/*
 * $Id: GNUregex.c,v 1.12 2001/01/07 09:55:22 hno Exp $
 */

/* Extended regular expression matching and search library,
 * version 0.12.
 * (Implements POSIX draft P10003.2/D11.2, except for
 * internationalization features.)
 *
 * Copyright (C) 1993 Free Software Foundation, Inc.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.  */

/* AIX requires this to be the first thing in the file. */
#if defined (_AIX) && !defined (REGEX_MALLOC)
#pragma alloca
#endif

#ifndef _GNU_SOURCE
#define _GNU_SOURCE 1
#endif

#include "config.h"

#if !HAVE_ALLOCA
#define REGEX_MALLOC 1
#endif

/* The `emacs' switch turns on certain matching commands
 * that make sense only in Emacs. */
//#ifdef emacs
//
//#include "lisp.h"
//#include "buffer.h"
//#include "syntax.h"
//
///* Emacs uses `NULL' as a predicate.  */
//#undef NULL
//
//#else /* not emacs */

/* We used to test for `BSTRING' here, but only GCC and Emacs define
 * `BSTRING', as far as I know, and neither of them use this code.  */
#if HAVE_STRING_H || STDC_HEADERS
       #include <string.h>
#else
       #include <strings.h>
#endif

#ifdef STDC_HEADERS
       #include <stdlib.h>
#else
       char *malloc();
       char *realloc();
#endif


/* Define the syntax stuff for \<, \>, etc.  */

/* This must be nonzero for the wordchar and notwordchar pattern
 * commands in re_match_2.  */
#ifndef Sword
       #define Sword 1
#endif

#ifdef SYNTAX_TABLE

extern char *re_syntax_table;

#else /* not SYNTAX_TABLE */

/* How many characters in the character set.  */
#define CHAR_SET_SIZE 256

static char re_syntax_table[CHAR_SET_SIZE];
static void
init_syntax_once(void)
{
    register int c;
    static int done = 0;

    if (done)
       return;

    memset(re_syntax_table, 0, sizeof re_syntax_table);

    for (c = 'a'; c <= 'z'; c++)
       re_syntax_table[c] = Sword;

    for (c = 'A'; c <= 'Z'; c++)
       re_syntax_table[c] = Sword;

    for (c = '0'; c <= '9'; c++)
       re_syntax_table[c] = Sword;

    re_syntax_table['_'] = Sword;

    done = 1;
}

#endif /* not SYNTAX_TABLE */

#define SYNTAX(c) re_syntax_table[c]

//#endif /* not emacs */

/* Get the interface, including the syntax bits.  */
#include "GNUregex.h"

/* isalpha etc. are used for the character classes.  */
#include <ctype.h>

#ifndef isascii
#define isascii(c) 1
#endif

#ifdef isblank
#define ISBLANK(c) (isascii (c) && isblank (c))
#else
#define ISBLANK(c) ((c) == ' ' || (c) == '\t')
#endif
#ifdef isgraph
#define ISGRAPH(c) (isascii (c) && isgraph (c))
#else
#define ISGRAPH(c) (isascii (c) && isprint (c) && !isspace (c))
#endif

#define ISPRINT(c) (isascii (c) && isprint (c))
#define ISDIGIT(c) (isascii (c) && isdigit (c))
#define ISALNUM(c) (isascii (c) && isalnum (c))
#define ISALPHA(c) (isascii (c) && isalpha (c))
#define ISCNTRL(c) (isascii (c) && iscntrl (c))
#define ISLOWER(c) (isascii (c) && islower (c))
#define ISPUNCT(c) (isascii (c) && ispunct (c))
#define ISSPACE(c) (isascii (c) && isspace (c))
#define ISUPPER(c) (isascii (c) && isupper (c))
#define ISXDIGIT(c) (isascii (c) && isxdigit (c))

#ifndef NULL
#define NULL 0
#endif

/* We remove any previous definition of `SIGN_EXTEND_CHAR',
 * since ours (we hope) works properly with all combinations of
 * machines, compilers, `char' and `unsigned char' argument types.
 * (Per Bothner suggested the basic approach.)  */
#undef SIGN_EXTEND_CHAR
#ifdef __STDC__
#define SIGN_EXTEND_CHAR(c) ((signed char) (c))
#else /* not __STDC__ */
/* As in Harbison and Steele.  */
#define SIGN_EXTEND_CHAR(c) ((((unsigned char) (c)) ^ 128) - 128)
#endif

/* Should we use malloc or alloca?  If REGEX_MALLOC is not defined, we
 * use `alloca' instead of `malloc'.  This is because using malloc in
 * re_search* or re_match* could cause memory leaks when C-g is used in
 * Emacs; also, malloc is slower and causes storage fragmentation.  On
 * the other hand, malloc is more portable, and easier to debug.
 *
 * Because we sometimes use alloca, some routines have to be macros,
 * not functions -- `alloca'-allocated space disappears at the end of the
 * function it is called in.  */

#ifdef REGEX_MALLOC

#define REGEX_ALLOCATE malloc
#define REGEX_REALLOCATE(source, osize, nsize) realloc (source, nsize)

#else /* not REGEX_MALLOC  */

/* Emacs already defines alloca, sometimes.  */
#ifndef alloca

/* Make alloca work the best possible way.  */
#ifdef __GNUC__
#define alloca __builtin_alloca
#else /* not __GNUC__ */
#if HAVE_ALLOCA_H
#include <alloca.h>
#else /* not __GNUC__ or HAVE_ALLOCA_H */
#ifndef _AIX                   /* Already did AIX, up at the top.  */
char *alloca();
#endif /* not _AIX */
#endif /* not HAVE_ALLOCA_H */
#endif /* not __GNUC__ */

#endif /* not alloca */

#define REGEX_ALLOCATE alloca

/* Assumes a `char *destination' variable.  */
#define REGEX_REALLOCATE(source, osize, nsize)                         \
  (destination = (char *) alloca (nsize),                              \
   xmemcpy (destination, source, osize),                               \
   destination)

#endif /* not REGEX_MALLOC */


/* True if `size1' is non-NULL and PTR is pointing anywhere inside
 * `string1' or just past its end.  This works if PTR is NULL, which is
 * a good thing.  */
#define FIRST_STRING_P(ptr)                                    \
  (size1 && string1 <= (ptr) && (ptr) <= string1 + size1)

/* (Re)Allocate N items of type T using malloc, or fail.  */
#define TALLOC(n, t) ((t *) malloc ((n) * sizeof (t)))
#define RETALLOC(addr, n, t) ((addr) = (t *) realloc (addr, (n) * sizeof (t)))
#define REGEX_TALLOC(n, t) ((t *) REGEX_ALLOCATE ((n) * sizeof (t)))

