_pos >= state->text_pos)
                return found_pos;
        }
        break;
    }
    case RE_OP_STRING_FLD_REV:
    {
        BOOL is_partial;
        Py_ssize_t limit;

        if (search || pattern->req_offset < 0)
            limit = state->slice_start;
        else {
            limit = state->slice_end - pattern->req_offset -
              (Py_ssize_t)pattern->req_string->value_count;
            if (limit < state->slice_start)
                limit = state->slice_start;
        }

        if (state->req_pos < 0 || state->text_pos < state->req_pos)
            /* First time or already passed it. */
            found_pos = string_search_fld_rev(state, pattern->req_string,
              state->text_pos, limit, &end_pos, &is_partial);
        else {
            found_pos = state->req_pos;
            end_pos = state->req_end;
            is_partial = FALSE;
        }

        if (found_pos < 0)
            /* The required string wasn't found. */
            return -1;

        if (!is_partial) {
            /* Record where the required string matched. */
            state->req_pos = found_pos;
            state->req_end = end_pos;
        }

        if (pattern->req_offset >= 0) {
            /* Step back from the required string to where we should start
             * matching.
             */
            found_pos += pattern->req_offset;
            if (found_pos <= state->text_pos)
                return found_pos;
        }
        break;
    }
    case RE_OP_STRING_IGN:
    {
        BOOL is_partial;
        Py_ssize_t limit;

        if (search || pattern->req_offset < 0)
            limit = state->slice_end;
        else {
            limit = state->slice_start + pattern->req_offset +
              (Py_ssize_t)pattern->req_string->value_count;
            if (limit > state->slice_end || limit < 0)
                limit = state->slice_end;
        }

        if (state->req_pos < 0 || state->text_pos > state->req_pos)
            /* First time or already passed it. */
            found_pos = string_search_ign(state, pattern->req_string,
              state->text_pos, limit, &is_partial);
        else {
            found_pos = state->req_pos;
            end_pos = state->req_end;
            is_partial = FALSE;
        }

        if (found_pos < 0)
            /* The required string wasn't found. */
            return -1;

        if (!is_partial) {
            /* Record where the required string matched. */
            state->req_pos = found_pos;
            state->req_end = found_pos +
              (Py_ssize_t)pattern->req_string->value_count;
        }

        if (pattern->req_offset >= 0) {
            /* Step back from the required string to where we should start
             * matching.
             */
            found_pos -= pattern->req_offset;
            if (found_pos >= state->text_pos)
                return found_pos;
        }
        break;
    }
    case RE_OP_STRING_IGN_REV:
    {
        BOOL is_partial;
        Py_ssize_t limit;

        if (search || pattern->req_offset < 0)
            limit = state->slice_start;
        else {
            limit = state->slice_end - pattern->req_offset -
              (Py_ssize_t)pattern->req_string->value_count;
            if (limit < state->slice_start)
                limit = state->slice_start;
        }

        if (state->req_pos < 0 || state->text_pos < state->req_pos)
            /* First time or already passed it. */
            found_pos = string_search_ign_rev(state, pattern->req_string,
              state->text_pos, limit, &is_partial);
        else {
            found_pos = state->req_pos;
            end_pos = state->req_end;
            is_partial = FALSE;
        }

        if (found_pos < 0)
            /* The required string wasn't found. */
            return -1;

        if (!is_partial) {
            /* Record where the required string matched. */
            state->req_pos = found_pos;
            state->req_end = found_pos -
              (Py_ssize_t)pattern->req_string->value_count;
        }

        if (pattern->req_offset >= 0) {
            /* Step back from the required string to where we should start
             * matching.
             */
            found_pos += pattern->req_offset;
            if (found_pos <= state->text_pos)
                return found_pos;
        }
        break;
    }
    case RE_OP_STRING_REV:
    {
        BOOL is_partial;
        Py_ssize_t limit;

        if (search || pattern->req_offset < 0)
            limit = state->slice_start;
        else {
            limit = state->slice_end - pattern->req_offset -
              (Py_ssize_t)pattern->req_string->value_count;
            if (limit < state->slice_start)
                limit = state->slice_start;
        }

        if (state->req_pos < 0 || state->text_pos < state->req_pos)
            /* First time or already passed it. */
            found_pos = string_search_rev(state, pattern->req_string,
              state->text_pos, limit, &is_partial);
        else {
            found_pos = state->req_pos;
            end_pos = state->req_end;
            is_partial = FALSE;
        }

        if (found_pos < 0)
            /* The required string wasn't found. */
            return -1;

        if (!is_partial) {
            /* Record where the required string matched. */
            state->req_pos = found_pos;
            state->req_end = found_pos -
              (Py_ssize_t)pattern->req_string->value_count;
        }

        if (pattern->req_offset >= 0) {
            /* Step back from the required string to where we should start
             * matching.
             */
            found_pos += pattern->req_offset;
            if (found_pos <= state->text_pos)
                return found_pos;
        }
        break;
    }
    }

    /* Start matching from the current position. */
    return state->text_pos;
}

/* Tries to match a character pattern. */
Py_LOCAL_INLINE(int) match_one(RE_State* state, RE_Node* node, Py_ssize_t
  text_pos) {
    switch (node->op) {
    case RE_OP_ANY:
        return try_match_ANY(state, node, text_pos);
    case RE_OP_ANY_ALL:
        return try_match_ANY_ALL(state, node, text_pos);
    case RE_OP_ANY_ALL_REV:
        return try_match_ANY_ALL_REV(state, node, text_pos);
    case RE_OP_ANY_REV:
        return try_match_ANY_REV(state, node, text_pos);
    case RE_OP_ANY_U:
        return try_match_ANY_U(state, node, text_pos);
    case RE_OP_ANY_U_REV:
        return try_match_ANY_U_REV(state, node, text_pos);
    case RE_OP_CHARACTER:
        return try_match_CHARACTER(state, node, text_pos);
    case RE_OP_CHARACTER_IGN:
        return try_match_CHARACTER_IGN(state, node, text_pos);
    case RE_OP_CHARACTER_IGN_REV:
        return try_match_CHARACTER_IGN_REV(state, node, text_pos);
    case RE_OP_CHARACTER_REV:
        return try_match_CHARACTER_REV(state, node, text_pos);
    case RE_OP_PROPERTY:
        return try_match_PROPERTY(state, node, text_pos);
    case RE_OP_PROPERTY_IGN:
        return try_match_PROPERTY_IGN(state, node, text_pos);
    case RE_OP_PROPERTY_IGN_REV:
        return try_match_PROPERTY_IGN_REV(state, node, text_pos);
    case RE_OP_PROPERTY_REV:
        return try_match_PROPERTY_REV(state, node, text_pos);
    case RE_OP_RANGE:
        return try_match_RANGE(state, node, text_pos);
    case RE_OP_RANGE_IGN:
        return try_match_RANGE_IGN(state, node, text_pos);
    case RE_OP_RANGE_IGN_REV:
        return try_match_RANGE_IGN_REV(state, node, text_pos);
    case RE_OP_RANGE_REV:
        return try_match_RANGE_REV(state, node, text_pos);
    case RE_OP_SET_DIFF:
    case RE_OP_SET_INTER:
    case RE_OP_SET_SYM_DIFF:
    case RE_OP_SET_UNION:
        return try_match_SET(state, node, text_pos);
    case RE_OP_SET_DIFF_IGN:
    case RE_OP_SET_INTER_IGN:
    case RE_OP_SET_SYM_DIFF_IGN:
    case RE_OP_SET_UNION_IGN:
        return try_match_SET_IGN(state, node, text_pos);
    case RE_OP_SET_DIFF_IGN_REV:
    case RE_OP_SET_INTER_IGN_REV:
    case RE_OP_SET_SYM_DIFF_IGN_REV:
    case RE_OP_SET_UNION_IGN_REV:
        return try_match_SET_IGN_REV(state, node, text_pos);
    case RE_OP_SET_DIFF_REV:
    case RE_OP_SET_INTER_REV:
    case RE_OP_SET_SYM_DIFF_REV:
    case RE_OP_SET_UNION_REV:
        return try_match_SET_REV(state, node, text_pos);
    }

    return FALSE;
}

/* Tests whether 2 nodes contains the same values. */
Py_LOCAL_INLINE(BOOL) same_values(RE_Node* node_1, RE_Node* node_2) {
    size_t i;

    if (node_1->value_count != node_2->value_count)
        return FALSE;

    for (i = 0; i < node_1->value_count; i++) {
        if (node_1->values[i] != node_2->values[i])
            return FALSE;
    }

    return TRUE;
}

/* Tests whether 2 nodes are equivalent (both string-like in the same way). */
Py_LOCAL_INLINE(BOOL) equivalent_nodes(RE_Node* node_1, RE_Node* node_2) {
    switch (node_1->op) {
    case RE_OP_CHARACTER:
    case RE_OP_STRING:
        switch (node_2->op) {
        case RE_OP_CHARACTER:
        case RE_OP_STRING:
            return same_values(node_1, node_2);
        }
        break;
    case RE_OP_CHARACTER_IGN:
    case RE_OP_STRING_IGN:
        switch (node_2->op) {
        case RE_OP_CHARACTER_IGN:
        case RE_OP_STRING_IGN:
            return same_values(node_1, node_2);
        }
        break;
    case RE_OP_CHARACTER_IGN_REV:
    case RE_OP_STRING_IGN_REV:
        switch (node_2->op) {
        case RE_OP_CHARACTER_IGN_REV:
        case RE_OP_STRING_IGN_REV:
            return same_values(node_1, node_2);
        }
        break;
    case RE_OP_CHARACTER_REV:
    case RE_OP_STRING_REV:
        switch (node_2->op) {
        case RE_OP_CHARACTER_REV:
        case RE_OP_STRING_REV:
            return same_values(node_1, node_2);
        }
        break;
    }

    return FALSE;
}

/* Saves the match as the best POSIX match (leftmost longest) found so far. */
Py_LOCAL_INLINE(BOOL) save_best_match(RE_State* state) {
    size_t group_count;
    size_t g;

    state->best_match_pos = state->match_pos;
    state->best_text_pos = state->text_pos;
    state->found_match = TRUE;

    Py_MEMCPY(state->best_fuzzy_counts, state->fuzzy_counts,
      sizeof(state->fuzzy_counts));

    group_count = state->pattern->true_group_count;
    if (group_count == 0)
        return TRUE;

    if (!state->best_match_groups) {
        /* Allocate storage for the groups of the best match. */
        state->best_match_groups = (RE_GroupData*)safe_alloc(state, group_count
          * sizeof(RE_GroupData));
        if (!state->best_match_groups)
            return FALSE;

        memset(state->best_match_groups, 0, group_count *
          sizeof(RE_GroupData));

        for (g = 0; g < group_count; g++) {
            RE_GroupData* best;
            RE_GroupData* group;

            best = &state->best_match_groups[g];
            group = &state->groups[g];

            best->capacity = group->capacity;
            best->captures = (RE_GroupSpan*)safe_alloc(state, best->capacity *
              sizeof(RE_GroupSpan));
            if (!best->captures)
                return FALSE;
        }
    }

    /* Copy the group spans and captures. */
    for (g = 0; g < group_count; g++) {
        RE_GroupData* best;
        RE_GroupData* group;

        best = &state->best_match_groups[g];
        group = &state->groups[g];

        best->count = group->count;
        best->current = group->current;

        if (best->count > best->capacity) {
            RE_GroupSpan* new_captures;

            /* We need more space for the captures. */
            best->capacity = best->count;
            new_captures = (RE_GroupSpan*)safe_realloc(state, best->captures,
              best->capacity * sizeof(RE_GroupSpan));
            if (!new_captures)
                return FALSE;
            best->captures = new_captures;
        }

        /* Copy the captures for this group. */
        Py_MEMCPY(best->captures, group->captures, group->count *
          sizeof(RE_GroupSpan));
    }

    return TRUE;
}

/* Restores the best match for a POSIX match (leftmost longest). */
Py_LOCAL_INLINE(void) restore_best_match(RE_State* state) {
    size_t group_count;
    size_t g;

    if (!state->found_match)
        return;

    state->match_pos = state->best_match_pos;
    state->text_pos = state->best_text_pos;

    Py_MEMCPY(state->fuzzy_counts, state->best_fuzzy_counts,
      sizeof(state->fuzzy_counts));

    group_count = state->pattern->true_group_count;
    if (group_count == 0)
        return;

    /* Copy the group spans and captures. */
    for (g = 0; g < group_count; g++) {
        RE_GroupData* group;
        RE_GroupData* best;

        group = &state->groups[g];
        best = &state->best_match_groups[g];

        group->count = best->count;
        group->current = best->current;

        /* Copy the captures for this group. */
        Py_MEMCPY(group->captures, best->captures, best->count *
          sizeof(RE_GroupSpan));
    }
}

/* Checks whether the new match is better than the current match for a POSIX
 * match (leftmost longest) and saves it if it is.
 */
Py_LOCAL_INLINE(BOOL) check_posix_match(RE_State* state) {
    Py_ssize_t best_length;
    Py_ssize_t new_length;

    if (!state->found_match)
        return save_best_match(state);

    /* Check the overall match. */
    if (state->reverse) {
        /* We're searching backwards. */
        best_length = state->match_pos - state->best_text_pos;
        new_length = state->match_pos - state->text_pos;
    } else {
        /* We're searching forwards. */
        best_length = state->best_text_pos - state->match_pos;
        new_length = state->text_pos - state->match_pos;
    }

    if (new_length > best_length)
        /* It's a longer match. */
        return save_best_match(state);

    return TRUE;
}

/* Checks whether the current position is at the end of the text. */
Py_LOCAL_INLINE(int) at_end(RE_State* state) {
    return state->reverse ? state->text_pos == state->slice_start :
      state->text_pos == state->slice_end;
}

/* Checks whether 2 spans match. */
Py_LOCAL_INLINE(BOOL) same_span(RE_GroupSpan span_1, RE_GroupSpan span_2) {
    return span_1.start == span_2.start && span_1.end == span_2.end;
}

/* Checks whether a span matches that of a group. */
Py_LOCAL_INLINE(BOOL) same_span_as_group(RE_GroupData* group, RE_GroupSpan
  span) {
    return group->current >= 0 && same_span(group->captures[group->current],
      span);
}

/* Checks whether 2 groupus have the same spam. */
Py_LOCAL_INLINE(BOOL) same_span_of_group(RE_GroupData* group_1, RE_GroupData*
  group_2) {
    return (group_1->current >= 0 && group_2->current >= 0 &&
      same_span(group_1->captures[group_1->current],
      group_2->captures[group_2->current])) || (group_1->current < 0 &&
      group_2->current < 0);
}

/* Performs a depth-first match or search from the context. */
Py_LOCAL_INLINE(int) basic_match(RE_State* state, BOOL search) {
    RE_EncodingTable* encoding;
    RE_LocaleInfo* locale_info;
    PatternObject* pattern;
    RE_Node* start_node;
    RE_NextNode start_pair;
    Py_UCS4 (*char_at)(void* text, Py_ssize_t pos);
    Py_ssize_t pattern_step; /* The overall step of the pattern (forwards or backwards). */
    Py_ssize_t string_pos;
    BOOL do_search_start;
    Py_ssize_t found_pos;
    int status;
    RE_Node* node;
    int folded_pos;
    int gfolded_pos;
    TRACE(("<<basic_match>>\n"))

    encoding = state->encoding;
    locale_info = state->locale_info;
    pattern = state->pattern;
    start_node = pattern->start_node;

    /* Look beyond any initial group node. */
    start_pair.node = start_node;
    start_pair.test = pattern->start_test;

    /* Is the pattern anchored to the start or end of the string? */
    switch (start_pair.test->op) {
    case RE_OP_END_OF_STRING:
        if (state->reverse) {
            /* Searching backwards. */
            if (state->text_pos != state->text_length)
                return RE_ERROR_FAILURE;

            /* Don't bother to search further because it's anchored. */
            search = FALSE;
        }
        break;
    case RE_OP_START_OF_STRING:
        if (!state->reverse) {
            /* Searching forwards. */
            if (state->text_pos != 0)
                return RE_ERROR_FAILURE;

            /* Don't bother to search further because it's anchored. */
            search = FALSE;
        }
        break;
    }

    char_at = state->char_at;
    pattern_step = state->reverse ? -1 : 1;
    string_pos = -1;
    do_search_start = pattern->do_search_start;
    state->fewest_errors = state->max_errors;

    if (do_search_start && pattern->req_string &&
      equivalent_nodes(start_pair.test, pattern->req_string))
        do_search_start = FALSE;

start_match:
    if (state->iterations == 0 && safe_check_cancel(state))
        return RE_ERROR_CANCELLED;

    if (!push_uint8(state, &state->bstack, RE_OP_FAILURE))
        return RE_ERROR_MEMORY;
    if (!push_bstack(state))
        return RE_ERROR_MEMORY;

    /* sstack: -
     *
     * bstack: FAILURE
     *
     * pstack: bstack
     */

    /* Clear the fuzzy counts. */
    if (state->is_fuzzy)
        memset(state->fuzzy_counts, 0, sizeof(state->fuzzy_counts));

    /* If we're searching, advance along the string until there could be a
     * match.
     */
    if (pattern->pattern_call_ref >= 0) {
        RE_GuardList* guard_list;

        guard_list = &state->group_call_guard_list[pattern->pattern_call_ref];
        guard_list->count = 0;
        guard_list->last_text_pos = -1;
    }

    /* Locate the required string, if there's one, unless this is a recursive
     * call of 'basic_match'.
     */
    if (!pattern->req_string || state->text_pos < state->req_pos)
        found_pos = state->text_pos;
    else {
        found_pos = locate_required_string(state, search);
        if (found_pos < 0)
            return RE_ERROR_FAILURE;
    }

    if (search) {
        state->text_pos = found_pos;

        if (do_search_start) {
            RE_Position new_position;

next_match_1:
            /* 'search_start' will clear 'do_search_start' if it can't perform
             * a fast search for the next possible match. This enables us to
             * avoid the overhead of the call subsequently.
             */
            status = search_start(state, &start_pair, &new_position, 0);
            if (status == RE_ERROR_PARTIAL) {
                state->match_pos = new_position.text_pos;
                return status;
            } else if (status != RE_ERROR_SUCCESS)
                return status;

            node = new_position.node;
            state->text_pos = new_position.text_pos;

            if (node->op == RE_OP_SUCCESS) {
                /* Must the match advance past its start? */
                if (state->text_pos != state->search_anchor ||
                  !state->must_advance)
                    return RE_ERROR_SUCCESS;

                state->text_pos = state->match_pos + pattern_step;
                goto next_match_1;
            }

            /* 'do_search_start' may have been cleared. */
            do_search_start = pattern->do_search_start;
        } else {
            /* Avoiding 'search_start', which we've found can't perform a fast
             * search for the next possible match.
             */
            node = start_node;

next_match_2:
            if (state->reverse) {
                if (state->text_pos < state->slice_start) {
                    if (state->partial_side == RE_PARTIAL_LEFT)
                        return RE_ERROR_PARTIAL;

                    return RE_ERROR_FAILURE;
                }
            } else {
                if (state->text_pos > state->slice_end) {
                    if (state-> partial_side == RE_PARTIAL_RIGHT)
                        return RE_ERROR_PARTIAL;

                    return RE_ERROR_FAILURE;
                }
            }

            state->match_pos = state->text_pos;

            if (node->op == RE_OP_SUCCESS) {
                /* Must the match advance past its start? */
                if (state->text_pos != state->search_anchor ||
                  !state->must_advance) {
                    BOOL success;

                    if (state->match_all) {
                        /* We want to match all of the slice. */
                        if (state->reverse)
                            success = state->text_pos == state->slice_start;
                        else
                            success = state->text_pos == state->slice_end;
                    } else
                        success = TRUE;

                    if (success)
                        return RE_ERROR_SUCCESS;
                }

                state->text_pos = state->match_pos + pattern_step;
                goto next_match_2;
            }
        }
    } else {
        /* The start position is anchored to the current position. */
        if (found_pos != state->text_pos)
            return RE_ERROR_FAILURE;

        node = start_node;
    }

advance:
    /* The main matching loop. */
    for (;;) {
        TRACE(("%" PY_FORMAT_SIZE_T "d|", state->text_pos))

        /* Should we abort the matching? */
        state->iterations += 0x100U;

        if (state->iterations == 0 && safe_check_cancel(state))
            return RE_ERROR_CANCELLED;

        switch (node->op) {
        case RE_OP_ANY: /* Any character except a newline. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = try_match_ANY(state, node, state->text_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS) {
                ++state->text_pos;
                node = node->next_1.node;
            } else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 1);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_ANY_ALL: /* Any character at all. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = try_match_ANY_ALL(state, node, state->text_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS) {
                ++state->text_pos;
                node = node->next_1.node;
            } else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 1);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_ANY_ALL_REV: /* Any character at all, backwards. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = try_match_ANY_ALL_REV(state, node, state->text_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS) {
                --state->text_pos;
                node = node->next_1.node;
            } else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, -1);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_ANY_REV: /* Any character except a newline, backwards. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = try_match_ANY_REV(state, node, state->text_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS) {
                --state->text_pos;
                node = node->next_1.node;
            } else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, -1);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_ANY_U: /* Any character except a line separator. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = try_match_ANY_U(state, node, state->text_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS) {
                ++state->text_pos;
                node = node->next_1.node;
            } else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 1);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_ANY_U_REV: /* Any character except a line separator, backwards. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = try_match_ANY_U_REV(state, node, state->text_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS) {
                --state->text_pos;
                node = node->next_1.node;
            } else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, -1);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_ATOMIC: /* Start of an atomic group. */
            TRACE(("%s\n", re_op_text[node->op]))

            if (!push_captures(state, &state->bstack))
                return RE_ERROR_MEMORY;
            if (!push_fuzzy_counts(state, &state->bstack, state->fuzzy_counts))
                return RE_ERROR_MEMORY;
            if (!push_size(state, &state->bstack, state->capture_change))
                return RE_ERROR_MEMORY;
            if (!push_sstack(state))
                return RE_ERROR_MEMORY;
            if (!push_uint8(state, &state->bstack, RE_OP_ATOMIC))
                return RE_ERROR_MEMORY;
            if (!push_bstack(state))
                return RE_ERROR_MEMORY;

            /* bstack: captures fuzzy_counts capture_change sstack ATOMIC
             *
             * pstack: bstack
             */

            node = node->next_1.node;
            break;
        case RE_OP_BOUNDARY: /* At a word boundary. */
            TRACE(("%s %d\n", re_op_text[node->op], node->match))

            status = try_match_BOUNDARY(state, node, state->text_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS)
                node = node->next_1.node;
            else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 0);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_BRANCH: /* 2-way branch. */
        {
            RE_Position next_position;
            TRACE(("%s\n", re_op_text[node->op]))

            status = try_match(state, &node->next_1, state->text_pos,
              &next_position);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS) {
                if (!push_ssize(state, &state->bstack, state->text_pos))
                    return RE_ERROR_MEMORY;
                if (!push_pointer(state, &state->bstack,
                  node->nonstring.next_2.node))
                    return RE_ERROR_MEMORY;
                if (!push_uint8(state, &state->bstack, RE_OP_BRANCH))
                    return RE_ERROR_MEMORY;

                /* bstack: text_pos node BRANCH */

                node = next_position.node;
                state->text_pos = next_position.text_pos;
            } else
                node = node->nonstring.next_2.node;
            break;
        }
        case RE_OP_CALL_REF: /* A group call reference. */
        {
            TRACE(("%s %d\n", re_op_text[node->op], node->values[0]))

            if (!push_pointer(state, &state->sstack, NULL))
                return RE_ERROR_MEMORY;
            if (!push_uint8(state, &state->bstack, RE_OP_CALL_REF))
                return RE_ERROR_MEMORY;

            /* sstack: NULL
             *
             * bstack: CALL_REF
             */

            node = node->next_1.node;
            break;
        }
        case RE_OP_CHARACTER: /* A character. */
            TRACE(("%s %d %d\n", re_op_text[node->op], node->match,
              node->values[0]))

            if (state->text_pos >= state->text_length && state->partial_side ==
              RE_PARTIAL_RIGHT)
                return RE_ERROR_PARTIAL;

            if (state->text_pos < state->slice_end &&
              matches_CHARACTER(encoding, locale_info, node,
              char_at(state->text, state->text_pos)) == node->match) {
                state->text_pos += node->step;
                node = node->next_1.node;
            } else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 1);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_CHARACTER_IGN: /* A character, ignoring case. */
            TRACE(("%s %d %d\n", re_op_text[node->op], node->match,
              node->values[0]))

            if (state->text_pos >= state->text_length && state->partial_side ==
              RE_PARTIAL_RIGHT)
                return RE_ERROR_PARTIAL;

            if (state->text_pos < state->slice_end &&
              matches_CHARACTER_IGN(encoding, locale_info, node,
              char_at(state->text, state->text_pos)) == node->match) {
                state->text_pos += node->step;
                node = node->next_1.node;
            } else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 1);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_CHARACTER_IGN_REV: /* A character, backwards, ignoring case. */
            TRACE(("%s %d %d\n", re_op_text[node->op], node->match,
              node->values[0]))

            if (state->text_pos <= 0 && state->partial_side == RE_PARTIAL_LEFT)
                return RE_ERROR_PARTIAL;

            if (state->text_pos > state->slice_start &&
              matches_CHARACTER_IGN(encoding, locale_info, node,
              char_at(state->text, state->text_pos - 1)) == node->match) {
                state->text_pos += node->step;
                node = node->next_1.node;
            } else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, -1);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_CHARACTER_REV: /* A character, backwards. */
            TRACE(("%s %d %d\n", re_op_text[node->op], node->match,
              node->values[0]))

            if (state->text_pos <= 0 && state->partial_side == RE_PARTIAL_LEFT)
                return RE_ERROR_PARTIAL;

            if (state->text_pos > state->slice_start &&
              matches_CHARACTER(encoding, locale_info, node,
              char_at(state->text, state->text_pos - 1)) == node->match) {
                state->text_pos += node->step;
                node = node->next_1.node;
            } else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, -1);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_CONDITIONAL: /* Start of a conditional subpattern. */
        {
            RE_LookaroundStateData data_l;
            TRACE(("%s %d\n", re_op_text[node->op], node->match))

            data_l.node = node;
            data_l.slice_start = state->slice_start;
            data_l.slice_end = state->slice_end;
            data_l.text_pos = state->text_pos;

            if (!ByteStack_push_block(state, &state->sstack, (void*)&data_l,
              sizeof(data_l)))
                return RE_ERROR_MEMORY;
            if (!push_captures(state, &state->bstack))
                return RE_ERROR_MEMORY;
            if (!push_repeats(state, &state->bstack))
                return RE_ERROR_MEMORY;
            if (!push_fuzzy_counts(state, &state->bstack, state->fuzzy_counts))
                return RE_ERROR_MEMORY;
            if (!push_size(state, &state->bstack, state->capture_change))
                return RE_ERROR_MEMORY;
            if (!push_sstack(state))
                return RE_ERROR_MEMORY;
            if (!push_uint8(state, &state->bstack, RE_OP_CONDITIONAL))
                return RE_ERROR_MEMORY;
            if (!push_bstack(state))
                return RE_ERROR_MEMORY;

            /* sstack: node slice_start slice_end text_pos
             *
             * bstack: captures repeats fuzzy_counts capture_change sstack
             * CONDITIONAL
             *
             * pstack: bstack
             */

            state->slice_start = 0;
            state->slice_end = state->text_length;

            node = node->next_1.node;
            break;
        }
        case RE_OP_DEFAULT_BOUNDARY: /* At a default word boundary. */
            TRACE(("%s %d\n", re_op_text[node->op], node->match))

            status = try_match_DEFAULT_BOUNDARY(state, node, state->text_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS)
                node = node->next_1.node;
            else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 0);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_DEFAULT_END_OF_WORD: /* At the default end of a word. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = try_match_DEFAULT_END_OF_WORD(state, node,
              state->text_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS)
                node = node->next_1.node;
            else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 0);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_DEFAULT_START_OF_WORD: /* At the default start of a word. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = try_match_DEFAULT_START_OF_WORD(state, node,
              state->text_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS)
                node = node->next_1.node;
            else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 0);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_END_ATOMIC: /* End of an atomic group. */
            TRACE(("%s\n", re_op_text[node->op]))

            /* sstack: ...
             *
             * bstack: captures fuzzy_counts capture_change sstack ATOMIC ...
             *
             * pstack: bstack
             */

            if (!pop_bstack(state))
                return RE_ERROR_MEMORY;

            /* sstack: ...
             *
             * bstack: captures fuzzy_counts capture_change sstack ATOMIC
             *
             * pstack: -
             */

            if (!drop_uint8(state, &state->bstack))
                return RE_ERROR_MEMORY;
            if (!pop_sstack(state))
                return RE_ERROR_MEMORY;

            /* sstack: -
             *
             * bstack: captures fuzzy_counts capture_change
             *
             * pstack: -
             */

            if (!push_uint8(state, &state->bstack, RE_OP_END_ATOMIC))
                return RE_ERROR_MEMORY;

            /* bstack: captures fuzzy_counts capture_change END_ATOMIC
             *
             * pstack: -
             */

            node = node->next_1.node;
            break;
        case RE_OP_END_CONDITIONAL: /* End of a conditional subpattern. */
        {
            RE_Node* conditional;
            RE_LookaroundStateData data_l;
            TRACE(("%s\n", re_op_text[node->op]))

            /* sstack: node slice_start slice_end text_pos ...
             *
             * bstack: captures repeats fuzzy_counts capture_change sstack
             * CONDITIONAL ...
             *
             * pstack: bstack
             */

            if (!pop_bstack(state))
                return RE_ERROR_MEMORY;

            /* sstack: node slice_start slice_end text_pos ...
             *
             * bstack: captures repeats fuzzy_counts capture_change sstack
             * CONDITIONAL
             *
             * pstack: -
             */

            if (!drop_uint8(state, &state->bstack))
                return RE_ERROR_MEMORY;
            if (!pop_sstack(state))
                return RE_ERROR_MEMORY;

            /* sstack: node slice_start slice_end text_pos
             *
             * bstack: captures repeats fuzzy_counts capture_change
             *
             * pstack: -
             */

            if (!ByteStack_pop_block(state, &state->sstack, (void*)&data_l,
              sizeof(data_l)))
                return RE_ERROR_MEMORY;

            state->text_pos = data_l.text_pos;
            state->slice_end = data_l.slice_end;
            state->slice_start = data_l.slice_start;
            conditional = data_l.node;

            /* sstack: -
             *
             * bstack: captures repeats fuzzy_counts capture_change
             *
             * pstack: -
             */

            if (conditional->match) {
                /* It's a positive lookaround that's succeeded. */
                if (!push_uint8(state, &state->bstack, RE_OP_END_CONDITIONAL))
                    return RE_ERROR_MEMORY;

                /* sstack: -
                 *
                 * bstack: captures repeats fuzzy_counts capture_change
                 * END_CONDITIONAL
                 *
                 * pstack: -
                 */

                /* Go to the 'true' branch. */
                node = node->next_1.node;
            } else {
                /* It's a negative lookaround that's succeeded. */
                if (!pop_size(state, &state->bstack, &state->capture_change))
                    return RE_ERROR_MEMORY;
                if (!pop_fuzzy_counts(state, &state->bstack,
                  state->fuzzy_counts))
                    return RE_ERROR_MEMORY;
                if (!pop_repeats(state, &state->bstack))
                    return RE_ERROR_MEMORY;
                if (!pop_captures(state, &state->bstack))
                    return RE_ERROR_MEMORY;

                /* sstack: -
                 *
                 * bstack: -
                 *
                 * pstack: -
                 */

                /* Go to the 'false' branch. */
                node = node->nonstring.next_2.node;
            }
            break;
        }
        case RE_OP_END_FUZZY: /* End of fuzzy matching. */
        {
            RE_Node* outer_node;
            size_t outer_counts[RE_FUZZY_COUNT];
            size_t total_counts[RE_FUZZY_COUNT];
            TRACE(("%s\n", re_op_text[node->op]))

            /* sstack: outer_counts outer_node
             *
             * bstack: -
             */

            /* Are the inner constraints OK? */
            if (!fuzzy_within_constraints(state->fuzzy_counts,
              state->fuzzy_node, state->max_errors))
                goto backtrack;

            if (!pop_pointer(state, &state->sstack, (void*)&outer_node))
                return RE_ERROR_MEMORY;
            if (!pop_fuzzy_counts(state, &state->sstack, outer_counts))
                return RE_ERROR_MEMORY;

            /* sstack: -
             *
             * bstack: -
             */

            /* Add the inner counts to the outer counts. */
            total_counts[RE_FUZZY_SUB] = outer_counts[RE_FUZZY_SUB] +
              state->fuzzy_counts[RE_FUZZY_SUB];
            total_counts[RE_FUZZY_INS] = outer_counts[RE_FUZZY_INS] +
              state->fuzzy_counts[RE_FUZZY_INS];
            total_counts[RE_FUZZY_DEL] = outer_counts[RE_FUZZY_DEL] +
              state->fuzzy_counts[RE_FUZZY_DEL];

            /* Is the total number of errors OK? */
            state->total_errors = total_errors(total_counts);

            if (state->total_errors > state->max_errors) {
                if (!push_fuzzy_counts(state, &state->sstack, outer_counts))
                    return RE_ERROR_MEMORY;
                if (!push_pointer(state, &state->sstack, outer_node))
                    return RE_ERROR_MEMORY;

                /* sstack: outer_counts outer_node
                 *
                 * bstack: -
                 */
                goto backtrack;
            }

            /* Save the inner fuzzy info. */
            if (!push_fuzzy_counts(state, &state->bstack, state->fuzzy_counts))
                return RE_ERROR_MEMORY;
            if (!push_pointer(state, &state->bstack, state->fuzzy_node))
                return RE_ERROR_MEMORY;
            if (!push_ssize(state, &state->bstack, state->text_pos))
                return RE_ERROR_MEMORY;
            if (!push_pointer(state, &state->bstack, node))
                return RE_ERROR_MEMORY;
            if (!push_uint8(state, &state->bstack, RE_OP_END_FUZZY))
                return RE_ERROR_MEMORY;

            Py_MEMCPY(state->fuzzy_counts, total_counts, sizeof(total_counts));
            state->fuzzy_node = outer_node;

            /* sstack: -
             *
             * bstack: inner_counts inner_node text_pos end_fuzzy_node
             * END_FUZZY
             */

            node = node->next_1.node;
            break;
        }
        case RE_OP_END_GREEDY_REPEAT: /* End of a greedy repeat. */
        {
            RE_CODE index;
            RE_RepeatData* rp_data;
            BOOL changed;
            BOOL try_body;
            int body_status;
            RE_Position next_body_position;
            BOOL try_tail;
            int tail_status;
            RE_Position next_tail_position;
            RE_BodyEndStateData data_be;
            TRACE(("%s %d\n", re_op_text[node->op], node->values[0]))

            /* Repeat indexes are 0-based. */
            index = node->values[0];
            rp_data = &state->repeats[index];

            /* The body has matched successfully at this position. */
            if (!guard_repeat(state, index, rp_data->start, RE_STATUS_BODY,
              FALSE))
                return RE_ERROR_MEMORY;

            ++rp_data->count;

            /* Have we advanced through the text or has a capture group change?
             */
            changed = rp_data->capture_change != state->capture_change ||
              state->text_pos != rp_data->start;

            /* Additional checks are needed if there's fuzzy matching. */
            if (changed && state->is_fuzzy && rp_data->count >=
              node->values[1])
                changed = !(node->step == 1 ? state->text_pos >=
                  state->slice_end : state->text_pos <= state->slice_start);

            /* The counts are of type size_t, so the format needs to specify
             * that.
             */
            TRACE(("min is %u, max is %u, count is %" PY_FORMAT_SIZE_T "u\n",
              node->values[1], node->values[2], rp_data->count))

            /* Could the body or tail match? */
            try_body = changed && (rp_data->count < node->values[2] ||
              ~node->values[2] == 0) && !is_repeat_guarded(state, index,
              state->text_pos, RE_STATUS_BODY);
            if (try_body) {
                body_status = try_match(state, &node->next_1, state->text_pos,
                  &next_body_position);
                if (body_status < 0) {
                    if (body_status == RE_ERROR_PARTIAL && rp_data->count >=
                      node->values[1] && at_end(state))
                        body_status = RE_ERROR_FAILURE;
                    else
                        return body_status;
                }

                if (body_status == RE_ERROR_FAILURE)
                    try_body = FALSE;
            } else
                body_status = RE_ERROR_FAILURE;

            try_tail = (!changed || rp_data->count >= node->values[1]) &&
              !is_repeat_guarded(state, index, state->text_pos,
              RE_STATUS_TAIL);
            if (try_tail) {
                tail_status = try_match(state, &node->nonstring.next_2,
                  state->text_pos, &next_tail_position);
                if (tail_status < 0)
                    return tail_status;

                if (tail_status == RE_ERROR_FAILURE)
                    try_tail = FALSE;
            } else
                tail_status = RE_ERROR_FAILURE;

            if (!try_body && !try_tail) {
                /* Neither the body nor the tail could match. */
                --rp_data->count;
                goto backtrack;
            }

            if (body_status < 0 || (body_status == 0 && tail_status < 0))
                return RE_ERROR_PARTIAL;

            /* Record info in case we backtrack into the body. */

            data_be.count = rp_data->count - 1;
            data_be.start = rp_data->start;
            data_be.capture_change = rp_data->capture_change;
            data_be.index = index;

            if (!ByteStack_push_block(state, &state->bstack, (void*)&data_be,
              sizeof(data_be)))
                return RE_ERROR_MEMORY;
            if (!push_uint8(state, &state->bstack, RE_OP_BODY_END))
                return RE_ERROR_MEMORY;

            /* bstack: count start capture_change index BODY_END */

            if (try_body) {
                /* Both the body and the tail could match. */
                if (try_tail) {
                    /* The body takes precedence. If the body fails to match
                     * then we want to try the tail before backtracking
                     * further.
                     */
                    RE_MatchBodyTailStateData data_mbt;

                    /* Record backtracking info for matching the tail. */
                    data_mbt.position = next_tail_position;
                    data_mbt.count = rp_data->count;
                    data_mbt.start = rp_data->start;
                    data_mbt.capture_change = rp_data->capture_change;
                    data_mbt.index = index;
                    data_mbt.text_pos = state->text_pos;

                    if (!ByteStack_push_block(state, &state->bstack,
                      (void*)&data_mbt, sizeof(data_mbt)))
                        return RE_ERROR_MEMORY;
                    if (!push_uint8(state, &state->bstack, RE_OP_MATCH_TAIL))
                        return RE_ERROR_MEMORY;

                    /* bstack: position count start capture_change index
                     * text_pos MATCH_TAIL
                     */
                }

                /* Record backtracking info in case the body fails to match. */
                if (!push_code(state, &state->bstack, index))
                    return RE_ERROR_MEMORY;
                if (!push_ssize(state, &state->bstack, state->text_pos))
                    return RE_ERROR_MEMORY;
                if (!push_uint8(state, &state->bstack, RE_OP_BODY_START))
                    return RE_ERROR_MEMORY;

                /* bstack: index text_pos BODY_START */

                rp_data->capture_change = state->capture_change;
                rp_data->start = state->text_pos;

                /* Advance into the body. */
                node = next_body_position.node;
                state->text_pos = next_body_position.text_pos;
            } else {
                /* Only the tail could match. */

                /* Advance into the tail. */
                node = next_tail_position.node;
                state->text_pos = next_tail_position.text_pos;
            }
            break;
        }
        case RE_OP_END_GROUP: /* End of a capture group. */
        {
            RE_CODE private_index;
            RE_CODE public_index;
            RE_GroupData* group;
            BOOL capture;
            TRACE(("%s %d\n", re_op_text[node->op], node->values[1]))

            /* Capture group indexes are 1-based (excluding group 0, which is
             * the entire matched string).
             */
            private_index = node->values[0];
            public_index = node->values[1];
            group = &state->groups[private_index - 1];
            capture = (BOOL)node->values[2];

            if (capture) {
                RE_GroupSpan span;
                RE_GroupStateData data_g;

                /* sstack: start
                 *
                 * bstack: -
                 */

                if (!pop_ssize(state, &state->sstack, &span.start))
                    return RE_ERROR_MEMORY;

                span.end = state->text_pos;

                data_g.text_pos = span.start;
                data_g.current = group->current;
                data_g.capture_change = state->capture_change;
                data_g.private_index = private_index;
                data_g.public_index = public_index;

                if (!ByteStack_push_block(state, &state->bstack,
                  (void*)&data_g, sizeof(data_g)))
                    return RE_ERROR_MEMORY;

                if (pattern->group_info[private_index - 1].referenced &&
                  !same_span_as_group(group, span))
                    ++state->capture_change;

                if (!save_capture(state, private_index, public_index, span))
                    return RE_ERROR_MEMORY;
                group->current = (Py_ssize_t)group->count - 1;
            } else {
                if (!push_ssize(state, &state->sstack, state->text_pos))
                    return RE_ERROR_MEMORY;
            }

            if (!push_bool(state, &state->bstack, capture))
                return RE_ERROR_MEMORY;
            if (!push_uint8(state, &state->bstack, RE_OP_END_GROUP))
                return RE_ERROR_MEMORY;

            /* If capturing:
             *
             * sstack: -
             *
             * bstack: start current capture_change private_index public_index
             * TRUE END_GROUP
             *
             * else:
             *
             * sstack: end
             *
             * bstack: FALSE END_GROUP
             */

            node = node->next_1.node;
            break;
        }
        case RE_OP_END_LAZY_REPEAT: /* End of a lazy repeat. */
        {
            RE_CODE index;
            RE_RepeatData* rp_data;
            BOOL changed;
            BOOL try_body;
            int body_status;
            RE_Position next_body_position;
            BOOL try_tail;
            int tail_status;
            RE_Position next_tail_position;
            RE_BodyEndStateData data_be;
            TRACE(("%s %d\n", re_op_text[node->op], node->values[0]))

            /* Repeat indexes are 0-based. */
            index = node->values[0];
            rp_data = &state->repeats[index];

            /* The body has matched successfully at this position. */
            if (!guard_repeat(state, index, rp_data->start, RE_STATUS_BODY,
              FALSE))
                return RE_ERROR_MEMORY;

            ++rp_data->count;

            /* Have we advanced through the text or has a capture group change?
             */
            changed = rp_data->capture_change != state->capture_change ||
              state->text_pos != rp_data->start;

            /* Additional checks are needed if there's fuzzy matching. */
            if (changed && state->is_fuzzy && rp_data->count >=
              node->values[1])
                changed = !(node->step == 1 ? state->text_pos >=
                  state->slice_end : state->text_pos <= state->slice_start);

            /* The counts are of type size_t, so the format needs to specify
             * that.
             */
            TRACE(("min is %u, max is %u, count is %" PY_FORMAT_SIZE_T "u\n",
              node->values[1], node->values[2], rp_data->count))

            /* Could the body or tail match? */
            try_body = changed && (rp_data->count < node->values[2] ||
              ~node->values[2] == 0) && !is_repeat_guarded(state, index,
              state->text_pos, RE_STATUS_BODY);
            if (try_body) {
                body_status = try_match(state, &node->next_1, state->text_pos,
                  &next_body_position);
                if (body_status < 0)
                    return body_status;

                if (body_status == RE_ERROR_FAILURE)
                    try_body = FALSE;
            } else
                body_status = RE_ERROR_FAILURE;

            try_tail = (!changed || rp_data->count >= node->values[1]);
            if (try_tail) {
                tail_status = try_match(state, &node->nonstring.next_2,
                  state->text_pos, &next_tail_position);
                if (tail_status < 0)
                    return tail_status;

                if (tail_status == RE_ERROR_FAILURE)
                    try_tail = FALSE;
            } else
                tail_status = RE_ERROR_FAILURE;

            if (!try_body && !try_tail) {
                /* Neither the body nor the tail could match. */
                --rp_data->count;
                goto backtrack;
            }

            if (body_status < 0 || (body_status == 0 && tail_status < 0))
                return RE_ERROR_PARTIAL;

            /* Record info in case we backtrack into the body. */
            data_be.count = rp_data->count - 1;
            data_be.start = rp_data->start;
            data_be.capture_change = rp_data->capture_change;
            data_be.index = index;

            if (!ByteStack_push_block(state, &state->bstack, (void*)&data_be,
              sizeof(data_be)))
                return RE_ERROR_MEMORY;
            if (!push_uint8(state, &state->bstack, RE_OP_BODY_END))
                return RE_ERROR_MEMORY;

            /* bstack: count start capture_change index BODY_END */

            if (try_body) {
                /* Both the body and the tail could match. */
                if (try_tail) {
                    /* The tail takes precedence. If the tail fails to match
                     * then we want to try the body before backtracking
                     * further.
                     */
                    RE_MatchBodyTailStateData data_mbt;

                    /* Record backtracking info for matching the body. */

                    data_mbt.position = next_body_position;
                    data_mbt.count = rp_data->count;
                    data_mbt.start = rp_data->start;
                    data_mbt.capture_change = rp_data->capture_change;
                    data_mbt.index = index;
                    data_mbt.text_pos = state->text_pos;

                    if (!ByteStack_push_block(state, &state->bstack,
                      (void*)&data_mbt, sizeof(data_mbt)))
                        return RE_ERROR_MEMORY;
                    if (!push_uint8(state, &state->bstack, RE_OP_MATCH_BODY))
                        return RE_ERROR_MEMORY;

                    /* bstack: position count start capture_change index
                     * text_pos MATCH_BODY
                     */

                    /* Advance into the tail. */
                    node = next_tail_position.node;
                    state->text_pos = next_tail_position.text_pos;
                } else {
                    /* Only the body could match. */

                    /* Record backtracking info in case the body fails to
                     * match.
                     */
                    if (!push_code(state, &state->bstack, index))
                        return RE_ERROR_MEMORY;
                    if (!push_ssize(state, &state->bstack, state->text_pos))
                        return RE_ERROR_MEMORY;
                    if (!push_uint8(state, &state->bstack, RE_OP_BODY_START))
                        return RE_ERROR_MEMORY;

                    /* bstack: index text_pos BODY_START */

                    rp_data->capture_change = state->capture_change;
                    rp_data->start = state->text_pos;

                    /* Advance into the body. */
                    node = next_body_position.node;
                    state->text_pos = next_body_position.text_pos;
                }
            } else {
                /* Only the tail could match. */

                /* Advance into the tail. */
                node = next_tail_position.node;
                state->text_pos = next_tail_position.text_pos;
            }
            break;
        }
        case RE_OP_END_LOOKAROUND: /* End of a lookaround subpattern. */
        {
            RE_LookaroundStateData data_l;
            RE_Node* lookaround;
            TRACE(("%s\n", re_op_text[node->op]))

            /* sstack: node slice_start slice_end text_pos ...
             *
             * bstack: [captures TRUE | FALSE] repeats fuzzy_counts
             * capture_change sstack LOOKAROUND ...
             *
             * pstack: bstack
             */

            if (!pop_bstack(state))
                return RE_ERROR_MEMORY;

            /* sstack: node slice_start slice_end text_pos ...
             *
             * bstack: [captures TRUE | FALSE] repeats fuzzy_counts
             * capture_change sstack LOOKAROUND
             *
             * pstack: -
             */

            if (!drop_uint8(state, &state->bstack))
                return RE_ERROR_MEMORY;
            if (!pop_sstack(state))
                return RE_ERROR_MEMORY;

            /* sstack: node slice_start slice_end text_pos
             *
             * bstack: [captures TRUE | FALSE] repeats fuzzy_counts
             * capture_change
             *
             * pstack: -
             */

            if (!ByteStack_pop_block(state, &state->sstack, (void*)&data_l,
              sizeof(data_l)))
                return RE_ERROR_MEMORY;

            state->text_pos = data_l.text_pos;
            state->slice_end = data_l.slice_end;
            state->slice_start = data_l.slice_start;
            lookaround = data_l.node;

            /* sstack: -
             *
             * bstack: [captures TRUE | FALSE] repeats fuzzy_counts
             * capture_change
             *
             * pstack: -
             */

            if (lookaround->match) {
                /* It's a positive lookaround that's succeeded. */
                if (!push_uint8(state, &state->bstack, RE_OP_END_LOOKAROUND))
                    return RE_ERROR_MEMORY;

                /* sstack: -
                 *
                 * bstack: [captures TRUE | FALSE] repeats fuzzy_counts
                 * capture_change END_LOOKAROUND
                 *
                 * pstack: -
                 */

                /* Go to the 'true' branch. */
                node = node->next_1.node;
            } else {
                BOOL has_groups;

                /* It's a negative lookaround that's succeeded. */
                if (!pop_size(state, &state->bstack, &state->capture_change))
                    return RE_ERROR_MEMORY;
                if (!pop_fuzzy_counts(state, &state->bstack,
                  state->fuzzy_counts))
                    return RE_ERROR_MEMORY;
                if (!pop_bool(state, &state->bstack, &has_groups))
                    return RE_ERROR_MEMORY;
                if (has_groups) {
                    if (!pop_captures(state, &state->bstack))
                        return RE_ERROR_MEMORY;
                }

                /* sstack: -
                 *
                 * bstack: -
                 *
                 * pstack: -
                 */

                /* Go to the 'false' branch. */
                goto backtrack;
            }
            break;
        }
        case RE_OP_END_OF_LINE: /* At the end of a line. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = try_match_END_OF_LINE(state, node, state->text_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS)
                node = node->next_1.node;
            else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 0);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_END_OF_LINE_U: /* At the end of a line. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = try_match_END_OF_LINE_U(state, node, state->text_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS)
                node = node->next_1.node;
            else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 0);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_END_OF_STRING: /* At the end of the string. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = try_match_END_OF_STRING(state, node, state->text_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS)
                node = node->next_1.node;
            else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 0);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_END_OF_STRING_LINE: /* At the end of string or final newline. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = try_match_END_OF_STRING_LINE(state, node,
              state->text_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS)
                node = node->next_1.node;
            else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 0);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_END_OF_STRING_LINE_U: /* At the end of string or final newline. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = try_match_END_OF_STRING_LINE_U(state, node,
              state->text_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS)
                node = node->next_1.node;
            else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 0);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_END_OF_WORD: /* At the end of a word. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = try_match_END_OF_WORD(state, node, state->text_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS)
                node = node->next_1.node;
            else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 0);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_FAILURE: /* Failure. */
            goto backtrack;
        case RE_OP_FUZZY: /* Fuzzy matching. */
        {
            TRACE(("%s\n", re_op_text[node->op]))

            /* Save the outer fuzzy info. */
            if (!push_fuzzy_counts(state, &state->sstack, state->fuzzy_counts))
                return RE_ERROR_MEMORY;
            if (!push_pointer(state, &state->sstack, state->fuzzy_node))
                return RE_ERROR_MEMORY;

            /* Initialise the inner fuzzy info. */
            memset(state->fuzzy_counts, 0, sizeof(state->fuzzy_counts));
            state->fuzzy_node = node;

            if (!push_uint8(state, &state->bstack, RE_OP_FUZZY))
                return RE_ERROR_MEMORY;

            /* sstack: outer_counts outer_node
             *
             * bstack: FUZZY
             */

            node = node->next_1.node;
            break;
        }
        case RE_OP_GRAPHEME_BOUNDARY: /* At a grapheme boundary. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = try_match_GRAPHEME_BOUNDARY(state, node, state->text_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS)
                node = node->next_1.node;
            else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 0);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_GREEDY_REPEAT: /* Greedy repeat. */
        {
            RE_CODE index;
            RE_RepeatData* rp_data;
            BOOL try_body;
            int body_status;
            RE_Position next_body_position;
            BOOL try_tail;
            int tail_status;
            RE_Position next_tail_position;
            RE_RepeatStateData data_r;
            TRACE(("%s %d\n", re_op_text[node->op], node->values[0]))

            /* Repeat indexes are 0-based. */
            index = node->values[0];
            rp_data = &state->repeats[index];

            /* We might need to backtrack into the head, so save the current
             * repeat.
             */

            data_r.count = rp_data->count;
            data_r.start = rp_data->start;
            data_r.capture_change = rp_data->capture_change;
            data_r.index = index;
            data_r.text_pos = state->text_pos;

            if (!ByteStack_push_block(state, &state->bstack, (void*)&data_r,
              sizeof(data_r)))
                return RE_ERROR_MEMORY;
            if (!push_uint8(state, &state->bstack, RE_OP_GREEDY_REPEAT))
                return RE_ERROR_MEMORY;

            /* bstack: count start capture_change index text_pos GREEDY_REPEAT
             */

            /* Initialise the new repeat. */
            rp_data->count = 0;
            rp_data->start = state->text_pos;
            rp_data->capture_change = state->capture_change;

            /* Could the body or tail match? */
            try_body = node->values[2] > 0 && !is_repeat_guarded(state, index,
              state->text_pos, RE_STATUS_BODY);
            if (try_body) {
                body_status = try_match(state, &node->next_1, state->text_pos,
                  &next_body_position);
                if (body_status < 0)
                    return body_status;

                if (body_status == RE_ERROR_FAILURE)
                    try_body = FALSE;
            } else
                body_status = RE_ERROR_FAILURE;

            try_tail = node->values[1] == 0;
            if (try_tail) {
                tail_status = try_match(state, &node->nonstring.next_2,
                  state->text_pos, &next_tail_position);
                if (tail_status < 0)
                    return tail_status;

                if (tail_status == RE_ERROR_FAILURE)
                    try_tail = FALSE;
            } else
                tail_status = RE_ERROR_FAILURE;
            if (!try_body && !try_tail)
                /* Neither the body nor the tail could match. */
                goto backtrack;

            if (body_status < 0 || (body_status == 0 && tail_status < 0))
                return RE_ERROR_PARTIAL;

            if (try_body) {
                if (try_tail) {
                    /* Both the body and the tail could match, but the body
                     * takes precedence. If the body fails to match then we
                     * want to try the tail before backtracking further.
                     */
                    RE_MatchBodyTailStateData data_mbt;

                    /* Record backtracking info for matching the tail. */
                    data_mbt.position = next_tail_position;
                    data_mbt.count = rp_data->count;
                    data_mbt.start = rp_data->start;
                    data_mbt.capture_change = rp_data->capture_change;
                    data_mbt.index = index;
                    data_mbt.text_pos = state->text_pos;

                    if (!ByteStack_push_block(state, &state->bstack,
                      (void*)&data_mbt, sizeof(data_mbt)))
                        return RE_ERROR_MEMORY;
                    if (!push_uint8(state, &state->bstack, RE_OP_MATCH_TAIL))
                        return RE_ERROR_MEMORY;

                    /* bstack: position count start capture_change index
                     * text_pos MATCH_TAIL
                     */
                }

                /* Advance into the body. */
                node = next_body_position.node;
                state->text_pos = next_body_position.text_pos;
            } else {
                /* Only the tail could match. */

                /* Advance into the tail. */
                node = next_tail_position.node;
                state->text_pos = next_tail_position.text_pos;
            }
            break;
        }
        case RE_OP_GREEDY_REPEAT_ONE: /* Greedy repeat for one character. */
        {
            RE_CODE index;
            RE_RepeatData* rp_data;
            size_t count;
            BOOL is_partial;
            BOOL match;
            TRACE(("%s %d\n", re_op_text[node->op], node->values[0]))

            /* Repeat indexes are 0-based. */
            index = node->values[0];
            rp_data = &state->repeats[index];

            if (is_repeat_guarded(state, index, state->text_pos,
              RE_STATUS_BODY))
                goto backtrack;

            /* Count how many times the character repeats, up to the maximum.
             */
            count = count_one(state, node->nonstring.next_2.node,
              state->text_pos, node->values[2], &is_partial);
            if (is_partial) {
                state->text_pos += (Py_ssize_t)count * node->step;
                return RE_ERROR_PARTIAL;
            }

            /* Unmatch until it's not guarded. */
            match = FALSE;
            for (;;) {
                if (count < node->values[1])
                    /* The number of repeats is below the minimum. */
                    break;

                if (!is_repeat_guarded(state, index, state->text_pos +
                  (Py_ssize_t)count * node->step, RE_STATUS_TAIL)) {
                    /* It's not guarded at this position. */
                    match = TRUE;
                    break;
                }

                if (count == 0)
                    break;

                --count;
            }

            if (!match) {
                /* The repeat has failed to match at this position. */
                if (!guard_repeat(state, index, state->text_pos,
                  RE_STATUS_BODY, TRUE))
                    return RE_ERROR_MEMORY;
                goto backtrack;
            }

            if (count > node->values[1]) {
                /* Record the backtracking info. */
                RE_RepeatOneStateData data_ro;

                data_ro.count = rp_data->count;
                data_ro.start = rp_data->start;
                data_ro.node = node;
                data_ro.index = index;

                if (!ByteStack_push_block(state, &state->bstack,
                  (void*)&data_ro, sizeof(data_ro)))
                    return RE_ERROR_MEMORY;
                if (!push_uint8(state, &state->bstack,
                  RE_OP_GREEDY_REPEAT_ONE))
                    return RE_ERROR_MEMORY;

                /* bstack: count start node index GREEDY_REPEAT_ONE */

                rp_data->start = state->text_pos;
                rp_data->count = count;
            }

            /* Advance into the tail. */
            state->text_pos += (Py_ssize_t)count * node->step;
            node = node->next_1.node;
            break;
        }
        case RE_OP_GROUP_CALL: /* Group call. */
        {
            size_t index;
            RE_Node* next_node;
            size_t r;
            TRACE(("%s %d\n", re_op_text[node->op], node->values[0]))

            index = node->values[0];
            next_node = node->next_1.node;

            /* For the caller. */
            if (!push_groups(state, &state->sstack))
                return RE_ERROR_MEMORY;
            if (!push_repeats(state, &state->sstack))
                return RE_ERROR_MEMORY;
            if (!push_size(state, &state->sstack, state->capture_change))
                return RE_ERROR_MEMORY;
            if (!push_pointer(state, &state->sstack, next_node))
                return RE_ERROR_MEMORY;
            if (!push_uint8(state, &state->bstack, RE_OP_GROUP_CALL))
                return RE_ERROR_MEMORY;

            /* sstack: caller_groups caller_repeats capture_change return_node
             *
             * bstack: GROUP_CALL
             */

            /* Clear the repeat guards for the group call. They'll be restored
             * on return.
             */
            for (r = 0; r < state->pattern->repeat_count; r++) {
                RE_RepeatData* repeat;

                repeat = &state->repeats[r];
                repeat->body_guard_list.count = 0;
                repeat->body_guard_list.last_text_pos = -1;
                repeat->tail_guard_list.count = 0;
                repeat->tail_guard_list.last_text_pos = -1;
            }

            /* Call a group, skipping its CALL_REF node. */
            node = pattern->call_ref_info[index].node->next_1.node;
            break;
        }
        case RE_OP_GROUP_EXISTS: /* Capture group exists. */
        {
            RE_CODE index;
            TRACE(("%s %d\n", re_op_text[node->op], node->values[0]))

            /* Capture group indexes are 1-based (excluding group 0, which is
             * the entire matched string).
             *
             * Check whether the captured text, if any, exists at this position
             * in the string.
             *
             * A group index of 0, however, means that it's a DEFINE, which we
             * should skip.
             */
            index = node->values[0];

            if (index == 0)
                /* Skip past the body. */
                node = node->nonstring.next_2.node;
            else {
                RE_GroupData* group;

                group = &state->groups[index - 1];
                if (group->current >= 0)
                    /* The 'true' branch. */
                    node = node->next_1.node;
                else
                    /* The 'false' branch. */
                    node = node->nonstring.next_2.node;
            }
            break;
        }
        case RE_OP_GROUP_RETURN: /* Group return. */
        {
            RE_Node* return_node;
            TRACE(("%s\n", re_op_text[node->op]))

            /* If called:
             *
             * sstack: caller_groups caller_repeats capture_change return_node
             *
             * bstack: -
             *
             * else:
             *
             * sstack: NULL
             *
             * bstack: -
             */

            if (!pop_pointer(state, &state->sstack, (void*)&return_node))
                return RE_ERROR_MEMORY;

            if (return_node) {
                /* The group was called. */
                node = return_node;

                /* For the callee. */
                if (!push_groups(state, &state->bstack))
                    return RE_ERROR_MEMORY;
                if (!push_repeats(state, &state->bstack))
                    return RE_ERROR_MEMORY;
                if (!push_size(state, &state->bstack, state->capture_change))
                    return RE_ERROR_MEMORY;
                if (!push_pointer(state, &state->bstack, return_node))
                    return RE_ERROR_MEMORY;
                if (!push_uint8(state, &state->bstack, RE_OP_GROUP_RETURN))
                    return RE_ERROR_MEMORY;

                /* For the caller. */
                if (!pop_size(state, &state->sstack, &state->capture_change))
                    return RE_ERROR_MEMORY;
                if (!pop_repeats(state, &state->sstack))
                    return RE_ERROR_MEMORY;
                if (!pop_groups(state, &state->sstack))
                    return RE_ERROR_MEMORY;
            } else {
                /* The group was not called. */
                if (!push_pointer(state, &state->bstack, NULL))
                    return RE_ERROR_MEMORY;
                if (!push_uint8(state, &state->bstack, RE_OP_GROUP_RETURN))
                    return RE_ERROR_MEMORY;

                node = node->next_1.node;
            }

            /* If called:
             *
             * sstack: -
             *
             * bstack: callee_groups callee_repeats capture_change return_node
             * GROUP_RETURN
             *
             * else:
             *
             * sstack: -
             *
             * bstack: NULL GROUP_RETURN
             */
            break;
        }
        case RE_OP_KEEP: /* Keep. */
            TRACE(("%s\n", re_op_text[node->op]))

            if (!push_ssize(state, &state->bstack, state->match_pos))
                return RE_ERROR_MEMORY;
            if (!push_uint8(state, &state->bstack, RE_OP_KEEP))
                return RE_ERROR_MEMORY;

            /* bstack: match_pos KEEP */

            state->match_pos = state->text_pos;

            node = node->next_1.node;
            break;
        case RE_OP_LAZY_REPEAT: /* Lazy repeat. */
        {
            RE_CODE index;
            RE_RepeatData* rp_data;
            BOOL changed;
            BOOL try_body;
            int body_status;
            RE_Position next_body_position;
            BOOL try_tail;
            int tail_status;
            RE_Position next_tail_position;
            RE_RepeatStateData data_r;
            TRACE(("%s %d\n", re_op_text[node->op], node->values[0]))

            /* Repeat indexes are 0-based. */
            index = node->values[0];
            rp_data = &state->repeats[index];

            /* Has a capture group change? */
            changed = rp_data->capture_change != state->capture_change;

            /* We might need to backtrack into the head, so save the current
             * repeat.
             */

            data_r.count = rp_data->count;
            data_r.start = rp_data->start;
            data_r.capture_change = rp_data->capture_change;
            data_r.index = index;
            data_r.text_pos = state->text_pos;

            if (!ByteStack_push_block(state, &state->bstack, (void*)&data_r,
              sizeof(data_r)))
                return RE_ERROR_MEMORY;
            if (!push_uint8(state, &state->bstack, RE_OP_LAZY_REPEAT))
                return RE_ERROR_MEMORY;

            /* bstack: count start capture_change index text_pos LAZY_REPEAT */

            /* Initialise the new repeat. */
            rp_data->count = 0;
            rp_data->start = state->text_pos;
            rp_data->capture_change = state->capture_change;

            /* Could the body or tail match? */
            try_body = (changed && state->is_fuzzy) || (node->values[2] > 0 &&
              !is_repeat_guarded(state, index, state->text_pos,
              RE_STATUS_BODY));
            if (try_body) {
                body_status = try_match(state, &node->next_1, state->text_pos,
                  &next_body_position);
                if (body_status < 0)
                    return body_status;

                if (body_status == RE_ERROR_FAILURE)
                    try_body = FALSE;
            } else
                body_status = RE_ERROR_FAILURE;

            try_tail = node->values[1] == 0;
            if (try_tail) {
                tail_status = try_match(state, &node->nonstring.next_2,
                  state->text_pos, &next_tail_position);
                if (tail_status < 0)
                    return tail_status;

                if (tail_status == RE_ERROR_FAILURE)
                    try_tail = FALSE;
            } else
                tail_status = RE_ERROR_FAILURE;

            if (!try_body && !try_tail)
                /* Neither the body nor the tail could match. */
                goto backtrack;

            if (body_status < 0 || (body_status == 0 && tail_status < 0))
                return RE_ERROR_PARTIAL;

            if (try_body) {
                if (try_tail) {
                    /* Both the body and the tail could match, but the tail
                     * takes precedence. If the tail fails to match then we
                     * want to try the body before backtracking further.
                     */
                    RE_MatchBodyTailStateData data_mbt;

                    /* Record backtracking info for matching the body. */
                    data_mbt.position = next_body_position;
                    data_mbt.count = rp_data->count;
                    data_mbt.start = rp_data->start;
                    data_mbt.capture_change = rp_data->capture_change;
                    data_mbt.index = index;
                    data_mbt.text_pos = state->text_pos;

                    if (!ByteStack_push_block(state, &state->bstack,
                      (void*)&data_mbt, sizeof(data_mbt)))
                        return RE_ERROR_MEMORY;
                    if (!push_uint8(state, &state->bstack, RE_OP_MATCH_BODY))
                        return RE_ERROR_MEMORY;

                    /* bstack: position count start capture_change index
                     * text_pos MATCH_BODY
                     */

                    /* Advance into the tail. */
                    node = next_tail_position.node;
                    state->text_pos = next_tail_position.text_pos;
                } else {
                    /* Advance into the body. */
                    node = next_body_position.node;
                    state->text_pos = next_body_position.text_pos;
                }
            } else {
                /* Only the tail could match. */

                /* Advance into the tail. */
                node = next_tail_position.node;
                state->text_pos = next_tail_position.text_pos;
            }
            break;
        }
        case RE_OP_LAZY_REPEAT_ONE: /* Lazy repeat for one character. */
        {
            RE_CODE index;
            RE_RepeatData* rp_data;
            size_t count;
            BOOL is_partial;
            TRACE(("%s %d\n", re_op_text[node->op], node->values[0]))

            /* Repeat indexes are 0-based. */
            index = node->values[0];
            rp_data = &state->repeats[index];

            if (is_repeat_guarded(state, index, state->text_pos,
              RE_STATUS_BODY))
                goto backtrack;

            /* Count how many times the character repeats, up to the minimum.
             */
            count = count_one(state, node->nonstring.next_2.node,
              state->text_pos, node->values[1], &is_partial);
            if (is_partial) {
                state->text_pos += (Py_ssize_t)count * node->step;
                return RE_ERROR_PARTIAL;
            }

            /* Have we matched at least the minimum? */
            if (count < node->values[1]) {
                /* The repeat has failed to match at this position. */
                if (!guard_repeat(state, index, state->text_pos,
                  RE_STATUS_BODY, TRUE))
                    return RE_ERROR_MEMORY;
                goto backtrack;
            }

            if (count < node->values[2]) {
                /* The match is shorter than the maximum, so we might need to
                 * backtrack the repeat to consume more.
                 */
                RE_RepeatOneStateData data_ro;

                data_ro.count = rp_data->count;
                data_ro.start = rp_data->start;
                data_ro.node = node;
                data_ro.index = index;

                if (!ByteStack_push_block(state, &state->bstack,
                  (void*)&data_ro, sizeof(data_ro)))
                    return RE_ERROR_MEMORY;
                if (!push_uint8(state, &state->bstack, RE_OP_LAZY_REPEAT_ONE))
                    return RE_ERROR_MEMORY;

                /* bstack: count start node index LAZY_REPEAT_ONE */

                /* Get the offset to the repeat values in the context. */
                rp_data = &state->repeats[index];

                rp_data->start = state->text_pos;
                rp_data->count = count;
            }

            /* Advance into the tail. */
            state->text_pos += (Py_ssize_t)count * node->step;
            node = node->next_1.node;
            break;
        }
        case RE_OP_LOOKAROUND: /* Start of a lookaround subpattern. */
        {
            RE_LookaroundStateData data_l;
            BOOL has_groups;
            TRACE(("%s %d\n", re_op_text[node->op], node->match))

            data_l.node = node;
            data_l.slice_start = state->slice_start;
            data_l.slice_end = state->slice_end;
            data_l.text_pos = state->text_pos;

            if (!ByteStack_push_block(state, &state->sstack, (void*)&data_l,
              sizeof(data_l)))
                return RE_ERROR_MEMORY;
            has_groups = (node->status & RE_STATUS_HAS_GROUPS) != 0;
            if (has_groups) {
                if (!push_captures(state, &state->bstack))
                    return RE_ERROR_MEMORY;
            }
            if (!push_bool(state, &state->bstack, has_groups))
                return RE_ERROR_MEMORY;
            if (!push_fuzzy_counts(state, &state->bstack, state->fuzzy_counts))
                return RE_ERROR_MEMORY;
            if (!push_size(state, &state->bstack, state->capture_change))
                return RE_ERROR_MEMORY;
            if (!push_sstack(state))
                return RE_ERROR_MEMORY;
            if (!push_uint8(state, &state->bstack, RE_OP_LOOKAROUND))
                return RE_ERROR_MEMORY;
            if (!push_bstack(state))
                return RE_ERROR_MEMORY;

            /* sstack: node slice_start slice_end text_pos
             *
             * bstack: [captures TRUE | FALSE] repeats fuzzy_counts
             * capture_change sstack LOOKAROUND
             *
             * pstack: bstack
             */

            state->slice_start = 0;
            state->slice_end = state->text_length;

            node = node->next_1.node;
            break;
        }
        case RE_OP_PROPERTY: /* A property. */
            TRACE(("%s %d %d\n", re_op_text[node->op], node->match,
              node->values[0]))

            if (state->text_pos >= state->text_length && state->partial_side ==
              RE_PARTIAL_RIGHT)
                return RE_ERROR_PARTIAL;

            if (state->text_pos < state->slice_end &&
              matches_PROPERTY(encoding, locale_info, node,
              char_at(state->text, state->text_pos)) == node->match) {
                state->text_pos += node->step;
                node = node->next_1.node;
            } else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 1);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_PROPERTY_IGN: /* A property, ignoring case. */
            TRACE(("%s %d %d\n", re_op_text[node->op], node->match,
              node->values[0]))

            if (state->text_pos >= state->text_length && state->partial_side ==
              RE_PARTIAL_RIGHT)
                return RE_ERROR_PARTIAL;

            if (state->text_pos < state->slice_end &&
              matches_PROPERTY_IGN(encoding, locale_info, node,
              char_at(state->text, state->text_pos)) == node->match) {
                state->text_pos += node->step;
                node = node->next_1.node;
            } else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 1);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_PROPERTY_IGN_REV: /* A property, backwards, ignoring case. */
            TRACE(("%s %d %d\n", re_op_text[node->op], node->match,
              node->values[0]))

            if (state->text_pos <= 0 && state->partial_side == RE_PARTIAL_LEFT)
                return RE_ERROR_PARTIAL;

            if (state->text_pos > state->slice_start &&
              matches_PROPERTY_IGN(encoding, locale_info, node,
              char_at(state->text, state->text_pos - 1)) == node->match) {
                state->text_pos += node->step;
                node = node->next_1.node;
            } else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, -1);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_PROPERTY_REV: /* A property, backwards. */
            TRACE(("%s %d %d\n", re_op_text[node->op], node->match,
              node->values[0]))

            if (state->text_pos <= 0 && state->partial_side == RE_PARTIAL_LEFT)
                return RE_ERROR_PARTIAL;

            if (state->text_pos > state->slice_start &&
              matches_PROPERTY(encoding, locale_info, node,
              char_at(state->text, state->text_pos - 1)) == node->match) {
                state->text_pos += node->step;
                node = node->next_1.node;
            } else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, -1);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_PRUNE: /* Prune the backtracking. */
            TRACE(("%s\n", re_op_text[node->op]))

            /* bstack: ... | ...
             *
             * pstack: bstack
             */

            /* Prune the backtracking back to an appropriate backtracking
             * point.
             */
            top_bstack(state);

            /* bstack: ...
             *
             * pstack: bstack
             */

            node = node->next_1.node;
            break;
        case RE_OP_RANGE: /* A range. */
            TRACE(("%s %d %d %d\n", re_op_text[node->op], node->match,
              node->values[0], node->values[1]))

            if (state->text_pos >= state->text_length && state->partial_side ==
              RE_PARTIAL_RIGHT)
                return RE_ERROR_PARTIAL;

            if (state->text_pos < state->slice_end && matches_RANGE(encoding,
              locale_info, node, char_at(state->text, state->text_pos)) ==
              node->match) {
                state->text_pos += node->step;
                node = node->next_1.node;
            } else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 1);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_RANGE_IGN: /* A range, ignoring case. */
            TRACE(("%s %d %d %d\n", re_op_text[node->op], node->match,
              node->values[0], node->values[1]))

            if (state->text_pos >= state->text_length && state->partial_side ==
              RE_PARTIAL_RIGHT)
                return RE_ERROR_PARTIAL;

            if (state->text_pos < state->slice_end &&
              matches_RANGE_IGN(encoding, locale_info, node,
              char_at(state->text, state->text_pos)) == node->match) {
                state->text_pos += node->step;
                node = node->next_1.node;
            } else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 1);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_RANGE_IGN_REV: /* A range, backwards, ignoring case. */
            TRACE(("%s %d %d %d\n", re_op_text[node->op], node->match,
              node->values[0], node->values[1]))

            if (state->text_pos <= 0 && state->partial_side == RE_PARTIAL_LEFT)
                return RE_ERROR_PARTIAL;

            if (state->text_pos > state->slice_start &&
              matches_RANGE_IGN(encoding, locale_info, node,
              char_at(state->text, state->text_pos - 1)) == node->match) {
                state->text_pos += node->step;
                node = node->next_1.node;
            } else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, -1);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_RANGE_REV: /* A range, backwards. */
            TRACE(("%s %d %d %d\n", re_op_text[node->op], node->match,
              node->values[0], node->values[1]))

            if (state->text_pos <= 0 && state->partial_side == RE_PARTIAL_LEFT)
                return RE_ERROR_PARTIAL;

            if (state->text_pos > state->slice_start && matches_RANGE(encoding,
              locale_info, node, char_at(state->text, state->text_pos - 1)) ==
              node->match) {
                state->text_pos += node->step;
                node = node->next_1.node;
            } else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, -1);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_REF_GROUP: /* Reference to a capture group. */
        {
            RE_GroupData* group;
            RE_GroupSpan* span;
            TRACE(("%s %d\n", re_op_text[node->op], node->values[0]))

            /* Capture group indexes are 1-based (excluding group 0, which is
             * the entire matched string).
             *
             * Check whether the captured text, if any, exists at this position
             * in the string.
             */

            /* Did the group capture anything? */
            group = &state->groups[node->values[0] - 1];
            if (group->current < 0)
                goto backtrack;

            span = &group->captures[group->current];

            if (string_pos < 0)
                string_pos = span->start;

            /* Try comparing. */
            while (string_pos < span->end) {
                if (state->text_pos >= state->text_length &&
                  state->partial_side == RE_PARTIAL_RIGHT)
                    return RE_ERROR_PARTIAL;

                if (state->text_pos < state->slice_end &&
                  same_char(char_at(state->text, state->text_pos),
                  char_at(state->text, string_pos))) {
                    ++string_pos;
                    ++state->text_pos;
                } else if (node->status & RE_STATUS_FUZZY) {
                    status = fuzzy_match_string(state, search,
                      &state->text_pos, node, &string_pos, 1);
                    if (status < 0)
                        return status;

                    if (status == RE_ERROR_FAILURE) {
                        string_pos = -1;
                        goto backtrack;
                    }
                } else {
                    string_pos = -1;
                    goto backtrack;
                }
            }

            string_pos = -1;

            /* Successful match. */
            node = node->next_1.node;
            break;
        }
        case RE_OP_REF_GROUP_FLD: /* Reference to a capture group, ignoring case. */
        {
            RE_GroupData* group;
            RE_GroupSpan* span;
            int (*full_case_fold)(RE_LocaleInfo* locale_info, Py_UCS4 ch,
              Py_UCS4* folded);
            int folded_len;
            int gfolded_len;
            Py_UCS4 folded[RE_MAX_FOLDED];
            Py_UCS4 gfolded[RE_MAX_FOLDED];
            TRACE(("%s %d\n", re_op_text[node->op], node->values[0]))

            /* Capture group indexes are 1-based (excluding group 0, which is
             * the entire matched string).
             *
             * Check whether the captured text, if any, exists at this position
             * in the string.
             */

            /* Did the group capture anything? */
            group = &state->groups[node->values[0] - 1];
            if (group->current < 0)
                goto backtrack;

            span = &group->captures[group->current];

            full_case_fold = encoding->full_case_fold;

            if (string_pos < 0) {
                string_pos = span->start;
                folded_pos = 0;
                folded_len = 0;
                gfolded_pos = 0;
                gfolded_len = 0;
            } else {
                folded_len = full_case_fold(locale_info, char_at(state->text,
                  state->text_pos), folded);
                gfolded_len = full_case_fold(locale_info, char_at(state->text,
                  string_pos), gfolded);
            }

            /* Try comparing. */
            while (string_pos < span->end) {
                /* Case-fold at current position in text. */
                if (folded_pos >= folded_len) {
                    if (state->text_pos >= state->text_length &&
                      state->partial_side == RE_PARTIAL_RIGHT)
                        return RE_ERROR_PARTIAL;

                    if (state->text_pos < state->slice_end)
                        folded_len = full_case_fold(locale_info,
                          char_at(state->text, state->text_pos), folded);
                    else
                        folded_len = 0;

                    folded_pos = 0;
                }

                /* Case-fold at current position in group. */
                if (gfolded_pos >= gfolded_len) {
                    gfolded_len = full_case_fold(locale_info,
                      char_at(state->text, string_pos), gfolded);
                    gfolded_pos = 0;
                }

                if (folded_pos < folded_len && same_char_ign(encoding,
                  locale_info,
                   gfolded[gfolded_pos],
                   folded[folded_pos])) {
                    ++folded_pos;
                    ++gfolded_pos;
                } else if (node->status & RE_STATUS_FUZZY) {
                    status = fuzzy_match_group_fld(state, search,
                      &state->text_pos, node, &folded_pos, folded_len,
                      &string_pos, &gfolded_pos, gfolded_len, 1);
                    if (status < 0)
                        return status;

                    if (status == RE_ERROR_FAILURE) {
                        string_pos = -1;
                        goto backtrack;
                    }
                } else {
                    string_pos = -1;
                    goto backtrack;
                }

                if (folded_pos >= folded_len && folded_len > 0)
                    ++state->text_pos;

                if (gfolded_pos >= gfolded_len)
                    ++string_pos;
            }

            string_pos = -1;

            if (folded_pos < folded_len || gfolded_pos < gfolded_len)
                goto backtrack;

            /* Successful match. */
            node = node->next_1.node;
            break;
        }
        case RE_OP_REF_GROUP_FLD_REV: /* Reference to a capture group, ignoring case. */
        {
            RE_GroupData* group;
            RE_GroupSpan* span;
            int (*full_case_fold)(RE_LocaleInfo* locale_info, Py_UCS4 ch,
              Py_UCS4* folded);
            int folded_len;
            int gfolded_len;
            Py_UCS4 folded[RE_MAX_FOLDED];
            Py_UCS4 gfolded[RE_MAX_FOLDED];
            TRACE(("%s %d\n", re_op_text[node->op], node->values[0]))

            /* Capture group indexes are 1-based (excluding group 0, which is
             * the entire matched string).
             *
             * Check whether the captured text, if any, exists at this position
             * in the string.
             */

            /* Did the group capture anything? */
            group = &state->groups[node->values[0] - 1];
            if (group->current < 0)
                goto backtrack;

            span = &group->captures[group->current];

            full_case_fold = encoding->full_case_fold;

            if (string_pos < 0) {
                string_pos = span->end;
                folded_pos = 0;
                folded_len = 0;
                gfolded_pos = 0;
                gfolded_len = 0;
            } else {
                folded_len = full_case_fold(locale_info, char_at(state->text,
                  state->text_pos - 1), folded);
                gfolded_len = full_case_fold(locale_info, char_at(state->text,
                  string_pos - 1), gfolded);
            }

            /* Try comparing. */
            while (string_pos > span->start) {
                /* Case-fold at current position in text. */
                if (folded_pos <= 0) {
                    if (state->text_pos <= 0 && state->partial_side ==
                      RE_PARTIAL_LEFT)
                        return RE_ERROR_PARTIAL;

                    if (state->text_pos > state->slice_start)
                        folded_len = full_case_fold(locale_info,
                          char_at(state->text, state->text_pos - 1), folded);
                    else
                        folded_len = 0;

                    folded_pos = folded_len;
                }

                /* Case-fold at current position in group. */
                if (gfolded_pos <= 0) {
                    gfolded_len = full_case_fold(locale_info,
                      char_at(state->text, string_pos - 1), gfolded);
                    gfolded_pos = gfolded_len;
                }

                if (folded_pos > 0 && same_char_ign(encoding, locale_info,
                   gfolded[gfolded_pos - 1],
                   folded[folded_pos - 1])) {
                    --folded_pos;
                    --gfolded_pos;
                } else if (node->status & RE_STATUS_FUZZY) {
                    status = fuzzy_match_group_fld(state, search,
                      &state->text_pos, node, &folded_pos, folded_len,
                      &string_pos, &gfolded_pos, gfolded_len, -1);
                    if (status < 0)
                        return status;

                    if (status == RE_ERROR_FAILURE) {
                        string_pos = -1;
                        goto backtrack;
                    }
                } else {
                    string_pos = -1;
                    goto backtrack;
                }

                if (folded_pos <= 0 && folded_len > 0)
                    --state->text_pos;

                if (gfolded_pos <= 0)
                    --string_pos;
            }

            string_pos = -1;

            if (folded_pos > 0 || gfolded_pos > 0)
                goto backtrack;

            /* Successful match. */
            node = node->next_1.node;
            break;
        }
        case RE_OP_REF_GROUP_IGN: /* Reference to a capture group, ignoring case. */
        {
            RE_GroupData* group;
            RE_GroupSpan* span;
            TRACE(("%s %d\n", re_op_text[node->op], node->values[0]))

            /* Capture group indexes are 1-based (excluding group 0, which is
             * the entire matched string).
             *
             * Check whether the captured text, if any, exists at this position
             * in the string.
             */

            /* Did the group capture anything? */
            group = &state->groups[node->values[0] - 1];
            if (group->current < 0)
                goto backtrack;

            span = &group->captures[group->current];

            if (string_pos < 0)
                string_pos = span->start;

            /* Try comparing. */
            while (string_pos < span->end) {
                if (state->text_pos >= state->text_length &&
                  state->partial_side == RE_PARTIAL_RIGHT)
                    return RE_ERROR_PARTIAL;

                if (state->text_pos < state->slice_end &&
                  same_char_ign(encoding, locale_info, char_at(state->text,
                  state->text_pos), char_at(state->text, string_pos))) {
                    ++string_pos;
                    ++state->text_pos;
                } else if (node->status & RE_STATUS_FUZZY) {
                    status = fuzzy_match_string(state, search,
                      &state->text_pos, node, &string_pos, 1);
                    if (status < 0)
                        return status;

                    if (status == RE_ERROR_FAILURE) {
                        string_pos = -1;
                        goto backtrack;
                    }
                } else {
                    string_pos = -1;
                    goto backtrack;
                }
            }

            string_pos = -1;

            /* Successful match. */
            node = node->next_1.node;
            break;
        }
        case RE_OP_REF_GROUP_IGN_REV: /* Reference to a capture group, ignoring case. */
        {
            RE_GroupData* group;
            RE_GroupSpan* span;
            TRACE(("%s %d\n", re_op_text[node->op], node->values[0]))

            /* Capture group indexes are 1-based (excluding group 0, which is
             * the entire matched string).
             *
             * Check whether the captured text, if any, exists at this position
             * in the string.
             */

            /* Did the group capture anything? */
            group = &state->groups[node->values[0] - 1];
            if (group->current < 0)
                goto backtrack;

            span = &group->captures[group->current];

            if (string_pos < 0)
                string_pos = span->end;

            /* Try comparing. */
            while (string_pos > span->start) {
                if (state->text_pos <= 0 && state->partial_side ==
                  RE_PARTIAL_LEFT)
                    return RE_ERROR_PARTIAL;

                if (state->text_pos > state->slice_start &&
                  same_char_ign(encoding, locale_info, char_at(state->text,
                  state->text_pos - 1), char_at(state->text, string_pos - 1)))
                  {
                    --string_pos;
                    --state->text_pos;
                } else if (node->status & RE_STATUS_FUZZY) {
                    status = fuzzy_match_string(state, search,
                      &state->text_pos, node, &string_pos, -1);
                    if (status < 0)
                        return status;

                    if (status == RE_ERROR_FAILURE) {
                        string_pos = -1;
                        goto backtrack;
                    }
                } else {
                    string_pos = -1;
                    goto backtrack;
                }
            }

            string_pos = -1;

            /* Successful match. */
            node = node->next_1.node;
            break;
        }
        case RE_OP_REF_GROUP_REV: /* Reference to a capture group. */
        {
            RE_GroupData* group;
            RE_GroupSpan* span;
            TRACE(("%s %d\n", re_op_text[node->op], node->values[0]))

            /* Capture group indexes are 1-based (excluding group 0, which is
             * the entire matched string).
             *
             * Check whether the captured text, if any, exists at this position
             * in the string.
             */

            /* Did the group capture anything? */
            group = &state->groups[node->values[0] - 1];
            if (group->current < 0)
                goto backtrack;

            span = &group->captures[group->current];

            if (string_pos < 0)
                string_pos = span->end;

            /* Try comparing. */
            while (string_pos > span->start) {
                if (state->text_pos <= 0 && state->partial_side ==
                  RE_PARTIAL_LEFT)
                    return RE_ERROR_PARTIAL;

                if (state->text_pos > state->slice_start &&
                  same_char(char_at(state->text, state->text_pos - 1),
                  char_at(state->text, string_pos - 1))) {
                    --string_pos;
                    --state->text_pos;
                } else if (node->status & RE_STATUS_FUZZY) {
                    status = fuzzy_match_string(state, search,
                      &state->text_pos, node, &string_pos, -1);
                    if (status < 0)
                        return status;

                    if (status == RE_ERROR_FAILURE) {
                        string_pos = -1;
                        goto backtrack;
                    }
                } else {
                    string_pos = -1;
                    goto backtrack;
                }
            }

            string_pos = -1;

            /* Successful match. */
            node = node->next_1.node;
            break;
        }
        case RE_OP_SEARCH_ANCHOR: /* At the start of the search. */
            TRACE(("%s %d\n", re_op_text[node->op], node->values[0]))

            if (state->text_pos == state->search_anchor)
                node = node->next_1.node;
            else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 0);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_SET_DIFF: /* Set difference. */
        case RE_OP_SET_INTER: /* Set intersection. */
        case RE_OP_SET_SYM_DIFF: /* Set symmetric difference. */
        case RE_OP_SET_UNION: /* Set union. */
            TRACE(("%s %d\n", re_op_text[node->op], node->match))

            if (state->text_pos >= state->text_length && state->partial_side ==
              RE_PARTIAL_RIGHT)
                return RE_ERROR_PARTIAL;

            if (state->text_pos < state->slice_end && matches_SET(encoding,
              locale_info, node, char_at(state->text, state->text_pos)) ==
              node->match) {
                state->text_pos += node->step;
                node = node->next_1.node;
            } else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 1);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_SET_DIFF_IGN: /* Set difference, ignoring case. */
        case RE_OP_SET_INTER_IGN: /* Set intersection, ignoring case. */
        case RE_OP_SET_SYM_DIFF_IGN: /* Set symmetric difference, ignoring case. */
        case RE_OP_SET_UNION_IGN: /* Set union, ignoring case. */
            TRACE(("%s %d\n", re_op_text[node->op], node->match))

            if (state->text_pos >= state->text_length && state->partial_side ==
              RE_PARTIAL_RIGHT)
                return RE_ERROR_PARTIAL;

            if (state->text_pos < state->slice_end && matches_SET_IGN(encoding,
              locale_info, node, char_at(state->text, state->text_pos)) ==
              node->match) {
                state->text_pos += node->step;
                node = node->next_1.node;
            } else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 1);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_SET_DIFF_IGN_REV: /* Set difference, ignoring case. */
        case RE_OP_SET_INTER_IGN_REV: /* Set intersection, ignoring case. */
        case RE_OP_SET_SYM_DIFF_IGN_REV: /* Set symmetric difference, ignoring case. */
        case RE_OP_SET_UNION_IGN_REV: /* Set union, ignoring case. */
            TRACE(("%s %d\n", re_op_text[node->op], node->match))

            if (state->text_pos <= 0 && state->partial_side == RE_PARTIAL_LEFT)
                return RE_ERROR_PARTIAL;

            if (state->text_pos > state->slice_start &&
              matches_SET_IGN(encoding, locale_info, node, char_at(state->text,
              state->text_pos - 1)) == node->match) {
                state->text_pos += node->step;
                node = node->next_1.node;
            } else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, -1);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_SET_DIFF_REV: /* Set difference. */
        case RE_OP_SET_INTER_REV: /* Set intersection. */
        case RE_OP_SET_SYM_DIFF_REV: /* Set symmetric difference. */
        case RE_OP_SET_UNION_REV: /* Set union. */
            TRACE(("%s %d\n", re_op_text[node->op], node->match))

            if (state->text_pos <= 0 && state->partial_side == RE_PARTIAL_LEFT)
                return RE_ERROR_PARTIAL;

            if (state->text_pos > state->slice_start && matches_SET(encoding,
              locale_info, node, char_at(state->text, state->text_pos - 1)) ==
              node->match) {
                state->text_pos += node->step;
                node = node->next_1.node;
            } else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, -1);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_SKIP: /* Skip the part of the text already matched. */
            TRACE(("%s\n", re_op_text[node->op]))

            /* bstack: ... | ...
             *
             * pstack: bstack
             */

            if (node->status & RE_STATUS_REVERSE)
                state->slice_end = state->text_pos;
            else
                state->slice_start = state->text_pos;

            /* Prune the backtracking back to an appropriate backtracking
             * point.
             */
            top_bstack(state);

            /* bstack: ...
             *
             * pstack: bstack
             */

            node = node->next_1.node;
            break;
        case RE_OP_START_GROUP: /* Start of a capture group. */
        {
            RE_CODE private_index;
            RE_CODE public_index;
            RE_GroupData* group;
            BOOL capture;
            TRACE(("%s %d\n", re_op_text[node->op], node->values[1]))

            /* Capture group indexes are 1-based (excluding group 0, which is
             * the entire matched string).
             */
            private_index = node->values[0];
            public_index = node->values[1];
            group = &state->groups[private_index - 1];
            capture = (BOOL)node->values[2];

            if (capture) {
                RE_GroupSpan span;
                RE_GroupStateData data_g;

                /* sstack: end
                 *
                 * bstack: -
                 */

                if (!pop_ssize(state, &state->sstack, &span.end))
                    return RE_ERROR_MEMORY;

                span.start = state->text_pos;

                data_g.text_pos = span.end;
                data_g.current = group->current;
                data_g.capture_change = state->capture_change;
                data_g.private_index = private_index;
                data_g.public_index = public_index;

                if (!ByteStack_push_block(state, &state->bstack,
                  (void*)&data_g, sizeof(data_g)))
                    return RE_ERROR_MEMORY;

                if (pattern->group_info[private_index - 1].referenced &&
                  !same_span_as_group(group, span))
                    ++state->capture_change;

                if (!save_capture(state, private_index, public_index, span))
                    return RE_ERROR_MEMORY;
                group->current = (Py_ssize_t)group->count - 1;
            } else {
                if (!push_ssize(state, &state->sstack, state->text_pos))
                    return RE_ERROR_MEMORY;
            }

            if (!push_bool(state, &state->bstack, capture))
                return RE_ERROR_MEMORY;
            if (!push_uint8(state, &state->bstack, RE_OP_START_GROUP))
                return RE_ERROR_MEMORY;

            /* If capturing:
             *
             * sstack: -
             *
             * bstack: end current capture_change private_index public_index
             * TRUE START_GROUP
             *
             * else:
             *
             * sstack: start
             *
             * bstack: FALSE START_GROUP
             */

            node = node->next_1.node;
            break;
        }
        case RE_OP_START_OF_LINE: /* At the start of a line. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = try_match_START_OF_LINE(state, node, state->text_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS)
                node = node->next_1.node;
            else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 0);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_START_OF_LINE_U: /* At the start of a line. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = try_match_START_OF_LINE_U(state, node, state->text_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS)
                node = node->next_1.node;
            else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 0);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_START_OF_STRING: /* At the start of the string. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = try_match_START_OF_STRING(state, node, state->text_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS)
                node = node->next_1.node;
            else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 0);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_START_OF_WORD: /* At the start of a word. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = try_match_START_OF_WORD(state, node, state->text_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS)
                node = node->next_1.node;
            else if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_match_item(state, search, &state->text_pos,
                  &node, 0);
                if (status < 0)
                    return status;

                if (status == RE_ERROR_FAILURE)
                    goto backtrack;
            } else
                goto backtrack;
            break;
        case RE_OP_STRING: /* A string. */
        {
            Py_ssize_t length;
            RE_CODE* values;
            TRACE(("%s %zd\n", re_op_text[node->op], node->value_count))

            if ((node->status & RE_STATUS_REQUIRED) && state->text_pos ==
              state->req_pos && string_pos < 0)
                state->text_pos = state->req_end;
            else {
                length = (Py_ssize_t)node->value_count;

                if (string_pos < 0)
                    string_pos = 0;

                values = node->values;

                /* Try comparing. */
                while (string_pos < length) {
                    if (state->text_pos >= state->text_length &&
                      state->partial_side == RE_PARTIAL_RIGHT)
                        return RE_ERROR_PARTIAL;

                    if (state->text_pos < state->slice_end &&
                      same_char(char_at(state->text, state->text_pos),
                      values[string_pos])) {
                        ++string_pos;
                        ++state->text_pos;
                    } else if (node->status & RE_STATUS_FUZZY) {
                        status = fuzzy_match_string(state, search,
                          &state->text_pos, node, &string_pos, 1);
                        if (status < 0)
                            return status;

                        if (status == RE_ERROR_FAILURE) {
                            string_pos = -1;
                            goto backtrack;
                        }
                    } else {
                        string_pos = -1;
                        goto backtrack;
                    }
                }
            }

            if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_insert(state, state->text_pos, 1,
                  node->next_1.node);
                if (status < 0)
                    return status;
            }

            string_pos = -1;

            /* Successful match. */
            node = node->next_1.node;
            break;
        }
        case RE_OP_STRING_FLD: /* A string, ignoring case. */
        {
            Py_ssize_t length;
            int (*full_case_fold)(RE_LocaleInfo* locale_info, Py_UCS4 ch,
              Py_UCS4* folded);
            RE_CODE* values;
            int folded_len;
            Py_UCS4 folded[RE_MAX_FOLDED];
            TRACE(("%s %zd\n", re_op_text[node->op], node->value_count))

            if ((node->status & RE_STATUS_REQUIRED) && state->text_pos ==
              state->req_pos && string_pos < 0)
                state->text_pos = state->req_end;
            else {
                length = (Py_ssize_t)node->value_count;

                full_case_fold = encoding->full_case_fold;

                if (string_pos < 0) {
                    string_pos = 0;
                    folded_pos = 0;
                    folded_len = 0;
                } else {
                    folded_len = full_case_fold(locale_info,
                      char_at(state->text, state->text_pos), folded);
                    if (folded_pos >= folded_len) {
                        if (state->text_pos >= state->slice_end)
                            goto backtrack;

                        ++state->text_pos;
                        folded_pos = 0;
                        folded_len = 0;
                    }
                }

                values = node->values;

                /* Try comparing. */
                while (string_pos < length) {
                    if (folded_pos >= folded_len) {
                        if (state->text_pos >= state->text_length &&
                          state->partial_side == RE_PARTIAL_RIGHT)
                            return RE_ERROR_PARTIAL;

                        if (state->text_pos < state->slice_end)
                            folded_len = full_case_fold(locale_info,
                              char_at(state->text, state->text_pos), folded);
                        else
                            folded_len = 0;

                        folded_pos = 0;
                    }

                    if (folded_pos < folded_len && same_char_ign(encoding,
                      locale_info, values[string_pos], folded[folded_pos])) {
                        ++string_pos;
                        ++folded_pos;

                        if (folded_pos >= folded_len)
                            ++state->text_pos;
                    } else if (node->status & RE_STATUS_FUZZY) {
                        status = fuzzy_match_string_fld(state, search,
                          &state->text_pos, node, &string_pos, &folded_pos,
                          folded_len, 1);
                        if (status < 0)
                            return status;

                        if (status == RE_ERROR_FAILURE) {
                            string_pos = -1;
                            goto backtrack;
                        }

                        if (folded_pos >= folded_len && folded_len > 0)
                            ++state->text_pos;
                    } else {
                        string_pos = -1;
                        goto backtrack;
                    }
                }

                if (node->status & RE_STATUS_FUZZY) {
                    while (folded_pos < folded_len) {
                        status = fuzzy_match_string_fld(state, search,
                          &state->text_pos, node, &string_pos, &folded_pos,
                          folded_len, 1);
                        if (status < 0)
                            return status;

                        if (status == RE_ERROR_FAILURE) {
                            string_pos = -1;
                            goto backtrack;
                        }

                        if (folded_pos >= folded_len && folded_len > 0)
                            ++state->text_pos;
                    }
                }

                string_pos = -1;

                if (folded_pos < folded_len)
                    goto backtrack;
            }

            /* Successful match. */
            node = node->next_1.node;
            break;
        }
        case RE_OP_STRING_FLD_REV: /* A string, ignoring case. */
        {
            Py_ssize_t length;
            int (*full_case_fold)(RE_LocaleInfo* locale_info, Py_UCS4 ch,
              Py_UCS4* folded);
            RE_CODE* values;
            int folded_len;
            Py_UCS4 folded[RE_MAX_FOLDED];
            TRACE(("%s %zd\n", re_op_text[node->op], node->value_count))

            if ((node->status & RE_STATUS_REQUIRED) && state->text_pos ==
              state->req_pos && string_pos < 0)
                state->text_pos = state->req_end;
            else {
                length = (Py_ssize_t)node->value_count;

                full_case_fold = encoding->full_case_fold;

                if (string_pos < 0) {
                    string_pos = length;
                    folded_pos = 0;
                    folded_len = 0;
                } else {
                    folded_len = full_case_fold(locale_info,
                      char_at(state->text, state->text_pos - 1), folded);
                    if (folded_pos <= 0) {
                        if (state->text_pos <= state->slice_start)
                            goto backtrack;

                        --state->text_pos;
                        folded_pos = 0;
                        folded_len = 0;
                    }
                }

                values = node->values;

                /* Try comparing. */
                while (string_pos > 0) {
                    if (folded_pos <= 0) {
                        if (state->text_pos <= 0 && state->partial_side ==
                          RE_PARTIAL_LEFT)
                            return RE_ERROR_PARTIAL;

                        if (state->text_pos > state->slice_start)
                            folded_len = full_case_fold(locale_info,
                              char_at(state->text, state->text_pos - 1),
                              folded);
                        else
                            folded_len = 0;

                        folded_pos = folded_len;
                    }

                    if (folded_pos > 0 && same_char_ign(encoding, locale_info,
                      values[string_pos - 1], folded[folded_pos - 1])) {
                        --string_pos;
                        --folded_pos;

                        if (folded_pos <= 0)
                            --state->text_pos;
                    } else if (node->status & RE_STATUS_FUZZY) {
                        status = fuzzy_match_string_fld(state, search,
                          &state->text_pos, node, &string_pos, &folded_pos,
                          folded_len, -1);
                        if (status < 0)
                            return status;

                        if (status == RE_ERROR_FAILURE) {
                            string_pos = -1;
                            goto backtrack;
                        }

                        if (folded_pos <= 0 && folded_len > 0)
                            --state->text_pos;
                    } else {
                        string_pos = -1;
                        goto backtrack;
                    }
                }

                if (node->status & RE_STATUS_FUZZY) {
                    while (folded_pos > 0) {
                        status = fuzzy_match_string_fld(state, search,
                          &state->text_pos, node, &string_pos, &folded_pos,
                          folded_len, -1);
                        if (status < 0)
                            return status;

                        if (status == RE_ERROR_FAILURE) {
                            string_pos = -1;
                            goto backtrack;
                        }

                        if (folded_pos <= 0 && folded_len > 0)
                            --state->text_pos;
                    }
                }

                string_pos = -1;

                if (folded_pos > 0)
                    goto backtrack;
            }

            /* Successful match. */
            node = node->next_1.node;
            break;
        }
        case RE_OP_STRING_IGN: /* A string, ignoring case. */
        {
            Py_ssize_t length;
            RE_CODE* values;
            TRACE(("%s %zd\n", re_op_text[node->op], node->value_count))

            if ((node->status & RE_STATUS_REQUIRED) && state->text_pos ==
              state->req_pos && string_pos < 0)
                state->text_pos = state->req_end;
            else {
                length = (Py_ssize_t)node->value_count;

                if (string_pos < 0)
                    string_pos = 0;

                values = node->values;

                /* Try comparing. */
                while (string_pos < length) {
                    if (state->text_pos >= state->text_length &&
                      state->partial_side == RE_PARTIAL_RIGHT)
                        return RE_ERROR_PARTIAL;

                    if (state->text_pos < state->slice_end &&
                      same_char_ign(encoding, locale_info, char_at(state->text,
                      state->text_pos), values[string_pos])) {
                        ++string_pos;
                        ++state->text_pos;
                    } else if (node->status & RE_STATUS_FUZZY) {
                        status = fuzzy_match_string(state, search,
                          &state->text_pos, node, &string_pos, 1);
                        if (status < 0)
                            return status;

                        if (status == RE_ERROR_FAILURE) {
                            string_pos = -1;
                            goto backtrack;
                        }
                    } else {
                        string_pos = -1;
                        goto backtrack;
                    }
                }
            }

            if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_insert(state, state->text_pos, 1,
                  node->next_1.node);
                if (status < 0)
                    return status;
            }

            string_pos = -1;

            /* Successful match. */
            node = node->next_1.node;
            break;
        }
        case RE_OP_STRING_IGN_REV: /* A string, ignoring case. */
        {
            Py_ssize_t length;
            RE_CODE* values;
            TRACE(("%s %zd\n", re_op_text[node->op], node->value_count))

            if ((node->status & RE_STATUS_REQUIRED) && state->text_pos ==
              state->req_pos && string_pos < 0)
                state->text_pos = state->req_end;
            else {
                length = (Py_ssize_t)node->value_count;

                if (string_pos < 0)
                    string_pos = length;

                values = node->values;

                /* Try comparing. */
                while (string_pos > 0) {
                    if (state->text_pos <= 0 && state->partial_side ==
                      RE_PARTIAL_LEFT)
                        return RE_ERROR_PARTIAL;

                    if (state->text_pos > state->slice_start &&
                      same_char_ign(encoding, locale_info, char_at(state->text,
                      state->text_pos - 1), values[string_pos - 1])) {
                        --string_pos;
                        --state->text_pos;
                    } else if (node->status & RE_STATUS_FUZZY) {
                        status = fuzzy_match_string(state, search,
                          &state->text_pos, node, &string_pos, -1);
                        if (status < 0)
                            return status;

                        if (status == RE_ERROR_FAILURE) {
                            string_pos = -1;
                            goto backtrack;
                        }
                    } else {
                        string_pos = -1;
                        goto backtrack;
                    }
                }
            }

            if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_insert(state, state->text_pos, -1,
                  node->next_1.node);
                if (status < 0)
                    return status;
            }

            string_pos = -1;

            /* Successful match. */
            node = node->next_1.node;
            break;
        }
        case RE_OP_STRING_REV: /* A string. */
        {
            Py_ssize_t length;
            RE_CODE* values;
            TRACE(("%s %zd\n", re_op_text[node->op], node->value_count))

            if ((node->status & RE_STATUS_REQUIRED) && state->text_pos ==
              state->req_pos && string_pos < 0)
                state->text_pos = state->req_end;
            else {
                length = (Py_ssize_t)node->value_count;

                if (string_pos < 0)
                    string_pos = length;

                values = node->values;

                /* Try comparing. */
                while (string_pos > 0) {
                    if (state->text_pos <= 0 && state->partial_side ==
                      RE_PARTIAL_LEFT)
                        return RE_ERROR_PARTIAL;

                    if (state->text_pos > state->slice_start &&
                      same_char(char_at(state->text, state->text_pos - 1),
                      values[string_pos - 1])) {
                        --string_pos;
                        --state->text_pos;
                    } else if (node->status & RE_STATUS_FUZZY) {
                        status = fuzzy_match_string(state, search,
                          &state->text_pos, node, &string_pos, -1);
                        if (status < 0)
                            return status;

                        if (status == RE_ERROR_FAILURE) {
                            string_pos = -1;
                            goto backtrack;
                        }
                    } else {
                        string_pos = -1;
                        goto backtrack;
                    }
                }
            }

            if (node->status & RE_STATUS_FUZZY) {
                status = fuzzy_insert(state, state->text_pos, -1,
                  node->next_1.node);
                if (status < 0)
                    return status;
            }

            string_pos = -1;

            /* Successful match. */
            node = node->next_1.node;
            break;
        }
        case RE_OP_STRING_SET: /* Member of a string set. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = string_set_match_fwdrev(state, node, FALSE);
            if (status < 0)
                return status;
            if (status == 0)
                goto backtrack;
            node = node->next_1.node;
            break;
        case RE_OP_STRING_SET_FLD: /* Member of a string set, ignoring case. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = string_set_match_fld_fwdrev(state, node, FALSE);
            if (status < 0)
                return status;
            if (status == 0)
                goto backtrack;
            node = node->next_1.node;
            break;
        case RE_OP_STRING_SET_FLD_REV: /* Member of a string set, ignoring case. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = string_set_match_fld_fwdrev(state, node, TRUE);
            if (status < 0)
                return status;
            if (status == 0)
                goto backtrack;
            node = node->next_1.node;
            break;
        case RE_OP_STRING_SET_IGN: /* Member of a string set, ignoring case. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = string_set_match_ign_fwdrev(state, node, FALSE);
            if (status < 0)
                return status;
            if (status == 0)
                goto backtrack;
            node = node->next_1.node;
            break;
        case RE_OP_STRING_SET_IGN_REV: /* Member of a string set, ignoring case. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = string_set_match_ign_fwdrev(state, node, TRUE);
            if (status < 0)
                return status;
            if (status == 0)
                goto backtrack;
            node = node->next_1.node;
            break;
        case RE_OP_STRING_SET_REV: /* Member of a string set. */
            TRACE(("%s\n", re_op_text[node->op]))

            status = string_set_match_fwdrev(state, node, TRUE);
            if (status < 0)
                return status;
            if (status == 0)
                goto backtrack;
            node = node->next_1.node;
            break;
        case RE_OP_SUCCESS: /* Success. */
            /* Must the match advance past its start? */
            TRACE(("%s\n", re_op_text[node->op]))

            if (state->text_pos == state->search_anchor && state->must_advance)
                goto backtrack;

            if (state->match_all) {
                /* We want to match all of the slice. */
                if (state->reverse) {
                    if (state->text_pos != state->slice_start)
                        goto backtrack;
                } else {
                    if (state->text_pos != state->slice_end)
                        goto backtrack;
                }
            }

            if (state->pattern->flags & RE_FLAG_POSIX) {
                /* If we're looking for a POSIX match, check whether this one
                 * is better and then keep looking.
                 */
                if (!check_posix_match(state))
                    return RE_ERROR_MEMORY;

                goto backtrack;
            }

            return RE_ERROR_SUCCESS;
        default: /* Illegal opcode! */
            TRACE(("UNKNOWN OP %d\n", node->op))
            return RE_ERROR_ILLEGAL;
        }
    }

backtrack:
    for (;;) {
        RE_UINT8 op;
        TRACE(("BACKTRACK "))

        /* Should we abort the matching? */
        state->iterations += 0x100U;

        if (state->iterations == 0 && safe_check_cancel(state))
            return RE_ERROR_CANCELLED;

        if (!pop_uint8(state, &state->bstack, &op))
            return RE_ERROR_MEMORY;

        switch (op) {
        case RE_OP_ANY: /* Any character except a newline. */
        case RE_OP_ANY_ALL: /* Any character at all. */
        case RE_OP_ANY_ALL_REV: /* Any character at all, backwards. */
        case RE_OP_ANY_REV: /* Any character except a newline, backwards. */
        case RE_OP_ANY_U: /* Any character except a line separator. */
        case RE_OP_ANY_U_REV: /* Any character except a line separator, backwards. */
        case RE_OP_CHARACTER: /* A character. */
        case RE_OP_CHARACTER_IGN: /* A character, ignoring case. */
        case RE_OP_CHARACTER_IGN_REV: /* A character, ignoring case, backwards. */
        case RE_OP_CHARACTER_REV: /* A character, backwards. */
        case RE_OP_PROPERTY: /* A property. */
        case RE_OP_PROPERTY_IGN: /* A property, ignoring case. */
        case RE_OP_PROPERTY_IGN_REV: /* A property, ignoring case, backwards. */
        case RE_OP_PROPERTY_REV: /* A property, backwards. */
        case RE_OP_RANGE: /* A range. */
        case RE_OP_RANGE_IGN: /* A range, ignoring case. */
        case RE_OP_RANGE_IGN_REV: /* A range, ignoring case, backwards. */
        case RE_OP_RANGE_REV: /* A range, backwards. */
        case RE_OP_SET_DIFF: /* Set difference. */
        case RE_OP_SET_DIFF_IGN: /* Set difference, ignoring case. */
        case RE_OP_SET_DIFF_IGN_REV: /* Set difference, ignoring case, backwards. */
        case RE_OP_SET_DIFF_REV: /* Set difference, backwards. */
        case RE_OP_SET_INTER: /* Set intersection. */
        case RE_OP_SET_INTER_IGN: /* Set intersection, ignoring case. */
        case RE_OP_SET_INTER_IGN_REV: /* Set intersection, ignoring case, backwards. */
        case RE_OP_SET_INTER_REV: /* Set intersection, backwards. */
        case RE_OP_SET_SYM_DIFF: /* Set symmetric difference. */
        case RE_OP_SET_SYM_DIFF_IGN: /* Set symmetric difference, ignoring case. */
        case RE_OP_SET_SYM_DIFF_IGN_REV: /* Set symmetric difference, ignoring case, backwards. */
        case RE_OP_SET_SYM_DIFF_REV: /* Set symmetric difference, backwards. */
        case RE_OP_SET_UNION: /* Set union. */
        case RE_OP_SET_UNION_IGN: /* Set union, ignoring case. */
        case RE_OP_SET_UNION_IGN_REV: /* Set union, ignoring case, backwards. */
        case RE_OP_SET_UNION_REV: /* Set union, backwards. */
            TRACE(("%s\n", re_op_text[op]))

            status = retry_fuzzy_match_item(state, op, search,
              &state->text_pos, &node, TRUE);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS)
                goto advance;
            break;
        case RE_OP_ATOMIC: /* Start of an atomic group. */
            TRACE(("%s\n", re_op_text[op]))