#define BYTEWIDTH 8            /* In bits.  */

#define STREQ(s1, s2) ((strcmp (s1, s2) == 0))

#define MAX(a, b) ((a) > (b) ? (a) : (b))
#define MIN(a, b) ((a) < (b) ? (a) : (b))

typedef char boolean;
#define false 0
#define true 1

/* These are the command codes that appear in compiled regular
 * expressions.  Some opcodes are followed by argument bytes.  A
 * command code can specify any interpretation whatsoever for its
 * arguments.  Zero bytes may appear in the compiled regular expression.
 *
 * The value of `exactn' is needed in search.c (search_buffer) in Emacs.
 * So regex.h defines a symbol `RE_EXACTN_VALUE' to be 1; the value of
 * `exactn' we use here must also be 1.  */

typedef enum {
    no_op = 0,

    /* Followed by one byte giving n, then by n literal bytes.  */
    exactn = 1,

    /* Matches any (more or less) character.  */
    anychar,

    /* Matches any one char belonging to specified set.  First
     * following byte is number of bitmap bytes.  Then come bytes
     * for a bitmap saying which chars are in.  Bits in each byte
     * are ordered low-bit-first.  A character is in the set if its
     * bit is 1.  A character too large to have a bit in the map is
     * automatically not in the set.  */
    charset,

    /* Same parameters as charset, but match any character that is
     * not one of those specified.  */
    charset_not,

    /* Start remembering the text that is matched, for storing in a
     * register.  Followed by one byte with the register number, in
     * the range 0 to one less than the pattern buffer's re_nsub
     * field.  Then followed by one byte with the number of groups
     * inner to this one.  (This last has to be part of the
     * start_memory only because we need it in the on_failure_jump
     * of re_match_2.)  */
    start_memory,

    /* Stop remembering the text that is matched and store it in a
     * memory register.  Followed by one byte with the register
     * number, in the range 0 to one less than `re_nsub' in the
     * pattern buffer, and one byte with the number of inner groups,
     * just like `start_memory'.  (We need the number of inner
     * groups here because we don't have any easy way of finding the
     * corresponding start_memory when we're at a stop_memory.)  */
    stop_memory,

    /* Match a duplicate of something remembered. Followed by one
     * byte containing the register number.  */
    duplicate,

    /* Fail unless at beginning of line.  */
    begline,

    /* Fail unless at end of line.  */
    endline,

    /* Succeeds if at beginning of buffer (if emacs) or at beginning
     * of string to be matched (if not).  */
    begbuf,

    /* Analogously, for end of buffer/string.  */
    endbuf,

    /* Followed by two byte relative address to which to jump.  */
    jump,

    /* Same as jump, but marks the end of an alternative.  */
    jump_past_alt,

    /* Followed by two-byte relative address of place to resume at
     * in case of failure.  */
    on_failure_jump,

    /* Like on_failure_jump, but pushes a placeholder instead of the
     * current string position when executed.  */
    on_failure_keep_string_jump,

    /* Throw away latest failure point and then jump to following
     * two-byte relative address.  */
    pop_failure_jump,

    /* Change to pop_failure_jump if know won't have to backtrack to
     * match; otherwise change to jump.  This is used to jump
     * back to the beginning of a repeat.  If what follows this jump
     * clearly won't match what the repeat does, such that we can be
     * sure that there is no use backtracking out of repetitions
     * already matched, then we change it to a pop_failure_jump.
     * Followed by two-byte address.  */
    maybe_pop_jump,

    /* Jump to following two-byte address, and push a dummy failure
     * point. This failure point will be thrown away if an attempt
     * is made to use it for a failure.  A `+' construct makes this
     * before the first repeat.  Also used as an intermediary kind
     * of jump when compiling an alternative.  */
    dummy_failure_jump,

    /* Push a dummy failure point and continue.  Used at the end of
     * alternatives.  */
    push_dummy_failure,

    /* Followed by two-byte relative address and two-byte number n.
     * After matching N times, jump to the address upon failure.  */
    succeed_n,

    /* Followed by two-byte relative address, and two-byte number n.
     * Jump to the address N times, then fail.  */
    jump_n,

    /* Set the following two-byte relative address to the
     * subsequent two-byte number.  The address *includes* the two
     * bytes of number.  */
    set_number_at,

    wordchar,                  /* Matches any word-constituent character.  */
    notwordchar,               /* Matches any char that is not a word-constituent.  */

    wordbeg,                   /* Succeeds if at word beginning.  */
    wordend,                   /* Succeeds if at word end.  */

    wordbound,                 /* Succeeds if at a word boundary.  */
    notwordbound               /* Succeeds if not at a word boundary.  */

#ifdef emacs
    ,before_dot,               /* Succeeds if before point.  */
    at_dot,                    /* Succeeds if at point.  */
    after_dot,                 /* Succeeds if after point.  */

    /* Matches any character whose syntax is specified.  Followed by
     * a byte which contains a syntax code, e.g., Sword.  */
    syntaxspec,

    /* Matches any character whose syntax is not that specified.  */
    notsyntaxspec
#endif                         /* emacs */
} re_opcode_t;

/* Common operations on the compiled pattern.  */

/* Store NUMBER in two contiguous bytes starting at DESTINATION.  */

#define STORE_NUMBER(destination, number)                              \
  do {                                                                 \
    (destination)[0] = (number) & 0377;                                        \
    (destination)[1] = (number) >> 8;                                  \
  } while (0)

/* Same as STORE_NUMBER, except increment DESTINATION to
 * the byte after where the number is stored.  Therefore, DESTINATION
 * must be an lvalue.  */

#define STORE_NUMBER_AND_INCR(destination, number)                     \
  do {                                                                 \
    STORE_NUMBER (destination, number);                                        \
    (destination) += 2;                                                        \
  } while (0)

/* Put into DESTINATION a number stored in two contiguous bytes starting
 * at SOURCE.  */

#define EXTRACT_NUMBER(destination, source)                            \
  do {                                                                 \
    (destination) = *(source) & 0377;                                  \
    (destination) += SIGN_EXTEND_CHAR (*((source) + 1)) << 8;          \
  } while (0)

#ifdef DEBUG
static void
extract_number(dest, source)
     int *dest;
     unsigned char *source;
{
    int temp = SIGN_EXTEND_CHAR(*(source + 1));
    *dest = *source & 0377;
    *dest += temp << 8;
}