            /* sstack: ...
             *
             * bstack: captures fuzzy_counts capture_change sstack
             *
             * pstack: bstack
             */

            if (!drop_bstack(state))
                return RE_ERROR_MEMORY;
            if (!pop_sstack(state))
                return RE_ERROR_MEMORY;

            /* sstack: -
             *
             * bstack: captures fuzzy_counts capture_change
             *
             * pstack: -
             */

            if (!pop_size(state, &state->bstack, &state->capture_change))
                return RE_ERROR_MEMORY;
            if (!pop_fuzzy_counts(state, &state->bstack, state->fuzzy_counts))
                return RE_ERROR_MEMORY;
            if (!pop_captures(state, &state->bstack))
                return RE_ERROR_MEMORY;
            break;
        case RE_OP_BODY_END:
        {
            RE_BodyEndStateData data_be;
            size_t capture_change;
            RE_CODE index;
            Py_ssize_t start;
            size_t count;
            RE_RepeatData* rp_data;

            /* bstack: count start capture_change index */

            if (!ByteStack_pop_block(state, &state->bstack, (void*)&data_be,
              sizeof(data_be)))
                return RE_ERROR_MEMORY;

            index = data_be.index;
            capture_change = data_be.capture_change;
            start = data_be.start;
            count = data_be.count;
            TRACE(("%s %d\n", re_op_text[op], index))

            /* We're backtracking into the body. */
            rp_data = &state->repeats[index];

            /* Restore the repeat info. */
            rp_data->count = count;
            rp_data->start = start;
            rp_data->capture_change = capture_change;
            break;
        }
        case RE_OP_BODY_START:
        {
            Py_ssize_t text_pos;
            RE_CODE index;

            /* bstack: index text_pos */

            if (!pop_ssize(state, &state->bstack, &text_pos))
                return RE_ERROR_MEMORY;
            if (!pop_code(state, &state->bstack, &index))
                return RE_ERROR_MEMORY;
            TRACE(("%s %d\n", re_op_text[op], index))

            /* The body may have failed to match at this position. */
            if (!guard_repeat(state, index, text_pos, RE_STATUS_BODY, TRUE))
                return RE_ERROR_MEMORY;
            break;
        }
        case RE_OP_BOUNDARY: /* At a word boundary. */
        case RE_OP_DEFAULT_BOUNDARY: /* At a default word boundary. */
        case RE_OP_DEFAULT_END_OF_WORD: /* At the default end of a word. */
        case RE_OP_DEFAULT_START_OF_WORD: /* At the default start of a word. */
        case RE_OP_END_OF_LINE: /* At the end of a line. */
        case RE_OP_END_OF_LINE_U: /* At the end of a line. */
        case RE_OP_END_OF_STRING: /* At the end of the string. */
        case RE_OP_END_OF_STRING_LINE: /* At the end of string or final newline. */
        case RE_OP_END_OF_STRING_LINE_U: /* At the end of string or final newline. */
        case RE_OP_END_OF_WORD: /* At the end of a word. */
        case RE_OP_GRAPHEME_BOUNDARY: /* On a grapheme boundary. */
        case RE_OP_START_OF_LINE: /* At the start of a line. */
        case RE_OP_START_OF_LINE_U: /* At the start of a line. */
        case RE_OP_START_OF_STRING: /* At the start of the string. */
        case RE_OP_START_OF_WORD: /* At the start of a word. */
            TRACE(("%s\n", re_op_text[bt_data->op]))

            status = retry_fuzzy_match_item(state, op, search,
              &state->text_pos, &node, FALSE);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS)
                goto advance;
            break;
        case RE_OP_BRANCH: /* 2-way branch. */
            TRACE(("%s\n", re_op_text[op]))

            /* sstack: -
             *
             * bstack: text_pos node
             */

            if (!pop_pointer(state, &state->bstack, (void*)&node))
                return RE_ERROR_MEMORY;
            if (!pop_ssize(state, &state->bstack, &state->text_pos))
                return RE_ERROR_MEMORY;
            goto advance;
        case RE_OP_CALL_REF: /* A group call ref. */
            TRACE(("%s\n", re_op_text[op]))

            /* sstack: NULL
             *
             * bstack: -
             */

            if (!drop_pointer(state, &state->sstack))
                return RE_ERROR_MEMORY;
            break;
        case RE_OP_CONDITIONAL: /* Conditional subpattern. */
        {
            RE_Node* conditional;
            RE_LookaroundStateData data_l;
            TRACE(("%s\n", re_op_text[op]))

            /* sstack: node slice_start slice_end text_pos ...
             *
             * bstack: captures repeats fuzzy_counts capture_change sstack
             *
             * pstack: bstack
             */

            if (!drop_bstack(state))
                return RE_ERROR_MEMORY;
            if (!pop_sstack(state))
                return RE_ERROR_MEMORY;

            /* sstack: node slice_start slice_end text_pos
             *
             * bstack: captures repeats fuzzy_counts capture_change
             *
             * pstack: -
             */

            if (!ByteStack_pop_block(state, &state->sstack, (void*)&data_l,
              sizeof(data_l)))
                return RE_ERROR_MEMORY;

            state->text_pos = data_l.text_pos;
            state->slice_end = data_l.slice_end;
            state->slice_start = data_l.slice_start;
            conditional = data_l.node;

            /* sstack: -
             *
             * bstack: captures repeats fuzzy_counts capture_change
             *
             * pstack: -
             */

            if (!pop_size(state, &state->bstack, &state->capture_change))
                return RE_ERROR_MEMORY;
            if (!pop_fuzzy_counts(state, &state->bstack, state->fuzzy_counts))
                return RE_ERROR_MEMORY;
            if (!pop_repeats(state, &state->bstack))
                return RE_ERROR_MEMORY;
            if (!pop_captures(state, &state->bstack))
                return RE_ERROR_MEMORY;

            /* sstack: -
             *
             * bstack: -
             *
             * pstack: -
             */

            if (conditional->match)
                /* It's a positive conditional that's failed. Go to the 'false'
                 * 'false' branch.
                 */
                node = conditional->nonstring.next_2.node;
            else
                /* It's a negative lookaround that's failed. Go to the 'true'
                 * branch.
                 */
                node = conditional->next_1.node;

            goto advance;
        }
        case RE_OP_END_ATOMIC: /* End of an atomic group. */
            TRACE(("%s\n", re_op_text[op]))

            /* bstack: captures fuzzy_counts capture_change */

            if (!pop_size(state, &state->bstack, &state->capture_change))
                return RE_ERROR_MEMORY;
            if (!pop_fuzzy_counts(state, &state->bstack, state->fuzzy_counts))
                return RE_ERROR_MEMORY;
            if (!pop_captures(state, &state->bstack))
                return RE_ERROR_MEMORY;
            break;
        case RE_OP_END_CONDITIONAL: /* End of a conditional subpattern. */
        {
            TRACE(("%s\n", re_op_text[op]))

            /* sstack: -
             *
             * bstack: captures repeats fuzzy_counts capture_change
             *
             * pstack: -
             */

            if (!pop_size(state, &state->bstack, &state->capture_change))
                return RE_ERROR_MEMORY;
            if (!pop_fuzzy_counts(state, &state->bstack, state->fuzzy_counts))
                return RE_ERROR_MEMORY;
            if (!pop_repeats(state, &state->bstack))
                return RE_ERROR_MEMORY;
            if (!pop_captures(state, &state->bstack))
                return RE_ERROR_MEMORY;

            /* sstack: -
             *
             * bstack: -
             *
             * pstack: -
             */
            break;
        }
        case RE_OP_END_FUZZY: /* End of fuzzy matching. */
        {
            RE_Node* inner_node;
            size_t inner_counts[RE_FUZZY_COUNT];
            TRACE(("%s\n", re_op_text[op]))

            /* sstack: -
             *
             * bstack: inner_counts inner_node text_pos end_fuzzy_node
             */

            if (!pop_pointer(state, &state->bstack, (void*)&node))
                return RE_ERROR_MEMORY;
            if (!pop_ssize(state, &state->bstack, &state->text_pos))
                return RE_ERROR_MEMORY;
            if (!pop_pointer(state, &state->bstack, (void*)&inner_node))
                return RE_ERROR_MEMORY;
            if (!pop_fuzzy_counts(state, &state->bstack, inner_counts))
                return RE_ERROR_MEMORY;

            /* sstack: -
             *
             * bstack: -
             */

            if (insertion_permitted(state, inner_node, inner_counts)) {
                RE_INT8 step;
                Py_ssize_t limit;

                /* Try another insertion. */
                if (inner_node->status & RE_STATUS_REVERSE) {
                    step = -1;
                    limit = state->slice_start;
                } else {
                    step = 1;
                    limit = state->slice_end;
                }

                if (state->text_pos != limit) {
                    if (!record_fuzzy(state, RE_FUZZY_INS, state->text_pos))
                        return RE_ERROR_MEMORY;
                    ++inner_counts[RE_FUZZY_INS];

                    state->text_pos += step;

                    /* Save the inner fuzzy info. */
                    if (!push_fuzzy_counts(state, &state->bstack,
                      inner_counts))
                        return RE_ERROR_MEMORY;
                    if (!push_pointer(state, &state->bstack, inner_node))
                        return RE_ERROR_MEMORY;
                    if (!push_ssize(state, &state->bstack, state->text_pos))
                        return RE_ERROR_MEMORY;
                    if (!push_pointer(state, &state->bstack, node))
                        return RE_ERROR_MEMORY;
                    if (!push_uint8(state, &state->bstack, RE_OP_END_FUZZY))
                        return RE_ERROR_MEMORY;

                    /* sstack: -
                     *
                     * bstack: inner_counts inner_node text_pos end_fuzzy_node
                     * END_FUZZY
                     */

                    ++state->fuzzy_counts[RE_FUZZY_INS];
                    state->total_errors = total_errors(state->fuzzy_counts);

                    node = node->next_1.node;
                    goto advance;
                }
            }

            /* Subtract the inner counts from the outer counts. */
            state->fuzzy_counts[RE_FUZZY_SUB] -= inner_counts[RE_FUZZY_SUB];
            state->fuzzy_counts[RE_FUZZY_INS] -= inner_counts[RE_FUZZY_INS];
            state->fuzzy_counts[RE_FUZZY_DEL] -= inner_counts[RE_FUZZY_DEL];

            /* Save the outer fuzzy info. */
            if (!push_fuzzy_counts(state, &state->sstack, state->fuzzy_counts))
                return RE_ERROR_MEMORY;
            if (!push_pointer(state, &state->sstack, state->fuzzy_node))
                return RE_ERROR_MEMORY;

            /* sstack: outer_counts outer_node
             *
             * bstack: -
             */

            /* Restore the inner fuzzy info. */
            Py_MEMCPY(state->fuzzy_counts, inner_counts,
              sizeof(state->fuzzy_counts));
            state->fuzzy_node = inner_node;
            break;
        }
        case RE_OP_END_GROUP: /* End of a capture group. */
        {
            BOOL capture;
            TRACE(("%s %d\n", re_op_text[op], public_index))

            /* If capturing:
             *
             * sstack: -
             *
             * bstack: start current capture_change private_index public_index
             * TRUE
             *
             * else:
             *
             * sstack: end
             *
             * bstack: FALSE
             */

            if (!pop_bool(state, &state->bstack, &capture))
                return RE_ERROR_MEMORY;

            if (capture) {
                RE_GroupStateData data_g;
                RE_CODE public_index;
                RE_CODE private_index;
                Py_ssize_t start;
                RE_GroupData* group;

                if (!ByteStack_pop_block(state, &state->bstack, (void*)&data_g,
                  sizeof(data_g)))
                    return RE_ERROR_MEMORY;

                public_index = data_g.public_index;
                private_index = data_g.private_index;
                state->capture_change = data_g.capture_change;
                group = &state->groups[private_index - 1];
                group->current = data_g.current;
                start = data_g.text_pos;
                if (!push_ssize(state, &state->sstack, start))
                    return RE_ERROR_MEMORY;

                unsave_capture(state, private_index, public_index);

                /* sstack: start
                 *
                 * bstack: -
                 */
            } else {
                if (!drop_ssize(state, &state->sstack))
                    return RE_ERROR_MEMORY;
            }
            break;
        }
        case RE_OP_END_LOOKAROUND: /* End of a lookaround subpattern. */
        {
            BOOL has_groups;
            TRACE(("%s\n", re_op_text[op]))

            /* sstack: -
             *
             * bstack: [captures TRUE | FALSE] repeats fuzzy_counts
             * capture_change
             *
             * pstack: -
             */

            if (!pop_size(state, &state->bstack, &state->capture_change))
                return RE_ERROR_MEMORY;
            if (!pop_fuzzy_counts(state, &state->bstack, state->fuzzy_counts))
                return RE_ERROR_MEMORY;
            if (!pop_bool(state, &state->bstack, &has_groups))
                return RE_ERROR_MEMORY;
            if (has_groups) {
                if (!pop_captures(state, &state->bstack))
                    return RE_ERROR_MEMORY;
            }

            /* sstack: -
             *
             * bstack: -
             *
             * pstack: -
             */
            break;
        }
        case RE_OP_FAILURE: /* Failure. */
            TRACE(("%s\n", re_op_text[op]))

            /* Have we been looking for a POSIX match? */
            if (state->found_match) {
                restore_best_match(state);
                return RE_OP_SUCCESS;
            }

            /* Do we have to advance? */
            if (!search)
                return RE_ERROR_FAILURE;

            /* Can we advance? */
            state->text_pos = state->match_pos;

            if (state->reverse) {
                if (state->text_pos <= state->slice_start)
                    return RE_ERROR_FAILURE;
            } else {
                if (state->text_pos >= state->slice_end)
                    return RE_ERROR_FAILURE;
            }

            /* Skip over any repeated leading characters. */
            switch (start_node->op) {
            case RE_OP_GREEDY_REPEAT_ONE:
            case RE_OP_LAZY_REPEAT_ONE:
            {
                size_t count;
                BOOL is_partial;

                /* How many characters did the repeat actually match? */
                count = count_one(state, start_node->nonstring.next_2.node,
                  state->text_pos, start_node->values[2], &is_partial);

                /* If it's fewer than the maximum then skip over those
                 * characters.
                 */
                if (count < start_node->values[2])
                    state->text_pos += (Py_ssize_t)count * pattern_step;
                break;
            }
            }

            /* Advance and try to match again. We also need to check whether we
             * need to skip.
             */
            if (state->reverse) {
                if (state->text_pos > state->slice_end)
                    state->text_pos = state->slice_end;
                else
                    --state->text_pos;
            } else {
                if (state->text_pos < state->slice_start)
                    state->text_pos = state->slice_start;
                else
                    ++state->text_pos;
            }

            /* Clear the groups. */
            clear_groups(state);

            /* Reset the guards. */
            reset_guards(state);

            /* Reset the stacks. */
            ByteStack_reset(state, &state->sstack);
            ByteStack_reset(state, &state->bstack);
            ByteStack_reset(state, &state->pstack);
            goto start_match;
        case RE_OP_FUZZY: /* Fuzzy matching. */
            TRACE(("%s\n", re_op_text[op]))

            /* sstack: outer_counts outer_node
             *
             * bstack: -
             */

            /* Restore the outer fuzzy info. */
            if (!pop_pointer(state, &state->sstack, (void*)&state->fuzzy_node))
                return RE_ERROR_MEMORY;
            if (!pop_fuzzy_counts(state, &state->sstack, state->fuzzy_counts))
                return RE_ERROR_MEMORY;
            break;
        case RE_OP_FUZZY_INSERT:
            TRACE(("%s\n", re_op_text[op]))

            status = retry_fuzzy_insert(state, &state->text_pos, &node);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS)
                goto advance;

            string_pos = -1;
            break;
        case RE_OP_GREEDY_REPEAT: /* Greedy repeat. */
        case RE_OP_LAZY_REPEAT: /* Lazy repeat. */
        {
            RE_RepeatStateData data_r;
            Py_ssize_t text_pos;
            RE_CODE index;
            size_t capture_change;
            Py_ssize_t start;
            size_t count;
            RE_RepeatData* rp_data;
            TRACE(("%s\n", re_op_text[op]))

            /* bstack: count start capture_change index text_pos */

            if (!ByteStack_pop_block(state, &state->bstack, (void*)&data_r,
              sizeof(data_r)))
                return RE_ERROR_MEMORY;

            text_pos = data_r.text_pos;
            index = data_r.index;
            capture_change = data_r.capture_change;
            start = data_r.start;
            count = data_r.count;

            /* The repeat failed to match. */
            rp_data = &state->repeats[index];

            /* The body may have failed to match at this position. */
            if (!guard_repeat(state, index, text_pos, RE_STATUS_BODY, TRUE))
                return RE_ERROR_MEMORY;

            /* Restore the previous repeat. */
            rp_data->count = count;
            rp_data->start = start;
            rp_data->capture_change = capture_change;
            break;
        }
        case RE_OP_GREEDY_REPEAT_ONE: /* Greedy repeat for one character. */
        {
            RE_RepeatOneStateData data_ro;
            RE_CODE index;
            Py_ssize_t start;
            size_t saved_count;
            RE_RepeatData* rp_data;
            size_t count;
            Py_ssize_t step;
            Py_ssize_t pos;
            Py_ssize_t limit;
            RE_Node* test;
            BOOL match;
            BOOL m;
            TRACE(("%s\n", re_op_text[op]))

            /* bstack: count start node index */

            if (!ByteStack_pop_block(state, &state->bstack,
              (void*)&data_ro,sizeof(data_ro)))
                return RE_ERROR_MEMORY;

            index = data_ro.index;
            node = data_ro.node;
            start = data_ro.start;
            saved_count = data_ro.count;

            rp_data = &state->repeats[index];

            /* Unmatch one character at a time until the tail could match or we
             * have reached the minimum.
             */
            state->text_pos = rp_data->start;

            count = rp_data->count;
            step = node->nonstring.next_2.test->step;
            pos = state->text_pos + (Py_ssize_t)count * step;
            limit = state->text_pos + (Py_ssize_t)node->values[1] * step;

            /* The tail failed to match at this position. */
            if (!guard_repeat(state, index, pos, RE_STATUS_TAIL, TRUE))
                return RE_ERROR_MEMORY;

            /* A (*SKIP) might have changed the size of the slice. */
            if (step > 0) {
                if (limit < state->slice_start)
                    limit = state->slice_start;
            } else {
                if (limit > state->slice_end)
                    limit = state->slice_end;
            }

            if (pos == limit) {
                /* We've backtracked the repeat as far as we can. */
                rp_data->start = start;
                rp_data->count = saved_count;
                break;
            }

            test = node->next_1.test;

            m = test->match;
            index = node->values[0];

            match = FALSE;

            if (test->status & RE_STATUS_FUZZY) {
                for (;;) {
                    RE_Position next_position;

                    pos -= step;

                    status = try_match(state, &node->next_1, pos,
                      &next_position);
                    if (status < 0)
                        return status;

                    if (status != RE_ERROR_FAILURE && !is_repeat_guarded(state,
                      index, pos, RE_STATUS_TAIL)) {
                        match = TRUE;
                        break;
                    }

                    if (pos == limit)
                        break;
                }
            } else {
                /* A repeated single-character match is often followed by a
                 * literal, so checking specially for it can be a good
                 * optimisation when working with long strings.
                 */
                switch (test->op) {
                case RE_OP_CHARACTER:
                {
                    Py_UCS4 ch;

                    ch = test->values[0];

                    for (;;) {
                        --pos;

                        if (same_char(char_at(state->text, pos), ch) == m &&
                          !is_repeat_guarded(state, index, pos,
                          RE_STATUS_TAIL)) {
                            match = TRUE;
                            break;
                        }

                        if (pos == limit)
                            break;
                    }
                    break;
                }
                case RE_OP_CHARACTER_IGN:
                {
                    Py_UCS4 ch;

                    ch = test->values[0];

                    for (;;) {
                        --pos;

                        if (same_char_ign(encoding, locale_info,
                          char_at(state->text, pos), ch) == m &&
                          !is_repeat_guarded(state, index, pos,
                          RE_STATUS_TAIL)) {
                            match = TRUE;
                            break;
                        }

                        if (pos == limit)
                            break;
                    }
                    break;
                }
                case RE_OP_CHARACTER_IGN_REV:
                {
                    Py_UCS4 ch;

                    ch = test->values[0];

                    for (;;) {
                        ++pos;

                        if (same_char_ign(encoding, locale_info,
                          char_at(state->text, pos - 1), ch) == m &&
                          !is_repeat_guarded(state, index, pos,
                          RE_STATUS_TAIL)) {
                            match = TRUE;
                            break;
                        }

                        if (pos == limit)
                            break;
                    }
                    break;
                }
                case RE_OP_CHARACTER_REV:
                {
                    Py_UCS4 ch;

                    ch = test->values[0];

                    for (;;) {
                        ++pos;

                        if (same_char(char_at(state->text, pos - 1), ch) == m
                          && !is_repeat_guarded(state, index, pos,
                          RE_STATUS_TAIL)) {
                            match = TRUE;
                            break;
                        }

                        if (pos == limit)
                            break;
                    }
                    break;
                }
                case RE_OP_STRING:
                {
                    Py_ssize_t length;

                    length = (Py_ssize_t)test->value_count;

                    /* The tail is a string. We don't want to go off the end of
                     * the slice.
                     */
                    pos = min_ssize_t(pos - 1, state->slice_end - length);

                    for (;;) {
                        Py_ssize_t found;
                        BOOL is_partial;

                        if (pos < limit)
                            break;

                        found = string_search_rev(state, test, pos + length,
                          limit, &is_partial);
                        if (is_partial)
                            return RE_ERROR_PARTIAL;

                        if (found < 0)
                            break;

                        pos = found - length;

                        if (!is_repeat_guarded(state, index, pos,
                          RE_STATUS_TAIL)) {
                            match = TRUE;
                            break;
                        }

                        --pos;
                    }
                    break;
                }
                case RE_OP_STRING_FLD:
                {
                    int (*full_case_fold)(RE_LocaleInfo* locale_info, Py_UCS4
                      ch, Py_UCS4* folded);
                    Py_ssize_t folded_length;
                    size_t i;
                    Py_UCS4 folded[RE_MAX_FOLDED];

                    full_case_fold = encoding->full_case_fold;

                    folded_length = 0;
                    for (i = 0; i < test->value_count; i++)
                        folded_length += full_case_fold(locale_info,
                          test->values[i], folded);

                    /* The tail is a string. We don't want to go off the end of
                     * the slice.
                     */
                    pos = min_ssize_t(pos - 1, state->slice_end -
                      folded_length);

                    for (;;) {
                        Py_ssize_t found;
                        Py_ssize_t new_pos;
                        BOOL is_partial;

                        if (pos < limit)
                            break;

                        found = string_search_fld_rev(state, test, pos +
                          folded_length, limit, &new_pos, &is_partial);
                        if (is_partial)
                            return RE_ERROR_PARTIAL;

                        if (found < 0)
                            break;

                        pos = found - folded_length;

                        if (!is_repeat_guarded(state, index, pos,
                          RE_STATUS_TAIL)) {
                            match = TRUE;
                            break;
                        }

                        --pos;
                    }
                    break;
                }
                case RE_OP_STRING_FLD_REV:
                {
                    int (*full_case_fold)(RE_LocaleInfo* locale_info, Py_UCS4
                      ch, Py_UCS4* folded);
                    Py_ssize_t folded_length;
                    size_t i;
                    Py_UCS4 folded[RE_MAX_FOLDED];

                    full_case_fold = encoding->full_case_fold;

                    folded_length = 0;
                    for (i = 0; i < test->value_count; i++)
                        folded_length += full_case_fold(locale_info,
                          test->values[i], folded);

                    /* The tail is a string. We don't want to go off the end of
                     * the slice.
                     */
                    pos = max_ssize_t(pos + 1, state->slice_start +
                      folded_length);

                    for (;;) {
                        Py_ssize_t found;
                        Py_ssize_t new_pos;
                        BOOL is_partial;

                        if (pos > limit)
                            break;

                        found = string_search_fld(state, test, pos -
                          folded_length, limit, &new_pos, &is_partial);
                        if (is_partial)
                            return RE_ERROR_PARTIAL;

                        if (found < 0)
                            break;

                        pos = found + folded_length;

                        if (!is_repeat_guarded(state, index, pos,
                          RE_STATUS_TAIL)) {
                            match = TRUE;
                            break;
                        }

                        ++pos;
                    }
                    break;
                }
                case RE_OP_STRING_IGN:
                {
                    Py_ssize_t length;

                    length = (Py_ssize_t)test->value_count;

                    /* The tail is a string. We don't want to go off the end of
                     * the slice.
                     */
                    pos = min_ssize_t(pos - 1, state->slice_end - length);

                    for (;;) {
                        Py_ssize_t found;
                        BOOL is_partial;

                        if (pos < limit)
                            break;

                        found = string_search_ign_rev(state, test, pos +
                          length, limit, &is_partial);
                        if (is_partial)
                            return RE_ERROR_PARTIAL;

                        if (found < 0)
                            break;

                        pos = found - length;

                        if (!is_repeat_guarded(state, index, pos,
                          RE_STATUS_TAIL)) {
                            match = TRUE;
                            break;
                        }

                        --pos;
                    }
                    break;
                }
                case RE_OP_STRING_IGN_REV:
                {
                    Py_ssize_t length;

                    length = (Py_ssize_t)test->value_count;

                    /* The tail is a string. We don't want to go off the end of
                     * the slice.
                     */
                    pos = max_ssize_t(pos + 1, state->slice_start + length);

                    for (;;) {
                        Py_ssize_t found;
                        BOOL is_partial;

                        if (pos > limit)
                            break;

                        found = string_search_ign(state, test, pos - length,
                          limit, &is_partial);
                        if (is_partial)
                            return RE_ERROR_PARTIAL;

                        if (found < 0)
                            break;

                        pos = found + length;

                        if (!is_repeat_guarded(state, index, pos,
                          RE_STATUS_TAIL)) {
                            match = TRUE;
                            break;
                        }

                        ++pos;
                    }
                    break;
                }
                case RE_OP_STRING_REV:
                {
                    Py_ssize_t length;

                    length = (Py_ssize_t)test->value_count;

                    /* The tail is a string. We don't want to go off the end of
                     * the slice.
                     */
                    pos = max_ssize_t(pos + 1, state->slice_start + length);

                    for (;;) {
                        Py_ssize_t found;
                        BOOL is_partial;

                        if (pos > limit)
                            break;

                        found = string_search(state, test, pos - length, limit,
                          &is_partial);
                        if (is_partial)
                            return RE_ERROR_PARTIAL;

                        if (found < 0)
                            break;

                        pos = found + length;

                        if (!is_repeat_guarded(state, index, pos,
                          RE_STATUS_TAIL)) {
                            match = TRUE;
                            break;
                        }

                        ++pos;
                    }
                    break;
                }
                default:
                    for (;;) {
                        RE_Position next_position;

                        pos -= step;

                        status = try_match(state, &node->next_1, pos,
                          &next_position);
                        if (status < 0)
                            return status;

                        if (status == RE_ERROR_SUCCESS &&
                          !is_repeat_guarded(state, index, pos,
                          RE_STATUS_TAIL)) {
                            match = TRUE;
                            break;
                        }

                        if (pos == limit)
                            break;
                    }
                    break;
                }
            }

            if (match) {
                count = (size_t)abs_ssize_t(pos - state->text_pos);

                /* The tail could match. */
                if (count > node->values[1]) {
                    /* The match is longer than the minimum, so we might need
                     * to backtrack the repeat again to consume less.
                     */
                    RE_RepeatOneStateData data_ro;

                    rp_data->count = count;

                    data_ro.count = saved_count;
                    data_ro.start = start;
                    data_ro.node = node;
                    data_ro.index = index;

                    if (!ByteStack_push_block(state, &state->bstack,
                      (void*)&data_ro, sizeof(data_ro)))
                        return RE_ERROR_MEMORY;
                    if (!push_uint8(state, &state->bstack,
                      RE_OP_GREEDY_REPEAT_ONE))
                        return RE_ERROR_MEMORY;

                    /* bstack: count start node index GREEDY_REPEAT_ONE */
                } else {
                    /* We've reached or passed the minimum, so we won't need to
                     * backtrack the repeat again.
                     */
                    rp_data->start = start;
                    rp_data->count = saved_count;

                    /* Have we passed the minimum? */
                    if (count < node->values[1])
                        goto backtrack;
                }

                node = node->next_1.node;
                state->text_pos = pos;
                goto advance;
            } else {
                /* Don't try this repeated match again. */
                if (step > 0) {
                    if (!guard_repeat_range(state, index, limit, pos,
                      RE_STATUS_BODY, TRUE))
                        return RE_ERROR_MEMORY;
                } else if (step < 0) {
                    if (!guard_repeat_range(state, index, pos, limit,
                      RE_STATUS_BODY, TRUE))
                        return RE_ERROR_MEMORY;
                }

                /* We've backtracked the repeat as far as we can. */
                rp_data->start = start;
                rp_data->count = saved_count;
            }
            break;
        }
        case RE_OP_GROUP_CALL: /* Group call. */
        {
            TRACE(("%s\n", re_op_text[op]))

            /* sstack: caller_groups caller_repeats capture_change return_node
             *
             * bstack: -
             */

            if (!drop_pointer(state, &state->sstack))
                return RE_ERROR_MEMORY;

            /* For the caller. */
            if (!pop_size(state, &state->sstack, &state->capture_change))
                return RE_ERROR_MEMORY;
            if (!pop_repeats(state, &state->sstack))
                return RE_ERROR_MEMORY;
            if (!pop_groups(state, &state->sstack))
                return RE_ERROR_MEMORY;
            break;
        }
        case RE_OP_GROUP_RETURN: /* Group return. */
        {
            RE_Node* return_node;
            TRACE(("%s\n", re_op_text[op]))

            /* If called:
             *
             * sstack: -
             *
             * bstack: callee_groups callee_repeats capture_change return_node
             *
             * else:
             *
             * sstack: -
             *
             * bstack: NULL
             */

            if (!pop_pointer(state, &state->bstack, (void*)&return_node))
                return RE_ERROR_MEMORY;

            if (return_node) {
                /* For the caller. */
                if (!push_groups(state, &state->sstack))
                    return RE_ERROR_MEMORY;
                if (!push_repeats(state, &state->sstack))
                    return RE_ERROR_MEMORY;
                if (!push_size(state, &state->sstack, state->capture_change))
                    return RE_ERROR_MEMORY;
                if (!push_pointer(state, &state->sstack, return_node))
                    return RE_ERROR_MEMORY;

                /* sstack: caller_groups caller_repeats capture_change
                 * return_node
                 *
                 * bstack: callee_groups callee_repeats capture_change
                 */

                /* For the callee. */
                if (!pop_size(state, &state->bstack, &state->capture_change))
                    return RE_ERROR_MEMORY;
                if (!pop_repeats(state, &state->bstack))
                    return RE_ERROR_MEMORY;
                if (!pop_groups(state, &state->bstack))
                    return RE_ERROR_MEMORY;
            } else {
                if (!push_pointer(state, &state->sstack, NULL))
                    return RE_ERROR_MEMORY;
            }

            /* If called:
             *
             * sstack: caller_groups caller_repeats capture_change return_node
             *
             * bstack: -
             *
             * else:
             *
             * sstack: NULL
             *
             * bstack: -
             */
            break;
        }
        case RE_OP_KEEP: /* Keep. */
            /* bstack: match_pos */

            if (!pop_ssize(state, &state->bstack, &state->match_pos))
                return RE_ERROR_MEMORY;
            break;
        case RE_OP_LAZY_REPEAT_ONE: /* Lazy repeat for one character. */
        {
            RE_RepeatOneStateData data;
            RE_CODE index;
            Py_ssize_t start;
            size_t saved_count;
            RE_RepeatData* rp_data;
            size_t count;
            Py_ssize_t step;
            Py_ssize_t pos;
            Py_ssize_t available;
            size_t max_count;
            Py_ssize_t limit;
            RE_Node* repeated;
            RE_Node* test;
            BOOL match;
            Py_ssize_t skip_pos;
            BOOL m;
            TRACE(("%s\n", re_op_text[op]))

            /* bstack: count start node index */

            if (!ByteStack_pop_block(state, &state->bstack, (void*)&data,
              sizeof(data)))
                return RE_ERROR_MEMORY;

            index = data.index;
            node = data.node;
            start = data.start;
            saved_count = data.count;

            rp_data = &state->repeats[index];

            /* Match one character at a time until the tail could match or we
             * have reached the maximum.
             */
            state->text_pos = rp_data->start;
            count = rp_data->count;

            step = node->nonstring.next_2.test->step;
            pos = state->text_pos + (Py_ssize_t)count * step;
            available = step > 0 ? state->slice_end - state->text_pos :
              state->text_pos - state->slice_start;
            max_count = min_size_t((size_t)available, node->values[2]);
            limit = state->text_pos + (Py_ssize_t)max_count * step;

            repeated = node->nonstring.next_2.node;

            test = node->next_1.test;

            m = test->match;
            index = node->values[0];

            match = FALSE;
            skip_pos = -1;
            if (test->status & RE_STATUS_FUZZY) {
                for (;;) {
                    RE_Position next_position;

                    status = match_one(state, repeated, pos);
                    if (status < 0)
                        return status;

                    if (status == RE_ERROR_FAILURE)
                        break;

                    pos += step;

                    status = try_match(state, &node->next_1, pos,
                      &next_position);
                    if (status < 0)
                        return status;

                    if (status == RE_ERROR_SUCCESS && !is_repeat_guarded(state,
                      index, pos, RE_STATUS_TAIL)) {
                        match = TRUE;
                        break;
                    }

                    if (pos == limit)
                        break;
                }
            } else {
                /* A repeated single-character match is often followed by a
                 * literal, so checking specially for it can be a good
                 * optimisation when working with long strings.
                 */
                switch (test->op) {
                case RE_OP_CHARACTER:
                {
                    Py_UCS4 ch;

                    ch = test->values[0];

                    /* The tail is a character. We don't want to go off the end
                     * of the slice.
                     */
                    limit = min_ssize_t(limit, state->slice_end - 1);

                    for (;;) {
                        if (pos + 1 >= state->text_length &&
                          state->partial_side == RE_PARTIAL_RIGHT)
                            return RE_ERROR_PARTIAL;

                        if (pos >= limit)
                            break;

                        status = match_one(state, repeated, pos);
                        if (status < 0)
                            return status;

                        if (status == RE_ERROR_FAILURE)
                            break;

                        ++pos;

                        if (same_char(char_at(state->text, pos), ch) == m &&
                          !is_repeat_guarded(state, index, pos,
                          RE_STATUS_TAIL)) {
                            match = TRUE;
                            break;
                        }
                    }
                    break;
                }
                case RE_OP_CHARACTER_IGN:
                {
                    Py_UCS4 ch;

                    ch = test->values[0];

                    /* The tail is a character. We don't want to go off the end
                     * of the slice.
                     */
                    limit = min_ssize_t(limit, state->slice_end - 1);

                    for (;;) {
                        if (pos + 1 >= state->text_length &&
                          state->partial_side == RE_PARTIAL_RIGHT)
                            return RE_ERROR_PARTIAL;

                        if (pos >= limit)
                            break;

                        status = match_one(state, repeated, pos);
                        if (status < 0)
                            return status;

                        if (status == RE_ERROR_FAILURE)
                            break;

                        ++pos;

                        if (same_char_ign(encoding, locale_info,
                          char_at(state->text, pos), ch) == m &&
                          !is_repeat_guarded(state, index, pos,
                          RE_STATUS_TAIL)) {
                            match = TRUE;
                            break;
                        }
                    }
                    break;
                }
                case RE_OP_CHARACTER_IGN_REV:
                {
                    Py_UCS4 ch;

                    ch = test->values[0];

                    /* The tail is a character. We don't want to go off the end
                     * of the slice.
                     */
                    limit = max_ssize_t(limit, state->slice_start + 1);

                    for (;;) {
                        if (pos - 1 <= 0 && state->partial_side ==
                          RE_PARTIAL_LEFT)
                            return RE_ERROR_PARTIAL;

                        if (pos <= limit)
                            break;

                        status = match_one(state, repeated, pos);
                        if (status < 0)
                            return status;

                        if (status == RE_ERROR_FAILURE)
                            break;

                        --pos;

                        if (same_char_ign(encoding, locale_info,
                          char_at(state->text, pos - 1), ch) == m &&
                          !is_repeat_guarded(state, index, pos,
                          RE_STATUS_TAIL)) {
                            match = TRUE;
                            break;
                        }
                    }
                    break;
                }
                case RE_OP_CHARACTER_REV:
                {
                    Py_UCS4 ch;

                    ch = test->values[0];

                    /* The tail is a character. We don't want to go off the end
                     * of the slice.
                     */
                    limit = max_ssize_t(limit, state->slice_start + 1);

                    for (;;) {
                        if (pos - 1 <= 0 && state->partial_side ==
                          RE_PARTIAL_LEFT)
                            return RE_ERROR_PARTIAL;

                        if (pos <= limit)
                            break;

                        status = match_one(state, repeated, pos);
                        if (status < 0)
                            return status;

                        if (status == RE_ERROR_FAILURE)
                            break;

                        --pos;

                        if (same_char(char_at(state->text, pos - 1), ch) == m
                          && !is_repeat_guarded(state, index, pos,
                          RE_STATUS_TAIL)) {
                            match = TRUE;
                            break;
                        }
                    }
                    break;
                }
                case RE_OP_STRING:
                {
                    Py_ssize_t length;

                    length = (Py_ssize_t)test->value_count;

                    /* The tail is a string. We don't want to go off the end of
                     * the slice.
                     */
                    limit = min_ssize_t(limit, state->slice_end - length);

                    for (;;) {
                        Py_ssize_t found;
                        BOOL is_partial;

                        if (pos >= state->text_length && state->partial_side ==
                          RE_PARTIAL_RIGHT)
                            return RE_ERROR_PARTIAL;

                        if (pos >= limit)
                            break;

                        /* Look for the tail string. */
                        found = string_search(state, test, pos + 1, limit +
                          length, &is_partial);
                        if (is_partial)
                            return RE_ERROR_PARTIAL;

                        if (found < 0)
                            break;

                        if (repeated->op == RE_OP_ANY_ALL)
                            /* Anything can precede the tail. */
                            pos = found;
                        else {
                            /* Check that what precedes the tail will match. */
                            while (pos != found) {
                                status = match_one(state, repeated, pos);
                                if (status < 0)
                                    return status;

                                if (status == RE_ERROR_FAILURE)
                                    break;

                                ++pos;
                            }

                            if (pos != found)
                                /* Something preceding the tail didn't match.
                                 */
                                break;
                        }

                        if (!is_repeat_guarded(state, index, pos,
                          RE_STATUS_TAIL)) {
                            match = TRUE;
                            break;
                        }
                    }
                    break;
                }
                case RE_OP_STRING_FLD:
                {
                    /* The tail is a string. We don't want to go off the end of
                     * the slice.
                     */
                    limit = min_ssize_t(limit, state->slice_end);

                    for (;;) {
                        Py_ssize_t found;
                        Py_ssize_t new_pos;
                        BOOL is_partial;

                        if (pos >= state->text_length && state->partial_side ==
                          RE_PARTIAL_RIGHT)
                            return RE_ERROR_PARTIAL;

                        if (pos >= limit)
                            break;

                        /* Look for the tail string. */
                        found = string_search_fld(state, test, pos + 1, limit,
                          &new_pos, &is_partial);
                        if (is_partial)
                            return RE_ERROR_PARTIAL;

                        if (found < 0)
                            break;

                        if (repeated->op == RE_OP_ANY_ALL)
                            /* Anything can precede the tail. */
                            pos = found;
                        else {
                            /* Check that what precedes the tail will match. */
                            while (pos != found) {
                                status = match_one(state, repeated, pos);
                                if (status < 0)
                                    return status;

                                if (status == RE_ERROR_FAILURE)
                                    break;

                                ++pos;
                            }

                            if (pos != found)
                                /* Something preceding the tail didn't match.
                                 */
                                break;
                        }

                        if (!is_repeat_guarded(state, index, pos,
                          RE_STATUS_TAIL)) {
                            match = TRUE;
                            skip_pos = new_pos;
                            break;
                        }
                    }
                    break;
                }
                case RE_OP_STRING_FLD_REV:
                {
                    /* The tail is a string. We don't want to go off the end of
                     * the slice.
                     */
                    limit = max_ssize_t(limit, state->slice_start);

                    for (;;) {
                        Py_ssize_t found;
                        Py_ssize_t new_pos;
                        BOOL is_partial;

                        if (pos <= 0 && state->partial_side == RE_PARTIAL_LEFT)
                            return RE_ERROR_PARTIAL;

                        if (pos <= limit)
                            break;

                        /* Look for the tail string. */
                        found = string_search_fld_rev(state, test, pos - 1,
                          limit, &new_pos, &is_partial);
                        if (is_partial)
                            return RE_ERROR_PARTIAL;

                        if (found < 0)
                            break;

                        if (repeated->op == RE_OP_ANY_ALL)
                            /* Anything can precede the tail. */
                            pos = found;
                        else {
                            /* Check that what precedes the tail will match. */
                            while (pos != found) {
                                status = match_one(state, repeated, pos);
                                if (status < 0)
                                    return status;

                                if (status == RE_ERROR_FAILURE)
                                    break;

                                --pos;
                            }

                            if (pos != found)
                                /* Something preceding the tail didn't match.
                                 */
                                break;
                        }

                        if (!is_repeat_guarded(state, index, pos,
                          RE_STATUS_TAIL)) {
                            match = TRUE;
                            skip_pos = new_pos;
                            break;
                        }
                    }
                    break;
                }
                case RE_OP_STRING_IGN:
                {
                    Py_ssize_t length;

                    length = (Py_ssize_t)test->value_count;

                    /* The tail is a string. We don't want to go off the end of
                     * the slice.
                     */
                    limit = min_ssize_t(limit, state->slice_end - length);

                    for (;;) {
                        Py_ssize_t found;
                        BOOL is_partial;

                        if (pos >= state->text_length && state->partial_side ==
                          RE_PARTIAL_RIGHT)
                            return RE_ERROR_PARTIAL;

                        if (pos >= limit)
                            break;

                        /* Look for the tail string. */
                        found = string_search_ign(state, test, pos + 1, limit +
                          length, &is_partial);
                        if (is_partial)
                            return RE_ERROR_PARTIAL;

                        if (found < 0)
                            break;

                        if (repeated->op == RE_OP_ANY_ALL)
                            /* Anything can precede the tail. */
                            pos = found;
                        else {
                            /* Check that what precedes the tail will match. */
                            while (pos != found) {
                                status = match_one(state, repeated, pos);
                                if (status < 0)
                                    return status;

                                if (status == RE_ERROR_FAILURE)
                                    break;

                                ++pos;
                            }

                            if (pos != found)
                                /* Something preceding the tail didn't match.
                                 */
                                break;
                        }

                        if (!is_repeat_guarded(state, index, pos,
                          RE_STATUS_TAIL)) {
                            match = TRUE;
                            break;
                        }
                    }
                    break;
                }
                case RE_OP_STRING_IGN_REV:
                {
                    Py_ssize_t length;

                    length = (Py_ssize_t)test->value_count;

                    /* The tail is a string. We don't want to go off the end of
                     * the slice.
                     */
                    limit = max_ssize_t(limit, state->slice_start + length);

                    for (;;) {
                        Py_ssize_t found;
                        BOOL is_partial;

                        if (pos <= 0 && state->partial_side == RE_PARTIAL_LEFT)
                            return RE_ERROR_PARTIAL;

                        if (pos <= limit)
                            break;

                        /* Look for the tail string. */
                        found = string_search_ign_rev(state, test, pos - 1,
                          limit - length, &is_partial);
                        if (is_partial)
                            return RE_ERROR_PARTIAL;

                        if (found < 0)
                            break;

                        if (repeated->op == RE_OP_ANY_ALL)
                            /* Anything can precede the tail. */
                            pos = found;
                        else {
                            /* Check that what precedes the tail will match. */
                            while (pos != found) {
                                status = match_one(state, repeated, pos);
                                if (status < 0)
                                    return status;

                                if (status == RE_ERROR_FAILURE)
                                    break;

                                --pos;
                            }

                            if (pos != found)
                                /* Something preceding the tail didn't match.
                                 */
                                break;
                        }

                        if (!is_repeat_guarded(state, index, pos,
                          RE_STATUS_TAIL)) {
                            match = TRUE;
                            break;
                        }
                    }
                    break;
                }
                case RE_OP_STRING_REV:
                {
                    Py_ssize_t length;

                    length = (Py_ssize_t)test->value_count;

                    /* The tail is a string. We don't want to go off the end of
                     * the slice.
                     */
                    limit = max_ssize_t(limit, state->slice_start + length);

                    for (;;) {
                        Py_ssize_t found;
                        BOOL is_partial;

                        if (pos <= 0 && state->partial_side == RE_PARTIAL_LEFT)
                            return RE_ERROR_PARTIAL;

                        if (pos <= limit)
                            break;

                        /* Look for the tail string. */
                        found = string_search_rev(state, test, pos - 1, limit -
                          length, &is_partial);
                        if (is_partial)
                            return RE_ERROR_PARTIAL;

                        if (found < 0)
                            break;

                        if (repeated->op == RE_OP_ANY_ALL)
                            /* Anything can precede the tail. */
                            pos = found;
                        else {
                            /* Check that what precedes the tail will match. */
                            while (pos != found) {
                                status = match_one(state, repeated, pos);
                                if (status < 0)
                                    return status;

                                if (status == RE_ERROR_FAILURE)
                                    break;

                                --pos;
                            }

                            if (pos != found)
                                /* Something preceding the tail didn't match.
                                 */
                                break;
                        }

                        if (!is_repeat_guarded(state, index, pos,
                          RE_STATUS_TAIL)) {
                            match = TRUE;
                            break;
                        }
                    }
                    break;
                }
                default:
                    for (;;) {
                        RE_Position next_position;

                        status = match_one(state, repeated, pos);
                        if (status < 0)
                            return status;

                        if (status == RE_ERROR_FAILURE)
                            break;

                        pos += step;

                        status = try_match(state, &node->next_1, pos,
                          &next_position);
                        if (status < 0)
                            return RE_ERROR_PARTIAL;

                        if (status == RE_ERROR_SUCCESS &&
                          !is_repeat_guarded(state, index, pos,
                          RE_STATUS_TAIL)) {
                            match = TRUE;
                            break;
                        }

                        if (pos == limit)
                            break;
                    }
                    break;
                }
            }

            if (match) {
                /* The tail could match. */
                count = (size_t)abs_ssize_t(pos - state->text_pos);
                state->text_pos = pos;

                if (count < max_count) {
                    /* The match is shorter than the maximum, so we might need
                     * to backtrack the repeat again to consume more.
                     */
                    RE_RepeatOneStateData data_ro;

                    rp_data->count = count;

                    data_ro.count = saved_count;
                    data_ro.start = start;
                    data_ro.node = node;
                    data_ro.index = index;

                    if (!ByteStack_push_block(state, &state->bstack,
                      (void*)&data_ro, sizeof(data_ro)))
                        return RE_ERROR_MEMORY;
                    if (!push_uint8(state, &state->bstack,
                      RE_OP_LAZY_REPEAT_ONE))
                        return RE_ERROR_MEMORY;

                    /* bstack: count start node index LAZY_REPEAT_ONE */
                } else {
                    /* We've reached or passed the maximum, so we won't need to
                     * backtrack the repeat again.
                     */
                    rp_data->start = start;
                    rp_data->count = saved_count;

                    /* Have we passed the maximum? */
                    if (count > max_count)
                        goto backtrack;
                }

                node = node->next_1.node;

                if (skip_pos >= 0) {
                    state->text_pos = skip_pos;
                    node = node->next_1.node;
                }

                goto advance;
            } else {
                /* The tail couldn't match. */
                rp_data->start = start;
                rp_data->count = saved_count;
            }
            break;
        }
        case RE_OP_LOOKAROUND: /* Lookaround subpattern. */
        {
            RE_Node* lookaround;
            RE_LookaroundStateData data_l;
            BOOL has_groups;
            TRACE(("%s\n", re_op_text[op]))

            /* sstack: node slice_start slice_end text_pos ...
             *
             * bstack: [captures TRUE | FALSE] repeats fuzzy_counts
             * capture_change sstack
             *
             * pstack: bstack
             */

            if (!drop_bstack(state))
                return RE_ERROR_MEMORY;
            if (!pop_sstack(state))
                return RE_ERROR_MEMORY;

            /* sstack: node slice_start slice_end text_pos
             *
             * bstack: [captures TRUE | FALSE] repeats fuzzy_counts
             * capture_change
             *
             * pstack: -
             */

            if (!ByteStack_pop_block(state, &state->sstack, (void*)&data_l,
              sizeof(data_l)))
                return RE_ERROR_MEMORY;

            state->text_pos = data_l.text_pos;
            state->slice_end = data_l.slice_end;
            state->slice_start = data_l.slice_start;
            lookaround = data_l.node;

            /* sstack: -
             *
             * bstack: [captures TRUE | FALSE] repeats fuzzy_counts
             * capture_change
             *
             * pstack: -
             */

            if (!pop_size(state, &state->bstack, &state->capture_change))
                return RE_ERROR_MEMORY;
            if (!pop_fuzzy_counts(state, &state->bstack, state->fuzzy_counts))
                return RE_ERROR_MEMORY;
            if (!pop_bool(state, &state->bstack, &has_groups))
                return RE_ERROR_MEMORY;
            if (has_groups) {
                if (!pop_captures(state, &state->bstack))
                    return RE_ERROR_MEMORY;
            }

            /* sstack: -
             *
             * bstack: -
             *
             * pstack: -
             */

            if (!lookaround->match) {
                /* It's a negative lookaround that's failed. */

                node = lookaround->nonstring.next_2.node;
                goto advance;
            }
            break;
        }
        case RE_OP_MATCH_BODY:
        {
            RE_MatchBodyTailStateData data_mbt;
            Py_ssize_t text_pos;
            RE_CODE index;
            size_t capture_change;
            Py_ssize_t start;
            size_t count;
            RE_Position position;
            RE_RepeatData* rp_data;

            /* bstack: position count start capture_change index text_pos */

            if (!ByteStack_pop_block(state, &state->bstack, (void*)&data_mbt,
              sizeof(data_mbt)))
                return RE_ERROR_MEMORY;

            text_pos = data_mbt.text_pos;
            index = data_mbt.index;
            capture_change = data_mbt.capture_change;
            start = data_mbt.start;
            count = data_mbt.count;
            position = data_mbt.position;
            TRACE(("%s %d\n", re_op_text[op], index))

            /* We want to match the body. */
            rp_data = &state->repeats[index];

            /* Restore the repeat info. */
            rp_data->count = count;
            rp_data->start = start;
            rp_data->capture_change = capture_change;

            /* Record backtracking info in case the body fails to match. */
            if (!push_code(state, &state->bstack, index))
                return RE_ERROR_MEMORY;
            if (!push_ssize(state, &state->bstack, text_pos))
                return RE_ERROR_MEMORY;
            if (!push_uint8(state, &state->bstack, RE_OP_BODY_START))
                return RE_ERROR_MEMORY;

            /* bstack: index text_pos BODY_START */

            /* Advance into the body. */
            node = position.node;
            state->text_pos = position.text_pos;
            goto advance;
        }
        case RE_OP_MATCH_TAIL:
        {
            RE_MatchBodyTailStateData data_mbt;
            RE_CODE index;
            size_t capture_change;
            Py_ssize_t start;
            size_t count;
            RE_Position position;
            RE_RepeatData* rp_data;

            /* bstack: position count start capture_change index text_pos */

            if (!ByteStack_pop_block(state, &state->bstack, (void*)&data_mbt,
              sizeof(data_mbt)))
                return RE_ERROR_MEMORY;

            index = data_mbt.index;
            capture_change = data_mbt.capture_change;
            start = data_mbt.start;
            count = data_mbt.count;
            position = data_mbt.position;
            TRACE(("%s %d\n", re_op_text[op], index))

            /* We want to match the tail. */
            rp_data = &state->repeats[index];

            /* Restore the repeat info. */
            rp_data->count = count;
            rp_data->start = start;
            rp_data->capture_change = capture_change;

            /* Advance into the tail. */
            node = position.node;
            state->text_pos = position.text_pos;
            goto advance;
        }
        case RE_OP_REF_GROUP: /* Reference to a capture group. */
        case RE_OP_REF_GROUP_IGN: /* Reference to a capture group, ignoring case. */
        case RE_OP_REF_GROUP_IGN_REV: /* Reference to a capture group, backwards, ignoring case. */
        case RE_OP_REF_GROUP_REV: /* Reference to a capture group, backwards. */
        case RE_OP_STRING: /* A string. */
        case RE_OP_STRING_IGN: /* A string, ignoring case. */
        case RE_OP_STRING_IGN_REV: /* A string, backwards, ignoring case. */
        case RE_OP_STRING_REV: /* A string, backwards. */
        {
            TRACE(("%s\n", re_op_text[op]))

            status = retry_fuzzy_match_string(state, op, search,
              &state->text_pos, &node, &string_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS)
                goto advance;

            string_pos = -1;
            break;
        }
        case RE_OP_REF_GROUP_FLD: /* Reference to a capture group, ignoring case. */
        case RE_OP_REF_GROUP_FLD_REV: /* Reference to a capture group, backwards, ignoring case. */
        {
            TRACE(("%s\n", re_op_text[op]))

            status = retry_fuzzy_match_group_fld(state, op, search,
              &state->text_pos, &node, &folded_pos, &string_pos, &gfolded_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS)
                goto advance;

            string_pos = -1;
            break;
        }
        case RE_OP_START_GROUP: /* Start of a capture group. */
        {
            BOOL capture;
            TRACE(("%s %d\n", re_op_text[op], public_index))