#ifndef EXTRACT_MACROS         /* To debug the macros.  */
#undef EXTRACT_NUMBER
#define EXTRACT_NUMBER(dest, src) extract_number (&dest, src)
#endif /* not EXTRACT_MACROS */

#endif /* DEBUG */

/* Same as EXTRACT_NUMBER, except increment SOURCE to after the number.
 * SOURCE must be an lvalue.  */

#define EXTRACT_NUMBER_AND_INCR(destination, source)                   \
  do {                                                                 \
    EXTRACT_NUMBER (destination, source);                              \
    (source) += 2;                                                     \
  } while (0)

#ifdef DEBUG
static void
extract_number_and_incr(destination, source)
     int *destination;
     unsigned char **source;
{
    extract_number(destination, *source);
    *source += 2;
}

#ifndef EXTRACT_MACROS
#undef EXTRACT_NUMBER_AND_INCR
#define EXTRACT_NUMBER_AND_INCR(dest, src) \
  extract_number_and_incr (&dest, &src)
#endif /* not EXTRACT_MACROS */

#endif /* DEBUG */

/* If DEBUG is defined, Regex prints many voluminous messages about what
 * it is doing (if the variable `debug' is nonzero).  If linked with the
 * main program in `iregex.c', you can enter patterns and strings
 * interactively.  And if linked with the main program in `main.c' and
 * the other test files, you can run the already-written tests.  */

#ifdef DEBUG

/* We use standard I/O for debugging.  */
#include <stdio.h>

/* It is useful to test things that ``must'' be true when debugging.  */
#include <assert.h>

static int debug = 0;

#define DEBUG_STATEMENT(e) e
#define DEBUG_PRINT1(x) if (debug) printf (x)
#define DEBUG_PRINT2(x1, x2) if (debug) printf (x1, x2)
#define DEBUG_PRINT3(x1, x2, x3) if (debug) printf (x1, x2, x3)
#define DEBUG_PRINT4(x1, x2, x3, x4) if (debug) printf (x1, x2, x3, x4)
#define DEBUG_PRINT_COMPILED_PATTERN(p, s, e)                          \
  if (debug) print_partial_compiled_pattern (s, e)
#define DEBUG_PRINT_DOUBLE_STRING(w, s1, sz1, s2, sz2)                 \
  if (debug) print_double_string (w, s1, sz1, s2, sz2)


extern void printchar();

/* Print the fastmap in human-readable form.  */

void
print_fastmap(fastmap)
     char *fastmap;
{
    unsigned was_a_range = 0;
    unsigned i = 0;

    while (i < (1 << BYTEWIDTH)) {
       if (fastmap[i++]) {
           was_a_range = 0;
           printchar(i - 1);
           while (i < (1 << BYTEWIDTH) && fastmap[i]) {
               was_a_range = 1;
               i++;
           }
           if (was_a_range) {
               printf("-");
               printchar(i - 1);
           }
       }
    }
    putchar('\n');
}


/* Print a compiled pattern string in human-readable form, starting at
 * the START pointer into it and ending just before the pointer END.  */

void
print_partial_compiled_pattern(start, end)
     unsigned char *start;
     unsigned char *end;
{
    int mcnt, mcnt2;
    unsigned char *p = start;
    unsigned char *pend = end;

    if (start == NULL) {
       printf("(null)\n");
       return;
    }
    /* Loop over pattern commands.  */
    while (p < pend) {
       switch ((re_opcode_t) * p++) {
       case no_op:
           printf("/no_op");
           break;

       case exactn:
           mcnt = *p++;
           printf("/exactn/%d", mcnt);
           do {
               putchar('/');
               printchar(*p++);
           }
           while (--mcnt);
           break;

       case start_memory:
           mcnt = *p++;
           printf("/start_memory/%d/%d", mcnt, *p++);
           break;

       case stop_memory:
           mcnt = *p++;
           printf("/stop_memory/%d/%d", mcnt, *p++);
           break;

       case duplicate:
           printf("/duplicate/%d", *p++);
           break;

       case anychar:
           printf("/anychar");
           break;

       case charset:
       case charset_not:
           {
               register int c;

               printf("/charset%s",
                   (re_opcode_t) * (p - 1) == charset_not ? "_not" : "");

               assert(p + *p < pend);

               for (c = 0; c < *p; c++) {
                   unsigned bit;
                   unsigned char map_byte = p[1 + c];

                   putchar('/');

                   for (bit = 0; bit < BYTEWIDTH; bit++)
                       if (map_byte & (1 << bit))
                           printchar(c * BYTEWIDTH + bit);
               }
               p += 1 + *p;
               break;
           }

       case begline:
           printf("/begline");
           break;

       case endline:
           printf("/endline");
           break;

       case on_failure_jump:
           extract_number_and_incr(&mcnt, &p);
           printf("/on_failure_jump/0/%d", mcnt);
           break;

       case on_failure_keep_string_jump:
           extract_number_and_incr(&mcnt, &p);
           printf("/on_failure_keep_string_jump/0/%d", mcnt);
           break;

       case dummy_failure_jump:
           extract_number_and_incr(&mcnt, &p);
           printf("/dummy_failure_jump/0/%d", mcnt);
           break;

       case push_dummy_failure:
           printf("/push_dummy_failure");
           break;

       case maybe_pop_jump:
           extract_number_and_incr(&mcnt, &p);
           printf("/maybe_pop_jump/0/%d", mcnt);
           break;

       case pop_failure_jump:
           extract_number_and_incr(&mcnt, &p);
           printf("/pop_failure_jump/0/%d", mcnt);
           break;

       case jump_past_alt:
           extract_number_and_incr(&mcnt, &p);
           printf("/jump_past_alt/0/%d", mcnt);
           break;

       case jump:
           extract_number_and_incr(&mcnt, &p);
           printf("/jump/0/%d", mcnt);
           break;

       case succeed_n:
           extract_number_and_incr(&mcnt, &p);
           extract_number_and_incr(&mcnt2, &p);
           printf("/succeed_n/0/%d/0/%d", mcnt, mcnt2);
           break;

       case jump_n:
           extract_number_and_incr(&mcnt, &p);
           extract_number_and_incr(&mcnt2, &p);
           printf("/jump_n/0/%d/0/%d", mcnt, mcnt2);
           break;

       case set_number_at:
           extract_number_and_incr(&mcnt, &p);
           extract_number_and_incr(&mcnt2, &p);
           printf("/set_number_at/0/%d/0/%d", mcnt, mcnt2);
           break;

       case wordbound:
           printf("/wordbound");
           break;

       case notwordbound:
           printf("/notwordbound");
           break;

       case wordbeg:
           printf("/wordbeg");
           break;

       case wordend:
           printf("/wordend");