            /* If capturing:
             *
             * sstack: -
             *
             * bstack: end current capture_change private_index public_index
             * TRUE
             *
             * else:
             *
             * sstack: start
             *
             * bstack: FALSE
             */

            if (!pop_bool(state, &state->bstack, &capture))
                return RE_ERROR_MEMORY;

            if (capture) {
                RE_GroupStateData data_g;
                RE_CODE public_index;
                RE_CODE private_index;
                Py_ssize_t end;
                RE_GroupData* group;

                if (!ByteStack_pop_block(state, &state->bstack, (void*)&data_g,
                  sizeof(data_g)))
                    return RE_ERROR_MEMORY;

                public_index = data_g.public_index;
                private_index = data_g.private_index;
                state->capture_change = data_g.capture_change;
                group = &state->groups[private_index - 1];
                group->current = data_g.current;
                end = data_g.text_pos;
                if (!push_ssize(state, &state->sstack, end))
                    return RE_ERROR_MEMORY;

                unsave_capture(state, private_index, public_index);

                /* sstack: end
                 *
                 * bstack: -
                 */
            } else {
                if (!drop_ssize(state, &state->sstack))
                    return RE_ERROR_MEMORY;
            }
            break;
        }
        case RE_OP_STRING_FLD: /* A string, ignoring case. */
        case RE_OP_STRING_FLD_REV: /* A string, backwards, ignoring case. */
        {
            TRACE(("%s\n", re_op_text[op]))

            status = retry_fuzzy_match_string_fld(state, op, search,
              &state->text_pos, &node, &string_pos, &folded_pos);
            if (status < 0)
                return status;

            if (status == RE_ERROR_SUCCESS)
                goto advance;

            string_pos = -1;
            break;
        }
        default:
            TRACE(("UNKNOWN OP %d\n", op))
            return RE_ERROR_ILLEGAL;
        }
    }
}

/* Saves group data for fuzzy matching. */
Py_LOCAL_INLINE(RE_GroupData*) save_captures(RE_State* state, RE_GroupData*
  saved_groups) {
    PatternObject* pattern;
    size_t g;

    /* Re-acquire the GIL. */
    acquire_GIL(state);

    pattern = state->pattern;

    if (!saved_groups) {
        saved_groups = (RE_GroupData*)re_alloc(pattern->true_group_count *
          sizeof(RE_GroupData));
        if (!saved_groups)
            goto error;

        memset(saved_groups, 0, pattern->true_group_count *
          sizeof(RE_GroupData));
    }

    for (g = 0; g < pattern->true_group_count; g++) {
        RE_GroupData* orig;
        RE_GroupData* copy;

        orig = &state->groups[g];
        copy = &saved_groups[g];

        if (orig->count > copy->capacity) {
            RE_GroupSpan* cap_copy;

            cap_copy = (RE_GroupSpan*)re_realloc(copy->captures, orig->count *
              sizeof(RE_GroupSpan));
            if (!cap_copy)
                goto error;

            copy->capacity = orig->count;
            copy->captures = cap_copy;
        }

        copy->count = orig->count;
        Py_MEMCPY(copy->captures, orig->captures, orig->count *
          sizeof(RE_GroupSpan));
        copy->current = orig->current;
    }

    /* Release the GIL. */
    release_GIL(state);

    return saved_groups;

error:
    if (saved_groups) {
        for (g = 0; g < pattern->true_group_count; g++)
            re_dealloc(saved_groups[g].captures);

        re_dealloc(saved_groups);
    }

    /* Release the GIL. */
    release_GIL(state);

    return NULL;
}

/* Restores group data for fuzzy matching. */
Py_LOCAL_INLINE(void) restore_groups(RE_State* state, RE_GroupData*
  saved_groups) {
    PatternObject* pattern;
    size_t g;

    /* Re-acquire the GIL. */
    acquire_GIL(state);

    pattern = state->pattern;

    for (g = 0; g < pattern->true_group_count; g++) {
        RE_GroupData* group;
        RE_GroupData* saved;

        group = &state->groups[g];
        saved = &saved_groups[g];

        group->count = saved->count;
        Py_MEMCPY(group->captures, saved->captures, saved->count *
          sizeof(RE_GroupSpan));
        group->current = saved->current;

        re_dealloc(saved->captures);
    }

    re_dealloc(saved_groups);

    /* Release the GIL. */
    release_GIL(state);
}

/* Discards group data for fuzzy matching. */
Py_LOCAL_INLINE(void) discard_groups(RE_State* state, RE_GroupData*
  saved_groups) {
    PatternObject* pattern;
    size_t g;

    /* Re-acquire the GIL. */
    acquire_GIL(state);

    pattern = state->pattern;

    for (g = 0; g < pattern->true_group_count; g++)
        re_dealloc(saved_groups[g].captures);

    re_dealloc(saved_groups);

    /* Release the GIL. */
    release_GIL(state);
}

/* Saves the fuzzy counts. */
Py_LOCAL_INLINE(void) save_fuzzy_counts(RE_State* state, size_t* fuzzy_counts)
  {
    Py_MEMCPY(fuzzy_counts, state->fuzzy_counts, sizeof(state->fuzzy_counts));
}

/* Restores the fuzzy counts. */
Py_LOCAL_INLINE(void) restore_fuzzy_counts(RE_State* state, size_t*
  fuzzy_counts) {
    Py_MEMCPY(state->fuzzy_counts, fuzzy_counts, sizeof(state->fuzzy_counts));
}

/* Makes the list of best matches found so far. */
Py_LOCAL_INLINE(void) make_best_list(RE_BestList* best_list) {
    best_list->capacity = 0;
    best_list->count = 0;
    best_list->entries = NULL;
}

/* Clears the list of best matches found so far. */
Py_LOCAL_INLINE(void) clear_best_list(RE_BestList* best_list) {
    best_list->count = 0;
}

/* Adds a new entry to the list of best matches found so far. */
Py_LOCAL_INLINE(BOOL) add_to_best_list(RE_State* state, RE_BestList* best_list,
  Py_ssize_t match_pos, Py_ssize_t text_pos) {
    RE_BestEntry* entry;

    if (best_list->count >= best_list->capacity) {
        size_t new_capacity;
        RE_BestEntry* new_entries;

        new_capacity = best_list->capacity * 2;

        if (new_capacity == 0)
            new_capacity = 16;

        new_entries = safe_realloc(state, best_list->entries, new_capacity *
          sizeof(RE_BestEntry));
        if (!new_entries)
            return FALSE;

        best_list->entries = new_entries;
        best_list->capacity = new_capacity;
    }

    entry = &best_list->entries[best_list->count++];
    entry->match_pos = match_pos;
    entry->text_pos = text_pos;

    return TRUE;
}

/* Destroy the list of best matches found so far. */
Py_LOCAL_INLINE(void) destroy_best_list(RE_State* state, RE_BestList*
  best_list) {
    if (best_list->entries)
        safe_dealloc(state, best_list->entries);
}

/* Performs a match or search from the current text position for a best fuzzy
 * match.
 */
Py_LOCAL_INLINE(int) do_best_fuzzy_match(RE_State* state, BOOL search) {
    Py_ssize_t available;
    int step;
    size_t fewest_errors;
    BOOL must_advance;
    BOOL found_match;
    RE_BestList best_list;
    RE_BestChangesList best_changes_list;
    Py_ssize_t start_pos;
    int status = RE_ERROR_FAILURE;
    TRACE(("<<do_best_fuzzy_match>>\n"))

    if (state->reverse) {
        available = state->text_pos - state->slice_start;
        step = -1;
    } else {
        available = state->slice_end - state->text_pos;
        step = 1;
    }

    /* The maximum permitted cost. */
    state->max_errors = PY_SSIZE_T_MAX;
    fewest_errors = PY_SSIZE_T_MAX;

    state->best_text_pos = state->reverse ? state->slice_start :
      state->slice_end;

    must_advance = state->must_advance;
    found_match = FALSE;

    make_best_list(&best_list);
    make_best_changes_list(&best_changes_list);

    /* Search the text for the best match. */
    start_pos = state->text_pos;
    while (state->slice_start <= start_pos && start_pos <= state->slice_end) {
        state->text_pos = start_pos;
        state->must_advance = must_advance;

        /* Initialise the state. */
        init_match(state);

        status = RE_ERROR_SUCCESS;
        if (state->max_errors == 0 && state->partial_side == RE_PARTIAL_NONE) {
            /* An exact match, and partial matches not permitted. */
            if (available < state->min_width || (available == 0 &&
              state->must_advance))
                status = RE_ERROR_FAILURE;
        }

        if (status == RE_ERROR_SUCCESS)
            status = basic_match(state, search);

        /* Has an error occurred, or is it a partial match? */
        if (status < 0)
            break;

        if (status == RE_ERROR_FAILURE)
            break;

        /* It was a successful match. */
        found_match = TRUE;

        if (state->total_errors < fewest_errors) {
            /* This match was better than any of the previous ones. */
            fewest_errors = state->total_errors;

            if (state->total_errors == 0)
                /* It was a perfect match. */
                break;

            /* Forget all the previous worse matches and remember this one. */
            clear_best_list(&best_list);
            if (!add_to_best_list(state, &best_list, state->match_pos,
              state->text_pos))
                goto error;

            clear_best_fuzzy_changes(state, &best_changes_list);
            if (!add_best_fuzzy_changes(state, &best_changes_list))
                goto error;
        } else if (state->total_errors == fewest_errors) {
            /* This match was as good as the previous matches. Remember this
             * one.
             */
            add_to_best_list(state, &best_list, state->match_pos,
              state->text_pos);
            if (!add_best_fuzzy_changes(state, &best_changes_list))
                goto error;
        }

        start_pos = state->match_pos;

        /* Should we keep searching? */
        if (!search)
            break;

        state->max_errors = fewest_errors - 1;
    }

    if (found_match) {
        RE_FuzzyChangesList* list;

        /* We found a match. */
        if (fewest_errors > 0) {
            /* It doesn't look like a perfect match. */
            size_t i;
            Py_ssize_t slice_start;
            Py_ssize_t slice_end;
            size_t error_limit;
            size_t best_fuzzy_counts[RE_FUZZY_COUNT];
            RE_FuzzyChangesList best_fuzzy_changes;
            RE_GroupData* best_groups;
            Py_ssize_t best_match_pos = 0;
            Py_ssize_t best_text_pos;

            slice_start = state->slice_start;
            slice_end = state->slice_end;

            error_limit = fewest_errors;

            if (error_limit > RE_MAX_ERRORS)
                error_limit = RE_MAX_ERRORS;

            best_groups = NULL;
            make_fuzzy_changes_list(&best_fuzzy_changes);

            /* Look again at the best of the matches that we've seen. */
            for (i = 0; i < best_list.count; i++) {
                RE_BestEntry* entry;
                Py_ssize_t max_offset;
                Py_ssize_t offset;

                /* Look for the best fit at this position. */
                entry = &best_list.entries[i];

                if (search) {
                    max_offset = state->reverse ? entry->match_pos -
                      state->slice_start : state->slice_end - entry->match_pos;

                    if (max_offset > (Py_ssize_t)fewest_errors)
                        max_offset = (Py_ssize_t)fewest_errors;

                    if (max_offset > (Py_ssize_t)error_limit)
                        max_offset = (Py_ssize_t)error_limit;
                } else
                    max_offset = 0;

                start_pos = entry->match_pos;
                offset = 0;

                while (offset <= max_offset) {
                    state->max_errors = 1;

                    while (state->max_errors <= error_limit) {
                        state->text_pos = start_pos;
                        init_match(state);
                        status = basic_match(state, FALSE);

                        if (status == RE_ERROR_SUCCESS) {
                            BOOL better = FALSE;

                            if (state->total_errors < error_limit || (i == 0 &&
                              offset == 0))
                                better = TRUE;
                            else if (state->total_errors == error_limit)
                                /* The cost is as low as the current best, but
                                 * is it earlier?
                                 */
                                better = state->reverse ? state->match_pos >
                                  best_match_pos : state->match_pos <
                                  best_match_pos;

                            if (better) {
                                save_fuzzy_counts(state, best_fuzzy_counts);
                                if (!save_fuzzy_changes(state,
                                  &best_fuzzy_changes))
                                    goto error;

                                best_groups = save_captures(state,
                                  best_groups);
                                if (!best_groups)
                                    goto error;

                                best_match_pos = state->match_pos;
                                best_text_pos = state->text_pos;
                                error_limit = state->total_errors;
                            }

                            break;
                        }

                        ++state->max_errors;
                    }

                    start_pos += step;
                    ++offset;
                }

                if (status == RE_ERROR_SUCCESS && state->total_errors == 0)
                    break;
            }

            if (best_groups) {
                status = RE_ERROR_SUCCESS;
                state->match_pos = best_match_pos;
                state->text_pos = best_text_pos;

                restore_groups(state, best_groups);
                restore_fuzzy_counts(state, best_fuzzy_counts);
                restore_fuzzy_changes(state, &best_fuzzy_changes);
            } else {
                /* None of the "best" matches could be improved on, so pick the
                 * first.
                 */
                RE_BestEntry* entry;

                /* Look at only the part of the string around the match. */
                entry = &best_list.entries[0];

                if (state->reverse) {
                    state->slice_start = entry->text_pos;
                    state->slice_end = entry->match_pos;
                } else {
                    state->slice_start = entry->match_pos;
                    state->slice_end = entry->text_pos;
                }

                /* We'll expand the part that we're looking at to take to
                 * compensate for any matching errors that have occurred.
                 */
                if (state->slice_start - slice_start >=
                  (Py_ssize_t)fewest_errors)
                    state->slice_start -= (Py_ssize_t)fewest_errors;
                else
                    state->slice_start = slice_start;

                if (slice_end - state->slice_end >= (Py_ssize_t)fewest_errors)
                    state->slice_end += (Py_ssize_t)fewest_errors;
                else
                    state->slice_end = slice_end;

                state->max_errors = fewest_errors;
                state->text_pos = entry->match_pos;
                init_match(state);
                status = basic_match(state, search);
            }

            state->slice_start = slice_start;
            state->slice_end = slice_end;

            list = &best_changes_list.lists[0];
            state->fuzzy_changes.count = list->count;
            Py_MEMCPY(state->fuzzy_changes.items, list->items,
              (size_t)list->count * sizeof(RE_FuzzyChange));
        } else
            state->fuzzy_changes.count = 0;
    }

    destroy_best_list(state, &best_list);
    destroy_best_changes_list(state, &best_changes_list);

    return status;

error:
    destroy_best_list(state, &best_list);
    destroy_best_changes_list(state, &best_changes_list);
    return RE_ERROR_MEMORY;
}

/* Performs a match or search from the current text position for an enhanced
 * fuzzy match.
 */
Py_LOCAL_INLINE(int) do_enhanced_fuzzy_match(RE_State* state, BOOL search) {
    PatternObject* pattern;
    Py_ssize_t available;
    size_t fewest_errors;
    RE_GroupData* best_groups;
    Py_ssize_t best_match_pos;
    BOOL must_advance;
    Py_ssize_t slice_start;
    Py_ssize_t slice_end;
    int status;
    size_t best_fuzzy_counts[RE_FUZZY_COUNT];
    RE_FuzzyChangesList best_fuzzy_changes;
    Py_ssize_t best_text_pos = 0; /* Initialise to stop compiler warning. */
    TRACE(("<<do_enhanced_fuzzy_match>>\n"))

    pattern = state->pattern;

    make_changes_list(state, &best_fuzzy_changes);

    if (state->reverse)
        available = state->text_pos - state->slice_start;
    else
        available = state->slice_end - state->text_pos;

    /* The maximum permitted cost. */
    state->max_errors = PY_SSIZE_T_MAX;
    fewest_errors = PY_SSIZE_T_MAX;

    best_groups = NULL;

    state->best_match_pos = state->text_pos;
    state->best_text_pos = state->reverse ? state->slice_start :
      state->slice_end;

    best_match_pos = state->text_pos;
    must_advance = state->must_advance;

    slice_start = state->slice_start;
    slice_end = state->slice_end;

    for (;;) {
        /* If there's a better match, it won't start earlier in the string than
         * the current best match, so there's no need to start earlier than
         * that match.
         */
        state->must_advance = must_advance;

        /* Initialise the state. */
        init_match(state);

        status = RE_ERROR_SUCCESS;
        if (state->max_errors == 0 && state->partial_side == RE_PARTIAL_NONE) {
            /* An exact match, and partial matches not permitted. */
            if (available < state->min_width || (available == 0 &&
              state->must_advance))
                status = RE_ERROR_FAILURE;
        }

        if (status == RE_ERROR_SUCCESS)
            status = basic_match(state, search);

        /* Has an error occurred, or is it a partial match? */
        if (status < 0)
            break;

        if (status == RE_ERROR_SUCCESS) {
            BOOL better;

            better = state->total_errors < fewest_errors;

            if (better) {
                BOOL same_match;

                fewest_errors = state->total_errors;
                state->max_errors = fewest_errors;

                save_fuzzy_counts(state, best_fuzzy_counts);
                if (!save_fuzzy_changes(state, &best_fuzzy_changes))
                    goto error;

                same_match = state->match_pos == best_match_pos &&
                  state->text_pos == best_text_pos;
                same_match = FALSE;

                if (best_groups) {
                    size_t g;

                    /* Did we get the same match as the best so far? */
                    for (g = 0; same_match && g < pattern->public_group_count;
                      g++)
                        same_match = same_span_of_group(&state->groups[g],
                          &best_groups[g]);
                }

                /* Save the best result so far. */
                best_groups = save_captures(state, best_groups);
                if (!best_groups) {
                    status = RE_ERROR_MEMORY;
                    break;
                }

                best_match_pos = state->match_pos;
                best_text_pos = state->text_pos;

                if (same_match || state->total_errors == 0)
                    break;

                state->max_errors = state->total_errors;
                if (state->max_errors < RE_MAX_ERRORS)
                    --state->max_errors;
            } else
                break;

            if (state->reverse) {
                state->slice_start = state->text_pos;
                state->slice_end = state->match_pos;
            } else {
                state->slice_start = state->match_pos;
                state->slice_end = state->text_pos;
            }

            state->text_pos = state->match_pos;

            if (state->max_errors == PY_SSIZE_T_MAX)
                state->max_errors = 0;
        } else
            break;
    }

    if (status < 0 && status != RE_ERROR_PARTIAL)
        goto error;

    state->slice_start = slice_start;
    state->slice_end = slice_end;

    if (best_groups) {
        if (status == RE_ERROR_SUCCESS && state->total_errors == 0)
            /* We have a perfect match, so the previous best match. */
            discard_groups(state, best_groups);
        else {
            /* Restore the previous best match. */
            status = RE_ERROR_SUCCESS;

            state->match_pos = best_match_pos;
            state->text_pos = best_text_pos;

            restore_groups(state, best_groups);
            restore_fuzzy_counts(state, best_fuzzy_counts);
        }

        restore_fuzzy_changes(state, &best_fuzzy_changes);
    }

    destroy_changes_list(state, &best_fuzzy_changes);

    return status;

error:
    destroy_changes_list(state, &best_fuzzy_changes);
    return status;
}

/* Performs a match or search from the current text position for a simple fuzzy
 * match.
 */
Py_LOCAL_INLINE(int) do_simple_fuzzy_match(RE_State* state, BOOL search) {
    Py_ssize_t available;
    int status;
    TRACE(("<<do_simple_fuzzy_match>>\n"))

    if (state->reverse)
        available = state->text_pos - state->slice_start;
    else
        available = state->slice_end - state->text_pos;

    /* The maximum permitted cost. */
    state->max_errors = PY_SSIZE_T_MAX;

    state->best_match_pos = state->text_pos;
    state->best_text_pos = state->reverse ? state->slice_start :
      state->slice_end;

    /* Initialise the state. */
    init_match(state);

    status = RE_ERROR_SUCCESS;
    if (state->max_errors == 0 && state->partial_side == RE_PARTIAL_NONE) {
        /* An exact match, and partial matches not permitted. */
        if (available < state->min_width || (available == 0 &&
          state->must_advance))
            status = RE_ERROR_FAILURE;
    }

    if (status == RE_ERROR_SUCCESS)
        status = basic_match(state, search);

    return status;
}

/* Performs a match or search from the current text position for an exact
 * match.
 */
Py_LOCAL_INLINE(int) do_exact_match(RE_State* state, BOOL search) {
    Py_ssize_t available;
    int status;
    TRACE(("<<do_exact_match>>\n"))

    if (state->reverse)
        available = state->text_pos - state->slice_start;
    else
        available = state->slice_end - state->text_pos;

    /* The maximum permitted cost. */
    state->max_errors = 0;

    state->best_match_pos = state->text_pos;
    state->best_text_pos = state->reverse ? state->slice_start :
      state->slice_end;

    /* Initialise the state. */
    init_match(state);

    status = RE_ERROR_SUCCESS;
    if (state->max_errors == 0 && state->partial_side == RE_PARTIAL_NONE) {
        /* An exact match, and partial matches not permitted. */
        if (available < state->min_width || (available == 0 &&
          state->must_advance))
            status = RE_ERROR_FAILURE;
    }

    if (status == RE_ERROR_SUCCESS)
        status = basic_match(state, search);

    return status;
}

/* Performs the requested kind (i.e. fuzziness) of match. */
Py_LOCAL_INLINE(int) do_match_2(RE_State* state, BOOL search) {
    PatternObject* pattern;

    pattern = state->pattern;

    if (!pattern->is_fuzzy)
        return do_exact_match(state, search);

    if (pattern->flags & RE_FLAG_BESTMATCH)
        return do_best_fuzzy_match(state, search);

    if (pattern->flags & RE_FLAG_ENHANCEMATCH)
        return do_enhanced_fuzzy_match(state, search);

    return do_simple_fuzzy_match(state, search);
}

/* Performs a match or search from the current text position.
 *
 * The state can sometimes be shared across threads. In such instances there's
 * a lock (mutex) on it. The lock is held for the duration of matching.
 */
Py_LOCAL_INLINE(int) do_match(RE_State* state, BOOL search) {
    PatternObject* pattern;
    int status;
    TRACE(("<<do_match>>\n"))

    pattern = state->pattern;

    /* Is there enough to search? */
    if (state->reverse) {
        if (state->text_pos < state->slice_start)
            return FALSE;
    } else {
        if (state->text_pos > state->slice_end)
            return FALSE;
    }

    /* Release the GIL. */
    release_GIL(state);

    /* Perform a normal match, but fall back to a partial match if requested.
     */
    if (state->partial_side == RE_PARTIAL_NONE)
        /* Normal match. */
        status = do_match_2(state, search);
    else {
        int partial_side;
        Py_ssize_t text_pos;

        partial_side = state->partial_side;
        text_pos = state->text_pos;

        /* Try a normal match first. */
        state->partial_side = RE_PARTIAL_NONE;

        status = do_match_2(state, search);

        state->partial_side = partial_side;

        if (status == RE_ERROR_FAILURE) {
            /* Fall back to the partial match as originally requested. */
            state->text_pos = text_pos;
            status = do_match_2(state, search);
        }
    }

    if (status == RE_ERROR_SUCCESS || status == RE_ERROR_PARTIAL) {
        Py_ssize_t max_end_index;
        RE_GroupInfo* group_info;
        size_t g;

        /* Store the results. */
        state->lastindex = -1;
        state->lastgroup = -1;
        max_end_index = -1;

        if (status == RE_ERROR_PARTIAL) {
            /* We've matched up to the limit of the slice. */
            if (state->reverse)
                state->text_pos = state->slice_start;
            else
                state->text_pos = state->slice_end;
        }

        /* Store the capture groups. */
        group_info = pattern->group_info;

        for (g = 0; g < pattern->public_group_count; g++) {
            RE_GroupData* group;

            group = &state->groups[g];

            if (group->current >= 0 && group_info[g].end_index > max_end_index)
              {
                max_end_index = group_info[g].end_index;
                state->lastindex = (Py_ssize_t)g + 1;
                if (group_info[g].has_name)
                    state->lastgroup = (Py_ssize_t)g + 1;
            }
        }
    }

    /* Re-acquire the GIL. */
    acquire_GIL(state);

    if (status < 0 && status != RE_ERROR_PARTIAL && !PyErr_Occurred())
        set_error(status, NULL);

    return status;
}

/* Gets a string from a Python object.
 *
 * If the function returns true and str_info->should_release is true then it's
 * the responsibility of the caller to release the buffer when it's no longer
 * needed.
 */
Py_LOCAL_INLINE(BOOL) get_string(PyObject* string, RE_StringInfo* str_info) {
    /* Given a Python object, return a data pointer, a length (in characters),
     * and a character size. Return FALSE if the object is not a string (or not
     * compatible).
     */
    /* Unicode objects do not support the buffer API. So, get the data directly
     * instead.
     */
    if (PyUnicode_Check(string)) {
        /* Unicode strings don't always support the buffer interface. */
#if PY_VERSION_HEX >= 0x03030000
        if (PyUnicode_READY(string) == -1)
            return FALSE;

        str_info->characters = (void*)PyUnicode_DATA(string);
        str_info->length = PyUnicode_GET_LENGTH(string);
        str_info->charsize = PyUnicode_KIND(string);
#else
        str_info->characters = (void*)PyUnicode_AS_DATA(string);
        str_info->length = PyUnicode_GET_SIZE(string);
        str_info->charsize = sizeof(Py_UNICODE);
#endif
        str_info->is_unicode = TRUE;
        str_info->should_release = FALSE;
        return TRUE;
    }

#if defined(PYPY_VERSION)
    if (PyBytes_Check(string)) {
        /* Bytestrings don't always support the buffer interface. */
        str_info->characters = (void*)PyBytes_AS_STRING(string);
        str_info->length = PyBytes_GET_SIZE(string);
        str_info->charsize = 1;
        str_info->is_unicode = FALSE;
        str_info->should_release = FALSE;
        return TRUE;
    }

#endif
    /* Get pointer to string buffer. */
    if (PyObject_GetBuffer(string, &str_info->view, PyBUF_SIMPLE) != 0) {
        PyErr_SetString(PyExc_TypeError, "expected string or buffer");
        return FALSE;
    }

    if (!str_info->view.buf) {
        PyBuffer_Release(&str_info->view);
        PyErr_SetString(PyExc_ValueError, "buffer is NULL");
        return FALSE;
    }

    str_info->should_release = TRUE;

    str_info->characters = str_info->view.buf;
    str_info->length = str_info->view.len;
    str_info->charsize = 1;
    str_info->is_unicode = FALSE;

    return TRUE;
}

/* Deallocates the groups storage. */
Py_LOCAL_INLINE(void) dealloc_groups(RE_GroupData* groups, size_t group_count)
  {
    size_t g;

    if (!groups)
        return;

    for (g = 0; g < group_count; g++)
        re_dealloc(groups[g].captures);

    re_dealloc(groups);
}

/* Initialises a state object. */
Py_LOCAL_INLINE(BOOL) state_init_2(RE_State* state, PatternObject* pattern,
  PyObject* string, RE_StringInfo* str_info, Py_ssize_t start, Py_ssize_t end,
  BOOL overlapped, int concurrent, BOOL partial, BOOL use_lock, BOOL
  visible_captures, BOOL match_all, Py_ssize_t timeout) {
    Py_ssize_t final_pos;
    int p;

    state->thread_state = NULL;

    ByteStack_init(state, &state->sstack);
    ByteStack_init(state, &state->bstack);
    ByteStack_init(state, &state->pstack);

    /* We might already have some cached storage we can use for bstack. */
    if (pattern->stack_storage) {
        state->bstack.storage = pattern->stack_storage;
        state->bstack.capacity = pattern->stack_capacity;
        pattern->stack_storage = NULL;
        pattern->stack_capacity = 0;
    }

    state->groups = NULL;
    state->best_match_groups = NULL;
    state->repeats = NULL;
    state->visible_captures = visible_captures;
    state->match_all = match_all;
    state->lock = NULL;
    state->fuzzy_guards = NULL;
    state->group_call_guard_list = NULL;
    state->req_pos = -1;
    state->is_fuzzy = pattern->is_fuzzy;

    /* The call guards used by recursive patterns. */
    if (pattern->call_ref_info_count > 0) {
        state->group_call_guard_list =
          (RE_GuardList*)re_alloc(pattern->call_ref_info_count *
          sizeof(RE_GuardList));
        if (!state->group_call_guard_list)
            goto error;
        memset(state->group_call_guard_list, 0, pattern->call_ref_info_count *
          sizeof(RE_GuardList));
    }

    /* The capture groups. */
    if (pattern->true_group_count) {
        size_t g;

        if (pattern->groups_storage) {
            state->groups = pattern->groups_storage;
            pattern->groups_storage = NULL;
        } else {
            state->groups = (RE_GroupData*)re_alloc(pattern->true_group_count *
              sizeof(RE_GroupData));
            if (!state->groups)
                goto error;
            memset(state->groups, 0, pattern->true_group_count *
              sizeof(RE_GroupData));

            for (g = 0; g < pattern->true_group_count; g++) {
                RE_GroupSpan* captures;

                captures = (RE_GroupSpan*)re_alloc(sizeof(RE_GroupSpan));
                if (!captures) {
                    size_t i;

                    for (i = 0; i < g; i++)
                        re_dealloc(state->groups[i].captures);

                    goto error;
                }

                state->groups[g].captures = captures;
                state->groups[g].capacity = 1;
            }
        }
    }

    /* Adjust boundaries. */
    if (start < 0)
        start += str_info->length;
    if (start < 0)
        start = 0;
    else if (start > str_info->length)
        start = str_info->length;

    if (end < 0)
        end += str_info->length;
    if (end < 0)
        end = 0;
    else if (end > str_info->length)
        end = str_info->length;

    state->overlapped = overlapped;
    state->min_width = pattern->min_width;

    /* Initialise the getters and setters for the character size. */
    state->charsize = str_info->charsize;
    state->is_unicode = str_info->is_unicode;

    /* Are we using a buffer object? If so, we need to copy the info. */
    state->should_release = str_info->should_release;
    if (state->should_release)
        state->view = str_info->view;

    switch (state->charsize) {
    case 1:
        state->char_at = bytes1_char_at;
        state->set_char_at = bytes1_set_char_at;
        state->point_to = bytes1_point_to;
        break;
    case 2:
        state->char_at = bytes2_char_at;
        state->set_char_at = bytes2_set_char_at;
        state->point_to = bytes2_point_to;
        break;
    case 4:
        state->char_at = bytes4_char_at;
        state->set_char_at = bytes4_set_char_at;
        state->point_to = bytes4_point_to;
        break;
    default:
        goto error;
    }

    state->encoding = pattern->encoding;
    state->locale_info = pattern->locale_info;

    /* The state object contains a reference to the string and also a pointer
     * to its contents.
     *
     * The documentation says that the end of the slice behaves like the end of
     * the string.
     */
    state->text = str_info->characters;
    state->text_length = end;

    state->reverse = (pattern->flags & RE_FLAG_REVERSE) != 0;
    if (partial)
        state->partial_side = state->reverse ? RE_PARTIAL_LEFT :
          RE_PARTIAL_RIGHT;
    else
        state->partial_side = RE_PARTIAL_NONE;

    state->slice_start = start;
    state->slice_end = state->text_length;
    state->text_pos = state->reverse ? state->slice_end : state->slice_start;

    /* Point to the final newline and line separator if it's at the end of the
     * string, otherwise just -1.
     */
    state->final_newline = -1;
    state->final_line_sep = -1;
    final_pos = state->text_length - 1;
    if (final_pos >= 0) {
        Py_UCS4 ch;

        ch = state->char_at(state->text, final_pos);
        if (ch == 0x0A) {
            /* The string ends with LF. */
            state->final_newline = final_pos;
            state->final_line_sep = final_pos;

            /* Does the string end with CR/LF? */
            --final_pos;
            if (final_pos >= 0 && state->char_at(state->text, final_pos) ==
              0x0D)
                state->final_line_sep = final_pos;
        } else {
            /* The string doesn't end with LF, but it could be another kind of
             * line separator.
             */
            if (state->encoding->is_line_sep(ch))
                state->final_line_sep = final_pos;
        }
    }

    /* If the 'new' behaviour is enabled then split correctly on zero-width
     * matches.
     */
    state->version_0 = (pattern->flags & RE_FLAG_VERSION1) == 0;
    state->must_advance = FALSE;

    state->pattern = pattern;
    state->string = string;

    if (pattern->repeat_count) {
        if (pattern->repeats_storage) {
            state->repeats = pattern->repeats_storage;
            pattern->repeats_storage = NULL;
        } else {
            state->repeats = (RE_RepeatData*)re_alloc(pattern->repeat_count *
              sizeof(RE_RepeatData));
            if (!state->repeats)
                goto error;
            memset(state->repeats, 0, pattern->repeat_count *
              sizeof(RE_RepeatData));
        }
    }

    if (pattern->fuzzy_count) {
        state->fuzzy_guards = (RE_FuzzyGuards*)re_alloc(pattern->fuzzy_count *
          sizeof(RE_FuzzyGuards));
        if (!state->fuzzy_guards)
            goto error;
        memset(state->fuzzy_guards, 0, pattern->fuzzy_count *
          sizeof(RE_FuzzyGuards));
    }

    state->fuzzy_changes.capacity = 0;
    state->fuzzy_changes.count = 0;
    state->fuzzy_changes.items = NULL;

    Py_INCREF(state->pattern);
    Py_INCREF(state->string);

    /* Multithreading is allowed during matching when explicitly enabled or on
     * immutable strings.
     */
    switch (concurrent) {
    case RE_CONC_NO:
        state->is_multithreaded = FALSE;
        break;
    case RE_CONC_YES:
        state->is_multithreaded = TRUE;
        break;
    default:
        state->is_multithreaded = PyUnicode_Check(string) ||
          PyBytes_Check(string);
        break;
    }

    state->timeout = timeout;
    state->start_time = clock();

    /* A state struct can sometimes be shared across threads. In such
     * instances, if multithreading is enabled we need to protect the state
     * with a lock (mutex) during matching.
     */
    if (state->is_multithreaded && use_lock)
        state->lock = PyThread_allocate_lock();

    for (p = 0; p < MAX_SEARCH_POSITIONS; p++)
        state->search_positions[p].start_pos = -1;

    return TRUE;

error:
    re_dealloc(state->group_call_guard_list);
    re_dealloc(state->repeats);
    dealloc_groups(state->groups, pattern->true_group_count);
    re_dealloc(state->fuzzy_guards);
    state->repeats = NULL;
    state->groups = NULL;
    state->fuzzy_guards = NULL;
    return FALSE;
}

/* Checks that the string has the same charsize as the pattern. */
Py_LOCAL_INLINE(BOOL) check_compatible(PatternObject* pattern, BOOL unicode) {
    if (PyBytes_Check(pattern->pattern)) {
        if (unicode) {
            PyErr_SetString(PyExc_TypeError,
              "cannot use a bytes pattern on a string-like object");
            return FALSE;
        }
    } else {
        if (!unicode) {
            PyErr_SetString(PyExc_TypeError,
              "cannot use a string pattern on a bytes-like object");
            return FALSE;
        }
    }

    return TRUE;
}

/* Releases the string's buffer, if necessary. */
Py_LOCAL_INLINE(void) release_buffer(RE_StringInfo* str_info) {
    if (str_info->should_release)
        PyBuffer_Release(&str_info->view);
}

/* Initialises a state object. */
Py_LOCAL_INLINE(BOOL) state_init(RE_State* state, PatternObject* pattern,
  PyObject* string, Py_ssize_t start, Py_ssize_t end, BOOL overlapped, int
  concurrent, BOOL partial, BOOL use_lock, BOOL visible_captures, BOOL
  match_all, Py_ssize_t timeout) {
    RE_StringInfo str_info;

    /* Get the string to search or match. */
    if (!get_string(string, &str_info))
        return FALSE;

    /* If we fail to initialise the state then we need to release the buffer if
     * the string is a buffer object.
     */
    if (!check_compatible(pattern, str_info.is_unicode)) {
        release_buffer(&str_info);
        return FALSE;
    }

    if (!state_init_2(state, pattern, string, &str_info, start, end,
      overlapped, concurrent, partial, use_lock, visible_captures, match_all,
      timeout)) {
        release_buffer(&str_info);
        return FALSE;
    }

    /* The state has been initialised successfully, so now the state has the
     * responsibility of releasing the buffer if the string is a buffer object.
     */
    return TRUE;
}

/* Deallocates repeat data. */
Py_LOCAL_INLINE(void) dealloc_repeats(RE_RepeatData* repeats, size_t
  repeat_count) {
    size_t i;

    if (!repeats)
        return;

    for (i = 0; i < repeat_count; i++) {
        re_dealloc(repeats[i].body_guard_list.spans);
        re_dealloc(repeats[i].tail_guard_list.spans);
    }

    re_dealloc(repeats);
}

/* Deallocates fuzzy guards. */
Py_LOCAL_INLINE(void) dealloc_fuzzy_guards(RE_FuzzyGuards* guards, size_t
  fuzzy_count) {
    size_t i;

    if (!guards)
        return;

    for (i = 0; i < fuzzy_count; i++) {
        re_dealloc(guards[i].body_guard_list.spans);
        re_dealloc(guards[i].tail_guard_list.spans);
    }

    re_dealloc(guards);
}

/* Finalises a state object, discarding its contents. */
Py_LOCAL_INLINE(void) state_fini(RE_State* state) {
    PatternObject* pattern;
    size_t i;

    /* Discard the lock (mutex) if there's one. */
    if (state->lock)
        PyThread_free_lock(state->lock);

    pattern = state->pattern;

    /* If possible cache the storage of bstack. */
    if (!pattern->stack_storage) {
        pattern->stack_storage = state->bstack.storage;
        pattern->stack_capacity = state->bstack.capacity;
        state->bstack.storage = NULL;
        state->bstack.capacity = 0;
        state->bstack.count = 0;

        /* Limit the size of the cached storage to <= 64KB. */
        if (pattern->stack_capacity > 0x10000) {
            BYTE* new_storage;

            new_storage = re_realloc(pattern->stack_storage, 0x10000);
            if (new_storage) {
                pattern->stack_storage = new_storage;
                pattern->stack_capacity = 0x10000;
            }
        }
    }

    /* Clear the stacks. */
    ByteStack_fini(state, &state->sstack);
    ByteStack_fini(state, &state->bstack);
    ByteStack_fini(state, &state->pstack);

    if (state->best_match_groups)
        dealloc_groups(state->best_match_groups, pattern->true_group_count);

    if (pattern->groups_storage)
        dealloc_groups(state->groups, pattern->true_group_count);
    else
        pattern->groups_storage = state->groups;

    if (pattern->repeats_storage)
        dealloc_repeats(state->repeats, pattern->repeat_count);
    else
        pattern->repeats_storage = state->repeats;

    for (i = 0; i < pattern->call_ref_info_count; i++)
        re_dealloc(state->group_call_guard_list[i].spans);

    if (state->group_call_guard_list)
        re_dealloc(state->group_call_guard_list);

    if (state->fuzzy_guards)
        dealloc_fuzzy_guards(state->fuzzy_guards, pattern->fuzzy_count);

    re_dealloc(state->fuzzy_changes.items);

    Py_DECREF(state->pattern);
    Py_DECREF(state->string);

    if (state->should_release)
        PyBuffer_Release(&state->view);
}

/* Converts a string index to an integer.
 *
 * If the index is None then the default will be returned.
 */
Py_LOCAL_INLINE(Py_ssize_t) as_string_index(PyObject* obj, Py_ssize_t def) {
    Py_ssize_t value;

    if (obj == Py_None)
        return def;

    value = PyLong_AsLong(obj);
    if (!(value == -1 && PyErr_Occurred()))
        return value;

    set_error(RE_ERROR_INDEX, NULL);
    return 0;
}

/* Deallocates a MatchObject. */
static void match_dealloc(PyObject* self_) {
    MatchObject* self;

    self = (MatchObject*)self_;

    Py_XDECREF(self->string);
    Py_XDECREF(self->substring);
    Py_DECREF(self->pattern);
    if (self->groups)
        re_dealloc(self->groups);
    if (self->fuzzy_changes)
        re_dealloc(self->fuzzy_changes);
    Py_XDECREF(self->regs);
    PyObject_DEL(self);
}

#if PY_VERSION_HEX >= 0x03040000
/* Ensures that the string is the immutable Unicode string or bytestring.
 * DECREFs the original string if a copy is returned.
 */
Py_LOCAL_INLINE(PyObject*) ensure_immutable(PyObject* string) {
    PyObject* new_string;

    if (PyUnicode_CheckExact(string) || PyBytes_CheckExact(string))
        return string;

    if (PyUnicode_Check(string))
        new_string = PyUnicode_FromObject(string);
    else
        new_string = PyBytes_FromObject(string);

    Py_DECREF(string);

    return new_string;
}

#endif
/* Restricts a value to a range. */
Py_LOCAL_INLINE(Py_ssize_t) limited_range(Py_ssize_t value, Py_ssize_t lower,
  Py_ssize_t upper) {
    if (value < lower)
        return lower;

    if (value > upper)
        return upper;

    return value;
}

/* Gets a slice from a Unicode string. */
Py_LOCAL_INLINE(PyObject*) unicode_slice(PyObject* string, Py_ssize_t start,
  Py_ssize_t end) {
    Py_ssize_t length;
#if PY_VERSION_HEX < 0x03030000
    Py_UNICODE* buffer;
#endif

    length = PyUnicode_GET_SIZE(string);
    start = limited_range(start, 0, length);
    end = limited_range(end, 0, length);

#if PY_VERSION_HEX >= 0x03030000
    return PyUnicode_Substring(string, start, end);
#else
    buffer = PyUnicode_AsUnicode(string);

    return PyUnicode_FromUnicode(buffer + start, end - start);
#endif
}

/* Gets a slice from a bytestring. */
Py_LOCAL_INLINE(PyObject*) bytes_slice(PyObject* string, Py_ssize_t start,
  Py_ssize_t end) {
    Py_ssize_t length;
    char* buffer;

    length = PyBytes_GET_SIZE(string);
    start = limited_range(start, 0, length);
    end = limited_range(end, 0, length);

    buffer = PyBytes_AsString(string);

    return PyBytes_FromStringAndSize(buffer + start, end - start);
}

/* Gets a slice from a string, returning either a Unicode string or a
 * bytestring.
 */
Py_LOCAL_INLINE(PyObject*) get_slice(PyObject* string, Py_ssize_t start,
  Py_ssize_t end) {
    if (PyUnicode_Check(string))
        return unicode_slice(string, start, end);

    if (PyBytes_Check(string))
        return bytes_slice(string, start, end);

#if PY_VERSION_HEX >= 0x03040000
    return ensure_immutable(PySequence_GetSlice(string, start, end));
#else
    return PySequence_GetSlice(string, start, end);
#endif
}

/* Gets a MatchObject's group by integer index. */
static PyObject* match_get_group_by_index(MatchObject* self, Py_ssize_t index,
  PyObject* def) {
    RE_GroupData* group;
    RE_GroupSpan* span;

    if (index < 0 || (size_t)index > self->group_count) {
        /* Raise error if we were given a bad group number. */
        set_error(RE_ERROR_NO_SUCH_GROUP, NULL);
        return NULL;
    }

    if (index == 0)
        return get_slice(self->substring, self->match_start -
          self->substring_offset, self->match_end - self->substring_offset);

    /* Capture group indexes are 1-based (excluding group 0, which is the
     * entire matched string).
     */
    group = &self->groups[index - 1];

    if (group->current < 0) {
        /* Return default value if the string or group is undefined. */
        Py_INCREF(def);
        return def;
    }

    span = &group->captures[group->current];

    return get_slice(self->substring, span->start - self->substring_offset,
      span->end - self->substring_offset);
}

/* Gets a MatchObject's start by integer index. */
static PyObject* match_get_start_by_index(MatchObject* self, Py_ssize_t index)
  {
    RE_GroupData* group;
    RE_GroupSpan* span;

    if (index < 0 || (size_t)index > self->group_count) {
        /* Raise error if we were given a bad group number. */
        set_error(RE_ERROR_NO_SUCH_GROUP, NULL);
        return NULL;
    }

    if (index == 0)
        return Py_BuildValue("n", self->match_start);

    /* Capture group indexes are 1-based (excluding group 0, which is the
     * entire matched string).
     */
    group = &self->groups[index - 1];

    if (group->current < 0)
        return Py_BuildValue("n", (Py_ssize_t)-1);

    span = &group->captures[group->current];

    return Py_BuildValue("n", span->start);
}

/* Gets a MatchObject's starts by integer index. */
static PyObject* match_get_starts_by_index(MatchObject* self, Py_ssize_t index)
  {
    RE_GroupData* group;
    PyObject* result;
    PyObject* item;
    size_t i;

    if (index < 0 || (size_t)index > self->group_count) {
        /* Raise error if we were given a bad group number. */
        set_error(RE_ERROR_NO_SUCH_GROUP, NULL);
        return NULL;
    }

    if (index == 0) {
        result = PyList_New(1);
        if (!result)
            return NULL;

        item = Py_BuildValue("n", self->match_start);
        if (!item)
            goto error;

        /* PyList_SET_ITEM borrows the reference. */
        PyList_SET_ITEM(result, 0, item);

        return result;
    }

    /* Capture group indexes are 1-based (excluding group 0, which is the
     * entire matched string).
     */
    group = &self->groups[index - 1];

    result = PyList_New((Py_ssize_t)group->count);
    if (!result)
        return NULL;

    for (i = 0; i < group->count; i++) {
        item = Py_BuildValue("n", group->captures[i].start);
        if (!item)
            goto error;

        /* PyList_SET_ITEM borrows the reference. */
        PyList_SET_ITEM(result, i, item);
    }

    return result;

error:
    Py_DECREF(result);
    return NULL;
}

/* Gets a MatchObject's end by integer index. */
static PyObject* match_get_end_by_index(MatchObject* self, Py_ssize_t index) {
    RE_GroupData* group;
    RE_GroupSpan* span;

    if (index < 0 || (size_t)index > self->group_count) {
        /* Raise error if we were given a bad group number. */
        set_error(RE_ERROR_NO_SUCH_GROUP, NULL);
        return NULL;
    }

    if (index == 0)
        return Py_BuildValue("n", self->match_end);

    /* Capture group indexes are 1-based (excluding group 0, which is the
     * entire matched string).
     */
    group = &self->groups[index - 1];

    if (group->current < 0)
        return Py_BuildValue("n", (Py_ssize_t)-1);

    span = &group->captures[group->current];

    return Py_BuildValue("n", span->end);
}

/* Gets a MatchObject's ends by integer index. */
static PyObject* match_get_ends_by_index(MatchObject* self, Py_ssize_t index) {
    RE_GroupData* group;
    PyObject* result;
    PyObject* item;
    size_t i;

    if (index < 0 || (size_t)index > self->group_count) {
        /* Raise error if we were given a bad group number. */
        set_error(RE_ERROR_NO_SUCH_GROUP, NULL);
        return NULL;
    }

    if (index == 0) {
        result = PyList_New(1);
        if (!result)
            return NULL;

        item = Py_BuildValue("n", self->match_end);
        if (!item)
            goto error;

        /* PyList_SET_ITEM borrows the reference. */
        PyList_SET_ITEM(result, 0, item);

        return result;
    }

    /* Capture group indexes are 1-based (excluding group 0, which is the
     * entire matched string).
     */
    group = &self->groups[index - 1];

    result = PyList_New((Py_ssize_t)group->count);
    if (!result)
        return NULL;

    for (i = 0; i < group->count; i++) {
        item = Py_BuildValue("n", group->captures[i].end);
        if (!item)
            goto error;

        /* PyList_SET_ITEM borrows the reference. */
        PyList_SET_ITEM(result, i, item);
    }

    return result;

error:
    Py_DECREF(result);
    return NULL;
}

/* Gets a MatchObject's span by integer index. */
static PyObject* match_get_span_by_index(MatchObject* self, Py_ssize_t index) {
    RE_GroupData* group;
    RE_GroupSpan* span;

    if (index < 0 || (size_t)index > self->group_count) {
        /* Raise error if we were given a bad group number. */
        set_error(RE_ERROR_NO_SUCH_GROUP, NULL);
        return NULL;
    }

    if (index == 0)
        return Py_BuildValue("nn", self->match_start, self->match_end);

    /* Capture group indexes are 1-based (excluding group 0, which is the
     * entire matched string).
     */
    group = &self->groups[index - 1];

    if (group->current < 0)
        return Py_BuildValue("nn", (Py_ssize_t)-1, (Py_ssize_t)-1);

    span = &group->captures[group->current];

    return Py_BuildValue("nn", span->start, span->end);
}

/* Gets a MatchObject's spans by integer index. */
static PyObject* match_get_spans_by_index(MatchObject* self, Py_ssize_t index)
  {
    PyObject* result;
    PyObject* item;
    RE_GroupData* group;
    size_t i;

    if (index < 0 || (size_t)index > self->group_count) {
        /* Raise error if we were given a bad group number. */
        set_error(RE_ERROR_NO_SUCH_GROUP, NULL);
        return NULL;
    }

    if (index == 0) {
        result = PyList_New(1);
        if (!result)
            return NULL;

        item = Py_BuildValue("nn", self->match_start, self->match_end);
        if (!item)
            goto error;

        /* PyList_SET_ITEM borrows the reference. */
        PyList_SET_ITEM(result, 0, item);

        return result;
    }

    /* Capture group indexes are 1-based (excluding group 0, which is the
     * entire matched string).
     */
    group = &self->groups[index - 1];

    result = PyList_New((Py_ssize_t)group->count);
    if (!result)
        return NULL;

    for (i = 0; i < group->count; i++) {
        item = Py_BuildValue("nn", group->captures[i].start,
          group->captures[i].end);
        if (!item)
            goto error;

        /* PyList_SET_ITEM borrows the reference. */
        PyList_SET_ITEM(result, i, item);
    }

    return result;

error:
    Py_DECREF(result);
    return NULL;
}

/* Gets a MatchObject's captures by integer index. */
static PyObject* match_get_captures_by_index(MatchObject* self, Py_ssize_t
  index) {
    PyObject* result;
    PyObject* slice;
    RE_GroupData* group;
    size_t i;

    if (index < 0 || (size_t)index > self->group_count) {
        /* Raise error if we were given a bad group number. */
        set_error(RE_ERROR_NO_SUCH_GROUP, NULL);
        return NULL;
    }

    if (index == 0) {
        result = PyList_New(1);
        if (!result)
            return NULL;

        slice = get_slice(self->substring, self->match_start -
          self->substring_offset, self->match_end - self->substring_offset);
        if (!slice)
            goto error;

        /* PyList_SET_ITEM borrows the reference. */
        PyList_SET_ITEM(result, 0, slice);

        return result;
    }

    /* Capture group indexes are 1-based (excluding group 0, which is the
     * entire matched string).
     */
    group = &self->groups[index - 1];

    result = PyList_New((Py_ssize_t)group->count);
    if (!result)
        return NULL;

    for (i = 0; i < group->count; i++) {
        slice = get_slice(self->substring, group->captures[i].start -
          self->substring_offset, group->captures[i].end -
          self->substring_offset);
        if (!slice)
            goto error;

        /* PyList_SET_ITEM borrows the reference. */
        PyList_SET_ITEM(result, i, slice);
    }

    return result;

error:
    Py_DECREF(result);
    return NULL;
}

/* Converts a group index to an integer. */
Py_LOCAL_INLINE(Py_ssize_t) as_group_index(PyObject* obj) {
    Py_ssize_t value;

    value = PyLong_AsLong(obj);
    if (!(value == -1 && PyErr_Occurred()))
        return value;

    set_error(RE_ERROR_INDEX, NULL);
    return -1;
}

/* Gets a MatchObject's group index.
 *
 * The supplied index can be an integer or a string (group name) object.
 */
Py_LOCAL_INLINE(Py_ssize_t) match_get_group_index(MatchObject* self, PyObject*
  index, BOOL allow_neg) {
    Py_ssize_t group;

    /* Is the index an integer? */
    group = as_group_index(index);
    if (!(group == -1 && PyErr_Occurred())) {
        Py_ssize_t min_group = 0;

        /* Adjust negative indices where valid and allowed. */
        if (group < 0 && allow_neg) {
            group += (Py_ssize_t)self->group_count + 1;
            min_group = 1;
        }

        if (min_group <= group && (size_t)group <= self->group_count)
            return group;

        return -1;
    }

    PyErr_Clear();

    /* The index might be a group name. */
    if (self->pattern->groupindex) {
        /* Look up the name. */
        index = PyObject_GetItem(self->pattern->groupindex, index);
        if (index) {
            /* Check that we have an integer. */
            group = as_group_index(index);
            Py_DECREF(index);
            if (!(group == -1 && PyErr_Occurred()))
                return group;
        }
    }

    PyErr_Clear();
    return -1;
}

/* Gets a MatchObject's group by object index. */
Py_LOCAL_INLINE(PyObject*) match_get_group(MatchObject* self, PyObject* index,
  PyObject* def, BOOL allow_neg) {
    /* Check that the index is an integer or a string. */
    if (PyLong_Check(index) || PyUnicode_Check(index) || PyBytes_Check(index))
        return match_get_group_by_index(self, match_get_group_index(self,
          index, allow_neg), def);

    set_error(RE_ERROR_GROUP_INDEX_TYPE, index);
    return NULL;
}

/* Gets info from a MatchObject by object index. */
Py_LOCAL_INLINE(PyObject*) get_by_arg(MatchObject* self, PyObject* index,
  RE_GetByIndexFunc get_by_index) {
    /* Check that the index is an integer or a string. */
    if (PyLong_Check(index) || PyUnicode_Check(index) || PyBytes_Check(index))
        return get_by_index(self, match_get_group_index(self, index, FALSE));

    set_error(RE_ERROR_GROUP_INDEX_TYPE, index);
    return NULL;
}

/* MatchObject's 'group' method. */
static PyObject* match_group(MatchObject* self, PyObject* args) {
    Py_ssize_t size;
    PyObject* result;
    Py_ssize_t i;

    size = PyTuple_GET_SIZE(args);

    switch (size) {
    case 0:
        /* group() */
        result = match_get_group_by_index(self, 0, Py_None);
        break;
    case 1:
        /* group(x). PyTuple_GET_ITEM borrows the reference. */
        result = match_get_group(self, PyTuple_GET_ITEM(args, 0), Py_None,
          FALSE);
        break;
    default:
        /* group(x, y, z, ...) */
        /* Fetch multiple items. */
        result = PyTuple_New(size);
        if (!result)
            return NULL;

        for (i = 0; i < size; i++) {
            PyObject* item;

            /* PyTuple_GET_ITEM borrows the reference. */
            item = match_get_group(self, PyTuple_GET_ITEM(args, i), Py_None,
              FALSE);
            if (!item) {
                Py_DECREF(result);
                return NULL;
            }

            /* PyTuple_SET_ITEM borrows the reference. */
            PyTuple_SET_ITEM(result, i, item);
        }
        break;
    }

    return result;
}

/* Generic method for getting info from a MatchObject. */
Py_LOCAL_INLINE(PyObject*) get_from_match(MatchObject* self, PyObject* args,
  RE_GetByIndexFunc get_by_index) {
    Py_ssize_t size;
    PyObject* result;
    Py_ssize_t i;

    size = PyTuple_GET_SIZE(args);

    switch (size) {
    case 0:
        /* get() */
        result = get_by_index(self, 0);
        break;
    case 1:
        /* get(x). PyTuple_GET_ITEM borrows the reference. */
        result = get_by_arg(self, PyTuple_GET_ITEM(args, 0), get_by_index);
        break;
    default:
        /* get(x, y, z, ...) */
        /* Fetch multiple items. */
        result = PyTuple_New(size);
        if (!result)
            return NULL;

        for (i = 0; i < size; i++) {
            PyObject* item;