#ifdef emacs
       case before_dot:
           printf("/before_dot");
           break;

       case at_dot:
           printf("/at_dot");
           break;

       case after_dot:
           printf("/after_dot");
           break;

       case syntaxspec:
           printf("/syntaxspec");
           mcnt = *p++;
           printf("/%d", mcnt);
           break;

       case notsyntaxspec:
           printf("/notsyntaxspec");
           mcnt = *p++;
           printf("/%d", mcnt);
           break;
#endif /* emacs */

       case wordchar:
           printf("/wordchar");
           break;

       case notwordchar:
           printf("/notwordchar");
           break;

       case begbuf:
           printf("/begbuf");
           break;

       case endbuf:
           printf("/endbuf");
           break;

       default:
           printf("?%d", *(p - 1));
       }
    }
    printf("/\n");
}


void
print_compiled_pattern(bufp)
     struct re_pattern_buffer *bufp;
{
    unsigned char *buffer = bufp->buffer;

    print_partial_compiled_pattern(buffer, buffer + bufp->used);
    printf("%d bytes used/%d bytes allocated.\n", bufp->used, bufp->allocated);

    if (bufp->fastmap_accurate && bufp->fastmap) {
       printf("fastmap: ");
       print_fastmap(bufp->fastmap);
    }
    printf("re_nsub: %d\t", bufp->re_nsub);
    printf("regs_alloc: %d\t", bufp->regs_allocated);
    printf("can_be_null: %d\t", bufp->can_be_null);
    printf("newline_anchor: %d\n", bufp->newline_anchor);
    printf("no_sub: %d\t", bufp->no_sub);
    printf("not_bol: %d\t", bufp->not_bol);
    printf("not_eol: %d\t", bufp->not_eol);
    printf("syntax: %d\n", bufp->syntax);
    /* Perhaps we should print the translate table?  */
}


void
print_double_string(where, string1, size1, string2, size2)
     const char *where;
     const char *string1;
     const char *string2;
     int size1;
     int size2;
{
    unsigned this_char;

    if (where == NULL)
       printf("(null)");
    else {
       if (FIRST_STRING_P(where)) {
           for (this_char = where - string1; this_char < size1; this_char++)
               printchar(string1[this_char]);

           where = string2;
       }
       for (this_char = where - string2; this_char < size2; this_char++)
           printchar(string2[this_char]);
    }
}

#else /* not DEBUG */

#undef assert
#define assert(e)

#define DEBUG_STATEMENT(e)
#define DEBUG_PRINT1(x)
#define DEBUG_PRINT2(x1, x2)
#define DEBUG_PRINT3(x1, x2, x3)
#define DEBUG_PRINT4(x1, x2, x3, x4)
#define DEBUG_PRINT_COMPILED_PATTERN(p, s, e)
#define DEBUG_PRINT_DOUBLE_STRING(w, s1, sz1, s2, sz2)

#endif /* not DEBUG */

/* Set by `re_set_syntax' to the current regexp syntax to recognize.  Can
 * also be assigned to arbitrarily: each pattern buffer stores its own
 * syntax, so it can be changed between regex compilations.  */
reg_syntax_t re_syntax_options = RE_SYNTAX_EMACS;


/* Specify the precise syntax of regexps for compilation.  This provides
 * for compatibility for various utilities which historically have
 * different, incompatible syntaxes.
 *
 * The argument SYNTAX is a bit mask comprised of the various bits
 * defined in regex.h.  We return the old syntax.  */

reg_syntax_t
re_set_syntax(reg_syntax_t  syntax)
{
    reg_syntax_t ret = re_syntax_options;

    re_syntax_options = syntax;
    return ret;
}

/* This table gives an error message for each of the error codes listed
 * in regex.h.  Obviously the order here has to be same as there.  */

static const char *re_error_msg[] =
{NULL,                         /* REG_NOERROR */
    "No match",                        /* REG_NOMATCH */
    "Invalid regular expression",      /* REG_BADPAT */
    "Invalid collation character",     /* REG_ECOLLATE */
    "Invalid character class name",    /* REG_ECTYPE */
    "Trailing backslash",      /* REG_EESCAPE */
    "Invalid back reference",  /* REG_ESUBREG */
    "Unmatched [ or [^",       /* REG_EBRACK */
    "Unmatched ( or \\(",      /* REG_EPAREN */
    "Unmatched \\{",           /* REG_EBRACE */
    "Invalid content of \\{\\}",       /* REG_BADBR */
    "Invalid range end",       /* REG_ERANGE */
    "Memory exhausted",                /* REG_ESPACE */
    "Invalid preceding regular expression",    /* REG_BADRPT */
    "Premature end of regular expression",     /* REG_EEND */
    "Regular expression too big",      /* REG_ESIZE */
    "Unmatched ) or \\)",      /* REG_ERPAREN */
};

/* Subroutine declarations and macros for regex_compile.  */

static void
store_op1(re_opcode_t op,unsigned char * loc, int  arg);
static void
store_op2(re_opcode_t op, unsigned char *loc, int arg1, int arg2);

static void
insert_op1(re_opcode_t  op, unsigned char *loc, int arg, unsigned char * end);
static void
insert_op2(re_opcode_t  op, unsigned char *loc, int arg1,int  arg2, unsigned char * end);

static boolean
at_begline_loc_p(const char *pattern, const char *p, reg_syntax_t syntax);
static boolean
at_endline_loc_p(const char *p, const char * pend, int syntax);



static reg_errcode_t
compile_range(const char **p_ptr, char *pend, char *  translate, reg_syntax_t  syntax, unsigned char * b);


/* Fetch the next character in the uncompiled pattern---translating it
 * if necessary.  Also cast from a signed character in the constant
 * string passed to us by the user to an unsigned char that we can use
 * as an array index (in, e.g., `translate').  */
#define PATFETCH(c)                                                    \
  do {if (p == pend) return REG_EEND;                                  \
    c = (unsigned char) *p++;                                          \
    if (translate) c = translate[c];                                   \
  } while (0)

/* Fetch the next character in the uncompiled pattern, with no
 * translation.  */
#define PATFETCH_RAW(c)                                                        \
  do {if (p == pend) return REG_EEND;                                  \
    c = (unsigned char) *p++;                                          \
  } while (0)

/* Go backwards one character in the pattern.  */
#define PATUNFETCH p--


/* If `translate' is non-null, return translate[D], else just D.  We
 * cast the subscript to translate because some data is declared as
 * `char *', to avoid warnings when a string constant is passed.  But
 * when we use a character as a subscript we must make it unsigned.  */
#define TRANSLATE(d) (translate ? translate[(unsigned char) (d)] : (d))