            /* PyTuple_GET_ITEM borrows the reference. */
            item = get_by_arg(self, PyTuple_GET_ITEM(args, i), get_by_index);
            if (!item) {
                Py_DECREF(result);
                return NULL;
            }

            /* PyTuple_SET_ITEM borrows the reference. */
            PyTuple_SET_ITEM(result, i, item);
        }
        break;
    }

    return result;
}

/* MatchObject's 'start' method. */
static PyObject* match_start(MatchObject* self, PyObject* args) {
    return get_from_match(self, args, match_get_start_by_index);
}

/* MatchObject's 'starts' method. */
static PyObject* match_starts(MatchObject* self, PyObject* args) {
    return get_from_match(self, args, match_get_starts_by_index);
}

/* MatchObject's 'end' method. */
static PyObject* match_end(MatchObject* self, PyObject* args) {
    return get_from_match(self, args, match_get_end_by_index);
}

/* MatchObject's 'ends' method. */
static PyObject* match_ends(MatchObject* self, PyObject* args) {
    return get_from_match(self, args, match_get_ends_by_index);
}

/* MatchObject's 'span' method. */
static PyObject* match_span(MatchObject* self, PyObject* args) {
    return get_from_match(self, args, match_get_span_by_index);
}

/* MatchObject's 'spans' method. */
static PyObject* match_spans(MatchObject* self, PyObject* args) {
    return get_from_match(self, args, match_get_spans_by_index);
}

/* MatchObject's 'captures' method. */
static PyObject* match_captures(MatchObject* self, PyObject* args) {
    return get_from_match(self, args, match_get_captures_by_index);
}

/* MatchObject's 'groups' method. */
static PyObject* match_groups(MatchObject* self, PyObject* args, PyObject*
  kwargs) {
    PyObject* result;
    size_t g;

    PyObject* def = Py_None;
    static char* kwlist[] = { "default", NULL };
    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|O:groups", kwlist, &def))
        return NULL;

    result = PyTuple_New((Py_ssize_t)self->group_count);
    if (!result)
        return NULL;

    /* Group 0 is the entire matched portion of the string. */
    for (g = 0; g < self->group_count; g++) {
        PyObject* item;

        item = match_get_group_by_index(self, (Py_ssize_t)g + 1, def);
        if (!item)
            goto error;

        /* PyTuple_SET_ITEM borrows the reference. */
        PyTuple_SET_ITEM(result, g, item);
    }

    return result;

error:
    Py_DECREF(result);
    return NULL;
}

/* MatchObject's 'groupdict' method. */
static PyObject* match_groupdict(MatchObject* self, PyObject* args, PyObject*
  kwargs) {
    PyObject* result;
    PyObject* keys;
    Py_ssize_t g;

    PyObject* def = Py_None;
    static char* kwlist[] = { "default", NULL };
    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|O:groupdict", kwlist,
      &def))
        return NULL;

    result = PyDict_New();
    if (!result || !self->pattern->groupindex)
        return result;

    keys = PyMapping_Keys(self->pattern->groupindex);
    if (!keys)
        goto failed;

    for (g = 0; g < PyList_GET_SIZE(keys); g++) {
        PyObject* key;
        PyObject* value;
        int status;

        /* PyList_GET_ITEM borrows a reference. */
        key = PyList_GET_ITEM(keys, g);
        if (!key)
            goto failed;

        value = match_get_group(self, key, def, FALSE);
        if (!value)
            goto failed;

        status = PyDict_SetItem(result, key, value);
        Py_DECREF(value);
        if (status < 0)
            goto failed;
    }

    Py_DECREF(keys);

    return result;

failed:
    Py_XDECREF(keys);
    Py_DECREF(result);
    return NULL;
}

/* MatchObject's 'capturesdict' method. */
static PyObject* match_capturesdict(MatchObject* self) {
    PyObject* result;
    PyObject* keys;
    Py_ssize_t g;

    result = PyDict_New();
    if (!result || !self->pattern->groupindex)
        return result;

    keys = PyMapping_Keys(self->pattern->groupindex);
    if (!keys)
        goto failed;

    for (g = 0; g < PyList_GET_SIZE(keys); g++) {
        PyObject* key;
        Py_ssize_t group;
        PyObject* captures;
        int status;

        /* PyList_GET_ITEM borrows a reference. */
        key = PyList_GET_ITEM(keys, g);
        if (!key)
            goto failed;

        group = match_get_group_index(self, key, FALSE);
        if (group < 0)
            goto failed;

        captures = match_get_captures_by_index(self, group);
        if (!captures)
            goto failed;

        status = PyDict_SetItem(result, key, captures);
        Py_DECREF(captures);
        if (status < 0)
            goto failed;
    }

    Py_DECREF(keys);

    return result;

failed:
    Py_XDECREF(keys);
    Py_DECREF(result);
    return NULL;
}

/* Gets a Python object by name from a named module. */
Py_LOCAL_INLINE(PyObject*) get_object(char* module_name, char* object_name) {
    PyObject* module;
    PyObject* object;

    module = PyImport_ImportModule(module_name);
    if (!module)
        return NULL;

    object = PyObject_GetAttrString(module, object_name);
    Py_DECREF(module);

    return object;
}

/* Calls a function in a module. */
Py_LOCAL_INLINE(PyObject*) call(char* module_name, char* function_name,
  PyObject* args) {
    PyObject* function;
    PyObject* result;

    if (!args)
        return NULL;

    function = get_object(module_name, function_name);
    if (!function)
        return NULL;

    result = PyObject_CallObject(function, args);
    Py_DECREF(function);
    Py_DECREF(args);

    return result;
}

/* Gets a replacement item from the replacement list.
 *
 * The replacement item could be a string literal or a group.
 */
Py_LOCAL_INLINE(PyObject*) get_match_replacement(MatchObject* self, PyObject*
  item, size_t group_count) {
    Py_ssize_t index;

    if (PyUnicode_Check(item) || PyBytes_Check(item)) {
        /* It's a literal, which can be added directly to the list. */
#if PY_VERSION_HEX >= 0x03040000

        /* ensure_immutable will DECREF the original item if it has to make an
         * immutable copy, but that original item might have a borrowed
         * reference, so we must INCREF it first in order to ensure it won't be
         * destroyed.
         */
        Py_INCREF(item);
        item = ensure_immutable(item);
#else
        Py_INCREF(item);
#endif
        return item;
    }

    /* Is it a group reference? */
    index = as_group_index(item);
    if (index == -1 && PyErr_Occurred()) {
        /* Not a group either! */
        set_error(RE_ERROR_REPLACEMENT, NULL);
        return NULL;
    }

    if (index == 0) {
        /* The entire matched portion of the string. */
        return get_slice(self->substring, self->match_start -
          self->substring_offset, self->match_end - self->substring_offset);
    } else if (index >= 1 && (size_t)index <= group_count) {
        /* A group. If it didn't match then return None instead. */
        RE_GroupData* group;

        group = &self->groups[index - 1];

        if (group->current >= 0) {
            RE_GroupSpan* span;

            span = &group->captures[group->current];

            return get_slice(self->substring, span->start -
              self->substring_offset, span->end - self->substring_offset);
        } else
            Py_RETURN_NONE;
    } else {
        /* No such group. */
        set_error(RE_ERROR_NO_SUCH_GROUP, NULL);
        return NULL;
    }
}

/* Initialises the join list. */
Py_LOCAL_INLINE(void) init_join_list(RE_JoinInfo* join_info, BOOL reversed,
  BOOL is_unicode) {
    join_info->list = NULL;
    join_info->item = NULL;
    join_info->reversed = reversed;
    join_info->is_unicode = is_unicode;
}

/* Adds an item to the join list. */
Py_LOCAL_INLINE(int) add_to_join_list(RE_JoinInfo* join_info, PyObject* item) {
    PyObject* new_item;
    int status;

    if (join_info->is_unicode) {
#if PY_VERSION_HEX >= 0x03040000
        if (PyUnicode_CheckExact(item)) {
#else
        if (PyUnicode_Check(item)) {
#endif
            new_item = item;
            Py_INCREF(new_item);
        } else {
            new_item = PyUnicode_FromObject(item);
            if (!new_item) {
                set_error(RE_ERROR_NOT_UNICODE, item);
                return RE_ERROR_NOT_UNICODE;
            }
        }
    } else {
#if PY_VERSION_HEX >= 0x03040000
        if (PyBytes_CheckExact(item)) {
#else
        if (PyBytes_Check(item)) {
#endif
            new_item = item;
            Py_INCREF(new_item);
        } else {
            new_item = PyBytes_FromObject(item);
            if (!new_item) {
                set_error(RE_ERROR_NOT_BYTES, item);
                return RE_ERROR_NOT_BYTES;
            }
        }
    }

    /* If the list already exists then just add the item to it. */
    if (join_info->list) {
        status = PyList_Append(join_info->list, new_item);
        if (status < 0)
            goto error;

        Py_DECREF(new_item);
        return status;
    }

    /* If we already have an item then we now have 2(!) and we need to put them
     * into a list.
     */
    if (join_info->item) {
        join_info->list = PyList_New(2);
        if (!join_info->list) {
            status = RE_ERROR_MEMORY;
            goto error;
        }

        /* PyList_SET_ITEM borrows the reference. */
        PyList_SET_ITEM(join_info->list, 0, join_info->item);
        join_info->item = NULL;

        /* PyList_SET_ITEM borrows the reference. */
        PyList_SET_ITEM(join_info->list, 1, new_item);
        return 0;
    }

    /* This is the first item. */
    join_info->item = new_item;

    return 0;

error:
    Py_DECREF(new_item);
    set_error(status, NULL);
    return status;
}

/* Clears the join list. */
Py_LOCAL_INLINE(void) clear_join_list(RE_JoinInfo* join_info) {
    Py_XDECREF(join_info->list);
    Py_XDECREF(join_info->item);
}

/* Joins together a list of strings for pattern_subx. */
Py_LOCAL_INLINE(PyObject*) join_list_info(RE_JoinInfo* join_info) {
    /* If the list already exists then just do the join. */
    if (join_info->list) {
        PyObject* joiner;
        PyObject* result;

        if (join_info->reversed)
            /* The list needs to be reversed before being joined. */
            PyList_Reverse(join_info->list);

        if (join_info->is_unicode) {
            /* Concatenate the Unicode strings. */
            joiner = PyUnicode_FromUnicode(NULL, 0);
            if (!joiner) {
                clear_join_list(join_info);
                return NULL;
            }

            result = PyUnicode_Join(joiner, join_info->list);
        } else {
            joiner = PyBytes_FromString("");
            if (!joiner) {
                clear_join_list(join_info);
                return NULL;
            }

            /* Concatenate the bytestrings. */
            result = _PyBytes_Join(joiner, join_info->list);
        }

        Py_DECREF(joiner);
        clear_join_list(join_info);

        return result;
    }

    /* If we have only 1 item, so we'll just return it. */
    if (join_info->item)
        return join_info->item;

    /* There are no items, so return an empty string. */
    if (join_info->is_unicode)
        return PyUnicode_FromUnicode(NULL, 0);
    else
        return PyBytes_FromString("");
}

/* Checks whether a string replacement is a literal.
 *
 * To keep it simple we'll say that a literal is a string which can be used
 * as-is.
 *
 * Returns its length if it is a literal, otherwise -1.
 */
Py_LOCAL_INLINE(Py_ssize_t) check_replacement_string(PyObject* str_replacement,
  unsigned char special_char) {
    RE_StringInfo str_info;
    Py_UCS4 (*char_at)(void* text, Py_ssize_t pos);
    Py_ssize_t pos;

    if (!get_string(str_replacement, &str_info))
        return -1;

    switch (str_info.charsize) {
    case 1:
        char_at = bytes1_char_at;
        break;
    case 2:
        char_at = bytes2_char_at;
        break;
    case 4:
        char_at = bytes4_char_at;
        break;
    default:
        release_buffer(&str_info);
        return -1;
    }

    for (pos = 0; pos < str_info.length; pos++) {
        if (char_at(str_info.characters, pos) == special_char) {
            release_buffer(&str_info);
            return -1;
        }
    }

    release_buffer(&str_info);

    return str_info.length;
}

/* MatchObject's 'expand' method. */
static PyObject* match_expand(MatchObject* self, PyObject* str_template) {
    Py_ssize_t literal_length;
    PyObject* replacement;
    RE_JoinInfo join_info;
    Py_ssize_t size;
    Py_ssize_t i;

    /* Is the template just a literal? */
    literal_length = check_replacement_string(str_template, '\\');
    if (literal_length >= 0) {
        /* It's a literal. */
        Py_INCREF(str_template);
        return str_template;
    }

    /* Hand the template to the template compiler. */
    replacement = call("regex.regex", "_compile_replacement_helper",
      PyTuple_Pack(2, self->pattern, str_template));
    if (!replacement)
        return NULL;

    init_join_list(&join_info, FALSE, PyUnicode_Check(self->string));

    /* Add each part of the template to the list. */
    size = PyList_GET_SIZE(replacement);
    for (i = 0; i < size; i++) {
        PyObject* item;
        PyObject* str_item;

        /* PyList_GET_ITEM borrows a reference. */
        item = PyList_GET_ITEM(replacement, i);
        str_item = get_match_replacement(self, item, self->group_count);
        if (!str_item)
            goto error;

        /* Add to the list. */
        if (str_item == Py_None)
            Py_DECREF(str_item);
        else {
            int status;

            status = add_to_join_list(&join_info, str_item);
            Py_DECREF(str_item);
            if (status < 0)
                goto error;
        }
    }

    Py_DECREF(replacement);

    /* Convert the list to a single string (also cleans up join_info). */
    return join_list_info(&join_info);

error:
    clear_join_list(&join_info);
    Py_DECREF(replacement);
    return NULL;
}

static PyTypeObject Capture_Type = {
    PyVarObject_HEAD_INIT(NULL,0)
    "_regex.Capture",
    sizeof(MatchObject)
};

/* Creates a new CaptureObject. */
Py_LOCAL_INLINE(PyObject*) make_capture_object(MatchObject** match_indirect,
  Py_ssize_t index) {
    CaptureObject* capture;

    capture = PyObject_NEW(CaptureObject, &Capture_Type);
    if (!capture)
        return NULL;

    capture->group_index = index;
    capture->match_indirect = match_indirect;

    return (PyObject*)capture;
}

/* Makes a MatchObject's capture dictionary. */
Py_LOCAL_INLINE(PyObject*) make_capture_dict(MatchObject* match, MatchObject**
  match_indirect) {
    PyObject* result;
    PyObject* keys;
    PyObject* values = NULL;
    Py_ssize_t g;

    result = PyDict_New();
    if (!result)
        return result;

    keys = PyMapping_Keys(match->pattern->groupindex);
    if (!keys)
        goto failed;

    values = PyMapping_Values(match->pattern->groupindex);
    if (!values)
        goto failed;

    for (g = 0; g < PyList_GET_SIZE(keys); g++) {
        PyObject* key;
        PyObject* value;
        Py_ssize_t v;
        int status;

        /* PyList_GET_ITEM borrows a reference. */
        key = PyList_GET_ITEM(keys, g);
        if (!key)
            goto failed;

        /* PyList_GET_ITEM borrows a reference. */
        value = PyList_GET_ITEM(values, g);
        if (!value)
            goto failed;

        v = PyLong_AsLong(value);
        if (v == -1 && PyErr_Occurred())
            goto failed;

        value = make_capture_object(match_indirect, v);
        if (!value)
            goto failed;

        status = PyDict_SetItem(result, key, value);
        Py_DECREF(value);
        if (status < 0)
            goto failed;
    }

    Py_DECREF(values);
    Py_DECREF(keys);

    return result;

failed:
    Py_XDECREF(values);
    Py_XDECREF(keys);
    Py_DECREF(result);
    return NULL;
}

/* MatchObject's 'expandf' method. */
static PyObject* match_expandf(MatchObject* self, PyObject* str_template) {
    PyObject* format_func;
    PyObject* args = NULL;
    size_t g;
    PyObject* kwargs = NULL;
    PyObject* result;

    format_func = PyObject_GetAttrString(str_template, "format");
    if (!format_func)
        return NULL;

    args = PyTuple_New((Py_ssize_t)self->group_count + 1);
    if (!args)
        goto error;

    for (g = 0; g < self->group_count + 1; g++)
        /* PyTuple_SetItem borrows the reference. */
        PyTuple_SetItem(args, (Py_ssize_t)g, make_capture_object(&self,
          (Py_ssize_t)g));

    kwargs = make_capture_dict(self, &self);
    if (!kwargs)
        goto error;

    result = PyObject_Call(format_func, args, kwargs);

    Py_DECREF(kwargs);
    Py_DECREF(args);
    Py_DECREF(format_func);

    return result;

error:
    Py_XDECREF(args);
    Py_DECREF(format_func);
    return NULL;
}

Py_LOCAL_INLINE(PyObject*) make_match_copy(MatchObject* self);

/* MatchObject's '__copy__' method. */
static PyObject* match_copy(MatchObject* self, PyObject* unused) {
    return make_match_copy(self);
}

/* MatchObject's '__deepcopy__' method. */
static PyObject* match_deepcopy(MatchObject* self, PyObject* memo) {
    return make_match_copy(self);
}

/* MatchObject's 'regs' attribute. */
static PyObject* match_regs(MatchObject* self) {
    PyObject* regs;
    PyObject* item;
    size_t g;

    if (self->regs) {
        Py_INCREF(self->regs);

        return self->regs;
    }

    regs = PyTuple_New((Py_ssize_t)self->group_count + 1);
    if (!regs)
        return NULL;

    item = Py_BuildValue("nn", self->match_start, self->match_end);
    if (!item)
        goto error;

    /* PyTuple_SET_ITEM borrows the reference. */
    PyTuple_SET_ITEM(regs, 0, item);

    for (g = 0; g < self->group_count; g++) {
        RE_GroupData* group;

        group = &self->groups[g];

        if (group->current < 0)
            item = Py_BuildValue("nn", (Py_ssize_t)-1, (Py_ssize_t)-1);
        else {
            RE_GroupSpan* span;

            span = &group->captures[group->current];
            item = Py_BuildValue("nn", span->start, span->end);
        }
        if (!item)
            goto error;

        /* PyTuple_SET_ITEM borrows the reference. */
        PyTuple_SET_ITEM(regs, g + 1, item);
    }

    self->regs = regs;

    Py_INCREF(self->regs);

    return self->regs;

error:
    Py_DECREF(regs);
    return NULL;
}

/* MatchObject's slice method. */
Py_LOCAL_INLINE(PyObject*) match_get_group_slice(MatchObject* self, PyObject*
  slice) {
    Py_ssize_t start;
    Py_ssize_t end;
    Py_ssize_t step;
    Py_ssize_t slice_length;

#if PY_VERSION_HEX >= 0x03020000
    if (PySlice_GetIndicesEx(slice, (Py_ssize_t)self->group_count + 1, &start,
      &end, &step, &slice_length) < 0)
#else
    if (PySlice_GetIndicesEx((PySliceObject*)slice,
      (Py_ssize_t)self->group_count + 1, &start, &end, &step, &slice_length) <
      0)
#endif
        return NULL;

    if (slice_length <= 0)
        return PyTuple_New(0);
    else {
        PyObject* result;
        Py_ssize_t cur;
        Py_ssize_t i;

        result = PyTuple_New(slice_length);
        if (!result)
            return NULL;

        cur = start;
        for (i = 0; i < slice_length; i++) {
            /* PyTuple_SetItem borrows the reference. */
            PyTuple_SetItem(result, i, match_get_group_by_index(self, cur,
              Py_None));
            cur += step;
        }

        return result;
    }
}

/* MatchObject's length method. */
Py_LOCAL_INLINE(Py_ssize_t) match_length(MatchObject* self) {
    return (Py_ssize_t)self->group_count + 1;
}

/* MatchObject's '__getitem__' method. */
static PyObject* match_getitem(MatchObject* self, PyObject* item) {
    if (PySlice_Check(item))
        return match_get_group_slice(self, item);

    return match_get_group(self, item, Py_None, TRUE);
}

/* Determines the portion of the target string which is covered by the group
 * captures.
 */
Py_LOCAL_INLINE(void) determine_target_substring(MatchObject* match,
  Py_ssize_t* slice_start, Py_ssize_t* slice_end) {
    Py_ssize_t start;
    Py_ssize_t end;
    size_t g;

    start = match->pos;
    end = match->endpos;

    for (g = 0; g < match->group_count; g++) {
        RE_GroupData* group;
        size_t c;

        group = &match->groups[g];

        for (c = 0; c < match->groups[g].count; c++) {
            RE_GroupSpan* span;

            span = &group->captures[c];
            if (span->start < start)
                start = span->start;
            if (span->end > end)
                end = span->end;
        }
    }

    *slice_start = start;
    *slice_end = end;
}

/* MatchObject's 'detach_string' method. */
static PyObject* match_detach_string(MatchObject* self, PyObject* unused) {
    if (self->string) {
        Py_ssize_t start;
        Py_ssize_t end;
        PyObject* substring;

        determine_target_substring(self, &start, &end);

        substring = get_slice(self->string, start, end);
        if (substring) {
            Py_XDECREF(self->substring);
            self->substring = substring;
            self->substring_offset = start;

            Py_DECREF(self->string);
            self->string = NULL;
        }
    }

    Py_RETURN_NONE;
}

/* The documentation of a MatchObject. */
PyDoc_STRVAR(match_group_doc,
    "group([group1, ...]) --> string or tuple of strings.\n\
    Return one or more subgroups of the match.  If there is a single argument,\n\
    the result is a single string, or None if the group did not contribute to\n\
    the match; if there are multiple arguments, the result is a tuple with one\n\
    item per argument; if there are no arguments, the whole match is returned.\n\
    Group 0 is the whole match.");

PyDoc_STRVAR(match_start_doc,
    "start([group1, ...]) --> int or tuple of ints.\n\
    Return the index of the start of one or more subgroups of the match.  If\n\
    there is a single argument, the result is an index, or -1 if the group did\n\
    not contribute to the match; if there are multiple arguments, the result is\n\
    a tuple with one item per argument; if there are no arguments, the index of\n\
    the start of the whole match is returned.  Group 0 is the whole match.");

PyDoc_STRVAR(match_end_doc,
    "end([group1, ...]) --> int or tuple of ints.\n\
    Return the index of the end of one or more subgroups of the match.  If there\n\
    is a single argument, the result is an index, or -1 if the group did not\n\
    contribute to the match; if there are multiple arguments, the result is a\n\
    tuple with one item per argument; if there are no arguments, the index of\n\
    the end of the whole match is returned.  Group 0 is the whole match.");

PyDoc_STRVAR(match_span_doc,
    "span([group1, ...]) --> 2-tuple of int or tuple of 2-tuple of ints.\n\
    Return the span (a 2-tuple of the indices of the start and end) of one or\n\
    more subgroups of the match.  If there is a single argument, the result is a\n\
    span, or (-1, -1) if the group did not contribute to the match; if there are\n\
    multiple arguments, the result is a tuple with one item per argument; if\n\
    there are no arguments, the span of the whole match is returned.  Group 0 is\n\
    the whole match.");

PyDoc_STRVAR(match_groups_doc,
    "groups(default=None) --> tuple of strings.\n\
    Return a tuple containing all the subgroups of the match.  The argument is\n\
    the default for groups that did not participate in the match.");

PyDoc_STRVAR(match_groupdict_doc,
    "groupdict(default=None) --> dict.\n\
    Return a dictionary containing all the named subgroups of the match, keyed\n\
    by the subgroup name.  The argument is the value to be given for groups that\n\
    did not participate in the match.");

PyDoc_STRVAR(match_capturesdict_doc,
    "capturesdict() --> dict.\n\
    Return a dictionary containing the captures of all the named subgroups of the\n\
    match, keyed by the subgroup name.");

PyDoc_STRVAR(match_expand_doc,
    "expand(template) --> string.\n\
    Return the string obtained by doing backslash substitution on the template,\n\
    as done by the sub() method.");

PyDoc_STRVAR(match_expandf_doc,
    "expandf(format) --> string.\n\
    Return the string obtained by using the format, as done by the subf()\n\
    method.");

PyDoc_STRVAR(match_captures_doc,
    "captures([group1, ...]) --> list of strings or tuple of list of strings.\n\
    Return the captures of one or more subgroups of the match.  If there is a\n\
    single argument, the result is a list of strings; if there are multiple\n\
    arguments, the result is a tuple of lists with one item per argument; if\n\
    there are no arguments, the captures of the whole match is returned.  Group\n\
    0 is the whole match.");

PyDoc_STRVAR(match_starts_doc,
    "starts([group1, ...]) --> list of ints or tuple of list of ints.\n\
    Return the indices of the starts of the captures of one or more subgroups of\n\
    the match.  If there is a single argument, the result is a list of indices;\n\
    if there are multiple arguments, the result is a tuple of lists with one\n\
    item per argument; if there are no arguments, the indices of the starts of\n\
    the captures of the whole match is returned.  Group 0 is the whole match.");

PyDoc_STRVAR(match_ends_doc,
    "ends([group1, ...]) --> list of ints or tuple of list of ints.\n\
    Return the indices of the ends of the captures of one or more subgroups of\n\
    the match.  If there is a single argument, the result is a list of indices;\n\
    if there are multiple arguments, the result is a tuple of lists with one\n\
    item per argument; if there are no arguments, the indices of the ends of the\n\
    captures of the whole match is returned.  Group 0 is the whole match.");

PyDoc_STRVAR(match_spans_doc,
    "spans([group1, ...]) --> list of 2-tuple of ints or tuple of list of 2-tuple of ints.\n\
    Return the spans (a 2-tuple of the indices of the start and end) of the\n\
    captures of one or more subgroups of the match.  If there is a single\n\
    argument, the result is a list of spans; if there are multiple arguments,\n\
    the result is a tuple of lists with one item per argument; if there are no\n\
    arguments, the spans of the captures of the whole match is returned.  Group\n\
    0 is the whole match.");

PyDoc_STRVAR(match_detach_string_doc,
    "detach_string()\n\
    Detaches the target string from the match object. The 'string' attribute\n\
    will become None.");

/* MatchObject's methods. */
static PyMethodDef match_methods[] = {
    {"group", (PyCFunction)match_group, METH_VARARGS, match_group_doc},
    {"start", (PyCFunction)match_start, METH_VARARGS, match_start_doc},
    {"end", (PyCFunction)match_end, METH_VARARGS, match_end_doc},
    {"span", (PyCFunction)match_span, METH_VARARGS, match_span_doc},
    {"groups", (PyCFunction)match_groups, METH_VARARGS|METH_KEYWORDS,
      match_groups_doc},
    {"groupdict", (PyCFunction)match_groupdict, METH_VARARGS|METH_KEYWORDS,
      match_groupdict_doc},
    {"capturesdict", (PyCFunction)match_capturesdict, METH_NOARGS,
      match_capturesdict_doc},
    {"expand", (PyCFunction)match_expand, METH_O, match_expand_doc},
    {"expandf", (PyCFunction)match_expandf, METH_O, match_expandf_doc},
    {"captures", (PyCFunction)match_captures, METH_VARARGS,
      match_captures_doc},
    {"starts", (PyCFunction)match_starts, METH_VARARGS, match_starts_doc},
    {"ends", (PyCFunction)match_ends, METH_VARARGS, match_ends_doc},
    {"spans", (PyCFunction)match_spans, METH_VARARGS, match_spans_doc},
    {"detach_string", (PyCFunction)match_detach_string, METH_NOARGS,
      match_detach_string_doc},
    {"__copy__", (PyCFunction)match_copy, METH_NOARGS},
    {"__deepcopy__", (PyCFunction)match_deepcopy, METH_O},
    {"__getitem__", (PyCFunction)match_getitem, METH_O|METH_COEXIST},
    {NULL, NULL}
};

PyDoc_STRVAR(match_doc, "Match object");

/* MatchObject's 'lastindex' attribute. */
static PyObject* match_lastindex(PyObject* self_) {
    MatchObject* self;

    self = (MatchObject*)self_;

    if (self->lastindex >= 0)
        return Py_BuildValue("n", self->lastindex);

    Py_RETURN_NONE;
}

/* MatchObject's 'lastgroup' attribute. */
static PyObject* match_lastgroup(PyObject* self_) {
    MatchObject* self;

    self = (MatchObject*)self_;

    if (self->pattern->indexgroup && self->lastgroup >= 0) {
        PyObject* index;
        PyObject* result;

        index = Py_BuildValue("n", self->lastgroup);

        /* PyDict_GetItem returns borrows a reference. */
        result = PyDict_GetItem(self->pattern->indexgroup, index);
        Py_DECREF(index);
        if (result) {
            Py_INCREF(result);
            return result;
        }
        PyErr_Clear();
    }

    Py_RETURN_NONE;
}

/* MatchObject's 'string' attribute. */
static PyObject* match_string(PyObject* self_) {
    MatchObject* self;

    self = (MatchObject*)self_;

    if (self->string) {
        Py_INCREF(self->string);
        return self->string;
    } else
        Py_RETURN_NONE;
}

/* MatchObject's 'fuzzy_counts' attribute. */
static PyObject* match_fuzzy_counts(PyObject* self_) {
    MatchObject* self;

    self = (MatchObject*)self_;

    return Py_BuildValue("nnn", self->fuzzy_counts[RE_FUZZY_SUB],
      self->fuzzy_counts[RE_FUZZY_INS], self->fuzzy_counts[RE_FUZZY_DEL]);
}

/* MatchObject's 'fuzzy_changes' attribute. */
static PyObject* match_fuzzy_changes(PyObject* self_) {
    MatchObject* self;
    PyObject* sub_changes;
    PyObject* ins_changes;
    PyObject* del_changes;
    size_t count;
    Py_ssize_t offset;
    size_t i;
    PyObject* result;

    self = (MatchObject*)self_;

    sub_changes = PyList_New(0);
    ins_changes = PyList_New(0);
    del_changes = PyList_New(0);
    if (!sub_changes || !ins_changes || !del_changes)
        goto error;

    count = self->fuzzy_counts[RE_FUZZY_SUB] + self->fuzzy_counts[RE_FUZZY_INS]
      + self->fuzzy_counts[RE_FUZZY_DEL];
    offset = 0;

    for (i = 0; i < count; i++) {
        RE_FuzzyChange* change;
        Py_ssize_t pos;
        PyObject* position;
        int status;

        change = &self->fuzzy_changes[i];

        pos = change->pos;
        if (change->type == RE_FUZZY_DEL) {
            pos += offset;
            ++offset;
        }

        position = Py_BuildValue("n", pos);
        if (!position)
            goto error;

        switch (change->type) {
        case RE_FUZZY_DEL:
            status = PyList_Append(del_changes, position);
            break;
        case RE_FUZZY_INS:
            status = PyList_Append(ins_changes, position);
            break;
        case RE_FUZZY_SUB:
            status = PyList_Append(sub_changes, position);
            break;
        default:
            status = 0;
            break;
        }

        Py_DECREF(position);

        if (status == -1)
            goto error;
    }

    result = PyTuple_Pack(3, sub_changes, ins_changes, del_changes);

    Py_DECREF(sub_changes);
    Py_DECREF(ins_changes);
    Py_DECREF(del_changes);

    return result;

error:
    Py_XDECREF(sub_changes);
    Py_XDECREF(ins_changes);
    Py_XDECREF(del_changes);
    return NULL;
}

static PyGetSetDef match_getset[] = {
    {"lastindex", (getter)match_lastindex, (setter)NULL,
      "The group number of the last matched capturing group, or None."},
    {"lastgroup", (getter)match_lastgroup, (setter)NULL,
      "The name of the last matched capturing group, or None."},
    {"regs", (getter)match_regs, (setter)NULL,
      "A tuple of the spans of the capturing groups."},
    {"string", (getter)match_string, (setter)NULL,
      "The string that was searched, or None if it has been detached."},
    {"fuzzy_counts", (getter)match_fuzzy_counts, (setter)NULL,
      "A tuple of the number of substitutions, insertions and deletions."},
    {"fuzzy_changes", (getter)match_fuzzy_changes, (setter)NULL,
      "A tuple of the positions of the substitutions, insertions and deletions."},
    {NULL} /* Sentinel */
};

static PyMemberDef match_members[] = {
    {"re", T_OBJECT, offsetof(MatchObject, pattern), READONLY,
      "The regex object that produced this match object."},
    {"pos", T_PYSSIZET, offsetof(MatchObject, pos), READONLY,
      "The position at which the regex engine starting searching."},
    {"endpos", T_PYSSIZET, offsetof(MatchObject, endpos), READONLY,
      "The final position beyond which the regex engine won't search."},
    {"partial", T_BOOL, offsetof(MatchObject, partial), READONLY,
      "Whether it's a partial match."},
    {NULL} /* Sentinel */
};

static PyMappingMethods match_as_mapping = {
    (lenfunc)match_length, /* mp_length */
    (binaryfunc)match_getitem, /* mp_subscript */
    0, /* mp_ass_subscript */
};

static PyTypeObject Match_Type = {
    PyVarObject_HEAD_INIT(NULL,0)
    "_regex.Match",
    sizeof(MatchObject)
};

/* Copies the groups. */
Py_LOCAL_INLINE(RE_GroupData*) copy_groups(RE_GroupData* groups, size_t
  group_count) {
    size_t span_count;
    size_t g;
    RE_GroupData* groups_copy;
    RE_GroupSpan* spans_copy;
    size_t offset;

    /* Calculate the total size of the group info. */
    span_count = 0;
    for (g = 0; g < group_count; g++)
        span_count += groups[g].count;

    /* Allocate the storage for the group info in a single block. */
    groups_copy = (RE_GroupData*)re_alloc(group_count * sizeof(RE_GroupData) +
      span_count * sizeof(RE_GroupSpan));
    if (!groups_copy)
        return NULL;

    /* The storage for the spans comes after the other group info. */
    spans_copy = (RE_GroupSpan*)&groups_copy[group_count];

    /* There's no need to initialise the spans info. */
    memset(groups_copy, 0, group_count * sizeof(RE_GroupData));

    offset = 0;
    for (g = 0; g < group_count; g++) {
        RE_GroupData* orig;
        RE_GroupData* copy;

        orig = &groups[g];
        copy = &groups_copy[g];

        copy->captures = &spans_copy[offset];
        offset += orig->count;

        if (orig->count > 0) {
            Py_MEMCPY(copy->captures, orig->captures, orig->count *
              sizeof(RE_GroupSpan));
            copy->capacity = orig->count;
            copy->count = orig->count;
        }

        copy->current = orig->current;
    }

    return groups_copy;
}

/* Makes a copy of a MatchObject. */
Py_LOCAL_INLINE(PyObject*) make_match_copy(MatchObject* self) {
    MatchObject* match;

    if (!self->string) {
        /* The target string has been detached, so the MatchObject is now
         * immutable.
         */
        Py_INCREF(self);
        return (PyObject*)self;
    }

    /* Create a MatchObject. */
    match = PyObject_NEW(MatchObject, &Match_Type);
    if (!match)
        return NULL;

    match->string = self->string;
    match->substring = self->substring;
    match->substring_offset = self->substring_offset;
    match->pattern = self->pattern;
    match->pos = self->pos;
    match->endpos = self->endpos;
    match->match_start = self->match_start;
    match->match_end = self->match_end;
    match->lastindex = self->lastindex;
    match->lastgroup = self->lastgroup;
    match->group_count = self->group_count;
    match->groups = NULL; /* Copy them later. */
    match->regs = self->regs;
    Py_MEMCPY(match->fuzzy_counts, self->fuzzy_counts,
      sizeof(self->fuzzy_counts));
    match->fuzzy_changes = NULL; /* Copy them later. */
    match->partial = self->partial;
    Py_INCREF(match->string);
    Py_INCREF(match->substring);
    Py_INCREF(match->pattern);
    Py_XINCREF(match->regs);

    /* Copy the groups to the MatchObject. */
    if (self->group_count > 0) {
        match->groups = copy_groups(self->groups, self->group_count);
        if (!match->groups) {
            Py_DECREF(match);
            return NULL;
        }
    }

    /* Copy the fuzzy changes to the MatchObject. */
    if (self->fuzzy_changes) {
        size_t total_changes;
        size_t size;

        total_changes = self->fuzzy_counts[RE_FUZZY_SUB] +
          self->fuzzy_counts[RE_FUZZY_INS] + self->fuzzy_counts[RE_FUZZY_DEL];
        size = (size_t)total_changes * sizeof(RE_FuzzyChange);
        match->fuzzy_changes = (RE_FuzzyChange*)re_alloc(size);
        if (!match->fuzzy_changes) {
            Py_DECREF(match);
            return NULL;
        }
        Py_MEMCPY(match->fuzzy_changes, self->fuzzy_changes, size);
    }

    return (PyObject*)match;
}

/* Creates a new MatchObject. */
Py_LOCAL_INLINE(PyObject*) pattern_new_match(PatternObject* pattern, RE_State*
  state, int status) {
    /* Create MatchObject (from state object). */
    if (status > 0 || status == RE_ERROR_PARTIAL) {
        MatchObject* match;

        /* Create a MatchObject. */
        match = PyObject_NEW(MatchObject, &Match_Type);
        if (!match)
            return NULL;

        match->string = state->string;
        match->substring = state->string;
        match->substring_offset = 0;
        match->pattern = pattern;
        match->regs = NULL;

        if (pattern->is_fuzzy)
            Py_MEMCPY(match->fuzzy_counts, state->fuzzy_counts,
              sizeof(state->fuzzy_counts));
        else
            memset(match->fuzzy_counts, 0, sizeof(match->fuzzy_counts));

        if (state->fuzzy_changes.count > 0) {
            size_t size;

            size = state->fuzzy_changes.count * sizeof(RE_FuzzyChange);
            match->fuzzy_changes = (RE_FuzzyChange*)re_alloc(size);
            if (!match->fuzzy_changes) {
                Py_DECREF(match);
                return NULL;
            }
            Py_MEMCPY(match->fuzzy_changes, state->fuzzy_changes.items, size);
        } else
            match->fuzzy_changes = NULL;

        match->partial = status == RE_ERROR_PARTIAL;
        Py_INCREF(match->string);
        Py_INCREF(match->substring);
        Py_INCREF(match->pattern);

        /* Copy the groups to the MatchObject. */
        if (pattern->public_group_count > 0) {
            match->groups = copy_groups(state->groups,
              pattern->public_group_count);
            if (!match->groups) {
                Py_DECREF(match);
                return NULL;
            }
        } else
            match->groups = NULL;

        match->group_count = pattern->public_group_count;

        match->pos = state->slice_start;
        match->endpos = state->slice_end;

        if (state->reverse) {
            match->match_start = state->text_pos;
            match->match_end = state->match_pos;
        } else {
            match->match_start = state->match_pos;
            match->match_end = state->text_pos;
        }

        match->lastindex = state->lastindex;
        match->lastgroup = state->lastgroup;

        return (PyObject*)match;
    } else if (status == 0) {
        /* No match. */
        Py_RETURN_NONE;
    } else {
        /* Internal error. */
        set_error(status, NULL);
        return NULL;
    }
}

/* Gets the text of a capture group from a state. */
Py_LOCAL_INLINE(PyObject*) state_get_group(RE_State* state, Py_ssize_t index,
  PyObject* string, BOOL empty) {
    RE_GroupData* group;
    Py_ssize_t start;
    Py_ssize_t end;

    group = &state->groups[index - 1];

    if (string != Py_None && index >= 1 && (size_t)index <=
      state->pattern->public_group_count && group->current >= 0) {
        RE_GroupSpan* span;

        span = &group->captures[group->current];
        start = span->start;
        end = span->end;
    } else if (empty)
        /* Want an empty string. */
        start = end = 0;
    else
        Py_RETURN_NONE;

    return get_slice(string, start, end);
}

/* Acquires the lock (mutex) on the state if there's one.
 *
 * It also increments the owner's refcount just to ensure that it won't be
 * destroyed by another thread.
 */
Py_LOCAL_INLINE(void) acquire_state_lock(PyObject* owner, RE_State* state) {
    if (state->lock) {
        /* In order to avoid deadlock we need to release the GIL while trying
         * to acquire the lock.
         */
        Py_INCREF(owner);
        if (!PyThread_acquire_lock(state->lock, 0)) {
            release_GIL(state);
            PyThread_acquire_lock(state->lock, 1);
            acquire_GIL(state);
        }
    }
}

/* Releases the lock (mutex) on the state if there's one.
 *
 * It also decrements the owner's refcount, which was incremented when the lock
 * was acquired.
 */
Py_LOCAL_INLINE(void) release_state_lock(PyObject* owner, RE_State* state) {
    if (state->lock) {
        PyThread_release_lock(state->lock);
        Py_DECREF(owner);
    }
}

/* Implements the functionality of ScanObject's search and match methods. */
Py_LOCAL_INLINE(PyObject*) scanner_search_or_match(ScannerObject* self, BOOL
  search) {
    RE_State* state;
    PyObject* match;

    state = &self->state;

    /* Acquire the state lock in case we're sharing the scanner object across
     * threads.
     */
    acquire_state_lock((PyObject*)self, state);

    if (self->status == RE_ERROR_FAILURE || self->status == RE_ERROR_PARTIAL) {
        /* No or partial match. */
        release_state_lock((PyObject*)self, state);
        Py_RETURN_NONE;
    } else if (self->status < 0) {
        /* Internal error. */
        release_state_lock((PyObject*)self, state);
        set_error(self->status, NULL);
        return NULL;
    }

    /* Look for another match. */
    self->status = do_match(state, search);
    if (self->status >= 0 || self->status == RE_ERROR_PARTIAL) {
        /* Create the match object. */
        match = pattern_new_match(self->pattern, state, self->status);

        if (search && state->overlapped) {
            /* Advance one character. */
            Py_ssize_t step;

            step = state->reverse ? -1 : 1;
            state->text_pos = state->match_pos + step;
            state->must_advance = FALSE;
        } else
            /* Don't allow 2 contiguous zero-width matches. */
            state->must_advance = state->text_pos == state->match_pos;
    } else
        /* Internal error. */
        match = NULL;

    /* Release the state lock. */
    release_state_lock((PyObject*)self, state);

    return match;
}

/* ScannerObject's 'match' method. */
static PyObject* scanner_match(ScannerObject* self, PyObject* unused) {
    return scanner_search_or_match(self, FALSE);
}

/* ScannerObject's 'search' method. */
static PyObject* scanner_search(ScannerObject* self, PyObject* unused) {
    return scanner_search_or_match(self, TRUE);
}

/* Returns an iterator for a ScannerObject.
 *
 * The iterator is actually the ScannerObject itself.
 */
static PyObject* scanner_iter(PyObject* self) {
    Py_INCREF(self);
    return self;
}

/* Gets the next result from a scanner iterator. */
static PyObject* scanner_iternext(PyObject* self) {
    PyObject* match;

    match = scanner_search((ScannerObject*)self, NULL);

    if (match == Py_None) {
        /* No match. */
        Py_DECREF(match);
        return NULL;
    }

    return match;
}

/* Makes a copy of a ScannerObject.
 *
 * It actually doesn't make a copy, just returns the original object.
 */
Py_LOCAL_INLINE(PyObject*) make_scanner_copy(ScannerObject* self) {
    Py_INCREF(self);
    return (PyObject*)self;
}

/* ScannerObject's '__copy__' method. */
static PyObject* scanner_copy(ScannerObject* self, PyObject* unused) {
    return make_scanner_copy(self);
}

/* ScannerObject's '__deepcopy__' method. */
static PyObject* scanner_deepcopy(ScannerObject* self, PyObject* memo) {
    return make_scanner_copy(self);
}

/* The documentation of a ScannerObject. */
PyDoc_STRVAR(scanner_match_doc,
    "match() --> MatchObject or None.\n\
    Match at the current position in the string.");

PyDoc_STRVAR(scanner_search_doc,
    "search() --> MatchObject or None.\n\
    Search from the current position in the string.");

/* ScannerObject's methods. */
static PyMethodDef scanner_methods[] = {
    {"match", (PyCFunction)scanner_match, METH_NOARGS, scanner_match_doc},
    {"search", (PyCFunction)scanner_search, METH_NOARGS, scanner_search_doc},
    {"__copy__", (PyCFunction)scanner_copy, METH_NOARGS},
    {"__deepcopy__", (PyCFunction)scanner_deepcopy, METH_O},
    {NULL, NULL}
};

PyDoc_STRVAR(scanner_doc, "Scanner object");

/* Deallocates a ScannerObject. */
static void scanner_dealloc(PyObject* self_) {
    ScannerObject* self;

    self = (ScannerObject*)self_;

    if (self->status != RE_ERROR_INITIALISING)
        state_fini(&self->state);
    Py_DECREF(self->pattern);
    PyObject_DEL(self);
}

static PyMemberDef scanner_members[] = {
    {"pattern", T_OBJECT, offsetof(ScannerObject, pattern), READONLY,
      "The regex object that produced this scanner object."},
    {NULL} /* Sentinel */
};

static PyTypeObject Scanner_Type = {
    PyVarObject_HEAD_INIT(NULL, 0)
    "_regex.Scanner",
    sizeof(ScannerObject)
};

/* Decodes a 'concurrent' argument. */
Py_LOCAL_INLINE(int) decode_concurrent(PyObject* concurrent) {
    Py_ssize_t value;

    if (concurrent == Py_None)
        return RE_CONC_DEFAULT;

    value = PyLong_AsLong(concurrent);
    if (value == -1 && PyErr_Occurred()) {
        set_error(RE_ERROR_CONCURRENT, NULL);
        return -1;
    }

    return value ? RE_CONC_YES : RE_CONC_NO;
}

/* Decodes a 'partial' argument. */
Py_LOCAL_INLINE(BOOL) decode_partial(PyObject* partial) {
    Py_ssize_t value;

    if (partial == Py_False)
        return FALSE;

    if (partial == Py_True)
        return TRUE;

    value = PyLong_AsLong(partial);
    if (value == -1 && PyErr_Occurred()) {
        PyErr_Clear();
        return TRUE;
    }

    return value != 0;
}

/* Decodes a 'timeout' argument. */
Py_LOCAL_INLINE(Py_ssize_t) decode_timeout(PyObject* timeout) {
    double value;

    if (timeout == Py_None)
        return RE_NO_TIMEOUT;

    value = PyFloat_AsDouble(timeout);
    if (value == -1.0 && PyErr_Occurred()) {
        set_error(RE_ERROR_BAD_TIMEOUT, NULL);
        return RE_BAD_TIMEOUT;
    }

    return value >= 0.0 ? (Py_ssize_t)(value * CLOCKS_PER_SEC) : RE_NO_TIMEOUT;
}

/* Creates a new ScannerObject. */
static PyObject* pattern_scanner(PatternObject* pattern, PyObject* args,
  PyObject* kwargs) {
    /* Create search state object. */
    ScannerObject* self;
    Py_ssize_t start;
    Py_ssize_t end;
    int conc;
    Py_ssize_t tim;
    BOOL part;

    PyObject* string;
    PyObject* pos = Py_None;
    PyObject* endpos = Py_None;
    Py_ssize_t overlapped = FALSE;
    PyObject* concurrent = Py_None;
    PyObject* timeout = Py_None;
    PyObject* partial = Py_False;
    static char* kwlist[] = { "string", "pos", "endpos", "overlapped",
      "concurrent", "partial", "timeout", NULL };
    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "O|OOnOOO:scanner", kwlist,
      &string, &pos, &endpos, &overlapped, &concurrent, &partial, &timeout))
        return NULL;

    start = as_string_index(pos, 0);
    if (start == -1 && PyErr_Occurred())
        return NULL;

    end = as_string_index(endpos, PY_SSIZE_T_MAX);
    if (end == -1 && PyErr_Occurred())
        return NULL;

    conc = decode_concurrent(concurrent);
    if (conc < 0)
        return NULL;

    tim = decode_timeout(timeout);
    if (tim == RE_BAD_TIMEOUT)
        return NULL;

    part = decode_partial(partial);

    /* Create a scanner object. */
    self = PyObject_NEW(ScannerObject, &Scanner_Type);
    if (!self)
        return NULL;

    self->pattern = pattern;
    Py_INCREF(self->pattern);
    self->status = RE_ERROR_INITIALISING;

    /* The MatchObject, and therefore repeated captures, will be visible. */
    if (!state_init(&self->state, pattern, string, start, end, overlapped != 0,
      conc, part, TRUE, TRUE, FALSE, tim)) {
        Py_DECREF(self);
        return NULL;
    }

    self->status = RE_ERROR_SUCCESS;

    return (PyObject*) self;
}

/* Performs the split for the SplitterObject. */
Py_LOCAL_INLINE(PyObject*) next_split_part(SplitterObject* self) {
    RE_State* state;
    PyObject* result = NULL; /* Initialise to stop compiler warning. */

    state = &self->state;

    /* Acquire the state lock in case we're sharing the splitter object across
     * threads.
     */
    acquire_state_lock((PyObject*)self, state);

    if (self->status == RE_ERROR_FAILURE || self->status == RE_ERROR_PARTIAL) {
        /* Finished. */
        release_state_lock((PyObject*)self, state);
        result = Py_False;
        Py_INCREF(result);
        return result;
    } else if (self->status < 0) {
        /* Internal error. */
        release_state_lock((PyObject*)self, state);
        set_error(self->status, NULL);
        return NULL;
    }

    if (self->index == 0) {
        if (self->split_count < self->maxsplit) {
#if PY_VERSION_HEX < 0x03070000
            Py_ssize_t step;
            Py_ssize_t end_pos;

            if (state->reverse) {
                step = -1;
                end_pos = state->slice_start;
            } else {
                step = 1;
                end_pos = state->slice_end;
            }

retry:
#endif
            self->status = do_match(state, TRUE);
            if (self->status < 0)
                goto error;

            if (self->status == RE_ERROR_SUCCESS) {
#if PY_VERSION_HEX < 0x03070000
                if (state->version_0) {
                    /* Version 0 behaviour is to advance one character if the
                     * split was zero-width. Unfortunately, this can give an
                     * incorrect result. GvR wants this behaviour to be
                     * retained so as not to break any existing software which
                     * might rely on it.
                     */
                    if (state->text_pos == state->match_pos) {
                        if (self->last_pos == end_pos)
                            goto no_match;

                        /* Advance one character. */
                        state->text_pos += step;
                        state->must_advance = FALSE;
                        goto retry;
                    }
                }

#endif
                ++self->split_count;

                /* Get segment before this match. */
                if (state->reverse)
                    result = get_slice(state->string, state->match_pos,
                      self->last_pos);
                else
                    result = get_slice(state->string, self->last_pos,
                      state->match_pos);
                if (!result)
                    goto error;

                self->last_pos = state->text_pos;

#if PY_VERSION_HEX >= 0x03070000
                /* Don't allow 2 contiguous zero-width matches. */
                state->must_advance = state->text_pos == state->match_pos;
#else
                /* Version 0 behaviour is to advance one character if the match
                 * was zero-width. Unfortunately, this can give an incorrect
                 * result. GvR wants this behaviour to be retained so as not to
                 * break any existing software which might rely on it.
                 */
                if (state->version_0) {
                    if (state->text_pos == state->match_pos)
                        /* Advance one character. */
                        state->text_pos += step;

                    state->must_advance = FALSE;
                } else
                    /* Don't allow a contiguous zero-width match. */
                    state->must_advance = TRUE;
#endif
            }
        } else
            goto no_match;

        if (self->status == RE_ERROR_FAILURE || self->status ==
          RE_ERROR_PARTIAL) {
no_match:
            /* Get segment following last match (even if empty). */
            if (state->reverse)
                result = get_slice(state->string, 0, self->last_pos);
            else
                result = get_slice(state->string, self->last_pos,
                  state->text_length);
            if (!result)
                goto error;
        }
    } else {
        /* Add group. */
        result = state_get_group(state, self->index, state->string, FALSE);
        if (!result)
            goto error;
    }

    ++self->index;
    if ((size_t)self->index > state->pattern->public_group_count)
        self->index = 0;

    /* Release the state lock. */
    release_state_lock((PyObject*)self, state);

    return result;

error:
    /* Release the state lock. */
    release_state_lock((PyObject*)self, state);

    return NULL;
}

/* SplitterObject's 'split' method. */
static PyObject* splitter_split(SplitterObject* self, PyObject* unused) {
    PyObject* result;

    result = next_split_part(self);

    if (result == Py_False) {
        /* The sentinel. */
        Py_DECREF(Py_False);
        Py_RETURN_NONE;
    }

    return result;
}

/* Returns an iterator for a SplitterObject.
 *
 * The iterator is actually the SplitterObject itself.
 */
static PyObject* splitter_iter(PyObject* self) {
    Py_INCREF(self);
    return self;
}

/* Gets the next result from a splitter iterator. */
static PyObject* splitter_iternext(PyObject* self) {
    PyObject* result;

    result = next_split_part((SplitterObject*)self);

    if (result == Py_False) {
        /* No match. */
        Py_DECREF(result);
        return NULL;
    }

    return result;
}

/* Makes a copy of a SplitterObject.
 *
 * It actually doesn't make a copy, just returns the original object.
 */
Py_LOCAL_INLINE(PyObject*) make_splitter_copy(SplitterObject* self) {
    Py_INCREF(self);
    return (PyObject*)self;
}

/* SplitterObject's '__copy__' method. */
static PyObject* splitter_copy(SplitterObject* self, PyObject* unused) {
    return make_splitter_copy(self);
}

/* SplitterObject's '__deepcopy__' method. */
static PyObject* splitter_deepcopy(SplitterObject* self, PyObject* memo) {
    return make_splitter_copy(self);
}

/* The documentation of a SplitterObject. */
PyDoc_STRVAR(splitter_split_doc,
    "split() --> string or None.\n\
    Return the next part of the split string.");

/* SplitterObject's methods. */
static PyMethodDef splitter_methods[] = {
    {"split", (PyCFunction)splitter_split, METH_NOARGS, splitter_split_doc},
    {"__copy__", (PyCFunction)splitter_copy, METH_NOARGS},
    {"__deepcopy__", (PyCFunction)splitter_deepcopy, METH_O},
    {NULL, NULL}
};

PyDoc_STRVAR(splitter_doc, "Splitter object");

/* Deallocates a SplitterObject. */
static void splitter_dealloc(PyObject* self_) {
    SplitterObject* self;

    self = (SplitterObject*)self_;

    if (self->status != RE_ERROR_INITIALISING)
        state_fini(&self->state);
    Py_DECREF(self->pattern);
    PyObject_DEL(self);
}

#if defined(PYPY_VERSION) && PY_VERSION_HEX < 0x05090000
Py_LOCAL_INLINE(BOOL) is_whitespace(Py_UCS4 c) {
    return 0x09 <= c && c <= 0x0D || c == ' ';
}

Py_LOCAL_INLINE(BOOL) is_digit(Py_UCS4 c) {
    return '0' <= c && c <= '9';
}

Py_LOCAL_INLINE(PyObject*) integer_from_unicode(PyObject* item) {
    int kind;
    void* data;
    Py_ssize_t length;
    char* buffer;
    Py_ssize_t count;
    Py_ssize_t index;
    PyObject* value;

    kind = PyUnicode_KIND(item);
    data = PyUnicode_DATA(item);
    length = PyUnicode_GET_LENGTH(item);
    buffer = (char*)re_alloc(length + 1);
    if (!buffer)
        return NULL;
    count = 0;

    for (index = 0; index < length; index++) {
        Py_UCS4 c;

        c = PyUnicode_READ(kind, data, index);
        if (is_whitespace(c) || c == '+' || c == '-' || is_digit(c))
            buffer[count++] = c;
        else
            goto error;
    }

    buffer[count] = '\0';

    value = PyLong_FromString(buffer, NULL, 0);
    re_dealloc(buffer);

    return value;

error:
    re_dealloc(buffer);
    PyErr_Format(PyExc_ValueError,
      "invalid literal for int() with base %d: %.200R", 10, item);
    return NULL;
}
#endif