/* Macros for outputting the compiled pattern into `buffer'.  */

/* If the buffer isn't allocated when it comes in, use this.  */
#define INIT_BUF_SIZE  32

/* Make sure we have at least N more bytes of space in buffer.  */
#define GET_BUFFER_SPACE(n)                                            \
    while (b - bufp->buffer + (n) > bufp->allocated)                   \
      EXTEND_BUFFER ()

/* Make sure we have one more byte of buffer space and then add C to it.  */
#define BUF_PUSH(c)                                                    \
  do {                                                                 \
    GET_BUFFER_SPACE (1);                                              \
    *b++ = (unsigned char) (c);                                                \
  } while (0)


/* Ensure we have two more bytes of buffer space and then append C1 and C2.  */
#define BUF_PUSH_2(c1, c2)                                             \
  do {                                                                 \
    GET_BUFFER_SPACE (2);                                              \
    *b++ = (unsigned char) (c1);                                       \
    *b++ = (unsigned char) (c2);                                       \
  } while (0)


/* As with BUF_PUSH_2, except for three bytes.  */
#define BUF_PUSH_3(c1, c2, c3)                                         \
  do {                                                                 \
    GET_BUFFER_SPACE (3);                                              \
    *b++ = (unsigned char) (c1);                                       \
    *b++ = (unsigned char) (c2);                                       \
    *b++ = (unsigned char) (c3);                                       \
  } while (0)


/* Store a jump with opcode OP at LOC to location TO.  We store a
 * relative address offset by the three bytes the jump itself occupies.  */
#define STORE_JUMP(op, loc, to) \
  store_op1 (op, loc, (to) - (loc) - 3)

/* Likewise, for a two-argument jump.  */
#define STORE_JUMP2(op, loc, to, arg) \
  store_op2 (op, loc, (to) - (loc) - 3, arg)

/* Like `STORE_JUMP', but for inserting.  Assume `b' is the buffer end.  */
#define INSERT_JUMP(op, loc, to) \
  insert_op1 (op, loc, (to) - (loc) - 3, b)

/* Like `STORE_JUMP2', but for inserting.  Assume `b' is the buffer end.  */
#define INSERT_JUMP2(op, loc, to, arg) \
  insert_op2 (op, loc, (to) - (loc) - 3, arg, b)


/* This is not an arbitrary limit: the arguments which represent offsets
 * into the pattern are two bytes long.  So if 2^16 bytes turns out to
 * be too small, many things would have to change.  */
#define MAX_BUF_SIZE (1L << 16)


/* Extend the buffer by twice its current size via realloc and
 * reset the pointers that pointed into the old block to point to the
 * correct places in the new one.  If extending the buffer results in it
 * being larger than MAX_BUF_SIZE, then flag memory exhausted.  */
#define EXTEND_BUFFER()                                                        \
  do {                                                                         \
    unsigned char *old_buffer = bufp->buffer;                          \
    if (bufp->allocated == MAX_BUF_SIZE)                               \
      return REG_ESIZE;                                                        \
    bufp->allocated <<= 1;                                             \
    if (bufp->allocated > MAX_BUF_SIZE)                                        \
      bufp->allocated = MAX_BUF_SIZE;                                  \
    bufp->buffer = (unsigned char *) realloc (bufp->buffer, bufp->allocated);\
    if (bufp->buffer == NULL)                                          \
      return REG_ESPACE;                                               \
    /* If the buffer moved, move all the pointers into it.  */         \
    if (old_buffer != bufp->buffer)                                    \
      {                                                                        \
        b = (b - old_buffer) + bufp->buffer;                           \
        begalt = (begalt - old_buffer) + bufp->buffer;                 \
        if (fixup_alt_jump)                                            \
          fixup_alt_jump = (fixup_alt_jump - old_buffer) + bufp->buffer;\
        if (laststart)                                                 \
          laststart = (laststart - old_buffer) + bufp->buffer;         \
        if (pending_exact)                                             \
          pending_exact = (pending_exact - old_buffer) + bufp->buffer; \
      }                                                                        \
  } while (0)


/* Since we have one byte reserved for the register number argument to
 * {start,stop}_memory, the maximum number of groups we can report
 * things about is what fits in that byte.  */
#define MAX_REGNUM 255

/* But patterns can have more than `MAX_REGNUM' registers.  We just
 * ignore the excess.  */
typedef unsigned regnum_t;


/* Macros for the compile stack.  */

/* Since offsets can go either forwards or backwards, this type needs to
 * be able to hold values from -(MAX_BUF_SIZE - 1) to MAX_BUF_SIZE - 1.  */
typedef int pattern_offset_t;

typedef struct {
    pattern_offset_t begalt_offset;
    pattern_offset_t fixup_alt_jump;
    pattern_offset_t inner_group_offset;
    pattern_offset_t laststart_offset;
    regnum_t regnum;
} compile_stack_elt_t;


typedef struct {
    compile_stack_elt_t *stack;
    unsigned size;
    unsigned avail;            /* Offset of next open position.  */
} compile_stack_type;

static boolean
group_in_compile_stack(compile_stack_type  compile_stack,regnum_t  regnum);

#define INIT_COMPILE_STACK_SIZE 32

#define COMPILE_STACK_EMPTY  (compile_stack.avail == 0)
#define COMPILE_STACK_FULL  (compile_stack.avail == compile_stack.size)

/* The next available element.  */
#define COMPILE_STACK_TOP (compile_stack.stack[compile_stack.avail])


/* Set the bit for character C in a list.  */
#define SET_LIST_BIT(c)                               \
  (b[((unsigned char) (c)) / BYTEWIDTH]               \
   |= 1 << (((unsigned char) c) % BYTEWIDTH))


/* Get the next unsigned number in the uncompiled pattern.  */
#define GET_UNSIGNED_NUMBER(num)                                       \
  { if (p != pend)                                                     \
     {                                                                 \
       PATFETCH (c);                                                   \
       while (ISDIGIT (c))                                             \
         {                                                             \
           if (num < 0)                                                        \
              num = 0;                                                 \
           num = num * 10 + c - '0';                                   \
           if (p == pend)                                              \
              break;                                                   \
           PATFETCH (c);                                               \
         }                                                             \
       }                                                               \
    }

#define CHAR_CLASS_MAX_LENGTH  6       /* Namely, `xdigit'.  */

#define IS_CHAR_CLASS(string)                                          \
   (STREQ (string, "alpha") || STREQ (string, "upper")                 \
    || STREQ (string, "lower") || STREQ (string, "digit")              \
    || STREQ (string, "alnum") || STREQ (string, "xdigit")             \
    || STREQ (string, "space") || STREQ (string, "print")              \
    || STREQ (string, "punct") || STREQ (string, "graph")              \
    || STREQ (string, "cntrl") || STREQ (string, "blank"))

/* `regex_compile' compiles PATTERN (of length SIZE) according to SYNTAX.
 * Returns one of error codes defined in `regex.h', or zero for success.
 *
 * Assumes the `allocated' (and perhaps `buffer') and `translate'
 * fields are set in BUFP on entry.
 *
 * If it succeeds, results are put in BUFP (if it returns an error, the
 * contents of BUFP are undefined):
 * `buffer' is the compiled pattern;
 * `syntax' is set to SYNTAX;
 * `used' is set to the length of the compiled pattern;
 * `fastmap_accurate' is zero;
 * `re_nsub' is the number of subexpressions in PATTERN;
 * `not_bol' and `not_eol' are zero;
 *
 * The `fastmap' and `newline_anchor' fields are neither
 * examined nor set.  */

static reg_errcode_t
regex_compile(const char *pattern, int size, reg_syntax_t  syntax, struct re_pattern_buffer * bufp)
{
    /* We fetch characters from PATTERN here.  Even though PATTERN is
     * `char *' (i.e., signed), we declare these variables as unsigned, so
     * they can be reliably used as array indices.  */
    register unsigned char c, c1;

    /* A random tempory spot in PATTERN.  */
    const char *p1;

    /* Points to the end of the buffer, where we should append.  */
    register unsigned char *b;

    /* Keeps track of unclosed groups.  */
    compile_stack_type compile_stack;

    /* Points to the current (ending) position in the pattern.  */
    const char *p = pattern;
    const char *pend = pattern + size;

    /* How to translate the characters in the pattern.  */
    char *translate = bufp->translate;

    /* Address of the count-byte of the most recently inserted `exactn'
     * command.  This makes it possible to tell if a new exact-match
     * character can be added to that command or if the character requires
     * a new `exactn' command.  */
    unsigned char *pending_exact = 0;

    /* Address of start of the most recently finished expression.
     * This tells, e.g., postfix * where to find the start of its
     * operand.  Reset at the beginning of groups and alternatives.  */
    unsigned char *laststart = 0;

    /* Address of beginning of regexp, or inside of last group.  */
    unsigned char *begalt;

    /* Place in the uncompiled pattern (i.e., the {) to
     * which to go back if the interval is invalid.  */
    const char *beg_interval;

    /* Address of the place where a forward jump should go to the end of
     * the containing expression.  Each alternative of an `or' -- except the
     * last -- ends with a forward jump of this sort.  */
    unsigned char *fixup_alt_jump = 0;

    /* Counts open-groups as they are encountered.  Remembered for the
     * matching close-group on the compile stack, so the same register
     * number is put in the stop_memory as the start_memory.  */
    regnum_t regnum = 0;

#ifdef DEBUG
    DEBUG_PRINT1("\nCompiling pattern: ");
    if (debug) {
       unsigned debug_count;

       for (debug_count = 0; debug_count < size; debug_count++)
           printchar(pattern[debug_count]);
       putchar('\n');
    }
#endif /* DEBUG */

    /* Initialize the compile stack.  */
    compile_stack.stack = TALLOC(INIT_COMPILE_STACK_SIZE, compile_stack_elt_t);
    if (compile_stack.stack == NULL)
       return REG_ESPACE;

    compile_stack.size = INIT_COMPILE_STACK_SIZE;
    compile_stack.avail = 0;

    /* Initialize the pattern buffer.  */
    bufp->syntax = syntax;
    bufp->fastmap_accurate = 0;
    bufp->not_bol = bufp->not_eol = 0;

    /* Set `used' to zero, so that if we return an error, the pattern
     * printer (for debugging) will think there's no pattern.  We reset it
     * at the end.  */
    bufp->used = 0;

    /* Always count groups, whether or not bufp->no_sub is set.  */
    bufp->re_nsub = 0;

#if !defined (emacs) && !defined (SYNTAX_TABLE)
    /* Initialize the syntax table.  */
    init_syntax_once();
#endif

    if (bufp->allocated == 0) {
       if (bufp->buffer) {     /* If zero allocated, but buffer is non-null, try to realloc
                                * enough space.  This loses if buffer's address is bogus, but
                                * that is the user's responsibility.  */
           RETALLOC(bufp->buffer, INIT_BUF_SIZE, unsigned char);
       } else {                /* Caller did not allocate a buffer.  Do it for them.  */
           bufp->buffer = TALLOC(INIT_BUF_SIZE, unsigned char);
       }
       if (!bufp->buffer)
           return REG_ESPACE;

       bufp->allocated = INIT_BUF_SIZE;
    }
    begalt = b = bufp->buffer;

    /* Loop through the uncompiled pattern until we're at the end.  */
    while (p != pend) {
       PATFETCH(c);

       switch (c) {
       case '^':
           {
               if (            /* If at start of pattern, it's an operator.  */
                   p == pattern + 1
               /* If context independent, it's an operator.  */
                   || syntax & RE_CONTEXT_INDEP_ANCHORS
               /* Otherwise, depends on what's come before.  */
                   || at_begline_loc_p(pattern, p, syntax))
                   BUF_PUSH(begline);
               else
                   goto normal_char;
           }
           break;


       case '$':
           {
               if (            /* If at end of pattern, it's an operator.  */
                   p == pend
               /* If context independent, it's an operator.  */
                   || syntax & RE_CONTEXT_INDEP_ANCHORS
               /* Otherwise, depends on what's next.  */
                   || at_endline_loc_p(p, pend, syntax))
                   BUF_PUSH(endline);
               else
                   goto normal_char;
           }
           break;


       case '+':
       case '?':
           if ((syntax & RE_BK_PLUS_QM)
               || (syntax & RE_LIMITED_OPS))
               goto normal_char;
         handle_plus:
       case '*':
           /* If there is no previous pattern... */
           if (!laststart) {
               if (syntax & RE_CONTEXT_INVALID_OPS)
                   return REG_BADRPT;
               else if (!(syntax & RE_CONTEXT_INDEP_OPS))
                   goto normal_char;
           } {
               /* Are we optimizing this jump?  */
               boolean keep_string_p = false;

               /* 1 means zero (many) matches is allowed.  */
               char zero_times_ok = 0, many_times_ok = 0;