/* Converts a captures index to an integer.
 *
 * A negative capture index in 'expandf' and 'subf' is passed as a string
 * because negative indexes are not supported by 'str.format'.
 */
Py_LOCAL_INLINE(Py_ssize_t) index_to_integer(PyObject* item) {
    Py_ssize_t value;

    value = PyLong_AsLong(item);
    if (!(value == -1 && PyErr_Occurred()))
        return value;

    PyErr_Clear();

    /* Is the index a string representation of an integer? */
    if (PyUnicode_Check(item)) {
        PyObject* int_obj;
#if PY_VERSION_HEX < 0x03030000
        Py_UNICODE* characters;
        Py_ssize_t length;
#endif

#if defined(PYPY_VERSION) && PY_VERSION_HEX < 0x05090000
        int_obj = integer_from_unicode(item);
#elif PY_VERSION_HEX >= 0x03030000
        int_obj = PyLong_FromUnicodeObject(item, 0);
#else
        characters = (Py_UNICODE*)PyUnicode_AS_DATA(item);
        length = PyUnicode_GET_SIZE(item);
        int_obj = PyLong_FromUnicode(characters, length, 0);
#endif
        if (!int_obj)
            goto error;

        value = PyLong_AsLong(int_obj);
        Py_DECREF(int_obj);
        if (!PyErr_Occurred())
            return value;
    } else if (PyBytes_Check(item)) {
        char* characters;
        PyObject* int_obj;

        characters = PyBytes_AsString(item);
        int_obj = PyLong_FromString(characters, NULL, 0);
        if (!int_obj)
            goto error;

        value = PyLong_AsLong(int_obj);
        Py_DECREF(int_obj);
        if (!PyErr_Occurred())
            return value;
    }

error:
    PyErr_Clear();
    PyErr_Format(PyExc_TypeError, "list indices must be integers, not %.200s",
      item->ob_type->tp_name);

    return -1;
}

/* CaptureObject's length method. */
Py_LOCAL_INLINE(Py_ssize_t) capture_length(CaptureObject* self) {
    MatchObject* match;
    RE_GroupData* group;

    if (self->group_index == 0)
        return 1;

    match = *self->match_indirect;
    group = &match->groups[self->group_index - 1];

    return (Py_ssize_t)group->count;
}

/* CaptureObject's '__getitem__' method. */
static PyObject* capture_getitem(CaptureObject* self, PyObject* item) {
    Py_ssize_t index;
    MatchObject* match;
    Py_ssize_t start;
    Py_ssize_t end;

    index = index_to_integer(item);
    if (index == -1 && PyErr_Occurred())
        return NULL;

    match = *self->match_indirect;

    if (self->group_index == 0) {
        if (index < 0)
            index += 1;

        if (index != 0) {
            PyErr_SetString(PyExc_IndexError, "list index out of range");
            return NULL;
        }

        start = match->match_start;
        end = match->match_end;
    } else {
        RE_GroupData* group;
        RE_GroupSpan* span;

        group = &match->groups[self->group_index - 1];

        if (index < 0)
            index += (Py_ssize_t)group->count;

        if (index < 0 || index >= (Py_ssize_t)group->count) {
            PyErr_SetString(PyExc_IndexError, "list index out of range");
            return NULL;
        }

        span = &group->captures[index];

        start = span->start;
        end = span->end;
    }

    return get_slice(match->substring, start - match->substring_offset, end -
      match->substring_offset);
}

static PyMappingMethods capture_as_mapping = {
    (lenfunc)capture_length, /* mp_length */
    (binaryfunc)capture_getitem, /* mp_subscript */
    0, /* mp_ass_subscript */
};

/* CaptureObject's methods. */
static PyMethodDef capture_methods[] = {
    {"__getitem__", (PyCFunction)capture_getitem, METH_O|METH_COEXIST},
    {NULL, NULL}
};

/* Deallocates a CaptureObject. */
static void capture_dealloc(PyObject* self_) {
    CaptureObject* self;

    self = (CaptureObject*)self_;
    PyObject_DEL(self);
}

/* CaptureObject's 'str' method. */
static PyObject* capture_str(PyObject* self_) {
    CaptureObject* self;
    MatchObject* match;

    self = (CaptureObject*)self_;
    match = *self->match_indirect;

    return match_get_group_by_index(match, self->group_index, Py_None);
}

static PyMemberDef splitter_members[] = {
    {"pattern", T_OBJECT, offsetof(SplitterObject, pattern), READONLY,
      "The regex object that produced this splitter object."},
    {NULL} /* Sentinel */
};

static PyTypeObject Splitter_Type = {
    PyVarObject_HEAD_INIT(NULL, 0)
    "_regex.Splitter",
    sizeof(SplitterObject)
};

/* Creates a new SplitterObject. */
Py_LOCAL_INLINE(PyObject*) pattern_splitter(PatternObject* pattern, PyObject*
  args, PyObject* kwargs) {
    /* Create split state object. */
    int conc;
    Py_ssize_t tim;
    SplitterObject* self;

    PyObject* string;
    Py_ssize_t maxsplit = 0;
    PyObject* concurrent = Py_None;
    PyObject* timeout = Py_None;
    static char* kwlist[] = { "string", "maxsplit", "concurrent", "timeout",
      NULL };
    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "O|nOO:splitter", kwlist,
      &string, &maxsplit, &concurrent, &timeout))
        return NULL;

    conc = decode_concurrent(concurrent);
    if (conc < 0)
        return NULL;

    tim = decode_timeout(timeout);
    if (tim == RE_BAD_TIMEOUT)
        return NULL;

    /* Create a splitter object. */
    self = PyObject_NEW(SplitterObject, &Splitter_Type);
    if (!self)
        return NULL;

    self->pattern = pattern;
    Py_INCREF(self->pattern);
    self->status = RE_ERROR_INITIALISING;

    if (maxsplit == 0)
        maxsplit = PY_SSIZE_T_MAX;

    /* The MatchObject, and therefore repeated captures, will not be visible.
     */
    if (!state_init(&self->state, pattern, string, 0, PY_SSIZE_T_MAX, FALSE,
      conc, FALSE, TRUE, FALSE, FALSE, tim)) {
        Py_DECREF(self);
        return NULL;
    }

    self->maxsplit = maxsplit;
    self->last_pos = self->state.reverse ? self->state.text_length : 0;
    self->split_count = 0;
    self->index = 0;
    self->status = RE_ERROR_SUCCESS;

    return (PyObject*) self;
}

/* Implements the functionality of PatternObject's search and match methods. */
Py_LOCAL_INLINE(PyObject*) pattern_search_or_match(PatternObject* self,
  PyObject* args, PyObject* kwargs, char* args_desc, BOOL search, BOOL
  match_all) {
    Py_ssize_t start;
    Py_ssize_t end;
    int conc;
    Py_ssize_t tim;
    BOOL part;
    RE_State state;
    int status;
    PyObject* match;

    PyObject* string;
    PyObject* pos = Py_None;
    PyObject* endpos = Py_None;
    PyObject* concurrent = Py_None;
    PyObject* timeout = Py_None;
    PyObject* partial = Py_False;
    static char* kwlist[] = { "string", "pos", "endpos", "concurrent",
      "partial", "timeout", NULL };
    /* When working with a short string, such as a line from a file, the
     * relative cost of PyArg_ParseTupleAndKeywords can be significant, and
     * it's worth not using it when there are only positional arguments.
     */
    Py_ssize_t arg_count;
    if (args && !kwargs && PyTuple_CheckExact(args))
        arg_count = PyTuple_GET_SIZE(args);
    else
        arg_count = -1;

    if (1 <= arg_count && arg_count <= 5) {
        /* PyTuple_GET_ITEM borrows the reference. */
        string = PyTuple_GET_ITEM(args, 0);
        if (arg_count >= 2)
            pos = PyTuple_GET_ITEM(args, 1);
        if (arg_count >= 3)
            endpos = PyTuple_GET_ITEM(args, 2);
        if (arg_count >= 4)
            concurrent = PyTuple_GET_ITEM(args, 3);
        if (arg_count >= 5)
            partial = PyTuple_GET_ITEM(args, 4);
        if (arg_count >= 6)
            timeout = PyTuple_GET_ITEM(args, 5);
    } else if (!PyArg_ParseTupleAndKeywords(args, kwargs, args_desc, kwlist,
      &string, &pos, &endpos, &concurrent, &partial, &timeout))
        return NULL;

    start = as_string_index(pos, 0);
    if (start == -1 && PyErr_Occurred())
        return NULL;

    end = as_string_index(endpos, PY_SSIZE_T_MAX);
    if (end == -1 && PyErr_Occurred())
        return NULL;

    conc = decode_concurrent(concurrent);
    if (conc < 0)
        return NULL;

    tim = decode_timeout(timeout);
    if (tim == RE_BAD_TIMEOUT)
        return NULL;

    part = decode_partial(partial);

    /* The MatchObject, and therefore repeated captures, will be visible. */
    if (!state_init(&state, self, string, start, end, FALSE, conc, part, FALSE,
      TRUE, match_all, tim))
        return NULL;

    status = do_match(&state, search);

    if (status >= 0 || status == RE_ERROR_PARTIAL)
        /* Create the match object. */
        match = pattern_new_match(self, &state, status);
    else
        match = NULL;

    state_fini(&state);

    return match;
}

/* PatternObject's 'match' method. */
static PyObject* pattern_match(PatternObject* self, PyObject* args, PyObject*
  kwargs) {
    return pattern_search_or_match(self, args, kwargs, "O|OOOOO:match", FALSE,
      FALSE);
}

/* PatternObject's 'fullmatch' method. */
static PyObject* pattern_fullmatch(PatternObject* self, PyObject* args,
  PyObject* kwargs) {
    return pattern_search_or_match(self, args, kwargs, "O|OOOOO:fullmatch",
      FALSE, TRUE);
}

/* PatternObject's 'search' method. */
static PyObject* pattern_search(PatternObject* self, PyObject* args, PyObject*
  kwargs) {
    return pattern_search_or_match(self, args, kwargs, "O|OOOOO:search", TRUE,
      FALSE);
}

/* Gets the limits of the matching. */
Py_LOCAL_INLINE(BOOL) get_limits(PyObject* pos, PyObject* endpos, Py_ssize_t
  length, Py_ssize_t* start, Py_ssize_t* end) {
    Py_ssize_t s;
    Py_ssize_t e;

    s = as_string_index(pos, 0);
    if (s == -1 && PyErr_Occurred())
        return FALSE;

    e = as_string_index(endpos, PY_SSIZE_T_MAX);
    if (e == -1 && PyErr_Occurred())
        return FALSE;

    /* Adjust boundaries. */
    if (s < 0)
        s += length;
    if (s < 0)
        s = 0;
    else if (s > length)
        s = length;

    if (e < 0)
        e += length;
    if (e < 0)
        e = 0;
    else if (e > length)
        e = length;

    *start = s;
    *end = e;

    return TRUE;
}

/* Gets a replacement item from the replacement list.
 *
 * The replacement item could be a string literal or a group.
 *
 * It can return None to represent an empty string.
 */
Py_LOCAL_INLINE(PyObject*) get_sub_replacement(PyObject* item, PyObject*
  string, RE_State* state, size_t group_count) {
    Py_ssize_t index;

    if (PyUnicode_CheckExact(item) || PyBytes_CheckExact(item)) {
        /* It's a literal, which can be added directly to the list. */
#if PY_VERSION_HEX >= 0x03040000

        /* ensure_immutable will DECREF the original item if it has to make an
         * immutable copy, but that original item might have a borrowed
         * reference, so we must INCREF it first in order to ensure it won't be
         * destroyed.
         */
        Py_INCREF(item);
        item = ensure_immutable(item);
#else
        Py_INCREF(item);
#endif
        return item;
    }

    /* Is it a group reference? */
    index = as_group_index(item);
    if (index == -1 && PyErr_Occurred()) {
        /* Not a group either! */
        set_error(RE_ERROR_REPLACEMENT, NULL);
        return NULL;
    }

    if (index == 0) {
        /* The entire matched portion of the string. */
        if (state->match_pos == state->text_pos) {
            /* Return None for "". */
            Py_RETURN_NONE;
        }

        if (state->reverse)
            return get_slice(string, state->text_pos, state->match_pos);
        else
            return get_slice(string, state->match_pos, state->text_pos);
    } else if (1 <= index && (size_t)index <= group_count) {
        /* A group. */
        RE_GroupData* group;
        RE_GroupSpan* span;

        group = &state->groups[index - 1];

        if (group->current < 0) {
            /* The group didn't match or is "", so return None for "". */
            Py_RETURN_NONE;
        }

        span = &group->captures[group->current];

        return get_slice(string, span->start, span->end);
    } else {
        /* No such group. */
        set_error(RE_ERROR_INVALID_GROUP_REF, NULL);
        return NULL;
    }
}

/* PatternObject's 'subx' method. */
Py_LOCAL_INLINE(PyObject*) pattern_subx(PatternObject* self, PyObject*
  str_template, PyObject* string, Py_ssize_t maxsub, int sub_type, PyObject*
  pos, PyObject* endpos, int concurrent, Py_ssize_t timeout) {
    RE_StringInfo str_info;
    Py_ssize_t start;
    Py_ssize_t end;
    BOOL is_callable = FALSE;
    PyObject* replacement = NULL;
    BOOL is_literal = FALSE;
    BOOL is_format = FALSE;
    BOOL is_template = FALSE;
    RE_State state;
    RE_JoinInfo join_info;
    Py_ssize_t sub_count;
    Py_ssize_t last_pos;
#if PY_VERSION_HEX < 0x03070000
    Py_ssize_t step;
#endif
    PyObject* item;
    MatchObject* match;
    BOOL built_capture = FALSE;
    PyObject* args = NULL;
    PyObject* kwargs = NULL;
    Py_ssize_t end_pos;

    /* Get the string. */
    if (!get_string(string, &str_info))
        return NULL;

    if (!check_compatible(self, str_info.is_unicode)) {
        release_buffer(&str_info);
        return NULL;
    }

    /* Get the limits of the search. */
    if (!get_limits(pos, endpos, str_info.length, &start, &end)) {
        release_buffer(&str_info);
        return NULL;
    }

    /* If the pattern is too long for the string, then take a shortcut, unless
     * it's a fuzzy pattern.
     */
    if (!self->is_fuzzy && self->min_width > end - start) {
        PyObject* result;

        Py_INCREF(string);

        if (sub_type & RE_SUBN)
            result = Py_BuildValue("Nn", string, 0);
        else
            result = string;

        release_buffer(&str_info);

        return result;
    }

    if (maxsub == 0)
        maxsub = PY_SSIZE_T_MAX;

    /* sub/subn takes either a function or a string template. */
    if (PyCallable_Check(str_template)) {
        /* It's callable. */
        is_callable = TRUE;

        replacement = str_template;
        Py_INCREF(replacement);
    } else if (sub_type & RE_SUBF) {
        /* Is it a literal format?
         *
         * To keep it simple we'll say that a literal is a string which can be
         * used as-is, so no placeholders.
         */
        Py_ssize_t literal_length;

        literal_length = check_replacement_string(str_template, '{');
        if (literal_length > 0) {
            /* It's a literal. */
            is_literal = TRUE;

            replacement = str_template;
            Py_INCREF(replacement);
        } else if (literal_length < 0) {
            /* It isn't a literal, so get the 'format' method. */
            is_format = TRUE;

            replacement = PyObject_GetAttrString(str_template, "format");
            if (!replacement) {
                release_buffer(&str_info);
                return NULL;
            }
        }
    } else {
        /* Is it a literal template?
         *
         * To keep it simple we'll say that a literal is a string which can be
         * used as-is, so no backslashes.
         */
        Py_ssize_t literal_length;

        literal_length = check_replacement_string(str_template, '\\');
        if (literal_length > 0) {
            /* It's a literal. */
            is_literal = TRUE;

            replacement = str_template;
            Py_INCREF(replacement);
        } else if (literal_length < 0 ) {
            /* It isn't a literal, so hand it over to the template compiler. */
            is_template = TRUE;

            replacement = call("regex.regex", "_compile_replacement_helper",
              PyTuple_Pack(2, self, str_template));
            if (!replacement) {
                release_buffer(&str_info);
                return NULL;
            }
        }
    }

    /* The MatchObject, and therefore repeated captures, will be visible only
     * if the replacement is callable or subf is used.
     */
    if (!state_init_2(&state, self, string, &str_info, start, end, FALSE,
      concurrent, FALSE, FALSE, is_callable || (sub_type & RE_SUBF) != 0,
      FALSE, timeout)) {
        release_buffer(&str_info);
        Py_XDECREF(replacement);
        return NULL;
    }

    init_join_list(&join_info, state.reverse, PyUnicode_Check(string));

    sub_count = 0;
    last_pos = state.reverse ? state.text_length : 0;
#if PY_VERSION_HEX < 0x03070000
    step = state.reverse ? -1 : 1;
#endif
    while (sub_count < maxsub) {
        int status;

        status = do_match(&state, TRUE);
        if (status < 0)
            goto error;

        if (status == 0)
            break;

        /* Append the segment before this match. */
        if (state.match_pos != last_pos) {
            if (state.reverse)
                item = get_slice(string, state.match_pos, last_pos);
            else
                item = get_slice(string, last_pos, state.match_pos);
            if (!item)
                goto error;

            /* Add to the list. */
            status = add_to_join_list(&join_info, item);
            Py_DECREF(item);
            if (status < 0)
                goto error;
        }

        /* Add this match. */
        if (is_literal) {
            /* The replacement is a literal string. */
            status = add_to_join_list(&join_info, replacement);
            if (status < 0)
                goto error;
        } else if (is_format) {
            /* The replacement is a format string. */
            size_t g;

            /* We need to create the arguments for the 'format' method. We'll
             * start by creating a MatchObject.
             */
            match = (MatchObject*)pattern_new_match(self, &state, 1);
            if (!match)
                goto error;

            /* We'll build the args and kwargs the first time. They'll be using
             * capture objects which refer to the match object indirectly; this
             * means that args and kwargs can be reused with different match
             * objects.
             */
            if (!built_capture) {
                /* The args are a tuple of the capture group matches. */
                args = PyTuple_New((Py_ssize_t)match->group_count + 1);
                if (!args) {
                    Py_DECREF(match);
                    goto error;
                }

                for (g = 0; g < match->group_count + 1; g++)
                    /* PyTuple_SetItem borrows the reference. */
                    PyTuple_SetItem(args, (Py_ssize_t)g,
                      make_capture_object(&match, (Py_ssize_t)g));

                /* The kwargs are a dict of the named capture group matches. */
                kwargs = make_capture_dict(match, &match);
                if (!kwargs) {
                    Py_DECREF(args);
                    Py_DECREF(match);
                    goto error;
                }

                built_capture = TRUE;
            }

            /* Call the 'format' method. */
            item = PyObject_Call(replacement, args, kwargs);

            Py_DECREF(match);
            if (!item)
                goto error;

            /* Add the result to the list. */
            status = add_to_join_list(&join_info, item);
            Py_DECREF(item);
            if (status < 0)
                goto error;
        } else if (is_template) {
            /* The replacement is a list template. */
            Py_ssize_t count;
            Py_ssize_t index;
            Py_ssize_t step;

            /* Add each part of the template to the list. */
            count = PyList_GET_SIZE(replacement);
            if (join_info.reversed) {
                /* We're searching backwards, so we'll be reversing the list
                 * when it's complete. Therefore, we need to add the items of
                 * the template in reverse order for them to be in the correct
                 * order after the reversal.
                 */
                index = count - 1;
                step = -1;
            } else {
                /* We're searching forwards. */
                index = 0;
                step = 1;
            }

            while (count > 0) {
                PyObject* item;
                PyObject* str_item;

                /* PyList_GET_ITEM borrows a reference. */
                item = PyList_GET_ITEM(replacement, index);
                str_item = get_sub_replacement(item, string, &state,
                  self->public_group_count);
                if (!str_item)
                    goto error;

                /* Add the result to the list. */
                if (str_item == Py_None)
                    /* None for "". */
                    Py_DECREF(str_item);
                else {
                    status = add_to_join_list(&join_info, str_item);
                    Py_DECREF(str_item);
                    if (status < 0)
                        goto error;
                }

                --count;
                index += step;
            }
        } else if (is_callable) {
            /* Pass a MatchObject to the replacement function. */
            PyObject* match;
            PyObject* args;

            /* We need to create a MatchObject to pass to the replacement
             * function.
             */
            match = pattern_new_match(self, &state, 1);
            if (!match)
                goto error;

            /* The args for the replacement function. */
            args = PyTuple_Pack(1, match);
            if (!args) {
                Py_DECREF(match);
                goto error;
            }

            /* Call the replacement function. */
            item = PyObject_CallObject(replacement, args);
            Py_DECREF(args);
            Py_DECREF(match);
            if (!item)
                goto error;

            /* Add the result to the list. */
            status = add_to_join_list(&join_info, item);
            Py_DECREF(item);
            if (status < 0)
                goto error;
        }

        ++sub_count;

        last_pos = state.text_pos;

#if PY_VERSION_HEX >= 0x03070000
        /* Don't allow 2 contiguous zero-width matches. */
        state.must_advance = state.match_pos == state.text_pos;
#else
        if (state.version_0) {
            /* Always advance after a zero-width match. */
            if (state.match_pos == state.text_pos) {
                state.text_pos += step;
                state.must_advance = FALSE;
            } else
                state.must_advance = TRUE;
        } else
            /* Don't allow 2 contiguous zero-width matches. */
            state.must_advance = state.match_pos == state.text_pos;
#endif
    }

    /* Get the segment following the last match. We use 'length' instead of
     * 'text_length' because the latter is truncated to 'slice_end', a
     * documented idiosyncracy of the 're' module.
     */
    end_pos = state.reverse ? 0 : str_info.length;
    if (last_pos != end_pos) {
        int status;

        /* The segment is part of the original string. */
        if (state.reverse)
            item = get_slice(string, 0, last_pos);
        else
            item = get_slice(string, last_pos, str_info.length);
        if (!item)
            goto error;

        status = add_to_join_list(&join_info, item);
        Py_DECREF(item);
        if (status < 0)
            goto error;
    }

    Py_XDECREF(replacement);

    /* Convert the list to a single string (also cleans up join_info). */
    item = join_list_info(&join_info);

    state_fini(&state);

    if (built_capture) {
        Py_DECREF(kwargs);
        Py_DECREF(args);
    }

    if (!item)
        return NULL;

    if (sub_type & RE_SUBN)
        return Py_BuildValue("Nn", item, sub_count);

    return item;

error:
    if (built_capture) {
        Py_DECREF(kwargs);
        Py_DECREF(args);
    }

    clear_join_list(&join_info);
    state_fini(&state);
    Py_XDECREF(replacement);
    return NULL;
}

/* PatternObject's 'sub' method. */
static PyObject* pattern_sub(PatternObject* self, PyObject* args, PyObject*
  kwargs) {
    int conc;
    Py_ssize_t tim;

    PyObject* replacement;
    PyObject* string;
    Py_ssize_t count = 0;
    PyObject* pos = Py_None;
    PyObject* endpos = Py_None;
    PyObject* concurrent = Py_None;
    PyObject* timeout = Py_None;
    static char* kwlist[] = { "repl", "string", "count", "pos", "endpos",
      "concurrent", "timeout", NULL };
    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "OO|nOOOO:sub", kwlist,
      &replacement, &string, &count, &pos, &endpos, &concurrent, &timeout))
        return NULL;

    conc = decode_concurrent(concurrent);
    if (conc < 0)
        return NULL;

    tim = decode_timeout(timeout);
    if (tim == RE_BAD_TIMEOUT)
        return NULL;

    return pattern_subx(self, replacement, string, count, RE_SUB, pos, endpos,
      conc, tim);
}

/* PatternObject's 'subf' method. */
static PyObject* pattern_subf(PatternObject* self, PyObject* args, PyObject*
  kwargs) {
    int conc;
    Py_ssize_t tim;

    PyObject* format;
    PyObject* string;
    Py_ssize_t count = 0;
    PyObject* pos = Py_None;
    PyObject* endpos = Py_None;
    PyObject* concurrent = Py_None;
    PyObject* timeout = Py_None;
    static char* kwlist[] = { "format", "string", "count", "pos", "endpos",
      "concurrent", "timeout", NULL };
    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "OO|nOOOO:sub", kwlist,
      &format, &string, &count, &pos, &endpos, &concurrent, &timeout))
        return NULL;

    conc = decode_concurrent(concurrent);
    if (conc < 0)
        return NULL;

    tim = decode_timeout(timeout);
    if (tim == RE_BAD_TIMEOUT)
        return NULL;

    return pattern_subx(self, format, string, count, RE_SUBF, pos, endpos,
      conc, tim);
}

/* PatternObject's 'subn' method. */
static PyObject* pattern_subn(PatternObject* self, PyObject* args, PyObject*
  kwargs) {
    int conc;
    Py_ssize_t tim;

    PyObject* replacement;
    PyObject* string;
    Py_ssize_t count = 0;
    PyObject* pos = Py_None;
    PyObject* endpos = Py_None;
    PyObject* concurrent = Py_None;
    PyObject* timeout = Py_None;
    static char* kwlist[] = { "repl", "string", "count", "pos", "endpos",
      "concurrent", "timeout", NULL };
    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "OO|nOOOO:subn", kwlist,
      &replacement, &string, &count, &pos, &endpos, &concurrent, &timeout))
        return NULL;

    conc = decode_concurrent(concurrent);
    if (conc < 0)
        return NULL;

    tim = decode_timeout(timeout);
    if (tim == RE_BAD_TIMEOUT)
        return NULL;

    return pattern_subx(self, replacement, string, count, RE_SUBN, pos, endpos,
      conc, tim);
}

/* PatternObject's 'subfn' method. */
static PyObject* pattern_subfn(PatternObject* self, PyObject* args, PyObject*
  kwargs) {
    int conc;
    Py_ssize_t tim;

    PyObject* format;
    PyObject* string;
    Py_ssize_t count = 0;
    PyObject* pos = Py_None;
    PyObject* endpos = Py_None;
    PyObject* concurrent = Py_None;
    PyObject* timeout = Py_None;
    static char* kwlist[] = { "format", "string", "count", "pos", "endpos",
      "concurrent", "timeout", NULL };
    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "OO|nOOOO:subn", kwlist,
      &format, &string, &count, &pos, &endpos, &concurrent, &timeout))
        return NULL;

    conc = decode_concurrent(concurrent);
    if (conc < 0)
        return NULL;

    tim = decode_timeout(timeout);
    if (tim == RE_BAD_TIMEOUT)
        return NULL;

    return pattern_subx(self, format, string, count, RE_SUBF | RE_SUBN, pos,
      endpos, conc, tim);
}

/* PatternObject's 'split' method. */
static PyObject* pattern_split(PatternObject* self, PyObject* args, PyObject*
  kwargs) {
    int conc;
    Py_ssize_t tim;
    RE_State state;
    PyObject* list;
    PyObject* item;
    int status;
    Py_ssize_t split_count;
    size_t g;
    Py_ssize_t start_pos;
#if PY_VERSION_HEX < 0x03070000
    Py_ssize_t end_pos;
    Py_ssize_t step;
#endif
    Py_ssize_t last_pos;

    PyObject* string;
    Py_ssize_t maxsplit = 0;
    PyObject* concurrent = Py_None;
    PyObject* timeout = Py_None;
    static char* kwlist[] = { "string", "maxsplit", "concurrent", "timeout",
      NULL };
    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "O|nOO:split", kwlist,
      &string, &maxsplit, &concurrent, &timeout))
        return NULL;

    if (maxsplit == 0)
        maxsplit = PY_SSIZE_T_MAX;

    conc = decode_concurrent(concurrent);
    if (conc < 0)
        return NULL;

    tim = decode_timeout(timeout);
    if (tim == RE_BAD_TIMEOUT)
        return NULL;

    /* The MatchObject, and therefore repeated captures, will not be visible.
     */
    if (!state_init(&state, self, string, 0, PY_SSIZE_T_MAX, FALSE, conc,
      FALSE, FALSE, FALSE, FALSE, tim))
        return NULL;

    list = PyList_New(0);
    if (!list) {
        state_fini(&state);
        return NULL;
    }

    split_count = 0;
    if (state.reverse) {
        start_pos = state.text_length;
#if PY_VERSION_HEX < 0x03070000
        end_pos = 0;
        step = -1;
#endif
    } else {
        start_pos = 0;
#if PY_VERSION_HEX < 0x03070000
        end_pos = state.text_length;
        step = 1;
#endif
    }

    last_pos = start_pos;
    while (split_count < maxsplit) {
        status = do_match(&state, TRUE);
        if (status < 0)
            goto error;

        if (status == 0)
            /* No more matches. */
            break;

#if PY_VERSION_HEX < 0x03070000
        if (state.version_0) {
            /* Version 0 behaviour is to advance one character if the split was
             * zero-width. Unfortunately, this can give an incorrect result.
             * GvR wants this behaviour to be retained so as not to break any
             * existing software which might rely on it.
             */
            if (state.text_pos == state.match_pos) {
                if (last_pos == end_pos)
                    break;

                /* Advance one character. */
                state.text_pos += step;
                state.must_advance = FALSE;
                continue;
            }
        }

#endif
        /* Get segment before this match. */
        if (state.reverse)
            item = get_slice(string, state.match_pos, last_pos);
        else
            item = get_slice(string, last_pos, state.match_pos);
        if (!item)
            goto error;

        status = PyList_Append(list, item);
        Py_DECREF(item);
        if (status < 0)
            goto error;

        /* Add groups (if any). */
        for (g = 1; g <= self->public_group_count; g++) {
            item = state_get_group(&state, (Py_ssize_t)g, string, FALSE);
            if (!item)
                goto error;

            status = PyList_Append(list, item);
            Py_DECREF(item);
            if (status < 0)
                goto error;
        }

        ++split_count;
        last_pos = state.text_pos;

#if PY_VERSION_HEX >= 0x03070000
        /* Don't allow 2 contiguous zero-width matches. */
        state.must_advance = state.text_pos == state.match_pos;
#else
        /* Version 0 behaviour is to advance one character if the match was
         * zero-width. Unfortunately, this can give an incorrect result. GvR
         * wants this behaviour to be retained so as not to break any existing
         * software which might rely on it.
         */
        if (state.version_0) {
            if (state.text_pos == state.match_pos)
                /* Advance one character. */
                state.text_pos += step;

            state.must_advance = FALSE;
        } else
            /* Don't allow a contiguous zero-width match. */
            state.must_advance = TRUE;
#endif
    }

    /* Get segment following last match (even if empty). */
    if (state.reverse)
        item = get_slice(string, 0, last_pos);
    else
        item = get_slice(string, last_pos, state.text_length);
    if (!item)
        goto error;

    status = PyList_Append(list, item);
    Py_DECREF(item);
    if (status < 0)
        goto error;

    state_fini(&state);

    return list;

error:
    Py_DECREF(list);
    state_fini(&state);
    return NULL;
}

/* PatternObject's 'splititer' method. */
static PyObject* pattern_splititer(PatternObject* pattern, PyObject* args,
  PyObject* kwargs) {
    return pattern_splitter(pattern, args, kwargs);
}

/* PatternObject's 'findall' method. */
static PyObject* pattern_findall(PatternObject* self, PyObject* args, PyObject*
  kwargs) {
    Py_ssize_t start;
    Py_ssize_t end;
    int conc;
    Py_ssize_t tim;
    RE_State state;
    PyObject* list;
    Py_ssize_t step;
    int status;
    Py_ssize_t b;
    Py_ssize_t e;
    size_t g;

    PyObject* string;
    PyObject* pos = Py_None;
    PyObject* endpos = Py_None;
    Py_ssize_t overlapped = FALSE;
    PyObject* concurrent = Py_None;
    PyObject* timeout = Py_None;
    static char* kwlist[] = { "string", "pos", "endpos", "overlapped",
      "concurrent", "timeout", NULL };
    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "O|OOnOO:findall", kwlist,
      &string, &pos, &endpos, &overlapped, &concurrent, &timeout))
        return NULL;

    start = as_string_index(pos, 0);
    if (start == -1 && PyErr_Occurred())
        return NULL;

    end = as_string_index(endpos, PY_SSIZE_T_MAX);
    if (end == -1 && PyErr_Occurred())
        return NULL;

    conc = decode_concurrent(concurrent);
    if (conc < 0)
        return NULL;

    tim = decode_timeout(timeout);
    if (tim == RE_BAD_TIMEOUT)
        return NULL;

    /* The MatchObject, and therefore repeated captures, will not be visible.
     */
    if (!state_init(&state, self, string, start, end, overlapped != 0, conc,
      FALSE, FALSE, FALSE, FALSE, tim))
        return NULL;

    list = PyList_New(0);
    if (!list) {
        state_fini(&state);
        return NULL;
    }

    step = state.reverse ? -1 : 1;
    while (state.slice_start <= state.text_pos && state.text_pos <=
      state.slice_end) {
        PyObject* item;

        status = do_match(&state, TRUE);
        if (status < 0)
            goto error;

        if (status == 0)
            break;

        /* Don't bother to build a MatchObject. */
        switch (self->visible_capture_count) {
        case 0:
            if (state.reverse) {
                b = state.text_pos;
                e = state.match_pos;
            } else {
                b = state.match_pos;
                e = state.text_pos;
            }
            item = get_slice(string, b, e);
            if (!item)
                goto error;
            break;
        case 1:
            item = state_get_group(&state, 1, string, TRUE);
            if (!item)
                goto error;
            break;
        default:
            item = PyTuple_New((Py_ssize_t)self->public_group_count);
            if (!item)
                goto error;

            for (g = 0; g < self->public_group_count; g++) {
                PyObject* o;

                o = state_get_group(&state, (Py_ssize_t)g + 1, string, TRUE);
                if (!o) {
                    Py_DECREF(item);
                    goto error;
                }

                /* PyTuple_SET_ITEM borrows the reference. */
                PyTuple_SET_ITEM(item, g, o);
            }
            break;
        }

        status = PyList_Append(list, item);
        Py_DECREF(item);
        if (status < 0)
            goto error;

        if (state.overlapped) {
            /* Advance one character. */
            state.text_pos = state.match_pos + step;
            state.must_advance = FALSE;
        } else
            /* Don't allow 2 contiguous zero-width matches. */
            state.must_advance = state.text_pos == state.match_pos;
    }

    state_fini(&state);

    return list;

error:
    Py_DECREF(list);
    state_fini(&state);
    return NULL;
}

/* PatternObject's 'finditer' method. */
static PyObject* pattern_finditer(PatternObject* pattern, PyObject* args,
  PyObject* kwargs) {
    return pattern_scanner(pattern, args, kwargs);
}

/* Makes a copy of a PatternObject.
 *
 * It actually doesn't make a copy, just returns the original object.
 */
Py_LOCAL_INLINE(PyObject*) make_pattern_copy(PatternObject* self) {
    Py_INCREF(self);
    return (PyObject*)self;
}

/* PatternObject's '__copy__' method. */
static PyObject* pattern_copy(PatternObject* self, PyObject* unused) {
    return make_pattern_copy(self);
}

/* PatternObject's '__deepcopy__' method. */
static PyObject* pattern_deepcopy(PatternObject* self, PyObject* memo) {
    return make_pattern_copy(self);
}

/* The documentation of a PatternObject. */
PyDoc_STRVAR(pattern_match_doc,
    "match(string, pos=None, endpos=None, concurrent=None, timeout=None) --> MatchObject or None.\n\
    Match zero or more characters at the beginning of the string.");

PyDoc_STRVAR(pattern_fullmatch_doc,
    "fullmatch(string, pos=None, endpos=None, concurrent=None, timeout=None) --> MatchObject or None.\n\
    Match zero or more characters against all of the string.");

PyDoc_STRVAR(pattern_search_doc,
    "search(string, pos=None, endpos=None, concurrent=None, timeout=None) --> MatchObject or None.\n\
    Search through string looking for a match, and return a corresponding\n\
    match object instance.  Return None if no match is found.");

PyDoc_STRVAR(pattern_sub_doc,
    "sub(repl, string, count=0, flags=0, pos=None, endpos=None, concurrent=None, timeout=None) --> newstring\n\
    Return the string obtained by replacing the leftmost (or rightmost with a\n\
    reverse pattern) non-overlapping occurrences of pattern in string by the\n\
    replacement repl.");

PyDoc_STRVAR(pattern_subf_doc,
    "subf(format, string, count=0, flags=0, pos=None, endpos=None, concurrent=None, timeout=None) --> newstring\n\
    Return the string obtained by replacing the leftmost (or rightmost with a\n\
    reverse pattern) non-overlapping occurrences of pattern in string by the\n\
    replacement format.");

PyDoc_STRVAR(pattern_subn_doc,
    "subn(repl, string, count=0, flags=0, pos=None, endpos=None, concurrent=None, timeout=None) --> (newstring, number of subs)\n\
    Return the tuple (new_string, number_of_subs_made) found by replacing the\n\
    leftmost (or rightmost with a reverse pattern) non-overlapping occurrences\n\
    of pattern with the replacement repl.");

PyDoc_STRVAR(pattern_subfn_doc,
    "subfn(format, string, count=0, flags=0, pos=None, endpos=None, concurrent=None, timeout=None) --> (newstring, number of subs)\n\
    Return the tuple (new_string, number_of_subs_made) found by replacing the\n\
    leftmost (or rightmost with a reverse pattern) non-overlapping occurrences\n\
    of pattern with the replacement format.");

PyDoc_STRVAR(pattern_split_doc,
    "split(string, string, maxsplit=0, concurrent=None, timeout=None) --> list.\n\
    Split string by the occurrences of pattern.");

PyDoc_STRVAR(pattern_splititer_doc,
    "splititer(string, maxsplit=0, concurrent=None, timeout=None) --> iterator.\n\
    Return an iterator yielding the parts of a split string.");

PyDoc_STRVAR(pattern_findall_doc,
    "findall(string, pos=None, endpos=None, overlapped=False, concurrent=None, timeout=None) --> list.\n\
    Return a list of all matches of pattern in string.  The matches may be\n\
    overlapped if overlapped is True.");

PyDoc_STRVAR(pattern_finditer_doc,
    "finditer(string, pos=None, endpos=None, overlapped=False, concurrent=None, timeout=None) --> iterator.\n\
    Return an iterator over all matches for the RE pattern in string.  The\n\
    matches may be overlapped if overlapped is True.  For each match, the\n\
    iterator returns a MatchObject.");

PyDoc_STRVAR(pattern_scanner_doc,
    "scanner(string, pos=None, endpos=None, overlapped=False, concurrent=None, timeout=None) --> scanner.\n\
    Return an scanner for the RE pattern in string.  The matches may be overlapped\n\
    if overlapped is True.");

/* The methods of a PatternObject. */
static PyMethodDef pattern_methods[] = {
    {"match", (PyCFunction)pattern_match, METH_VARARGS|METH_KEYWORDS,
      pattern_match_doc},
    {"fullmatch", (PyCFunction)pattern_fullmatch, METH_VARARGS|METH_KEYWORDS,
      pattern_fullmatch_doc},
    {"search", (PyCFunction)pattern_search, METH_VARARGS|METH_KEYWORDS,
      pattern_search_doc},
    {"sub", (PyCFunction)pattern_sub, METH_VARARGS|METH_KEYWORDS,
      pattern_sub_doc},
    {"subf", (PyCFunction)pattern_subf, METH_VARARGS|METH_KEYWORDS,
      pattern_subf_doc},
    {"subn", (PyCFunction)pattern_subn, METH_VARARGS|METH_KEYWORDS,
      pattern_subn_doc},
    {"subfn", (PyCFunction)pattern_subfn, METH_VARARGS|METH_KEYWORDS,
      pattern_subfn_doc},
    {"split", (PyCFunction)pattern_split, METH_VARARGS|METH_KEYWORDS,
      pattern_split_doc},
    {"splititer", (PyCFunction)pattern_splititer, METH_VARARGS|METH_KEYWORDS,
      pattern_splititer_doc},
    {"findall", (PyCFunction)pattern_findall, METH_VARARGS|METH_KEYWORDS,
      pattern_findall_doc},
    {"finditer", (PyCFunction)pattern_finditer, METH_VARARGS|METH_KEYWORDS,
      pattern_finditer_doc},
    {"scanner", (PyCFunction)pattern_scanner, METH_VARARGS|METH_KEYWORDS,
      pattern_scanner_doc},
    {"__copy__", (PyCFunction)pattern_copy, METH_NOARGS},
    {"__deepcopy__", (PyCFunction)pattern_deepcopy, METH_O},
    {NULL, NULL}
};

PyDoc_STRVAR(pattern_doc, "Compiled regex object");

/* Deallocates a PatternObject. */
static void pattern_dealloc(PyObject* self_) {
    PatternObject* self;
    size_t i;
    int partial_side;

    self = (PatternObject*)self_;

    /* Discard the nodes. */
    for (i = 0; i < self->node_count; i++) {
        RE_Node* node;

        node = self->node_list[i];
        re_dealloc(node->values);
        if (node->status & RE_STATUS_STRING) {
            re_dealloc(node->string.bad_character_offset);
            re_dealloc(node->string.good_suffix_offset);
        }
        re_dealloc(node);
    }
    re_dealloc(self->node_list);

    /* Discard the group info. */
    re_dealloc(self->group_info);

    /* Discard the call_ref info. */
    re_dealloc(self->call_ref_info);

    /* Discard the repeat info. */
    re_dealloc(self->repeat_info);

    dealloc_groups(self->groups_storage, self->true_group_count);

    dealloc_repeats(self->repeats_storage, self->repeat_count);

    re_dealloc(self->stack_storage);

    if (self->weakreflist)
        PyObject_ClearWeakRefs((PyObject*)self);
    Py_XDECREF(self->pattern);
    Py_XDECREF(self->groupindex);
    Py_XDECREF(self->indexgroup);

    for (partial_side = 0; partial_side < 2; partial_side++) {
        if (self->partial_named_lists[partial_side]) {
            for (i = 0; i < self->named_lists_count; i++)
                Py_XDECREF(self->partial_named_lists[partial_side][i]);

            re_dealloc(self->partial_named_lists[partial_side]);
        }
    }

    Py_DECREF(self->named_lists);
    Py_DECREF(self->named_list_indexes);
    Py_DECREF(self->required_chars);
    re_dealloc(self->locale_info);
    Py_DECREF(self->packed_code_list);
    PyObject_DEL(self);
}

/* Info about the various flags that can be passed in. */
typedef struct RE_FlagName {
    char* name;
    int value;
} RE_FlagName;

/* We won't bother about the U flag in Python 3. */
static RE_FlagName flag_names[] = {
    {"A", RE_FLAG_ASCII},
    {"B", RE_FLAG_BESTMATCH},
    {"D", RE_FLAG_DEBUG},
    {"S", RE_FLAG_DOTALL},
    {"F", RE_FLAG_FULLCASE},
    {"I", RE_FLAG_IGNORECASE},
    {"L", RE_FLAG_LOCALE},
    {"M", RE_FLAG_MULTILINE},
    {"P", RE_FLAG_POSIX},
    {"R", RE_FLAG_REVERSE},
    {"T", RE_FLAG_TEMPLATE},
    {"X", RE_FLAG_VERBOSE},
    {"V0", RE_FLAG_VERSION0},
    {"V1", RE_FLAG_VERSION1},
    {"W", RE_FLAG_WORD},
};

/* Appends a string to a list. */
Py_LOCAL_INLINE(BOOL) append_string(PyObject* list, char* string) {
    PyObject* item;
    int status;

    item = Py_BuildValue("U", string);
    if (!item)
        return FALSE;

    status = PyList_Append(list, item);
    Py_DECREF(item);
    if (status < 0)
        return FALSE;

    return TRUE;
}

/* Appends a (decimal) integer to a list. */
Py_LOCAL_INLINE(BOOL) append_integer(PyObject* list, Py_ssize_t value) {
    PyObject* int_obj;
    PyObject* repr_obj;
    int status;

    int_obj = Py_BuildValue("n", value);
    if (!int_obj)
        return FALSE;

    repr_obj = PyObject_Repr(int_obj);
    Py_DECREF(int_obj);
    if (!repr_obj)
        return FALSE;

    status = PyList_Append(list, repr_obj);
    Py_DECREF(repr_obj);
    if (status < 0)
        return FALSE;

    return TRUE;
}

/* Packs the code list that's needed for pickling. */
Py_LOCAL_INLINE(PyObject*) pack_code_list(RE_CODE* code, Py_ssize_t code_len) {
    Py_ssize_t max_size;
    RE_UINT8* packed;
    Py_ssize_t count;
    RE_UINT32 value;
    Py_ssize_t i;
    PyObject* packed_code_list;

    /* What is the maximum number of bytes needed to store it?
     *
     * A 32-bit RE_CODE might need 5 bytes ((32 + 6) / 7).
     */
    max_size = code_len * 5 + (Py_ssize_t)((sizeof(Py_ssize_t) * 8) + 6) / 7;

    packed = (RE_UINT8*)re_alloc((size_t)max_size);
    count = 0;

    /* Store the length of the code list. */
    value = (RE_UINT32)code_len;

    while (value >= 0x80) {
        packed[count++] = 0x80 | (RE_UINT8)(value & 0x7F);
        value >>= 7;
    }

    packed[count++] = (RE_UINT8)value;

    /* Store each of the elements of the code list. */
    for (i = 0; i < code_len; i++) {
        value = (RE_UINT32)code[i];

        while (value >= 0x80) {
            packed[count++] = 0x80 | (RE_UINT8)(value & 0x7F);
            value >>= 7;
        }

        packed[count++] = (RE_UINT8)value;
    }

    packed_code_list = PyBytes_FromStringAndSize((const char *)packed, count);
    re_dealloc(packed);

    return packed_code_list;
}

/* Unpacks the code list that's needed for pickling. */
Py_LOCAL_INLINE(PyObject*) unpack_code_list(PyObject* packed) {
    PyObject* code_list;
    RE_UINT8* packed_data;
    Py_ssize_t index;
    RE_UINT32 value;
    int shift;
    size_t count;

    code_list = PyList_New(0);
    if (!code_list)
        return NULL;

    packed_data = (RE_UINT8*)PyBytes_AsString(packed);
    index = 0;

    /* Unpack the length of the code list. */
    value = 0;
    shift = 0;

    while (packed_data[index] >= 0x80) {
        value |= (RE_UINT32)(packed_data[index++] & 0x7F) << shift;
        shift += 7;
    }

    value |= (RE_UINT32)packed_data[index++] << shift;
    count = (size_t)value;

    /* Unpack each of the elements of the code list. */
    while (count > 0) {
        PyObject* obj;
        int status;

        value = 0;
        shift = 0;

        while (packed_data[index] >= 0x80) {
            value |= (RE_UINT32)(packed_data[index++] & 0x7F) << shift;
            shift += 7;
        }

        value |= (RE_UINT32)packed_data[index++] << shift;
        obj = PyLong_FromSize_t((size_t)value);
        if (!obj)
            goto error;

        status = PyList_Append(code_list, obj);
        Py_DECREF(obj);
        if (status == -1)
            goto error;

        --count;
    }

    return code_list;

error:
    Py_DECREF(code_list);
    return NULL;
}

/* MatchObject's '__repr__' method. */
static PyObject* match_repr(PyObject* self_) {
    MatchObject* self;
    PyObject* list;
    PyObject* matched_substring;
    PyObject* matched_repr;
    int status;
    PyObject* separator;
    PyObject* result;

    self = (MatchObject*)self_;

    list = PyList_New(0);
    if (!list)
        return NULL;

    if (!append_string(list, "<regex.Match object; span=("))
        goto error;

    if (!append_integer(list, self->match_start))
        goto error;

    if (!append_string(list, ", "))
        goto error;

    if (!append_integer(list, self->match_end))
        goto error;

    if (!append_string(list, "), match="))
        goto error;

    matched_substring = get_slice(self->substring, self->match_start -
      self->substring_offset, self->match_end - self->substring_offset);
    if (!matched_substring)
        goto error;

    matched_repr = PyObject_Repr(matched_substring);
    Py_DECREF(matched_substring);
    if (!matched_repr)
        goto error;

    status = PyList_Append(list, matched_repr);
    Py_DECREF(matched_repr);
    if (status < 0)
        goto error;

    if (self->fuzzy_counts[RE_FUZZY_SUB] != 0 ||
      self->fuzzy_counts[RE_FUZZY_INS] != 0 || self->fuzzy_counts[RE_FUZZY_DEL]
      != 0) {
        if (!append_string(list, ", fuzzy_counts=("))
            goto error;

        if (!append_integer(list,
          (Py_ssize_t)self->fuzzy_counts[RE_FUZZY_SUB]))
            goto error;

        if (!append_string(list, ", "))
            goto error;

        if (!append_integer(list,
          (Py_ssize_t)self->fuzzy_counts[RE_FUZZY_INS]))
            goto error;

        if (!append_string(list, ", "))
            goto error;
        if (!append_integer(list,
          (Py_ssize_t)self->fuzzy_counts[RE_FUZZY_DEL]))
            goto error;

        if (!append_string(list, ")"))
            goto error;
    }

    if (self->partial) {
        if (!append_string(list, ", partial=True"))
            goto error;
    }

    if (!append_string(list, ">"))
        goto error;

    separator = Py_BuildValue("U", "");
    if (!separator)
        goto error;

    result = PyUnicode_Join(separator, list);
    Py_DECREF(separator);
    Py_DECREF(list);

    return result;

error:
    Py_DECREF(list);
    return NULL;
}

/* PatternObject's '__repr__' method. */
static PyObject* pattern_repr(PyObject* self_) {
    PatternObject* self;
    PyObject* list;
    PyObject* item;
    int status;
    int flag_count;
    unsigned int i;
    Py_ssize_t pos;
    PyObject* key;
    PyObject* value;
    PyObject* separator;
    PyObject* result;

    self = (PatternObject*)self_;

    list = PyList_New(0);
    if (!list)
        return NULL;

    if (!append_string(list, "regex.Regex("))
        goto error;

    item = PyObject_Repr(self->pattern);
    if (!item)
        goto error;

    status = PyList_Append(list, item);
    Py_DECREF(item);
    if (status < 0)
        goto error;

    flag_count = 0;
    for (i = 0; i < sizeof(flag_names) / sizeof(flag_names[0]); i++) {
        if (self->flags & flag_names[i].value) {
            if (flag_count == 0) {
                if (!append_string(list, ", flags="))
                    goto error;
            } else {
                if (!append_string(list, " | "))
                    goto error;
            }

            if (!append_string(list, "regex."))
                goto error;

            if (!append_string(list, flag_names[i].name))
                goto error;

            ++flag_count;
        }
    }

    pos = 0;
    /* PyDict_Next borrows references. */
    while (PyDict_Next(self->named_lists, &pos, &key, &value)) {
        if (!append_string(list, ", "))
            goto error;

        status = PyList_Append(list, key);
        if (status < 0)
            goto error;

        if (!append_string(list, "="))
            goto error;

        item = PyObject_Repr(value);
        if (!item)
            goto error;

        status = PyList_Append(list, item);
        Py_DECREF(item);
        if (status < 0)
            goto error;
    }

    if (!append_string(list, ")"))
        goto error;

    separator = Py_BuildValue("U", "");
    if (!separator)
        goto error;

    result = PyUnicode_Join(separator, list);
    Py_DECREF(separator);
    Py_DECREF(list);

    return result;

error:
    Py_DECREF(list);
    return NULL;
}

/* PatternObject's 'groupindex' method. */
static PyObject* pattern_groupindex(PyObject* self_) {
    PatternObject* self;

    self = (PatternObject*)self_;

    return PyDict_Copy(self->groupindex);
}

/* PatternObject's '_pickled_data' method. */
static PyObject* pattern_pickled_data(PyObject* self_) {
    PatternObject* self;
    PyObject* pickled_data;

    self = (PatternObject*)self_;

    /* Build the data needed for picking. */
    pickled_data = Py_BuildValue("OnOOOOOnOnn", self->pattern, self->flags,
      self->packed_code_list, self->groupindex, self->indexgroup,
      self->named_lists, self->named_list_indexes, self->req_offset,
      self->required_chars, self->req_flags, self->public_group_count);

    return pickled_data;
}

static PyGetSetDef pattern_getset[] = {
    {"groupindex", (getter)pattern_groupindex, (setter)NULL,
      "A dictionary mapping group names to group numbers."},
    {"_pickled_data", (getter)pattern_pickled_data, (setter)NULL,
      "Data used for pickling."},
    {NULL} /* Sentinel */
};

static PyMemberDef pattern_members[] = {
    {"pattern", T_OBJECT, offsetof(PatternObject, pattern), READONLY,
      "The pattern string from which the regex object was compiled."},
    {"flags", T_PYSSIZET, offsetof(PatternObject, flags), READONLY,
      "The regex matching flags."},
    {"groups", T_PYSSIZET, offsetof(PatternObject, public_group_count),
      READONLY, "The number of capturing groups in the pattern."},
    {"named_lists", T_OBJECT, offsetof(PatternObject, named_lists), READONLY,
      "The named lists used by the regex."},
    {NULL} /* Sentinel */
};

static PyTypeObject Pattern_Type = {
    PyVarObject_HEAD_INIT(NULL, 0)
    "_regex.Pattern",
    sizeof(PatternObject)
};

/* Building the nodes is made simpler by allowing branches to have a single
 * exit. These need to be removed.
 */
Py_LOCAL_INLINE(void) skip_one_way_branches(PatternObject* pattern) {
    BOOL modified;

    /* If a node refers to a 1-way branch then make the former refer to the
     * latter's destination. Repeat until they're all done.
     */
    do {
        size_t i;

        modified = FALSE;

        for (i = 0; i < pattern->node_count; i++) {
            RE_Node* node;
            RE_Node* next;

            node = pattern->node_list[i];

            /* Check the first destination. */
            next = node->next_1.node;
            if (next && next->op == RE_OP_BRANCH &&
              !next->nonstring.next_2.node) {
                node->next_1.node = next->next_1.node;
                modified = TRUE;
            }

            /* Check the second destination. */
            next = node->nonstring.next_2.node;
            if (next && next->op == RE_OP_BRANCH &&
              !next->nonstring.next_2.node) {
                node->nonstring.next_2.node = next->next_1.node;
                modified = TRUE;
            }
        }
    } while (modified);

    /* The start node might be a 1-way branch. Skip over it because it'll be
     * removed. It might even be the first in a chain.
     */
    while (pattern->start_node->op == RE_OP_BRANCH &&
      !pattern->start_node->nonstring.next_2.node)
        pattern->start_node = pattern->start_node->next_1.node;
}

/* Initialises a check stack. */
Py_LOCAL_INLINE(void) CheckStack_init(RE_CheckStack* stack) {
    stack->capacity = 0;
    stack->count = 0;
    stack->items = NULL;
}

/* Finalises a check stack. */
Py_LOCAL_INLINE(void) CheckStack_fini(RE_CheckStack* stack) {
    PyMem_Free(stack->items);
    stack->capacity = 0;
    stack->count = 0;
    stack->items = NULL;
}

/* Pushes an item onto a check stack. */
Py_LOCAL_INLINE(BOOL) CheckStack_push(RE_CheckStack* stack, RE_Node* node,
  RE_STATUS_T result) {
    RE_Check* check;

    if (stack->count >= stack->capacity) {
        size_t new_capacity;
        RE_Check* new_items;

        new_capacity = stack->capacity * 2;
        if (new_capacity == 0)
            new_capacity = 16;

        new_items = (RE_Check*)PyMem_Realloc(stack->items, new_capacity *
          sizeof(RE_Check));
        if (!new_items)
            return FALSE;

        stack->capacity = new_capacity;
        stack->items = new_items;
    }

    check = &stack->items[stack->count++];
    check->node = node;
    check->result = result;

    return TRUE;
}

/* Pops an item off a check stack. Returns NULL if the stack is empty. */
Py_LOCAL_INLINE(RE_Check*) CheckStack_pop(RE_CheckStack* stack) {
    return stack->count > 0 ? &stack->items[--stack->count] : NULL;
}

/* Adds guards to repeats which are followed by a reference to a group. */
Py_LOCAL_INLINE(RE_STATUS_T) add_repeat_guards(PatternObject* pattern, RE_Node*
  start_node) {
    RE_CheckStack stack;

    CheckStack_init(&stack);

    CheckStack_push(&stack, start_node, RE_STATUS_NEITHER);

    for (;;) {
        RE_Check* check;
        RE_Node* node;
        RE_STATUS_T result;

        check = CheckStack_pop(&stack);

        if (!check)
            break;

        node = check->node;
        result = check->result;

        if (!(node->status & RE_STATUS_VISITED_AG)) {
            switch (check->node->op) {
            case RE_OP_BRANCH:
            {
                RE_Node* branch_1;
                RE_Node* branch_2;
                BOOL visited_branch_1;
                BOOL visited_branch_2;

                branch_1 = node->next_1.node;
                branch_2 = node->nonstring.next_2.node;
                visited_branch_1 = (branch_1->status & RE_STATUS_VISITED_AG);
                visited_branch_2 = (branch_2->status & RE_STATUS_VISITED_AG);

                if (visited_branch_1 && visited_branch_2) {
                    RE_STATUS_T branch_1_result;
                    RE_STATUS_T branch_2_result;

                    branch_1_result = branch_1->status & (RE_STATUS_REPEAT |
                      RE_STATUS_REF);
                    branch_2_result = branch_2->status & (RE_STATUS_REPEAT |
                      RE_STATUS_REF);

                    node->status |= RE_STATUS_VISITED_AG | max_status_3(result,
                      branch_1_result, branch_2_result);
                } else {
                    CheckStack_push(&stack, node, result);
                    if (!visited_branch_2)
                        CheckStack_push(&stack, branch_2, RE_STATUS_NEITHER);
                    if (!visited_branch_1)
                        CheckStack_push(&stack, branch_1, RE_STATUS_NEITHER);
                }
                break;
            }
            case RE_OP_END_GREEDY_REPEAT:
            case RE_OP_END_LAZY_REPEAT:
                node->status |= RE_STATUS_VISITED_AG;
                break;
            case RE_OP_GREEDY_REPEAT:
            case RE_OP_LAZY_REPEAT:
            {
                BOOL limited;
                RE_Node* body;
                RE_Node* tail;
                BOOL visited_body;
                BOOL visited_tail;

                limited = ~node->values[2] != 0;

                body = node->next_1.node;
                tail = node->nonstring.next_2.node;
                visited_body = (body->status & RE_STATUS_VISITED_AG);
                visited_tail = (tail->status & RE_STATUS_VISITED_AG);

                if (visited_body && visited_tail) {
                    RE_STATUS_T body_result;
                    RE_STATUS_T tail_result;
                    RE_RepeatInfo* repeat_info;

                    body_result = body->status & (RE_STATUS_REPEAT |
                      RE_STATUS_REF);
                    tail_result = tail->status & (RE_STATUS_REPEAT |
                      RE_STATUS_REF);

                    repeat_info = &pattern->repeat_info[node->values[0]];
                    if (body_result != RE_STATUS_REF)
                        repeat_info->status |= RE_STATUS_BODY;
                    if (tail_result != RE_STATUS_REF)
                        repeat_info->status |= RE_STATUS_TAIL;

                    if (limited)
                        result = max_status_2(result, RE_STATUS_LIMITED);
                    else
                        result = max_status_2(result, RE_STATUS_REPEAT);
                    node->status |= RE_STATUS_VISITED_AG | max_status_3(result,
                      body_result, tail_result);
                } else {
                    CheckStack_push(&stack, node, result);
                    if (!visited_tail)
                        CheckStack_push(&stack, tail, RE_STATUS_NEITHER);
                    if (!visited_body) {
                        if (limited)
                            body->status |= RE_STATUS_VISITED_AG |
                              RE_STATUS_LIMITED;
                        else
                            CheckStack_push(&stack, body, RE_STATUS_NEITHER);
                    }
                }
                break;
            }
            case RE_OP_GREEDY_REPEAT_ONE:
            case RE_OP_LAZY_REPEAT_ONE:
            {
                RE_Node* tail;
                BOOL visited_tail;

                tail = node->next_1.node;
                visited_tail = (tail->status & RE_STATUS_VISITED_AG);

                if (visited_tail) {
                    BOOL limited;
                    RE_STATUS_T tail_result;
                    RE_RepeatInfo* repeat_info;

                    limited = ~node->values[2] != 0;

                    tail_result = tail->status & (RE_STATUS_REPEAT |
                      RE_STATUS_REF);

                    repeat_info = &pattern->repeat_info[node->values[0]];
                    repeat_info->status |= RE_STATUS_BODY;

                    if (tail_result != RE_STATUS_REF)
                        repeat_info->status |= RE_STATUS_TAIL;

                    if (limited)
                        result = max_status_2(result, RE_STATUS_LIMITED);
                    else
                        result = max_status_2(result, RE_STATUS_REPEAT);
                    node->status |= RE_STATUS_VISITED_AG | max_status_3(result,
                      RE_STATUS_REPEAT, tail_result);
                } else {
                    CheckStack_push(&stack, node, result);
                    CheckStack_push(&stack, tail, RE_STATUS_NEITHER);
                }
                break;
            }
            case RE_OP_GROUP_EXISTS:
            {
                RE_Node* branch_1;
                RE_Node* branch_2;
                BOOL visited_branch_1;
                BOOL visited_branch_2;

                branch_1 = node->next_1.node;
                branch_2 = node->nonstring.next_2.node;
                visited_branch_1 = (branch_1->status & RE_STATUS_VISITED_AG);
                visited_branch_2 = (branch_2->status & RE_STATUS_VISITED_AG);

                if (visited_branch_1 && visited_branch_2) {
                    RE_STATUS_T branch_1_result;
                    RE_STATUS_T branch_2_result;

                    branch_1_result = branch_1->status & (RE_STATUS_REPEAT |
                      RE_STATUS_REF);
                    branch_2_result = branch_2->status & (RE_STATUS_REPEAT |
                      RE_STATUS_REF);

                    node->status |= RE_STATUS_VISITED_AG | max_status_4(result,
                      branch_1_result, branch_2_result, RE_STATUS_REF);
                } else {
                    CheckStack_push(&stack, node, result);
                    if (!visited_branch_2)
                        CheckStack_push(&stack, branch_2, RE_STATUS_NEITHER);
                    if (!visited_branch_1)
                        CheckStack_push(&stack, branch_1, RE_STATUS_NEITHER);
                }
                break;
            }
            case RE_OP_REF_GROUP:
            case RE_OP_REF_GROUP_FLD:
            case RE_OP_REF_GROUP_FLD_REV:
            case RE_OP_REF_GROUP_IGN:
            case RE_OP_REF_GROUP_IGN_REV:
            case RE_OP_REF_GROUP_REV:
            {
                RE_Node* tail;
                BOOL visited_tail;

                tail = node->next_1.node;
                visited_tail = (tail->status & RE_STATUS_VISITED_AG);

                if (visited_tail)
                    node->status |= RE_STATUS_VISITED_AG | RE_STATUS_REF;
                else {
                    CheckStack_push(&stack, node, result);
                    CheckStack_push(&stack, tail, RE_STATUS_NEITHER);
                }
                break;
            }
            case RE_OP_SUCCESS:
                node->status |= RE_STATUS_VISITED_AG | result;
                break;
            default:
            {
                RE_Node* tail;
                BOOL visited_tail;
                RE_STATUS_T tail_result;

                tail = node->next_1.node;
                visited_tail = (tail->status & RE_STATUS_VISITED_AG);

                if (visited_tail) {
                    tail_result = tail->status & (RE_STATUS_REPEAT |
                      RE_STATUS_REF);
                    node->status |= RE_STATUS_VISITED_AG | tail_result;
                } else {
                    CheckStack_push(&stack, node, result);
                    CheckStack_push(&stack, node->next_1.node, result);
                }
                break;
            }
            }
        }
    }

    CheckStack_fini(&stack);

    return start_node->status & (RE_STATUS_REPEAT | RE_STATUS_REF);
}

/* Adds an index to a node's values unless it's already present.
 *
 * 'offset' is the offset of the index count within the values.
 */
Py_LOCAL_INLINE(BOOL) add_index(RE_Node* node, size_t offset, size_t index) {
    size_t index_count;
    size_t first_index;
    size_t i;
    RE_CODE* new_values;

    if (!node)
        return TRUE;

    index_count = node->values[offset];
    first_index = offset + 1;

    /* Is the index already present? */
    for (i = 0; i < index_count; i++) {
        if (node->values[first_index + i] == index)
            return TRUE;
    }

    /* Allocate more space for the new index. */
    new_values = re_realloc(node->values, (node->value_count + 1) *
      sizeof(RE_CODE));
    if (!new_values)
        return FALSE;

    ++node->value_count;
    node->values = new_values;

    node->values[first_index + node->values[offset]++] = (RE_CODE)index;

    return TRUE;
}

/* Records the index of every repeat and fuzzy section within atomic
 * subpatterns and lookarounds.
 */
Py_LOCAL_INLINE(BOOL) record_subpattern_repeats_and_fuzzy_sections(RE_Node*
  parent_node, size_t offset, size_t repeat_count, RE_Node* node) {
    while (node) {
        if (node->status & RE_STATUS_VISITED_REP)
            return TRUE;

        node->status |= RE_STATUS_VISITED_REP;

        switch (node->op) {
        case RE_OP_BRANCH:
        case RE_OP_GROUP_EXISTS:
            if (!record_subpattern_repeats_and_fuzzy_sections(parent_node,
              offset, repeat_count, node->next_1.node))
                return FALSE;
            node = node->nonstring.next_2.node;
            break;
        case RE_OP_END_FUZZY:
            node = node->next_1.node;
            break;
        case RE_OP_END_GREEDY_REPEAT:
        case RE_OP_END_LAZY_REPEAT:
            return TRUE;
        case RE_OP_FUZZY:
            /* Record the fuzzy index. */
            if (!add_index(parent_node, offset, repeat_count +
              node->values[0]))
                return FALSE;
            node = node->next_1.node;
            break;
        case RE_OP_GREEDY_REPEAT:
        case RE_OP_LAZY_REPEAT:
            /* Record the repeat index. */
            if (!add_index(parent_node, offset, node->values[0]))
                return FALSE;
            if (!record_subpattern_repeats_and_fuzzy_sections(parent_node,
              offset, repeat_count, node->next_1.node))
                return FALSE;
            node = node->nonstring.next_2.node;
            break;
        case RE_OP_GREEDY_REPEAT_ONE:
        case RE_OP_LAZY_REPEAT_ONE:
            /* Record the repeat index. */
            if (!add_index(parent_node, offset, node->values[0]))
                return FALSE;
            node = node->next_1.node;
            break;
        default:
            node = node->next_1.node;
            break;
        }
    }

    return TRUE;
}

/* Initialises a node stack. */
Py_LOCAL_INLINE(void) NodeStack_init(RE_NodeStack* stack) {
    stack->capacity = 0;
    stack->count = 0;
    stack->items = NULL;
}

/* Finalises a node stack. */
Py_LOCAL_INLINE(void) NodeStack_fini(RE_NodeStack* stack) {
    PyMem_Free(stack->items);
    stack->capacity = 0;
    stack->count = 0;
    stack->items = NULL;
}

/* Pushes an item onto a node stack. */
Py_LOCAL_INLINE(BOOL) NodeStack_push(RE_NodeStack* stack, RE_Node* node) {
    if (stack->count >= stack->capacity) {
        size_t new_capacity;
        RE_Node** new_items;

        new_capacity = stack->capacity * 2;
        if (new_capacity == 0)
            new_capacity = 16;

        new_items = (RE_Node**)PyMem_Realloc(stack->items, new_capacity *
          sizeof(RE_Node*));
        if (!new_items)
            return FALSE;

        stack->capacity = new_capacity;
        stack->items = new_items;
    }

    stack->items[stack->count++] = node;

    return TRUE;
}

/* Pops an item off a node stack. Returns NULL if the stack is empty. */
Py_LOCAL_INLINE(RE_Node*) NodeStack_pop(RE_NodeStack* stack) {
    return stack->count > 0 ? stack->items[--stack->count] : NULL;
}

/* Marks nodes which are being used as used. */
Py_LOCAL_INLINE(void) use_nodes(RE_Node* node) {
    RE_NodeStack stack;

    NodeStack_init(&stack);

    while (node) {
        while (node && !(node->status & RE_STATUS_USED)) {
            node->status |= RE_STATUS_USED;
            if (!(node->status & RE_STATUS_STRING)) {
                if (node->nonstring.next_2.node)
                    NodeStack_push(&stack, node->nonstring.next_2.node);
            }
            node = node->next_1.node;
        }
        node = NodeStack_pop(&stack);
    }

    NodeStack_fini(&stack);
}

/* Discards any unused nodes.
 *
 * Optimising the nodes might result in some nodes no longer being used.
 */
Py_LOCAL_INLINE(void) discard_unused_nodes(PatternObject* pattern) {
    size_t i;
    size_t new_count;

    /* Mark the nodes which are being used. */
    use_nodes(pattern->start_node);

    for (i = 0; i < pattern->call_ref_info_capacity; i++)
        use_nodes(pattern->call_ref_info[i].node);

    new_count = 0;
    for (i = 0; i < pattern->node_count; i++) {
        RE_Node* node;

        node = pattern->node_list[i];
        if (node->status & RE_STATUS_USED)
            pattern->node_list[new_count++] = node;
        else {
            re_dealloc(node->values);
            if (node->status & RE_STATUS_STRING) {
                re_dealloc(node->string.bad_character_offset);
                re_dealloc(node->string.good_suffix_offset);
            }
            re_dealloc(node);
        }
    }

    pattern->node_count = new_count;
}

/* Marks all the group which are named. Returns FALSE if there's an error. */
Py_LOCAL_INLINE(BOOL) mark_named_groups(PatternObject* pattern) {
    size_t i;

    for (i = 0; i < pattern->public_group_count; i++) {
        RE_GroupInfo* group_info;
        PyObject* index;
        int status;

        group_info = &pattern->group_info[i];
        index = Py_BuildValue("n", i + 1);
        if (!index)
            return FALSE;

        status = PyDict_Contains(pattern->indexgroup, index);
        Py_DECREF(index);
        if (status < 0)
            return FALSE;

        group_info->has_name = status == 1;
    }

    return TRUE;
}

/* Gets the test node.
 *
 * The test node lets the matcher look ahead in the pattern, allowing it to
 * avoid the cost of housekeeping, only to find that what follows doesn't match
 * anyway.
 */
Py_LOCAL_INLINE(void) set_test_node(RE_NextNode* next) {
    RE_Node* node = next->node;
    RE_Node* test;

    next->test = node;
    next->match_next = node;
    next->match_step = 0;

    if (!node)
        return;

    test = node;
    while (test->op == RE_OP_END_GROUP || test->op == RE_OP_START_GROUP)
        test = test->next_1.node;

    next->test = test;

    if (test != node)
        return;

    switch (test->op) {
    case RE_OP_ANY:
    case RE_OP_ANY_ALL:
    case RE_OP_ANY_ALL_REV:
    case RE_OP_ANY_REV:
    case RE_OP_ANY_U:
    case RE_OP_ANY_U_REV:
    case RE_OP_BOUNDARY:
    case RE_OP_CHARACTER:
    case RE_OP_CHARACTER_IGN:
    case RE_OP_CHARACTER_IGN_REV:
    case RE_OP_CHARACTER_REV:
    case RE_OP_DEFAULT_BOUNDARY:
    case RE_OP_DEFAULT_END_OF_WORD:
    case RE_OP_DEFAULT_START_OF_WORD:
    case RE_OP_END_OF_LINE:
    case RE_OP_END_OF_LINE_U:
    case RE_OP_END_OF_STRING:
    case RE_OP_END_OF_STRING_LINE:
    case RE_OP_END_OF_STRING_LINE_U:
    case RE_OP_END_OF_WORD:
    case RE_OP_GRAPHEME_BOUNDARY:
    case RE_OP_PROPERTY:
    case RE_OP_PROPERTY_IGN:
    case RE_OP_PROPERTY_IGN_REV:
    case RE_OP_PROPERTY_REV:
    case RE_OP_RANGE:
    case RE_OP_RANGE_IGN:
    case RE_OP_RANGE_IGN_REV:
    case RE_OP_RANGE_REV:
    case RE_OP_SEARCH_ANCHOR:
    case RE_OP_SET_DIFF:
    case RE_OP_SET_DIFF_IGN:
    case RE_OP_SET_DIFF_IGN_REV:
    case RE_OP_SET_DIFF_REV:
    case RE_OP_SET_INTER:
    case RE_OP_SET_INTER_IGN:
    case RE_OP_SET_INTER_IGN_REV:
    case RE_OP_SET_INTER_REV:
    case RE_OP_SET_SYM_DIFF:
    case RE_OP_SET_SYM_DIFF_IGN:
    case RE_OP_SET_SYM_DIFF_IGN_REV:
    case RE_OP_SET_SYM_DIFF_REV:
    case RE_OP_SET_UNION:
    case RE_OP_SET_UNION_IGN:
    case RE_OP_SET_UNION_IGN_REV:
    case RE_OP_SET_UNION_REV:
    case RE_OP_START_OF_LINE:
    case RE_OP_START_OF_LINE_U:
    case RE_OP_START_OF_STRING:
    case RE_OP_START_OF_WORD:
    case RE_OP_STRING:
    case RE_OP_STRING_FLD:
    case RE_OP_STRING_FLD_REV:
    case RE_OP_STRING_IGN:
    case RE_OP_STRING_IGN_REV:
    case RE_OP_STRING_REV:
        next->match_next = test->next_1.node;
        next->match_step = test->step;
        break;
    case RE_OP_GREEDY_REPEAT_ONE:
    case RE_OP_LAZY_REPEAT_ONE:
        if (test->values[1] > 0)
            next->test = test;
        break;
    }
}

/* Sets the test nodes. */
Py_LOCAL_INLINE(void) set_test_nodes(PatternObject* pattern) {
    RE_Node** node_list;
    size_t i;

    node_list = pattern->node_list;
    for (i = 0; i < pattern->node_count; i++) {
        RE_Node* node;

        node = node_list[i];
        set_test_node(&node->next_1);
        if (!(node->status & RE_STATUS_STRING))
            set_test_node(&node->nonstring.next_2);
    }
}

/* Optimises the pattern. */
Py_LOCAL_INLINE(BOOL) optimise_pattern(PatternObject* pattern) {
    size_t i;

    /* Building the nodes is made simpler by allowing branches to have a single
     * exit. These need to be removed.
     */
    skip_one_way_branches(pattern);

    /* Add position guards for repeat bodies containing a reference to a group
     * or repeat tails followed at some point by a reference to a group.
     */
    add_repeat_guards(pattern, pattern->start_node);

    /* Record the index of repeats and fuzzy sections within the body of atomic
     * and lookaround nodes.
     */
    if (!record_subpattern_repeats_and_fuzzy_sections(NULL, 0,
      pattern->repeat_count, pattern->start_node))
        return FALSE;

    for (i = 0; i < pattern->call_ref_info_count; i++) {
        RE_Node* node;

        node = pattern->call_ref_info[i].node;
        if (!record_subpattern_repeats_and_fuzzy_sections(NULL, 0,
          pattern->repeat_count, node))
            return FALSE;
    }

    /* Discard any unused nodes. */
    discard_unused_nodes(pattern);

    /* Set the test nodes. */
    set_test_nodes(pattern);

    /* Mark all the group that are named. */
    if (!mark_named_groups(pattern))
        return FALSE;

    return TRUE;
}

/* Creates a new pattern node. */
Py_LOCAL_INLINE(RE_Node*) create_node(PatternObject* pattern, RE_UINT8 op,
  RE_CODE flags, Py_ssize_t step, size_t value_count) {
    RE_Node* node;

    node = (RE_Node*)re_alloc(sizeof(*node));
    if (!node)
        return NULL;
    memset(node, 0, sizeof(RE_Node));

    node->value_count = value_count;

    if (node->value_count > 0) {
        node->values = (RE_CODE*)re_alloc(node->value_count * sizeof(RE_CODE));
        if (!node->values)
            goto error;
    } else
        node->values = NULL;

    node->op = op;
    node->match = (flags & RE_POSITIVE_OP) != 0;
    node->status = (RE_STATUS_T)(flags << RE_STATUS_SHIFT);
    node->step = step;

    /* Ensure that there's enough storage to record the new node. */
    if (pattern->node_count >= pattern->node_capacity) {
        size_t new_capacity;
        RE_Node** new_node_list;

        new_capacity = pattern->node_capacity * 2;

        if (new_capacity == 0)
            new_capacity = 16;

        new_node_list = (RE_Node**)re_realloc(pattern->node_list, new_capacity
          * sizeof(RE_Node*));
        if (!new_node_list)
            goto error;

        pattern->node_list = new_node_list;
        pattern->node_capacity = new_capacity;
    }

    /* Record the new node. */
    pattern->node_list[pattern->node_count++] = node;

    return node;

error:
    re_dealloc(node->values);
    re_dealloc(node);
    return NULL;
}

/* Adds a node as a next node for another node. */
Py_LOCAL_INLINE(void) add_node(RE_Node* node_1, RE_Node* node_2) {
    if (!node_1->next_1.node)
        node_1->next_1.node = node_2;
    else
        node_1->nonstring.next_2.node = node_2;
}

/* Ensures that the entry for a group's details actually exists. */
Py_LOCAL_INLINE(BOOL) ensure_group(PatternObject* pattern, size_t group) {
    size_t old_capacity;
    size_t new_capacity;
    RE_GroupInfo* new_group_info;

    if (group <= pattern->true_group_count)
        /* We already have an entry for the group. */
        return TRUE;

    /* Increase the storage capacity to include the new entry if it's
     * insufficient.
     */
    old_capacity = pattern->group_info_capacity;
    new_capacity = pattern->group_info_capacity;

    while (group > new_capacity)
        new_capacity += 16;

    if (new_capacity > old_capacity) {
        new_group_info = (RE_GroupInfo*)re_realloc(pattern->group_info,
          new_capacity * sizeof(RE_GroupInfo));
        if (!new_group_info)
            return FALSE;

        memset(new_group_info + old_capacity, 0, (new_capacity - old_capacity)
          * sizeof(RE_GroupInfo));

        pattern->group_info = new_group_info;
        pattern->group_info_capacity = new_capacity;
    }

    pattern->true_group_count = group;

    return TRUE;
}

/* Records that there's a reference to a group. */
Py_LOCAL_INLINE(BOOL) record_ref_group(PatternObject* pattern, size_t group) {
    if (!ensure_group(pattern, group))
        return FALSE;

    pattern->group_info[group - 1].referenced = TRUE;

    return TRUE;
}

/* Records that there's a new group. */
Py_LOCAL_INLINE(BOOL) record_group(PatternObject* pattern, size_t group,
  RE_Node* node) {
    if (!ensure_group(pattern, group))
        return FALSE;

    if (group >= 1) {
        RE_GroupInfo* info;

        info = &pattern->group_info[group - 1];
        info->end_index = (Py_ssize_t)pattern->true_group_count;
        info->node = node;
    }

    return TRUE;
}

/* Records that a group has closed. */
Py_LOCAL_INLINE(void) record_group_end(PatternObject* pattern, size_t group) {
    if (group >= 1)
        pattern->group_info[group - 1].end_index = ++pattern->group_end_index;
}

/* Ensures that the entry for a call_ref's details actually exists. */
Py_LOCAL_INLINE(BOOL) ensure_call_ref(PatternObject* pattern, size_t call_ref)
  {
    size_t old_capacity;
    size_t new_capacity;
    RE_CallRefInfo* new_call_ref_info;

    if (call_ref < pattern->call_ref_info_count)
        /* We already have an entry for the call_ref. */
        return TRUE;

    /* Increase the storage capacity to include the new entry if it's
     * insufficient.
     */
    old_capacity = pattern->call_ref_info_capacity;
    new_capacity = pattern->call_ref_info_capacity;
    while (call_ref >= new_capacity)
        new_capacity += 16;

    if (new_capacity > old_capacity) {
        new_call_ref_info = (RE_CallRefInfo*)re_realloc(pattern->call_ref_info,
          new_capacity * sizeof(RE_CallRefInfo));
        if (!new_call_ref_info)
            return FALSE;

        memset(new_call_ref_info + old_capacity, 0, (new_capacity -
          old_capacity) * sizeof(RE_CallRefInfo));

        pattern->call_ref_info = new_call_ref_info;
        pattern->call_ref_info_capacity = new_capacity;
    }

    pattern->call_ref_info_count = 1 + call_ref;

    return TRUE;
}

/* Records that a call_ref is defined. */
Py_LOCAL_INLINE(BOOL) record_call_ref_defined(PatternObject* pattern, size_t
  call_ref, RE_Node* node) {
    if (!ensure_call_ref(pattern, call_ref))
        return FALSE;

    pattern->call_ref_info[call_ref].defined = TRUE;
    pattern->call_ref_info[call_ref].node = node;

    return TRUE;
}

/* Records that a call_ref is used. */
Py_LOCAL_INLINE(BOOL) record_call_ref_used(PatternObject* pattern, size_t
  call_ref) {
    if (!ensure_call_ref(pattern, call_ref))
        return FALSE;

    pattern->call_ref_info[call_ref].used = TRUE;

    return TRUE;
}

/* Checks whether a node matches one and only one character. */
Py_LOCAL_INLINE(BOOL) sequence_matches_one(RE_Node* node) {
    while (node->op == RE_OP_BRANCH && !node->nonstring.next_2.node)
        node = node->next_1.node;

    if (node->next_1.node || (node->status & RE_STATUS_FUZZY))
        return FALSE;

    return node_matches_one_character(node);
}

/* Records a repeat. */
Py_LOCAL_INLINE(BOOL) record_repeat(PatternObject* pattern, size_t index,
  size_t repeat_depth) {
    size_t old_capacity;
    size_t new_capacity;

    /* Increase the storage capacity to include the new entry if it's
     * insufficient.
     */
    old_capacity = pattern->repeat_info_capacity;
    new_capacity = pattern->repeat_info_capacity;
    while (index >= new_capacity)
        new_capacity += 16;

    if (new_capacity > old_capacity) {
        RE_RepeatInfo* new_repeat_info;

        new_repeat_info = (RE_RepeatInfo*)re_realloc(pattern->repeat_info,
          new_capacity * sizeof(RE_RepeatInfo));
        if (!new_repeat_info)
            return FALSE;

        memset(new_repeat_info + old_capacity, 0, (new_capacity - old_capacity)
          * sizeof(RE_RepeatInfo));

        pattern->repeat_info = new_repeat_info;
        pattern->repeat_info_capacity = new_capacity;
    }

    if (index >= pattern->repeat_count)
        pattern->repeat_count = index + 1;

    if (repeat_depth > 0)
        pattern->repeat_info[index].status |= RE_STATUS_INNER;

    return TRUE;
}

Py_LOCAL_INLINE(Py_ssize_t) get_step(RE_CODE op) {
    switch (op) {
    case RE_OP_ANY:
    case RE_OP_ANY_ALL:
    case RE_OP_ANY_U:
    case RE_OP_CHARACTER:
    case RE_OP_CHARACTER_IGN:
    case RE_OP_PROPERTY:
    case RE_OP_PROPERTY_IGN:
    case RE_OP_RANGE:
    case RE_OP_RANGE_IGN:
    case RE_OP_SET_DIFF:
    case RE_OP_SET_DIFF_IGN:
    case RE_OP_SET_INTER:
    case RE_OP_SET_INTER_IGN:
    case RE_OP_SET_SYM_DIFF:
    case RE_OP_SET_SYM_DIFF_IGN:
    case RE_OP_SET_UNION:
    case RE_OP_SET_UNION_IGN:
    case RE_OP_STRING:
    case RE_OP_STRING_FLD:
    case RE_OP_STRING_IGN:
        return 1;
    case RE_OP_ANY_ALL_REV:
    case RE_OP_ANY_REV:
    case RE_OP_ANY_U_REV:
    case RE_OP_CHARACTER_IGN_REV:
    case RE_OP_CHARACTER_REV:
    case RE_OP_PROPERTY_IGN_REV:
    case RE_OP_PROPERTY_REV:
    case RE_OP_RANGE_IGN_REV:
    case RE_OP_RANGE_REV:
    case RE_OP_SET_DIFF_IGN_REV:
    case RE_OP_SET_DIFF_REV:
    case RE_OP_SET_INTER_IGN_REV:
    case RE_OP_SET_INTER_REV:
    case RE_OP_SET_SYM_DIFF_IGN_REV:
    case RE_OP_SET_SYM_DIFF_REV:
    case RE_OP_SET_UNION_IGN_REV:
    case RE_OP_SET_UNION_REV:
    case RE_OP_STRING_FLD_REV:
    case RE_OP_STRING_IGN_REV:
    case RE_OP_STRING_REV:
        return -1;
    }

    return 0;
}

Py_LOCAL_INLINE(int) build_sequence(RE_CompileArgs* args);

/* Builds an ANY node. */
Py_LOCAL_INLINE(int) build_ANY(RE_CompileArgs* args) {
    RE_UINT8 op;
    RE_CODE flags;
    Py_ssize_t step;
    RE_Node* node;

    /* codes: opcode, flags. */
    if (args->code + 1 > args->end_code)
        return RE_ERROR_ILLEGAL;

    op = (RE_UINT8)args->code[0];
    flags = args->code[1];

    step = get_step(op);

    /* Create the node. */
    node = create_node(args->pattern, op, flags, step, 0);
    if (!node)
        return RE_ERROR_MEMORY;

    args->code += 2;

    /* Append the node. */
    add_node(args->end, node);
    args->end = node;

    ++args->min_width;

    return RE_ERROR_SUCCESS;
}

/* Builds a FUZZY node. */
Py_LOCAL_INLINE(int) build_FUZZY(RE_CompileArgs* args) {
    RE_CODE flags;
    RE_Node* start_node;
    RE_Node* end_node;
    RE_CODE index;
    RE_CompileArgs subargs;
    int status;

    /* codes: opcode, flags, constraints, ..., end. */
    if (args->code + 13 > args->end_code)
        return RE_ERROR_ILLEGAL;

    flags = args->code[1];

    /* Create nodes for the start and end of the fuzzy sequence. */
    start_node = create_node(args->pattern, RE_OP_FUZZY, flags, 0, 13);
    end_node = create_node(args->pattern, RE_OP_END_FUZZY, flags, 0, 0);
    if (!start_node || !end_node)
        return RE_ERROR_MEMORY;

    index = (RE_CODE)args->pattern->fuzzy_count++;
    start_node->values[0] = index;

    /* The constraints consist of 4 pairs of limits and the cost equation. */
    start_node->values[RE_FUZZY_VAL_MIN_DEL] = args->code[2]; /* Deletion minimum. */
    start_node->values[RE_FUZZY_VAL_MIN_INS] = args->code[4]; /* Insertion minimum. */
    start_node->values[RE_FUZZY_VAL_MIN_SUB] = args->code[6]; /* Substitution minimum. */
    start_node->values[RE_FUZZY_VAL_MIN_ERR] = args->code[8]; /* Error minimum. */

    start_node->values[RE_FUZZY_VAL_MAX_DEL] = args->code[3]; /* Deletion maximum. */
    start_node->values[RE_FUZZY_VAL_MAX_INS] = args->code[5]; /* Insertion maximum. */
    start_node->values[RE_FUZZY_VAL_MAX_SUB] = args->code[7]; /* Substitution maximum. */
    start_node->values[RE_FUZZY_VAL_MAX_ERR] = args->code[9]; /* Error maximum. */

    start_node->values[RE_FUZZY_VAL_DEL_COST] = args->code[10]; /* Deletion cost. */
    start_node->values[RE_FUZZY_VAL_INS_COST] = args->code[11]; /* Insertion cost. */
    start_node->values[RE_FUZZY_VAL_SUB_COST] = args->code[12]; /* Substitution cost. */
    start_node->values[RE_FUZZY_VAL_MAX_COST] = args->code[13]; /* Total cost. */

    args->code += 14;

    subargs = *args;
    subargs.within_fuzzy = TRUE;

    /* Compile the sequence and check that we've reached the end of the
     * subpattern.
     */
    status = build_sequence(&subargs);
    if (status != RE_ERROR_SUCCESS)
        return status;

    if (subargs.code[0] != RE_OP_END)
        return RE_ERROR_ILLEGAL;

    args->code = subargs.code;
    args->min_width += subargs.min_width;
    args->has_captures |= subargs.has_captures;
    args->is_fuzzy = TRUE;
    args->has_groups |= subargs.has_groups;
    args->has_repeats |= subargs.has_repeats;
    args->visible_capture_count = subargs.visible_capture_count;

    ++args->code;

    /* Append the fuzzy sequence. */
    add_node(args->end, start_node);
    add_node(start_node, subargs.start);
    add_node(subargs.end, end_node);
    args->end = end_node;
    args->all_atomic = FALSE;

    return RE_ERROR_SUCCESS;
}

/* Builds an ATOMIC node. */
Py_LOCAL_INLINE(int) build_ATOMIC(RE_CompileArgs* args) {
    RE_Node* atomic_node;
    RE_CompileArgs subargs;
    int status;
    RE_Node* end_node;

    /* codes: opcode, ..., end. */
    if (args->code + 1 > args->end_code)
        return RE_ERROR_ILLEGAL;

    atomic_node = create_node(args->pattern, RE_OP_ATOMIC, 0, 0, 0);
    if (!atomic_node)
        return RE_ERROR_MEMORY;

    ++args->code;

    /* Compile the sequence and check that we've reached the end of it. */
    subargs = *args;

    status = build_sequence(&subargs);
    if (status != RE_ERROR_SUCCESS)
        return status;

    if (subargs.code[0] != RE_OP_END)
        return RE_ERROR_ILLEGAL;

    args->code = subargs.code;
    args->min_width += subargs.min_width;
    args->has_captures |= subargs.has_captures;
    args->is_fuzzy |= subargs.is_fuzzy;
    args->has_groups |= subargs.has_groups;
    args->has_repeats |= subargs.has_repeats;
    args->visible_capture_count = subargs.visible_capture_count;

    ++args->code;

    /* Check the subpattern. */
    if (subargs.has_groups)
        atomic_node->status |= RE_STATUS_HAS_GROUPS;

    if (subargs.has_repeats)
        atomic_node->status |= RE_STATUS_HAS_REPEATS;

    /* Create the node to terminate the subpattern. */
    end_node = create_node(subargs.pattern, RE_OP_END_ATOMIC, 0, 0, 0);
    if (!end_node)
        return RE_ERROR_MEMORY;

    /* Append the new sequence. */
    add_node(args->end, atomic_node);
    add_node(atomic_node, subargs.start);
    add_node(subargs.end, end_node);
    args->end = end_node;

    return RE_ERROR_SUCCESS;
}

/* Builds a BOUNDARY node. */
Py_LOCAL_INLINE(int) build_BOUNDARY(RE_CompileArgs* args) {
    RE_UINT8 op;
    RE_CODE flags;
    RE_Node* node;

    /* codes: opcode, flags. */
    if (args->code + 1 > args->end_code)
        return RE_ERROR_ILLEGAL;

    op = (RE_UINT8)args->code[0];
    flags = args->code[1];

    args->code += 2;

    /* Create the node. */
    node = create_node(args->pattern, op, flags, 0, 0);
    if (!node)
        return RE_ERROR_MEMORY;

    /* Append the node. */
    add_node(args->end, node);
    args->end = node;

    return RE_ERROR_SUCCESS;
}

/* Builds a BRANCH node. */
Py_LOCAL_INLINE(int) build_BRANCH(RE_CompileArgs* args) {
    RE_Node* branch_node;
    RE_Node* join_node;
    Py_ssize_t min_width;
    RE_CompileArgs subargs;
    int status;

    /* codes: opcode, ..., next, ..., end. */
    if (args->code + 2 > args->end_code)
        return RE_ERROR_ILLEGAL;

    /* Create nodes for the start and end of the branch sequence. */
    branch_node = create_node(args->pattern, RE_OP_BRANCH, 0, 0, 0);
    join_node = create_node(args->pattern, RE_OP_BRANCH, 0, 0, 0);
    if (!branch_node || !join_node)
        return RE_ERROR_MEMORY;

    /* Append the node. */
    add_node(args->end, branch_node);
    args->end = join_node;

    min_width = PY_SSIZE_T_MAX;

    subargs = *args;

    /* A branch in the regular expression is compiled into a series of 2-way
     * branches.
     */
    do {
        RE_Node* next_branch_node;

        /* Skip over the 'BRANCH' or 'NEXT' opcode. */
        ++subargs.code;

        /* Compile the sequence until the next 'BRANCH' or 'NEXT' opcode. */
        status = build_sequence(&subargs);
        if (status != RE_ERROR_SUCCESS)
            return status;

        min_width = min_ssize_t(min_width, subargs.min_width);

        args->has_captures |= subargs.has_captures;
        args->is_fuzzy |= subargs.is_fuzzy;
        args->has_groups |= subargs.has_groups;
        args->has_repeats |= subargs.has_repeats;

        /* Append the sequence. */
        add_node(branch_node, subargs.start);
        add_node(subargs.end, join_node);

        /* Create a start node for the next sequence and append it. */
        next_branch_node = create_node(subargs.pattern, RE_OP_BRANCH, 0, 0, 0);
        if (!next_branch_node)
            return RE_ERROR_MEMORY;

        add_node(branch_node, next_branch_node);
        branch_node = next_branch_node;
    } while (subargs.code < subargs.end_code && subargs.code[0] == RE_OP_NEXT);

    /* We should have reached the end of the branch. */
    if (subargs.code[0] != RE_OP_END)
        return RE_ERROR_ILLEGAL;

    args->code = subargs.code;
    args->visible_capture_count = subargs.visible_capture_count;

    ++args->code;
    args->min_width += min_width;
    args->all_atomic = FALSE;

    return RE_ERROR_SUCCESS;
}

/* Builds a CALL_REF node. */
Py_LOCAL_INLINE(int) build_CALL_REF(RE_CompileArgs* args) {
    RE_CODE call_ref;
    RE_Node* start_node;
    RE_Node* end_node;
    RE_CompileArgs subargs;
    int status;

    /* codes: opcode, call_ref. */
    if (args->code + 1 > args->end_code)
        return RE_ERROR_ILLEGAL;

    call_ref = args->code[1];

    args->code += 2;

    /* Create nodes for the start and end of the subpattern. */
    start_node = create_node(args->pattern, RE_OP_CALL_REF, 0, 0, 1);
    end_node = create_node(args->pattern, RE_OP_GROUP_RETURN, 0, 0, 0);
    if (!start_node || !end_node)
        return RE_ERROR_MEMORY;

    start_node->values[0] = call_ref;

    /* Compile the sequence and check that we've reached the end of the
     * subpattern.
     */
    subargs = *args;
    status = build_sequence(&subargs);
    if (status != RE_ERROR_SUCCESS)
        return status;

    if (subargs.code[0] != RE_OP_END)
        return RE_ERROR_ILLEGAL;

    args->code = subargs.code;
    args->min_width += subargs.min_width;
    args->has_captures |= subargs.has_captures;
    args->is_fuzzy |= subargs.is_fuzzy;
    args->has_groups |= subargs.has_groups;
    args->has_repeats |= subargs.has_repeats;
    args->visible_capture_count = subargs.visible_capture_count;

    ++args->code;

    /* Record that we defined a call_ref. */
    if (!record_call_ref_defined(args->pattern, call_ref, start_node))
        return RE_ERROR_MEMORY;

    /* Append the node. */
    add_node(args->end, start_node);
    add_node(start_node, subargs.start);
    add_node(subargs.end, end_node);
    args->end = end_node;
    args->all_atomic = FALSE;

    return RE_ERROR_SUCCESS;
}

/* Builds a CHARACTER or PROPERTY node. */
Py_LOCAL_INLINE(int) build_CHARACTER_or_PROPERTY(RE_CompileArgs* args) {
    RE_UINT8 op;
    RE_CODE flags;
    Py_ssize_t step;
    RE_Node* node;

    /* codes: opcode, flags, value. */
    if (args->code + 2 > args->end_code)
        return RE_ERROR_ILLEGAL;

    op = (RE_UINT8)args->code[0];
    flags = args->code[1];

    step = get_step(op);

    if (flags & RE_ZEROWIDTH_OP)
        step = 0;

    /* Create the node. */
    node = create_node(args->pattern, op, flags, step, 1);
    if (!node)
        return RE_ERROR_MEMORY;

    node->values[0] = args->code[2];

    args->code += 3;

    /* Append the node. */
    add_node(args->end, node);
    args->end = node;

    if (step != 0)
        ++args->min_width;

    return RE_ERROR_SUCCESS;
}

/* Builds a CONDITIONAL node. */
Py_LOCAL_INLINE(int) build_CONDITIONAL(RE_CompileArgs* args) {
    RE_CODE flags;
    BOOL forward;
    RE_Node* test_node;
    RE_CompileArgs subargs;
    int status;
    RE_Node* end_test_node;
    RE_Node* end_node;
    Py_ssize_t min_width;

    /* codes: opcode, flags, forward, ..., next, ..., next, ..., end. */
    if (args->code + 4 > args->end_code)
        return RE_ERROR_ILLEGAL;

    flags = args->code[1];
    forward = (BOOL)args->code[2];

    /* Create a node for the lookaround. */
    test_node = create_node(args->pattern, RE_OP_CONDITIONAL, flags, 0, 0);
    if (!test_node)
        return RE_ERROR_MEMORY;

    args->code += 3;

    add_node(args->end, test_node);

    /* Compile the lookaround test and check that we've reached the end of the
     * subpattern.
     */
    subargs = *args;
    subargs.forward = forward;
    status = build_sequence(&subargs);
    if (status != RE_ERROR_SUCCESS)
        return status;

    if (subargs.code[0] != RE_OP_NEXT)
        return RE_ERROR_ILLEGAL;

    args->code = subargs.code;
    args->has_captures |= subargs.has_captures;
    args->is_fuzzy |= subargs.is_fuzzy;
    args->has_groups |= subargs.has_groups;
    args->has_repeats |= subargs.has_repeats;
    args->visible_capture_count = subargs.visible_capture_count;

    ++args->code;

    /* Check the lookaround subpattern. */
    if (subargs.has_groups)
        test_node->status |= RE_STATUS_HAS_GROUPS;

    if (subargs.has_repeats)
        test_node->status |= RE_STATUS_HAS_REPEATS;

    /* Create the node to terminate the test. */
    end_test_node = create_node(args->pattern, RE_OP_END_CONDITIONAL, 0, 0, 0);
    if (!end_test_node)
        return RE_ERROR_MEMORY;

    /* test node -> test -> end test node */
    add_node(test_node, subargs.start);
    add_node(subargs.end, end_test_node);

    /* Compile the true branch. */
    subargs = *args;
    status = build_sequence(&subargs);
    if (status != RE_ERROR_SUCCESS)
        return status;

    /* Check the true branch. */
    args->code = subargs.code;
    args->has_captures |= subargs.has_captures;
    args->is_fuzzy |= subargs.is_fuzzy;
    args->has_groups |= subargs.has_groups;
    args->has_repeats |= subargs.has_repeats;
    args->visible_capture_count = subargs.visible_capture_count;

    min_width = subargs.min_width;

    /* Create the terminating node. */
    end_node = create_node(args->pattern, RE_OP_BRANCH, 0, 0, 0);
    if (!end_node)
        return RE_ERROR_MEMORY;

    /* end test node -> true branch -> end node */
    add_node(end_test_node, subargs.start);
    add_node(subargs.end, end_node);

    if (args->code[0] == RE_OP_NEXT) {
        /* There's a false branch. */
        ++args->code;

        /* Compile the false branch. */
        subargs.code = args->code;
        status = build_sequence(&subargs);
        if (status != RE_ERROR_SUCCESS)
            return status;

        /* Check the false branch. */
        args->code = subargs.code;
        args->has_captures |= subargs.has_captures;
        args->is_fuzzy |= subargs.is_fuzzy;
        args->has_groups |= subargs.has_groups;
        args->has_repeats |= subargs.has_repeats;
        args->visible_capture_count = subargs.visible_capture_count;

        min_width = min_ssize_t(min_width, subargs.min_width);

        /* test node -> false branch -> end node */
        add_node(test_node, subargs.start);
        add_node(subargs.end, end_node);
    } else {
        min_width = 0;

        /* test node -> end node */
        add_node(test_node, end_node);
    }

    if (args->code[0] != RE_OP_END)
        return RE_ERROR_ILLEGAL;

    args->min_width += min_width;

    ++args->code;

    args->end = end_node;
    args->all_atomic = FALSE;

    return RE_ERROR_SUCCESS;
}

/* Builds a GROUP node. */
Py_LOCAL_INLINE(int) build_GROUP(RE_CompileArgs* args) {
    BOOL forward;
    RE_CODE private_group;
    RE_CODE public_group;
    RE_Node* start_node;
    RE_Node* end_node;
    RE_CompileArgs subargs;
    int status;

    /* codes: opcode, forward, private_group, public_group, ..., end. */
    if (args->code + 3 > args->end_code)
        return RE_ERROR_ILLEGAL;

    forward = (BOOL)args->code[1];
    private_group = args->code[2];
    public_group = args->code[3];

    args->code += 4;

    /* Create nodes for the start and end of the capture group. */
    start_node = create_node(args->pattern, forward ? RE_OP_START_GROUP :
      RE_OP_END_GROUP, 0, 0, 3);
    end_node = create_node(args->pattern, forward ? RE_OP_END_GROUP :
      RE_OP_START_GROUP, 0, 0, 3);
    if (!start_node || !end_node)
        return RE_ERROR_MEMORY;

    start_node->values[0] = private_group;
    end_node->values[0] = private_group;
    start_node->values[1] = public_group;
    end_node->values[1] = public_group;

    /* Signal that the capture should be saved when it's complete. */
    start_node->values[2] = 0;
    end_node->values[2] = 1;

    /* Record that we have a new capture group. */
    if (!record_group(args->pattern, private_group, start_node))
        return RE_ERROR_MEMORY;

    /* Compile the sequence and check that we've reached the end of the capture
     * group.
     */
    subargs = *args;
    status = build_sequence(&subargs);
    if (status != RE_ERROR_SUCCESS)
        return status;

    if (subargs.code[0] != RE_OP_END)
        return RE_ERROR_ILLEGAL;

    args->code = subargs.code;
    args->min_width += subargs.min_width;
    args->has_captures |= subargs.has_captures | subargs.visible_captures;
    args->is_fuzzy |= subargs.is_fuzzy;
    args->has_groups |= TRUE;
    args->has_repeats |= subargs.has_repeats;
    args->visible_capture_count = subargs.visible_capture_count;

    if (!args->in_define)
        ++args->visible_capture_count;

    ++args->code;

    /* Record that the capture group has closed. */
    record_group_end(args->pattern, private_group);

    /* Append the capture group. */
    add_node(args->end, start_node);
    add_node(start_node, subargs.start);
    add_node(subargs.end, end_node);
    args->end = end_node;

    return RE_ERROR_SUCCESS;
}

/* Builds a GROUP_CALL node. */
Py_LOCAL_INLINE(int) build_GROUP_CALL(RE_CompileArgs* args) {
    RE_CODE call_ref;
    RE_Node* node;

    /* codes: opcode, call_ref. */
    if (args->code + 1 > args->end_code)
        return RE_ERROR_ILLEGAL;

    call_ref = args->code[1];

    /* Create the node. */
    node = create_node(args->pattern, RE_OP_GROUP_CALL, 0, 0, 1);
    if (!node)
        return RE_ERROR_MEMORY;

    node->values[0] = call_ref;

    node->status |= RE_STATUS_HAS_GROUPS;
    node->status |= RE_STATUS_HAS_REPEATS;

    args->code += 2;

    /* Record that we used a call_ref. */
    if (!record_call_ref_used(args->pattern, call_ref))
        return RE_ERROR_MEMORY;

    /* Append the node. */
    add_node(args->end, node);
    args->end = node;
    args->all_atomic = FALSE;

    return RE_ERROR_SUCCESS;
}

/* Builds a GROUP_EXISTS node. */
Py_LOCAL_INLINE(int) build_GROUP_EXISTS(RE_CompileArgs* args) {
    RE_CODE group;
    RE_Node* start_node;
    RE_Node* end_node;
    RE_CompileArgs subargs;
    int status;
    Py_ssize_t min_width;

    /* codes: opcode, ..., next, ..., end. */
    if (args->code + 2 > args->end_code)
        return RE_ERROR_ILLEGAL;

    group = args->code[1];

    args->code += 2;

    /* Record that we have a reference to a group. If group is 0, then we have
     * a DEFINE and not a true group.
     */
    if (group > 0 && !record_ref_group(args->pattern, group))
        return RE_ERROR_MEMORY;

    /* Create nodes for the start and end of the structure. */
    start_node = create_node(args->pattern, RE_OP_GROUP_EXISTS, 0, 0, 1);
    end_node = create_node(args->pattern, RE_OP_BRANCH, 0, 0, 0);
    if (!start_node || !end_node)
        return RE_ERROR_MEMORY;

    start_node->values[0] = group;

    subargs = *args;
    subargs.in_define = TRUE;
    status = build_sequence(&subargs);
    if (status != RE_ERROR_SUCCESS)
        return status;

    args->code = subargs.code;
    args->has_captures |= subargs.has_captures;
    args->is_fuzzy |= subargs.is_fuzzy;
    args->has_groups |= subargs.has_groups;
    args->has_repeats |= subargs.has_repeats;
    args->visible_capture_count = subargs.visible_capture_count;

    min_width = subargs.min_width;

    /* Append the start node. */
    add_node(args->end, start_node);
    add_node(start_node, subargs.start);

    if (args->code[0] == RE_OP_NEXT) {
        RE_Node* true_branch_end;

        ++args->code;

        true_branch_end = subargs.end;

        subargs.code = args->code;

        status = build_sequence(&subargs);
        if (status != RE_ERROR_SUCCESS)
            return status;

        args->code = subargs.code;
        args->has_captures |= subargs.has_captures;
        args->is_fuzzy |= subargs.is_fuzzy;
        args->visible_capture_count = subargs.visible_capture_count;

        if (group == 0) {
            /* Join the 2 branches end-to-end and bypass it. The sequence
             * itself will never be matched as a whole, so it doesn't matter.
             */
            min_width = 0;

            add_node(start_node, end_node);
            add_node(true_branch_end, subargs.start);
        } else {
            args->has_groups |= subargs.has_groups;
            args->has_repeats |= subargs.has_repeats;
            args->visible_capture_count = subargs.visible_capture_count;

            min_width = min_ssize_t(min_width, subargs.min_width);

            add_node(start_node, subargs.start);
            add_node(true_branch_end, end_node);
        }

        add_node(subargs.end, end_node);
    } else {
        add_node(start_node, end_node);
        add_node(subargs.end, end_node);

        min_width = 0;
    }

    args->min_width += min_width;

    if (args->code[0] != RE_OP_END)
        return RE_ERROR_ILLEGAL;

    ++args->code;

    args->end = end_node;
    args->all_atomic = FALSE;

    return RE_ERROR_SUCCESS;
}

/* Builds a LOOKAROUND node. */
Py_LOCAL_INLINE(int) build_LOOKAROUND(RE_CompileArgs* args) {
    RE_CODE flags;
    BOOL forward;
    RE_Node* lookaround_node;
    RE_CompileArgs subargs;
    int status;
    RE_Node* end_node;
    RE_Node* next_node;

    /* codes: opcode, flags, forward, ..., end. */
    if (args->code + 3 > args->end_code)
        return RE_ERROR_ILLEGAL;

    flags = args->code[1];
    forward = (BOOL)args->code[2];

    /* Create a node for the lookaround. */
    lookaround_node = create_node(args->pattern, RE_OP_LOOKAROUND, flags, 0,
      0);
    if (!lookaround_node)
        return RE_ERROR_MEMORY;

    args->code += 3;

    /* Compile the sequence and check that we've reached the end of the
     * subpattern.
     */
    subargs = *args;
    subargs.forward = forward;
    status = build_sequence(&subargs);
    if (status != RE_ERROR_SUCCESS)
        return status;

    if (subargs.code[0] != RE_OP_END)
        return RE_ERROR_ILLEGAL;

    args->code = subargs.code;
    ++args->code;

    /* Check the subpattern. */
    args->has_captures |= subargs.has_captures;
    args->is_fuzzy |= subargs.is_fuzzy;
    args->has_groups |= subargs.has_groups;
    args->has_repeats |= subargs.has_repeats;
    args->visible_capture_count = subargs.visible_capture_count;

    if (subargs.has_groups)
        lookaround_node->status |= RE_STATUS_HAS_GROUPS;

    if (subargs.has_repeats)
        lookaround_node->status |= RE_STATUS_HAS_REPEATS;

    /* Create the node to terminate the subpattern. */
    end_node = create_node(args->pattern, RE_OP_END_LOOKAROUND, 0, 0, 0);
    if (!end_node)
        return RE_ERROR_MEMORY;

    /* Make a continuation node. */
    next_node = create_node(args->pattern, RE_OP_BRANCH, 0, 0, 0);
    if (!next_node)
        return RE_ERROR_MEMORY;

    /* Append the new sequence. */
    add_node(args->end, lookaround_node);
    add_node(lookaround_node, subargs.start);
    add_node(lookaround_node, next_node);
    add_node(subargs.end, end_node);
    add_node(end_node, next_node);

    args->end = next_node;
    args->all_atomic = FALSE;

    return RE_ERROR_SUCCESS;
}

/* Builds a RANGE node. */
Py_LOCAL_INLINE(int) build_RANGE(RE_CompileArgs* args) {
    RE_UINT8 op;
    RE_CODE flags;
    Py_ssize_t step;
    RE_Node* node;

    /* codes: opcode, flags, lower, upper. */
    if (args->code + 3 > args->end_code)
        return RE_ERROR_ILLEGAL;

    op = (RE_UINT8)args->code[0];
    flags = args->code[1];

    step = get_step(op);

    if (flags & RE_ZEROWIDTH_OP)
        step = 0;