               /* If there is a sequence of repetition chars, collapse it
                * down to just one (the right one).  We can't combine
                * interval operators with these because of, e.g., `a{2}*',
                * which should only match an even number of `a's.  */

               for (;;) {
                   zero_times_ok |= c != '+';
                   many_times_ok |= c != '?';

                   if (p == pend)
                       break;

                   PATFETCH(c);

                   if (c == '*'
                       || (!(syntax & RE_BK_PLUS_QM) && (c == '+' || c == '?')));

                   else if (syntax & RE_BK_PLUS_QM && c == '\\') {
                       if (p == pend)
                           return REG_EESCAPE;

                       PATFETCH(c1);
                       if (!(c1 == '+' || c1 == '?')) {
                           PATUNFETCH;
                           PATUNFETCH;
                           break;
                       }
                       c = c1;
                   } else {
                       PATUNFETCH;
                       break;
                   }

                   /* If we get here, we found another repeat character.  */
               }

               /* Star, etc. applied to an empty pattern is equivalent
                * to an empty pattern.  */
               if (!laststart)
                   break;

               /* Now we know whether or not zero matches is allowed
                * and also whether or not two or more matches is allowed.  */
               if (many_times_ok) {    /* More than one repetition is allowed, so put in at the
                                        * end a backward relative jump from `b' to before the next
                                        * jump we're going to put in below (which jumps from
                                        * laststart to after this jump).
                                        *
                                        * But if we are at the `*' in the exact sequence `.*\n',
                                        * insert an unconditional jump backwards to the .,
                                        * instead of the beginning of the loop.  This way we only
                                        * push a failure point once, instead of every time
                                        * through the loop.  */
                   assert(p - 1 > pattern);

                   /* Allocate the space for the jump.  */
                   GET_BUFFER_SPACE(3);

                   /* We know we are not at the first character of the pattern,
                    * because laststart was nonzero.  And we've already
                    * incremented `p', by the way, to be the character after
                    * the `*'.  Do we have to do something analogous here
                    * for null bytes, because of RE_DOT_NOT_NULL?  */
                   if (TRANSLATE(*(p - 2)) == TRANSLATE('.')
                       && zero_times_ok
                       && p < pend && TRANSLATE(*p) == TRANSLATE('\n')
                       && !(syntax & RE_DOT_NEWLINE)) {        /* We have .*\n.  */
                       STORE_JUMP(jump, b, laststart);
                       keep_string_p = true;
                   } else
                       /* Anything else.  */
                       STORE_JUMP(maybe_pop_jump, b, laststart - 3);

                   /* We've added more stuff to the buffer.  */
                   b += 3;
               }
               /* On failure, jump from laststart to b + 3, which will be the
                * end of the buffer after this jump is inserted.  */
               GET_BUFFER_SPACE(3);
               INSERT_JUMP(keep_string_p ? on_failure_keep_string_jump
                   : on_failure_jump,
                   laststart, b + 3);
               pending_exact = 0;
               b += 3;

               if (!zero_times_ok) {
                   /* At least one repetition is required, so insert a
                    * `dummy_failure_jump' before the initial
                    * `on_failure_jump' instruction of the loop. This
                    * effects a skip over that instruction the first time
                    * we hit that loop.  */
                   GET_BUFFER_SPACE(3);
                   INSERT_JUMP(dummy_failure_jump, laststart, laststart + 6);
                   b += 3;
               }
           }
           break;


       case '.':
           laststart = b;
           BUF_PUSH(anychar);
           break;


       case '[':
           {
               boolean had_char_class = false;

               if (p == pend)
                   return REG_EBRACK;

               /* Ensure that we have enough space to push a charset: the
                * opcode, the length count, and the bitset; 34 bytes in all.  */
               GET_BUFFER_SPACE(34);

               laststart = b;

               /* We test `*p == '^' twice, instead of using an if
                * statement, so we only need one BUF_PUSH.  */
               BUF_PUSH(*p == '^' ? charset_not : charset);
               if (*p == '^')
                   p++;

               /* Remember the first position in the bracket expression.  */
               p1 = p;

               /* Push the number of bytes in the bitmap.  */
               BUF_PUSH((1 << BYTEWIDTH) / BYTEWIDTH);

               /* Clear the whole map.  */
               memset(b, 0, (1 << BYTEWIDTH) / BYTEWIDTH);

               /* charset_not matches newline according to a syntax bit.  */
               if ((re_opcode_t) b[-2] == charset_not
                   && (syntax & RE_HAT_LISTS_NOT_NEWLINE))
                   SET_LIST_BIT('\n');

               /* Read in characters and ranges, setting map bits.  */
               for (;;) {
                   if (p == pend)
                       return REG_EBRACK;

                   PATFETCH(c);

                   /* \ might escape characters inside [...] and [^...].  */
                   if ((syntax & RE_BACKSLASH_ESCAPE_IN_LISTS) && c == '\\') {
                       if (p == pend)
                           return REG_EESCAPE;

                       PATFETCH(c1);
                       SET_LIST_BIT(c1);
                       continue;
                   }
                   /* Could be the end of the bracket expression.  If it's
                    * not (i.e., when the bracket expression is `[]' so
                    * far), the ']' character bit gets set way below.  */
                   if (c == ']' && p != p1 + 1)
                       break;

                   /* Look ahead to see if it's a range when the last thing
                    * was a character class.  */
                   if (had_char_class && c == '-' && *p != ']')
                       return REG_ERANGE;

                   /* Look ahead to see if it's a range when the last thing
                    * was a character: if this is a hyphen not at the
                    * beginning or the end of a list, then it's the range
                    * operator.  */
                   if (c == '-'
                       && !(p - 2 >= pattern && p[-2] == '[')
                       && !(p - 3 >= pattern && p[-3] == '[' && p[-2] == '^')
                       && *p != ']') {
                       reg_errcode_t ret
                       = compile_range(&p, (char *)pend, translate, syntax, b);
                       if (ret != REG_NOERROR)
                           return ret;
                   } else if (p[0] == '-' && p[1] != ']') {    /* This handles ranges made up of characters only.  */
                       reg_errcode_t ret;

                       /* Move past the `-'.  */
                       PATFETCH(c1);

                       ret = compile_range(&p, (char *)pend, translate, syntax, b);
                       if (ret != REG_NOERROR)
                           return ret;
                   }
                   /* See if we're at the beginning of a possible character
                    * class.  */

                   else if (syntax & RE_CHAR_CLASSES && c == '[' && *p == ':') {       /* Leave room for the null.  */
                       char str[CHAR_CLASS_MAX_LENGTH + 1];

                       PATFETCH(c);
                       c1 = 0;