    /* Create the node. */
    node = create_node(args->pattern, op, flags, step, 2);
    if (!node)
        return RE_ERROR_MEMORY;

    node->values[0] = args->code[2];
    node->values[1] = args->code[3];

    args->code += 4;

    /* Append the node. */
    add_node(args->end, node);
    args->end = node;

    if (step != 0)
        ++args->min_width;

    return RE_ERROR_SUCCESS;
}

/* Builds a REF_GROUP node. */
Py_LOCAL_INLINE(int) build_REF_GROUP(RE_CompileArgs* args) {
    RE_CODE flags;
    RE_CODE group;
    RE_Node* node;

    /* codes: opcode, flags, group. */
    if (args->code + 2 > args->end_code)
        return RE_ERROR_ILLEGAL;

    flags = args->code[1];
    group = args->code[2];
    node = create_node(args->pattern, (RE_UINT8)args->code[0], flags, 0, 1);
    if (!node)
        return RE_ERROR_MEMORY;

    node->values[0] = group;

    args->code += 3;

    /* Record that we have a reference to a group. */
    if (!record_ref_group(args->pattern, group))
        return RE_ERROR_MEMORY;

    /* Append the reference. */
    add_node(args->end, node);
    args->end = node;

    return RE_ERROR_SUCCESS;
}

Py_LOCAL_INLINE(BOOL) section_contains_repeat(RE_CODE** code, RE_CODE*
  end_code);

/* Checks whether a subsection of code contains a repeat. */
Py_LOCAL_INLINE(BOOL) subsection_contains_repeat(int initial, RE_CODE** code,
  RE_CODE* end_code) {
    /* codes: code*initial, ..., (next, ..., )* end. */
    *code += initial;

    if (*code >= end_code)
        return FALSE;

    if (section_contains_repeat(code, end_code))
        return TRUE;

    while (*code < end_code && **code == RE_OP_NEXT) {
        ++(*code);

        if (*code >= end_code)
            return FALSE;

        if (section_contains_repeat(code, end_code))
            return TRUE;
    }

    if (*code >= end_code)
        return FALSE;

    ++(*code);

    return FALSE;
}

/* Checks whether a section of code contains a repeat. */
Py_LOCAL_INLINE(BOOL) section_contains_repeat(RE_CODE** code, RE_CODE*
  end_code) {
    while (*code < end_code) {
        /* The following code groups opcodes by format, not function. */
        switch ((*code)[0]) {
        case RE_OP_ANY:
        case RE_OP_ANY_ALL:
        case RE_OP_ANY_ALL_REV:
        case RE_OP_ANY_REV:
        case RE_OP_ANY_U:
        case RE_OP_ANY_U_REV:
        case RE_OP_FAILURE:
        case RE_OP_PRUNE:
        case RE_OP_SUCCESS:
            /* codes: opcode. */
            ++(*code);
            break;
        case RE_OP_ATOMIC:
        case RE_OP_BRANCH:
        case RE_OP_GROUP_EXISTS:
            /* codes: opcode, ..., (next, ..., )* end. */
            if (subsection_contains_repeat(1, code, end_code))
                return TRUE;
            break;
        case RE_OP_BOUNDARY:
        case RE_OP_CALL_REF:
        case RE_OP_DEFAULT_BOUNDARY:
        case RE_OP_DEFAULT_END_OF_WORD:
        case RE_OP_DEFAULT_START_OF_WORD:
        case RE_OP_END_OF_LINE:
        case RE_OP_END_OF_LINE_U:
        case RE_OP_END_OF_STRING:
        case RE_OP_END_OF_STRING_LINE:
        case RE_OP_END_OF_STRING_LINE_U:
        case RE_OP_END_OF_WORD:
        case RE_OP_GRAPHEME_BOUNDARY:
        case RE_OP_GROUP_CALL:
        case RE_OP_KEEP:
        case RE_OP_SEARCH_ANCHOR:
        case RE_OP_SKIP:
        case RE_OP_START_OF_LINE:
        case RE_OP_START_OF_LINE_U:
        case RE_OP_START_OF_STRING:
        case RE_OP_START_OF_WORD:
            /* codes: opcode, value. */
            *code += 2;
            break;
        case RE_OP_CHARACTER:
        case RE_OP_CHARACTER_IGN:
        case RE_OP_CHARACTER_IGN_REV:
        case RE_OP_CHARACTER_REV:
        case RE_OP_PROPERTY:
        case RE_OP_PROPERTY_IGN:
        case RE_OP_PROPERTY_IGN_REV:
        case RE_OP_PROPERTY_REV:
        case RE_OP_REF_GROUP:
        case RE_OP_REF_GROUP_FLD:
        case RE_OP_REF_GROUP_FLD_REV:
        case RE_OP_REF_GROUP_IGN:
        case RE_OP_REF_GROUP_IGN_REV:
        case RE_OP_REF_GROUP_REV:
            /* codes: opcode, value, value. */
            *code += 3;
            break;
        case RE_OP_CONDITIONAL:
        case RE_OP_FUZZY:
        case RE_OP_LOOKAROUND:
            /* codes: opcode, value, value, ..., (next, ..., )* end. */
            if (subsection_contains_repeat(3, code, end_code))
                return TRUE;
            break;
        case RE_OP_GREEDY_REPEAT:
        case RE_OP_LAZY_REPEAT:
            return TRUE;
        case RE_OP_GROUP:
            /* codes: opcode, value, value, value, ..., (next, ..., )* end. */
            if (subsection_contains_repeat(4, code, end_code))
                return TRUE;
            break;
        case RE_OP_RANGE:
        case RE_OP_RANGE_IGN:
        case RE_OP_RANGE_IGN_REV:
        case RE_OP_RANGE_REV:
        case RE_OP_STRING_SET:
        case RE_OP_STRING_SET_FLD:
        case RE_OP_STRING_SET_FLD_REV:
        case RE_OP_STRING_SET_IGN:
        case RE_OP_STRING_SET_IGN_REV:
        case RE_OP_STRING_SET_REV:
            /* codes: opcode, value, value, value. */
            *code += 4;
            break;
        case RE_OP_SET_DIFF:
        case RE_OP_SET_DIFF_IGN:
        case RE_OP_SET_DIFF_IGN_REV:
        case RE_OP_SET_DIFF_REV:
        case RE_OP_SET_INTER:
        case RE_OP_SET_INTER_IGN:
        case RE_OP_SET_INTER_IGN_REV:
        case RE_OP_SET_INTER_REV:
        case RE_OP_SET_SYM_DIFF:
        case RE_OP_SET_SYM_DIFF_IGN:
        case RE_OP_SET_SYM_DIFF_IGN_REV:
        case RE_OP_SET_SYM_DIFF_REV:
        case RE_OP_SET_UNION:
        case RE_OP_SET_UNION_IGN:
        case RE_OP_SET_UNION_IGN_REV:
        case RE_OP_SET_UNION_REV:
            /* codes: opcode, value, ..., (next, ..., )* end. */
            if (subsection_contains_repeat(2, code, end_code))
                return TRUE;
            break;
        case RE_OP_STRING:
        case RE_OP_STRING_FLD:
        case RE_OP_STRING_FLD_REV:
        case RE_OP_STRING_IGN:
        case RE_OP_STRING_IGN_REV:
        case RE_OP_STRING_REV:
            /* codes: opcode, value, length, .... */
            *code += 3 + (*code)[2];
            break;
        default:
            /* We've found an opcode which we don't recognise. We'll leave it
             * for the caller.
             */
            return FALSE;
        }
    }

    return FALSE;
}

/* Checks whether a section of code contains a repeat. */
Py_LOCAL_INLINE(BOOL) contains_repeat(RE_CODE* code, RE_CODE* end_code) {
    return section_contains_repeat(&code, end_code);
}

/* Builds a REPEAT node. */
Py_LOCAL_INLINE(int) build_REPEAT(RE_CompileArgs* args) {
    BOOL greedy;
    RE_CODE min_count;
    RE_CODE max_count;
    int status;

    /* codes: opcode, min_count, max_count, ..., end. */
    if (args->code + 3 > args->end_code)
        return RE_ERROR_ILLEGAL;

    greedy = args->code[0] == RE_OP_GREEDY_REPEAT;
    min_count = args->code[1];
    max_count = args->code[2];
    if (args->code[1] > args->code[2])
        return RE_ERROR_ILLEGAL;

    args->code += 3;

    if (min_count == 1 && max_count == 1) {
        /* Singly-repeated sequence. */
        RE_CompileArgs subargs;

        subargs = *args;
        status = build_sequence(&subargs);
        if (status != RE_ERROR_SUCCESS)
            return status;

        if (subargs.code[0] != RE_OP_END)
            return RE_ERROR_ILLEGAL;

        args->code = subargs.code;
        args->min_width += subargs.min_width;
        args->has_captures |= subargs.has_captures;
        args->is_fuzzy |= subargs.is_fuzzy;
        args->has_groups |= subargs.has_groups;
        args->has_repeats |= subargs.has_repeats;
        args->visible_capture_count = subargs.visible_capture_count;

        ++args->code;

        /* Append the sequence. */
        add_node(args->end, subargs.start);
        args->end = subargs.end;
    } else {
        /* Extract the minimum number of repeats out of a repeat if it contains
         * a repeat.
         */
        BOOL extracted_min;
        size_t index;
        RE_Node* repeat_node;
        RE_CompileArgs subargs;

        extracted_min = FALSE;

        if (min_count > 0 && contains_repeat(args->code, args->end_code)) {
            RE_CODE done_count;

            for (done_count = 0; done_count < min_count; done_count++) {
                subargs = *args;
                subargs.visible_captures = TRUE;

                status = build_sequence(&subargs);
                if (status != RE_ERROR_SUCCESS)
                    return status;

                if (subargs.code[0] != RE_OP_END)
                    return RE_ERROR_ILLEGAL;

                args->visible_capture_count = subargs.visible_capture_count;

                add_node(args->end, subargs.start);
                args->end = subargs.end;
            }

            args->min_width += (Py_ssize_t)min_count * subargs.min_width;
            args->has_captures |= subargs.has_captures;
            args->is_fuzzy |= subargs.is_fuzzy;
            args->has_groups |= subargs.has_groups;
            args->has_repeats |= subargs.has_repeats;

            min_count -= done_count;
            if (~max_count != 0)
                max_count -= done_count;
        }

        /* We've extract the minimum number of repeats. Are there any left? */
        if (extracted_min && max_count == 0) {
            /* All done. */
            args->code = subargs.code;
            ++args->code;
        } else {
            /* More to do. */
            index = args->pattern->repeat_count;

            /* Create the nodes for the repeat. */
            repeat_node = create_node(args->pattern, greedy ?
              RE_OP_GREEDY_REPEAT : RE_OP_LAZY_REPEAT, 0, args->forward ? 1 :
              -1, 4);
            if (!repeat_node || !record_repeat(args->pattern, index,
              args->repeat_depth))
                return RE_ERROR_MEMORY;

            repeat_node->values[0] = (RE_CODE)index;
            repeat_node->values[1] = min_count;
            repeat_node->values[2] = max_count;
            repeat_node->values[3] = args->forward;

            if (args->within_fuzzy)
                args->pattern->repeat_info[index].status |= RE_STATUS_BODY;

            /* Compile the 'body' and check that we've reached the end of it.
             */
            subargs = *args;
            subargs.visible_captures = TRUE;
            ++subargs.repeat_depth;
            status = build_sequence(&subargs);
            if (status != RE_ERROR_SUCCESS)
                return status;

            if (subargs.code[0] != RE_OP_END)
                return RE_ERROR_ILLEGAL;

            args->code = subargs.code;
            args->min_width += (Py_ssize_t)min_count * subargs.min_width;
            args->has_captures |= subargs.has_captures;
            args->is_fuzzy |= subargs.is_fuzzy;
            args->has_groups |= subargs.has_groups;
            args->has_repeats = TRUE;
            args->visible_capture_count = subargs.visible_capture_count;

            ++args->code;

            /* Is it a repeat of something which will match a single character?
             *
             * If it's in a fuzzy section then it won't be optimised as a
             * single-character repeat.
             */
            if (sequence_matches_one(subargs.start)) {
                repeat_node->op = greedy ? RE_OP_GREEDY_REPEAT_ONE :
                  RE_OP_LAZY_REPEAT_ONE;

                if (args->all_atomic && args->code < args->end_code &&
                  args->code[0] == RE_OP_END && !args->within_fuzzy)
                    repeat_node->status |= RE_STATUS_ALL_ATOMIC;

                /* Append the new sequence. */
                add_node(args->end, repeat_node);
                repeat_node->nonstring.next_2.node = subargs.start;
                args->end = repeat_node;
            } else {
                RE_Node* end_repeat_node;
                RE_Node* end_node;

                end_repeat_node = create_node(args->pattern, greedy ?
                  RE_OP_END_GREEDY_REPEAT : RE_OP_END_LAZY_REPEAT, 0,
                  args->forward ? 1 : -1, 4);
                if (!end_repeat_node)
                    return RE_ERROR_MEMORY;

                end_repeat_node->values[0] = repeat_node->values[0];
                end_repeat_node->values[1] = repeat_node->values[1];
                end_repeat_node->values[2] = repeat_node->values[2];
                end_repeat_node->values[3] = args->forward;

                end_node = create_node(args->pattern, RE_OP_BRANCH, 0, 0, 0);
                if (!end_node)
                    return RE_ERROR_MEMORY;

                if (args->all_atomic && args->code < args->end_code &&
                  args->code[0] == RE_OP_END && !args->within_fuzzy)
                    end_repeat_node->status |= RE_STATUS_ALL_ATOMIC;

                /* Append the new sequence. */
                add_node(args->end, repeat_node);
                add_node(repeat_node, subargs.start);
                add_node(repeat_node, end_node);
                add_node(subargs.end, end_repeat_node);
                add_node(end_repeat_node, subargs.start);
                add_node(end_repeat_node, end_node);
                args->end = end_node;
            }
        }
    }

    if (!(args->all_atomic && args->code < args->end_code && args->code[0] !=
      RE_OP_END && !args->within_fuzzy))
        args->all_atomic = FALSE;

    return RE_ERROR_SUCCESS;
}

/* Builds a STRING node. */
Py_LOCAL_INLINE(int) build_STRING(RE_CompileArgs* args, BOOL is_charset) {
    RE_CODE flags;
    RE_CODE length;
    RE_UINT8 op;
    Py_ssize_t step;
    RE_Node* node;
    size_t i;

    /* codes: opcode, flags, length, .... */
    flags = args->code[1];
    length = args->code[2];
    if (args->code + 3 + length > args->end_code)
        return RE_ERROR_ILLEGAL;

    op = (RE_UINT8)args->code[0];

    step = get_step(op);

    /* Create the node. */
    node = create_node(args->pattern, op, flags, step * (Py_ssize_t)length,
      length);
    if (!node)
        return RE_ERROR_MEMORY;
    if (!is_charset)
        node->status |= RE_STATUS_STRING;

    for (i = 0; i < length; i++)
        node->values[i] = args->code[3 + i];

    args->code += 3 + length;

    /* Append the node. */
    add_node(args->end, node);
    args->end = node;

    /* Because of full case-folding, one character in the text could match
     * multiple characters in the pattern.
     */
    if (op == RE_OP_STRING_FLD || op == RE_OP_STRING_FLD_REV)
        args->min_width += possible_unfolded_length((Py_ssize_t)length);
    else
        args->min_width += (Py_ssize_t)length;

    return RE_ERROR_SUCCESS;
}

/* Builds a SET node. */
Py_LOCAL_INLINE(int) build_SET(RE_CompileArgs* args) {
    RE_UINT8 op;
    RE_CODE flags;
    Py_ssize_t step;
    RE_Node* node;
    Py_ssize_t min_width;
    int status;

    /* codes: opcode, flags, ..., end. */
    op = (RE_UINT8)args->code[0];
    flags = args->code[1];

    step = get_step(op);

    if (flags & RE_ZEROWIDTH_OP)
        step = 0;

    node = create_node(args->pattern, op, flags, step, 0);
    if (!node)
        return RE_ERROR_MEMORY;

    args->code += 2;

    /* Append the node. */
    add_node(args->end, node);
    args->end = node;

    min_width = args->min_width;

    /* Compile the character set. */
    do {
        switch (args->code[0]) {
        case RE_OP_CHARACTER:
        case RE_OP_PROPERTY:
            status = build_CHARACTER_or_PROPERTY(args);
            if (status != RE_ERROR_SUCCESS)
                return status;
            break;
        case RE_OP_RANGE:
            status = build_RANGE(args);
            if (status != RE_ERROR_SUCCESS)
                return status;
            break;
        case RE_OP_SET_DIFF:
        case RE_OP_SET_INTER:
        case RE_OP_SET_SYM_DIFF:
        case RE_OP_SET_UNION:
            status = build_SET(args);
            if (status != RE_ERROR_SUCCESS)
                return status;
            break;
        case RE_OP_STRING:
            /* A set of characters. */
            status = build_STRING(args, TRUE);
            if (status != RE_ERROR_SUCCESS)
                return status;
            break;
        default:
            /* Illegal opcode for a character set. */
            return RE_ERROR_ILLEGAL;
        }
    } while (args->code < args->end_code && args->code[0] != RE_OP_END);

    /* Check that we've reached the end correctly. (The last opcode should be
     * 'END'.)
     */
    if (args->code >= args->end_code || args->code[0] != RE_OP_END)
        return RE_ERROR_ILLEGAL;

    ++args->code;

    /* At this point the set's members are in the main sequence. They need to
     * be moved out-of-line.
     */
    node->nonstring.next_2.node = node->next_1.node;
    node->next_1.node = NULL;
    args->end = node;

    args->min_width = min_width;

    if (step != 0)
        ++args->min_width;

    return RE_ERROR_SUCCESS;
}

/* Builds a STRING_SET node. */
Py_LOCAL_INLINE(int) build_STRING_SET(RE_CompileArgs* args) {
    RE_CODE index;
    RE_CODE min_len;
    RE_CODE max_len;
    RE_Node* node;

    /* codes: opcode, index, min_len, max_len. */
    if (args->code + 3 > args->end_code)
        return RE_ERROR_ILLEGAL;

    index = args->code[1];
    min_len = args->code[2];
    max_len = args->code[3];
    node = create_node(args->pattern, (RE_UINT8)args->code[0], 0, 0, 3);
    if (!node)
        return RE_ERROR_MEMORY;

    node->values[0] = index;
    node->values[1] = min_len;
    node->values[2] = max_len;

    args->code += 4;

    /* Append the reference. */
    add_node(args->end, node);
    args->end = node;

    return RE_ERROR_SUCCESS;
}

/* Builds a SUCCESS node . */
Py_LOCAL_INLINE(int) build_SUCCESS(RE_CompileArgs* args) {
    RE_Node* node;
    /* codes: opcode. */

    /* Create the node. */
    node = create_node(args->pattern, (RE_UINT8)args->code[0], 0, 0, 0);
    if (!node)
        return RE_ERROR_MEMORY;

    ++args->code;

    /* Append the node. */
    add_node(args->end, node);
    args->end = node;

    return RE_ERROR_SUCCESS;
}

/* Builds a zero-width node. */
Py_LOCAL_INLINE(int) build_zerowidth(RE_CompileArgs* args) {
    RE_CODE flags;
    RE_Node* node;

    /* codes: opcode, flags. */
    if (args->code + 1 > args->end_code)
        return RE_ERROR_ILLEGAL;

    flags = args->code[1];

    /* Create the node. */
    node = create_node(args->pattern, (RE_UINT8)args->code[0], flags, 0, 0);
    if (!node)
        return RE_ERROR_MEMORY;

    args->code += 2;

    /* Append the node. */
    add_node(args->end, node);
    args->end = node;

    return RE_ERROR_SUCCESS;
}

/* Builds a sequence of nodes from regular expression code. */
Py_LOCAL_INLINE(int) build_sequence(RE_CompileArgs* args) {
    int status;

    /* Guarantee that there's something to attach to. */
    args->start = create_node(args->pattern, RE_OP_BRANCH, 0, 0, 0);
    args->end = args->start;

    args->min_width = 0;
    args->has_captures = FALSE;
    args->is_fuzzy = FALSE;
    args->has_groups = FALSE;
    args->has_repeats = FALSE;
    args->all_atomic = TRUE;

    /* The sequence should end with an opcode we don't understand. If it
     * doesn't then the code is illegal.
     */
    while (args->code < args->end_code) {
        /* The following code groups opcodes by format, not function. */
        switch (args->code[0]) {
        case RE_OP_ANY:
        case RE_OP_ANY_ALL:
        case RE_OP_ANY_ALL_REV:
        case RE_OP_ANY_REV:
        case RE_OP_ANY_U:
        case RE_OP_ANY_U_REV:
            /* A simple opcode with no trailing codewords and width of 1. */
            status = build_ANY(args);
            if (status != RE_ERROR_SUCCESS)
                return status;
            break;
        case RE_OP_ATOMIC:
            /* An atomic sequence. */
            status = build_ATOMIC(args);
            if (status != RE_ERROR_SUCCESS)
                return status;
            break;
        case RE_OP_BOUNDARY:
        case RE_OP_DEFAULT_BOUNDARY:
        case RE_OP_DEFAULT_END_OF_WORD:
        case RE_OP_DEFAULT_START_OF_WORD:
        case RE_OP_END_OF_WORD:
        case RE_OP_GRAPHEME_BOUNDARY:
        case RE_OP_KEEP:
        case RE_OP_SKIP:
        case RE_OP_START_OF_WORD:
            /* A word or grapheme boundary. */
            status = build_BOUNDARY(args);
            if (status != RE_ERROR_SUCCESS)
                return status;
            break;
        case RE_OP_BRANCH:
            /* A 2-way branch. */
            status = build_BRANCH(args);
            if (status != RE_ERROR_SUCCESS)
                return status;
            break;
        case RE_OP_CALL_REF:
            /* A group call ref. */
            status = build_CALL_REF(args);
            if (status != RE_ERROR_SUCCESS)
                return status;
            break;
        case RE_OP_CHARACTER:
        case RE_OP_CHARACTER_IGN:
        case RE_OP_CHARACTER_IGN_REV:
        case RE_OP_CHARACTER_REV:
        case RE_OP_PROPERTY:
        case RE_OP_PROPERTY_IGN:
        case RE_OP_PROPERTY_IGN_REV:
        case RE_OP_PROPERTY_REV:
            /* A character literal or a property. */
            status = build_CHARACTER_or_PROPERTY(args);
            if (status != RE_ERROR_SUCCESS)
                return status;
            break;
        case RE_OP_CONDITIONAL:
            /* A lookaround conditional. */
            status = build_CONDITIONAL(args);
            if (status != RE_ERROR_SUCCESS)
                return status;
            break;
        case RE_OP_END_OF_LINE:
        case RE_OP_END_OF_LINE_U:
        case RE_OP_END_OF_STRING:
        case RE_OP_END_OF_STRING_LINE:
        case RE_OP_END_OF_STRING_LINE_U:
        case RE_OP_SEARCH_ANCHOR:
        case RE_OP_START_OF_LINE:
        case RE_OP_START_OF_LINE_U:
        case RE_OP_START_OF_STRING:
            /* A simple opcode with no trailing codewords and width of 0. */
            status = build_zerowidth(args);
            if (status != RE_ERROR_SUCCESS)
                return status;
            break;
        case RE_OP_FAILURE:
        case RE_OP_PRUNE:
        case RE_OP_SUCCESS:
            status = build_SUCCESS(args);
            if (status != RE_ERROR_SUCCESS)
                return status;
            break;
        case RE_OP_FUZZY:
            /* A fuzzy sequence. */
            status = build_FUZZY(args);
            if (status != RE_ERROR_SUCCESS)
                return status;
            break;
        case RE_OP_GREEDY_REPEAT:
        case RE_OP_LAZY_REPEAT:
            /* A repeated sequence. */
            status = build_REPEAT(args);
            if (status != RE_ERROR_SUCCESS)
                return status;
            break;
        case RE_OP_GROUP:
            /* A capture group. */
            status = build_GROUP(args);
            if (status != RE_ERROR_SUCCESS)
                return status;
            break;
        case RE_OP_GROUP_CALL:
            /* A group call. */
            status = build_GROUP_CALL(args);
            if (status != RE_ERROR_SUCCESS)
                return status;
            break;
        case RE_OP_GROUP_EXISTS:
            /* A conditional sequence. */
            status = build_GROUP_EXISTS(args);
            if (status != RE_ERROR_SUCCESS)
                return status;
            break;
        case RE_OP_LOOKAROUND:
            /* A lookaround. */
            status = build_LOOKAROUND(args);
            if (status != RE_ERROR_SUCCESS)
                return status;
            break;
        case RE_OP_RANGE:
        case RE_OP_RANGE_IGN:
        case RE_OP_RANGE_IGN_REV:
        case RE_OP_RANGE_REV:
            /* A range. */
            status = build_RANGE(args);
            if (status != RE_ERROR_SUCCESS)
                return status;
            break;
        case RE_OP_REF_GROUP:
        case RE_OP_REF_GROUP_FLD:
        case RE_OP_REF_GROUP_FLD_REV:
        case RE_OP_REF_GROUP_IGN:
        case RE_OP_REF_GROUP_IGN_REV:
        case RE_OP_REF_GROUP_REV:
            /* A reference to a group. */
            status = build_REF_GROUP(args);
            if (status != RE_ERROR_SUCCESS)
                return status;
            break;
        case RE_OP_SET_DIFF:
        case RE_OP_SET_DIFF_IGN:
        case RE_OP_SET_DIFF_IGN_REV:
        case RE_OP_SET_DIFF_REV:
        case RE_OP_SET_INTER:
        case RE_OP_SET_INTER_IGN:
        case RE_OP_SET_INTER_IGN_REV:
        case RE_OP_SET_INTER_REV:
        case RE_OP_SET_SYM_DIFF:
        case RE_OP_SET_SYM_DIFF_IGN:
        case RE_OP_SET_SYM_DIFF_IGN_REV:
        case RE_OP_SET_SYM_DIFF_REV:
        case RE_OP_SET_UNION:
        case RE_OP_SET_UNION_IGN:
        case RE_OP_SET_UNION_IGN_REV:
        case RE_OP_SET_UNION_REV:
            /* A set. */
            status = build_SET(args);
            if (status != RE_ERROR_SUCCESS)
                return status;
            break;
        case RE_OP_STRING:
        case RE_OP_STRING_FLD:
        case RE_OP_STRING_FLD_REV:
        case RE_OP_STRING_IGN:
        case RE_OP_STRING_IGN_REV:
        case RE_OP_STRING_REV:
            /* A string literal. */
            if (!build_STRING(args, FALSE))
                return FALSE;
            break;
        case RE_OP_STRING_SET:
        case RE_OP_STRING_SET_FLD:
        case RE_OP_STRING_SET_FLD_REV:
        case RE_OP_STRING_SET_IGN:
        case RE_OP_STRING_SET_IGN_REV:
        case RE_OP_STRING_SET_REV:
            /* A reference to a list. */
            status = build_STRING_SET(args);
            if (status != RE_ERROR_SUCCESS)
                return status;
            break;
        default:
            /* We've found an opcode which we don't recognise. We'll leave it
             * for the caller.
             */
            return RE_ERROR_SUCCESS;
        }
    }

    /* If we're here then we should be at the end of the code, otherwise we
     * have an error.
     */
    return args->code == args->end_code;
}

/* Compiles the regular expression code to 'nodes'.
 *
 * Various details about the regular expression are discovered during
 * compilation and stored in the PatternObject.
 */
Py_LOCAL_INLINE(BOOL) compile_to_nodes(RE_CODE* code, RE_CODE* end_code,
  PatternObject* pattern) {
    RE_CompileArgs args;
    int status;

    /* Compile a regex sequence and then check that we've reached the end
     * correctly. (The last opcode should be 'SUCCESS'.)
     *
     * If successful, 'start' and 'end' will point to the start and end nodes
     * of the compiled sequence.
     */
    args.code = code;
    args.end_code = end_code;
    args.pattern = pattern;
    args.forward = (pattern->flags & RE_FLAG_REVERSE) == 0;
    args.visible_captures = FALSE;
    args.has_captures = FALSE;
    args.repeat_depth = 0;
    args.is_fuzzy = FALSE;
    args.within_fuzzy = FALSE;
    args.visible_capture_count = 0;
    args.in_define = FALSE;
    status = build_sequence(&args);
    if (status == RE_ERROR_ILLEGAL)
        set_error(RE_ERROR_ILLEGAL, NULL);

    if (status != RE_ERROR_SUCCESS)
        return FALSE;

    pattern->min_width = args.min_width;
    pattern->is_fuzzy = args.is_fuzzy;
    pattern->do_search_start = TRUE;
    pattern->start_node = args.start;
    pattern->visible_capture_count = args.visible_capture_count;

    /* Optimise the pattern. */
    if (!optimise_pattern(pattern))
        return FALSE;

    pattern->start_test = locate_test_start(pattern->start_node);

    /* Get the call_ref for the entire pattern, if any. */
    if (pattern->start_node->op == RE_OP_CALL_REF)
        pattern->pattern_call_ref = (Py_ssize_t)pattern->start_node->values[0];
    else
        pattern->pattern_call_ref = -1;

    return TRUE;
}

/* Gets the required characters for a regex.
 *
 * In the event of an error, it just pretends that there are no required
 * characters.
 */
Py_LOCAL_INLINE(void) get_required_chars(PyObject* required_chars, RE_CODE**
  req_chars, size_t* req_length) {
    Py_ssize_t len;
    RE_CODE* chars;
    Py_ssize_t i;

    *req_chars = NULL;
    *req_length = 0;

    len = PyTuple_GET_SIZE(required_chars);
    if (len < 1 || PyErr_Occurred()) {
        PyErr_Clear();
        return;
    }

    chars = (RE_CODE*)re_alloc((size_t)len * sizeof(RE_CODE));
    if (!chars)
        goto error;

    for (i = 0; i < len; i++) {
        PyObject* o;
        size_t value;

        /* PyTuple_SET_ITEM borrows the reference. */
        o = PyTuple_GET_ITEM(required_chars, i);

        value = PyLong_AsUnsignedLong(o);
        if ((Py_ssize_t)value == -1 && PyErr_Occurred())
            goto error;

        chars[i] = (RE_CODE)value;
        if (chars[i] != value)
            goto error;
    }

    *req_chars = chars;
    *req_length = (size_t)len;

    return;

error:
    PyErr_Clear();
    re_dealloc(chars);
}

/* Makes a STRING node. */
Py_LOCAL_INLINE(RE_Node*) make_STRING_node(PatternObject* pattern, RE_UINT8 op,
  size_t length, RE_CODE* chars) {
    Py_ssize_t step;
    RE_Node* node;
    size_t i;

    step = get_step(op);

    /* Create the node. */
    node = create_node(pattern, op, 0, step * (Py_ssize_t)length, length);
    if (!node)
        return NULL;

    node->status |= RE_STATUS_STRING;

    for (i = 0; i < length; i++)
        node->values[i] = chars[i];

    return node;
}

/* Scans all of the characters in the current locale for their properties. */
Py_LOCAL_INLINE(void) scan_locale_chars(RE_LocaleInfo* locale_info) {
    int c;

    for (c = 0; c < 0x100; c++) {
        unsigned short props = 0;

        if (isalnum(c))
            props |= RE_LOCALE_ALNUM;
        if (isalpha(c))
            props |= RE_LOCALE_ALPHA;
        if (iscntrl(c))
            props |= RE_LOCALE_CNTRL;
        if (isdigit(c))
            props |= RE_LOCALE_DIGIT;
        if (isgraph(c))
            props |= RE_LOCALE_GRAPH;
        if (islower(c))
            props |= RE_LOCALE_LOWER;
        if (isprint(c))
            props |= RE_LOCALE_PRINT;
        if (ispunct(c))
            props |= RE_LOCALE_PUNCT;
        if (isspace(c))
            props |= RE_LOCALE_SPACE;
        if (isupper(c))
            props |= RE_LOCALE_UPPER;

        locale_info->properties[c] = props;
        locale_info->uppercase[c] = (unsigned char)toupper(c);
        locale_info->lowercase[c] = (unsigned char)tolower(c);
    }
}

/* Compiles regular expression code to a PatternObject.
 *
 * The regular expression code is provided as a list and is then compiled to
 * 'nodes'. Various details about the regular expression are discovered during
 * compilation and stored in the PatternObject.
 */
static PyObject* re_compile(PyObject* self_, PyObject* args) {
    PyObject* pattern;
    Py_ssize_t flags = 0;
    PyObject* code_list;
    PyObject* groupindex;
    PyObject* indexgroup;
    PyObject* named_lists;
    PyObject* named_list_indexes;
    Py_ssize_t req_offset;
    PyObject* required_chars;
    Py_ssize_t req_flags;
    size_t public_group_count;
    BOOL unpacked;
    Py_ssize_t code_len;
    RE_CODE* code;
    Py_ssize_t i;
    RE_CODE* req_chars;
    size_t req_length;
    PyObject* packed_code_list;
    PatternObject* self;
    BOOL unicode;
    BOOL locale;
    BOOL ascii;
    BOOL ok;

    if (!PyArg_ParseTuple(args, "OnOOOOOnOnn:re_compile", &pattern, &flags,
      &code_list, &groupindex, &indexgroup, &named_lists, &named_list_indexes,
      &req_offset, &required_chars, &req_flags, &public_group_count))
        return NULL;

    /* If it came from a pickled source, code_list will be a packed code list
     * in a bytestring.
     */
    if (PyBytes_Check(code_list)) {
        packed_code_list = code_list;
        code_list = unpack_code_list(packed_code_list);
        if (!code_list)
            return NULL;

        unpacked = TRUE;
    } else
        unpacked = FALSE;

    /* Read the regex code. */
    code_len = PyList_GET_SIZE(code_list);
    code = (RE_CODE*)re_alloc((size_t)code_len * sizeof(RE_CODE));
    if (!code) {
        if (unpacked) {
            /* code_list has been built from a packed code list. */
            Py_DECREF(code_list);
        }
        return NULL;
    }

    for (i = 0; i < code_len; i++) {
        PyObject* o;
        size_t value;

        /* PyList_GET_ITEM borrows a reference. */
        o = PyList_GET_ITEM(code_list, i);

        value = PyLong_AsUnsignedLong(o);
        if ((Py_ssize_t)value == -1 && PyErr_Occurred())
            goto error;

        code[i] = (RE_CODE)value;
        if (code[i] != value)
            goto error;
    }

    /* Get the required characters. */
    get_required_chars(required_chars, &req_chars, &req_length);

    if (!unpacked) {
        /* Pack the code list in case it's needed for pickling. */
        packed_code_list = pack_code_list(code, code_len);
        if (!packed_code_list) {
            set_error(RE_ERROR_MEMORY, NULL);
            re_dealloc(req_chars);
            re_dealloc(code);
            return NULL;
        }
    }

    /* Create the PatternObject. */
    self = PyObject_NEW(PatternObject, &Pattern_Type);
    if (!self) {
        set_error(RE_ERROR_MEMORY, NULL);
        if (unpacked) {
            Py_DECREF(code_list);
        } else {
            Py_DECREF(packed_code_list);
        }

        re_dealloc(req_chars);
        re_dealloc(code);
        return NULL;
    }

    /* Initialise the PatternObject. */
    self->pattern = pattern;
    self->flags = flags;
    self->packed_code_list = packed_code_list;
    self->weakreflist = NULL;
    self->start_node = NULL;
    self->repeat_count = 0;
    self->true_group_count = 0;
    self->public_group_count = public_group_count;
    self->visible_capture_count = 0;
    self->group_end_index = 0;
    self->groupindex = groupindex;
    self->indexgroup = indexgroup;
    self->named_lists = named_lists;
    self->named_lists_count = (size_t)PyDict_Size(named_lists);
    self->partial_named_lists[0] = NULL;
    self->partial_named_lists[1] = NULL;
    self->named_list_indexes = named_list_indexes;
    self->node_capacity = 0;
    self->node_count = 0;
    self->node_list = NULL;
    self->group_info_capacity = 0;
    self->group_info = NULL;
    self->call_ref_info_capacity = 0;
    self->call_ref_info_count = 0;
    self->call_ref_info = NULL;
    self->repeat_info_capacity = 0;
    self->repeat_info = NULL;
    self->groups_storage = NULL;
    self->repeats_storage = NULL;
    self->stack_storage = NULL;
    self->stack_capacity = 0;
    self->fuzzy_count = 0;
    self->req_offset = req_offset;
    self->required_chars = required_chars;
    self->req_flags = req_flags;
    self->req_string = NULL;
    self->locale_info = NULL;
    Py_INCREF(self->pattern);
    if (unpacked) {
        Py_INCREF(self->packed_code_list);
    }
    Py_INCREF(self->groupindex);
    Py_INCREF(self->indexgroup);
    Py_INCREF(self->named_lists);
    Py_INCREF(self->named_list_indexes);
    Py_INCREF(self->required_chars);

    /* Initialise the character encoding. */
    unicode = (flags & RE_FLAG_UNICODE) != 0;
    locale = (flags & RE_FLAG_LOCALE) != 0;
    ascii = (flags & RE_FLAG_ASCII) != 0;
    if (!unicode && !locale && !ascii) {
        if (PyBytes_Check(self->pattern))
            ascii = RE_FLAG_ASCII;
        else
            unicode = RE_FLAG_UNICODE;
    }
    if (unicode)
        self->encoding = &unicode_encoding;
    else if (locale)
        self->encoding = &locale_encoding;
    else if (ascii)
        self->encoding = &ascii_encoding;

    /* Compile the regular expression code to nodes. */
    ok = compile_to_nodes(code, code + code_len, self);

    /* We no longer need the regular expression code. */
    re_dealloc(code);

    if (!ok) {
        Py_DECREF(self);
        re_dealloc(req_chars);
        if (unpacked) {
            Py_DECREF(code_list);
        }
        return NULL;
    }

    /* Make a node for the required string, if there's one. */
    if (req_chars) {
        /* Remove the FULLCASE flag if it's not a Unicode pattern or not
         * ignoring case.
         */
        if (!(self->flags & RE_FLAG_UNICODE) || !(self->flags &
          RE_FLAG_IGNORECASE))
            req_flags &= ~RE_FLAG_FULLCASE;

        if (self->flags & RE_FLAG_REVERSE) {
            switch (req_flags) {
            case 0:
                self->req_string = make_STRING_node(self, RE_OP_STRING_REV,
                  req_length, req_chars);
                break;
            case RE_FLAG_IGNORECASE | RE_FLAG_FULLCASE:
                self->req_string = make_STRING_node(self, RE_OP_STRING_FLD_REV,
                  req_length, req_chars);
                break;
            case RE_FLAG_IGNORECASE:
                self->req_string = make_STRING_node(self, RE_OP_STRING_IGN_REV,
                  req_length, req_chars);
                break;
            }
        } else {
            switch (req_flags) {
            case 0:
                self->req_string = make_STRING_node(self, RE_OP_STRING,
                  req_length, req_chars);
                break;
            case RE_FLAG_IGNORECASE | RE_FLAG_FULLCASE:
                self->req_string = make_STRING_node(self, RE_OP_STRING_FLD,
                  req_length, req_chars);
                break;
            case RE_FLAG_IGNORECASE:
                self->req_string = make_STRING_node(self, RE_OP_STRING_IGN,
                  req_length, req_chars);
                break;
            }
        }

        re_dealloc(req_chars);
    }

    if (locale) {
        /* Store info about the characters in the locale for locale-sensitive
         * matching.
         */
        self->locale_info = re_alloc(sizeof(RE_LocaleInfo));
        if (!self->locale_info) {
            Py_DECREF(self);
            if (unpacked) {
                Py_DECREF(code_list);
            }
            return NULL;
        }

        scan_locale_chars(self->locale_info);
    }

    if (unpacked) {
        Py_DECREF(code_list);
    }

    return (PyObject*)self;

error:
    re_dealloc(code);
    set_error(RE_ERROR_ILLEGAL, NULL);
    if (unpacked) {
        Py_DECREF(code_list);
    }
    return NULL;
}

/* Gets the size of the codewords. */
static PyObject* get_code_size(PyObject* self, PyObject* unused) {
    return Py_BuildValue("n", sizeof(RE_CODE));
}

/* Gets the property dict. */
static PyObject* get_properties(PyObject* self_, PyObject* args) {
    Py_INCREF(property_dict);

    return property_dict;
}

/* Folds the case of a string. */
static PyObject* fold_case(PyObject* self_, PyObject* args) {
    RE_StringInfo str_info;
    Py_UCS4 (*char_at)(void* text, Py_ssize_t pos);
    RE_EncodingTable* encoding;
    RE_LocaleInfo locale_info;
    Py_ssize_t folded_charsize;
    void (*set_char_at)(void* text, Py_ssize_t pos, Py_UCS4 ch);
    Py_ssize_t buf_size;
    void* folded;
    Py_ssize_t folded_len;
    PyObject* result;

    Py_ssize_t flags;
    PyObject* string;
    if (!PyArg_ParseTuple(args, "nO:fold_case", &flags, &string))
        return NULL;

    if (!(flags & RE_FLAG_IGNORECASE)) {
        Py_INCREF(string);
        return string;
    }

    /* Get the string. */
    if (!get_string(string, &str_info))
        return NULL;

    /* Get the function for reading from the original string. */
    switch (str_info.charsize) {
    case 1:
        char_at = bytes1_char_at;
        break;
    case 2:
        char_at = bytes2_char_at;
        break;
    case 4:
        char_at = bytes4_char_at;
        break;
    default:
        release_buffer(&str_info);
        return NULL;
    }

    /* What's the encoding? */
    if (flags & RE_FLAG_UNICODE)
        encoding = &unicode_encoding;
    else if (flags & RE_FLAG_LOCALE) {
        encoding = &locale_encoding;
        scan_locale_chars(&locale_info);
    } else if (flags & RE_FLAG_ASCII)
        encoding = &ascii_encoding;
    else
        encoding = &unicode_encoding;

#if PY_VERSION_HEX >= 0x03030000
    /* Initially assume that the folded string will have the same width as the
     * original string (usually true).
     */
    folded_charsize = str_info.charsize;

    /* When folding a Unicode string, some codepoints in the range U+00..U+FF
     * are mapped to codepoints in the range U+0100..U+FFFF.
     */
    if (encoding == &unicode_encoding && str_info.charsize == 1)
        folded_charsize = 2;
#else
    /* The folded string will have the same width as the original string. */
    folded_charsize = str_info.charsize;
#endif

    /* Get the function for writing to the folded string. */
    switch (folded_charsize) {
    case 1:
        set_char_at = bytes1_set_char_at;
        break;
    case 2:
        set_char_at = bytes2_set_char_at;
        break;
    case 4:
        set_char_at = bytes4_set_char_at;
        break;
    default:
        release_buffer(&str_info);
        return NULL;
    }

    /* Allocate a buffer for the folded string. */
    if (flags & RE_FLAG_FULLCASE)
        /* When using full case-folding with Unicode, some single codepoints
         * are mapped to multiple codepoints.
         */
        buf_size = str_info.length * RE_MAX_FOLDED;
    else
        buf_size = str_info.length;

    folded = re_alloc((size_t)(buf_size * folded_charsize));
    if (!folded) {
        release_buffer(&str_info);
        return NULL;
    }

    /* Fold the case of the string. */
    folded_len = 0;

    if (flags & RE_FLAG_FULLCASE) {
        /* Full case-folding. */
        int (*full_case_fold)(RE_LocaleInfo* locale_info, Py_UCS4 ch, Py_UCS4*
          folded);
        Py_ssize_t i;
        Py_UCS4 codepoints[RE_MAX_FOLDED];

        full_case_fold = encoding->full_case_fold;

        for (i = 0; i < str_info.length; i++) {
            int count;
            int j;

            count = full_case_fold(&locale_info, char_at(str_info.characters,
              i), codepoints);
            for (j = 0; j < count; j++)
                set_char_at(folded, folded_len + j, codepoints[j]);

            folded_len += count;
        }
    } else {
        /* Simple case-folding. */
        Py_UCS4 (*simple_case_fold)(RE_LocaleInfo* locale_info, Py_UCS4 ch);
        Py_ssize_t i;

        simple_case_fold = encoding->simple_case_fold;

        for (i = 0; i < str_info.length; i++) {
            Py_UCS4 ch;

            ch = simple_case_fold(&locale_info, char_at(str_info.characters,
              i));
            set_char_at(folded, i, ch);
        }

        folded_len = str_info.length;
    }

    /* Build the result string. */
    if (str_info.is_unicode)
        result = build_unicode_value(folded, 0, folded_len, folded_charsize);
    else
        result = build_bytes_value(folded, 0, folded_len, folded_charsize);

    re_dealloc(folded);

    /* Release the original string's buffer. */
    release_buffer(&str_info);

    return result;
}

/* Returns a tuple of the Unicode characters that expand on full case-folding.
 */
static PyObject* get_expand_on_folding(PyObject* self, PyObject* unused) {
    int count;
    PyObject* result;
    int i;

    /* How many characters are there? */
    count = sizeof(re_expand_on_folding) / sizeof(re_expand_on_folding[0]);

    /* Put all the characters in a tuple. */
    result = PyTuple_New(count);
    if (!result)
        return NULL;

    for (i = 0; i < count; i++) {
#if PY_VERSION_HEX >= 0x03030000
        Py_UCS4 codepoint;
#else
        Py_UNICODE codepoint;
#endif
        PyObject* item;

        codepoint = re_expand_on_folding[i];

        item = build_unicode_value(&codepoint, 0, 1, sizeof(codepoint));
        if (!item)
            goto error;

        /* PyTuple_SetItem borrows the reference. */
        PyTuple_SetItem(result, i, item);
    }

    return result;

error:
    Py_DECREF(result);
    return NULL;
}

/* Returns whether a character has a given value for a Unicode property. */
static PyObject* has_property_value(PyObject* self_, PyObject* args) {
    BOOL v;

    Py_ssize_t property_value;
    Py_ssize_t character;
    if (!PyArg_ParseTuple(args, "nn:has_property_value", &property_value,
      &character))
        return NULL;

    v = unicode_has_property((RE_CODE)property_value, (Py_UCS4)character) ? 1 :
      0;

    return Py_BuildValue("n", v);
}

/* Returns a list of all the simple cases of a character.
 *
 * If full case-folding is turned on and the character also expands on full
 * case-folding, a None is appended to the list.
 */
static PyObject* get_all_cases(PyObject* self_, PyObject* args) {
    RE_EncodingTable* encoding;
    RE_LocaleInfo locale_info;
    int count;
    Py_UCS4 cases[RE_MAX_CASES];
    PyObject* result;
    int i;
    Py_UCS4 folded[RE_MAX_FOLDED];

    Py_ssize_t flags;
    Py_ssize_t character;
    if (!PyArg_ParseTuple(args, "nn:get_all_cases", &flags, &character))
        return NULL;

    /* What's the encoding? */
    if (flags & RE_FLAG_UNICODE)
        encoding = &unicode_encoding;
    else if (flags & RE_FLAG_LOCALE) {
        encoding = &locale_encoding;
        scan_locale_chars(&locale_info);
    } else if (flags & RE_FLAG_ASCII)
        encoding = &ascii_encoding;
    else
        encoding = &unicode_encoding;

    /* Get all the simple cases. */
    count = encoding->all_cases(&locale_info, (Py_UCS4)character, cases);

    result = PyList_New(count);
    if (!result)
        return NULL;

    for (i = 0; i < count; i++) {
        PyObject* item;

        item = Py_BuildValue("n", cases[i]);
        if (!item)
            goto error;

        /* PyList_SetItem borrows the reference. */
        PyList_SetItem(result, i, item);
    }

    /* If the character also expands on full case-folding, append a None. */
    if ((flags & RE_FULL_CASE_FOLDING) == RE_FULL_CASE_FOLDING) {
        count = encoding->full_case_fold(&locale_info, (Py_UCS4)character,
          folded);
        if (count > 1)
            PyList_Append(result, Py_None);
    }

    return result;

error:
    Py_DECREF(result);
    return NULL;
}

/* The table of the module's functions. */
static PyMethodDef _functions[] = {
    {"compile", (PyCFunction)re_compile, METH_VARARGS},
    {"get_code_size", (PyCFunction)get_code_size, METH_NOARGS},
    {"get_properties", (PyCFunction)get_properties, METH_VARARGS},
    {"fold_case", (PyCFunction)fold_case, METH_VARARGS},
    {"get_expand_on_folding", (PyCFunction)get_expand_on_folding, METH_NOARGS},
    {"has_property_value", (PyCFunction)has_property_value, METH_VARARGS},
    {"get_all_cases", (PyCFunction)get_all_cases, METH_VARARGS},
    {NULL, NULL}
};

/* Initialises the property dictionary. */
Py_LOCAL_INLINE(BOOL) init_property_dict(void) {
    size_t value_set_count;
    size_t i;
    PyObject** value_dicts;

    property_dict = NULL;

    /* How many value sets are there? */
    value_set_count = 0;

    for (i = 0; i < sizeof(re_property_values) / sizeof(re_property_values[0]);
      i++) {
        RE_PropertyValue* value;

        value = &re_property_values[i];
        if (value->value_set >= value_set_count)
            value_set_count = (size_t)value->value_set + 1;
    }

    /* Quick references for the value sets. */
    value_dicts = (PyObject**)re_alloc(value_set_count *
      sizeof(value_dicts[0]));
    if (!value_dicts)
        return FALSE;

    memset(value_dicts, 0, value_set_count * sizeof(value_dicts[0]));

    /* Build the property values dictionaries. */
    for (i = 0; i < sizeof(re_property_values) / sizeof(re_property_values[0]);
      i++) {
        RE_PropertyValue* value;
        PyObject* v;
        int status;

        value = &re_property_values[i];
        if (!value_dicts[value->value_set]) {
            value_dicts[value->value_set] = PyDict_New();
            if (!value_dicts[value->value_set])
                goto error;
        }

        v = Py_BuildValue("i", (int)value->id);
        if (!v)
            goto error;

        status = PyDict_SetItemString(value_dicts[value->value_set],
          re_strings[value->name], v);
        Py_DECREF(v);
        if (status < 0)
            goto error;
    }

    /* Build the property dictionary. */
    property_dict = PyDict_New();
    if (!property_dict)
        goto error;

    for (i = 0; i < sizeof(re_properties) / sizeof(re_properties[0]); i++) {
        RE_Property* property;
        PyObject* v;
        int status;

        property = &re_properties[i];
        v = Py_BuildValue("iO", (int)property->id,
          value_dicts[property->value_set]);
        if (!v)
            goto error;

        status = PyDict_SetItemString(property_dict,
          re_strings[property->name], v);
        Py_DECREF(v);
        if (status < 0)
            goto error;
    }

    /* DECREF the value sets. Any unused ones will be deallocated. */
    for (i = 0; i < value_set_count; i++)
        Py_XDECREF(value_dicts[i]);

    re_dealloc(value_dicts);

    return TRUE;

error:
    Py_XDECREF(property_dict);

    /* DECREF the value sets. */
    for (i = 0; i < value_set_count; i++)
        Py_XDECREF(value_dicts[i]);

    re_dealloc(value_dicts);

    return FALSE;
}

/* The module definition. */
static struct PyModuleDef regex_module = {
    PyModuleDef_HEAD_INIT,
    "_regex",
    NULL,
    -1,
    _functions,
    NULL,
    NULL,
    NULL,
    NULL
};

/* Initialises the module. */
PyMODINIT_FUNC PyInit__regex(void) {
    PyObject* m;
    PyObject* d;
    PyObject* x;

#if defined(VERBOSE)
    /* Unbuffered in case it crashes! */
    setvbuf(stdout, NULL, _IONBF, 0);

#endif
    /* Initialise Pattern_Type. */
    Pattern_Type.tp_dealloc = pattern_dealloc;
    Pattern_Type.tp_repr = pattern_repr;
    Pattern_Type.tp_flags = Py_TPFLAGS_DEFAULT;
    Pattern_Type.tp_doc = pattern_doc;
    Pattern_Type.tp_weaklistoffset = offsetof(PatternObject, weakreflist);
    Pattern_Type.tp_methods = pattern_methods;
    Pattern_Type.tp_members = pattern_members;
    Pattern_Type.tp_getset = pattern_getset;

    /* Initialise Match_Type. */
    Match_Type.tp_dealloc = match_dealloc;
    Match_Type.tp_repr = match_repr;
    Match_Type.tp_as_mapping = &match_as_mapping;
    Match_Type.tp_flags = Py_TPFLAGS_DEFAULT;
    Match_Type.tp_doc = match_doc;
    Match_Type.tp_methods = match_methods;
    Match_Type.tp_members = match_members;
    Match_Type.tp_getset = match_getset;

    /* Initialise Scanner_Type. */
    Scanner_Type.tp_dealloc = scanner_dealloc;
    Scanner_Type.tp_flags = Py_TPFLAGS_DEFAULT;
    Scanner_Type.tp_doc = scanner_doc;
    Scanner_Type.tp_iter = scanner_iter;
    Scanner_Type.tp_iternext = scanner_iternext;
    Scanner_Type.tp_methods = scanner_methods;
    Scanner_Type.tp_members = scanner_members;

    /* Initialise Splitter_Type. */
    Splitter_Type.tp_dealloc = splitter_dealloc;
    Splitter_Type.tp_flags = Py_TPFLAGS_DEFAULT;
    Splitter_Type.tp_doc = splitter_doc;
    Splitter_Type.tp_iter = splitter_iter;
    Splitter_Type.tp_iternext = splitter_iternext;
    Splitter_Type.tp_methods = splitter_methods;
    Splitter_Type.tp_members = splitter_members;

    /* Initialise Capture_Type. */
    Capture_Type.tp_dealloc = capture_dealloc;
    Capture_Type.tp_str = capture_str;
    Capture_Type.tp_as_mapping = &capture_as_mapping;
    Capture_Type.tp_flags = Py_TPFLAGS_DEFAULT;
    Capture_Type.tp_methods = capture_methods;

    /* Initialize object types */
    if (PyType_Ready(&Pattern_Type) < 0)
        return NULL;
    if (PyType_Ready(&Match_Type) < 0)
        return NULL;
    if (PyType_Ready(&Scanner_Type) < 0)
        return NULL;
    if (PyType_Ready(&Splitter_Type) < 0)
        return NULL;
    if (PyType_Ready(&Capture_Type) < 0)
        return NULL;

    error_exception = NULL;

    m = PyModule_Create(&regex_module);
    if (!m)
        return NULL;

    d = PyModule_GetDict(m);

    x = PyLong_FromLong(RE_MAGIC);
    if (x) {
        PyDict_SetItemString(d, "MAGIC", x);
        Py_DECREF(x);
    }

    x = PyLong_FromLong(sizeof(RE_CODE));
    if (x) {
        PyDict_SetItemString(d, "CODE_SIZE", x);
        Py_DECREF(x);
    }

    x = PyUnicode_FromString(copyright);
    if (x) {
        PyDict_SetItemString(d, "copyright", x);
        Py_DECREF(x);
    }

    /* Initialise the property dictionary. */
    if (!init_property_dict()) {
        Py_DECREF(m);
        return NULL;
    }

    return m;
}

/* vim:ts=4:sw=4:et */