                       /* If pattern is `[[:'.  */
                       if (p == pend)
                           return REG_EBRACK;

                       for (;;) {
                           PATFETCH(c);
                           if (c == ':' || c == ']' || p == pend
                               || c1 == CHAR_CLASS_MAX_LENGTH)
                               break;
                           str[c1++] = c;
                       }
                       str[c1] = '\0';

                       /* If isn't a word bracketed by `[:' and:`]':
                        * undo the ending character, the letters, and leave
                        * the leading `:' and `[' (but set bits for them).  */
                       if (c == ':' && *p == ']') {
                           int ch;
                           boolean is_alnum = STREQ(str, "alnum");
                           boolean is_alpha = STREQ(str, "alpha");
                           boolean is_blank = STREQ(str, "blank");
                           boolean is_cntrl = STREQ(str, "cntrl");
                           boolean is_digit = STREQ(str, "digit");
                           boolean is_graph = STREQ(str, "graph");
                           boolean is_lower = STREQ(str, "lower");
                           boolean is_print = STREQ(str, "print");
                           boolean is_punct = STREQ(str, "punct");
                           boolean is_space = STREQ(str, "space");
                           boolean is_upper = STREQ(str, "upper");
                           boolean is_xdigit = STREQ(str, "xdigit");

                           if (!IS_CHAR_CLASS(str))
                               return REG_ECTYPE;

                           /* Throw away the ] at the end of the character
                            * class.  */
                           PATFETCH(c);

                           if (p == pend)
                               return REG_EBRACK;

                           for (ch = 0; ch < 1 << BYTEWIDTH; ch++) {
                               if ((is_alnum && ISALNUM(ch))
                                   || (is_alpha && ISALPHA(ch))
                                   || (is_blank && ISBLANK(ch))
                                   || (is_cntrl && ISCNTRL(ch))
                                   || (is_digit && ISDIGIT(ch))
                                   || (is_graph && ISGRAPH(ch))
                                   || (is_lower && ISLOWER(ch))
                                   || (is_print && ISPRINT(ch))
                                   || (is_punct && ISPUNCT(ch))
                                   || (is_space && ISSPACE(ch))
                                   || (is_upper && ISUPPER(ch))
                                   || (is_xdigit && ISXDIGIT(ch)))
                                   SET_LIST_BIT(ch);
                           }
                           had_char_class = true;
                       } else {
                           c1++;
                           while (c1--)
                               PATUNFETCH;
                           SET_LIST_BIT('[');
                           SET_LIST_BIT(':');
                           had_char_class = false;
                       }
                   } else {
                       had_char_class = false;
                       SET_LIST_BIT(c);
                   }
               }

               /* Discard any (non)matching list bytes that are all 0 at the
                * end of the map.  Decrease the map-length byte too.  */
               while ((int) b[-1] > 0 && b[b[-1] - 1] == 0)
                   b[-1]--;
               b += b[-1];
           }
           break;


       case '(':
           if (syntax & RE_NO_BK_PARENS)
               goto handle_open;
           else
               goto normal_char;


       case ')':
           if (syntax & RE_NO_BK_PARENS)
               goto handle_close;
           else
               goto normal_char;


       case '\n':
           if (syntax & RE_NEWLINE_ALT)
               goto handle_alt;
           else
               goto normal_char;


       case '|':
           if (syntax & RE_NO_BK_VBAR)
               goto handle_alt;
           else
               goto normal_char;


       case '{':
           if (syntax & RE_INTERVALS && syntax & RE_NO_BK_BRACES)
               goto handle_interval;
           else
               goto normal_char;


       case '\\':
           if (p == pend)
               return REG_EESCAPE;

           /* Do not translate the character after the \, so that we can
            * distinguish, e.g., \B from \b, even if we normally would
            * translate, e.g., B to b.  */
           PATFETCH_RAW(c);

           switch (c) {
           case '(':
               if (syntax & RE_NO_BK_PARENS)
                   goto normal_backslash;

             handle_open:
               bufp->re_nsub++;
               regnum++;

               if (COMPILE_STACK_FULL) {
                   RETALLOC(compile_stack.stack, compile_stack.size << 1,
                       compile_stack_elt_t);
                   if (compile_stack.stack == NULL)
                       return REG_ESPACE;

                   compile_stack.size <<= 1;
               }
               /* These are the values to restore when we hit end of this
                * group.  They are all relative offsets, so that if the
                * whole pattern moves because of realloc, they will still
                * be valid.  */
               COMPILE_STACK_TOP.begalt_offset = begalt - bufp->buffer;
               COMPILE_STACK_TOP.fixup_alt_jump
                   = fixup_alt_jump ? fixup_alt_jump - bufp->buffer + 1 : 0;
               COMPILE_STACK_TOP.laststart_offset = b - bufp->buffer;
               COMPILE_STACK_TOP.regnum = regnum;

               /* We will eventually replace the 0 with the number of
                * groups inner to this one.  But do not push a
                * start_memory for groups beyond the last one we can
                * represent in the compiled pattern.  */
               if (regnum <= MAX_REGNUM) {
                   COMPILE_STACK_TOP.inner_group_offset = b - bufp->buffer + 2;
                   BUF_PUSH_3(start_memory, regnum, 0);
               }
               compile_stack.avail++;

               fixup_alt_jump = 0;
               laststart = 0;
               begalt = b;
               /* If we've reached MAX_REGNUM groups, then this open
                * won't actually generate any code, so we'll have to
                * clear pending_exact explicitly.  */
               pending_exact = 0;
               break;


           case ')':
               if (syntax & RE_NO_BK_PARENS)
                   goto normal_backslash;

               if (COMPILE_STACK_EMPTY) {
                   if (syntax & RE_UNMATCHED_RIGHT_PAREN_ORD)
                       goto normal_backslash;
                   else
                       return REG_ERPAREN;
               }
             handle_close:
               if (fixup_alt_jump) {   /* Push a dummy failure point at the end of the
                                        * alternative for a possible future
                                        * `pop_failure_jump' to pop.  See comments at
                                        * `push_dummy_failure' in `re_match_2'.  */
                   BUF_PUSH(push_dummy_failure);

                   /* We allocated space for this jump when we assigned
                    * to `fixup_alt_jump', in the `handle_alt' case below.  */
                   STORE_JUMP(jump_past_alt, fixup_alt_jump, b - 1);
               }
               /* See similar code for backslashed left paren above.  */
               if (COMPILE_STACK_EMPTY) {
                   if (syntax & RE_UNMATCHED_RIGHT_PAREN_ORD)
                       goto normal_char;
                   else
                       return REG_ERPAREN;
               }
               /* Since we just checked for an empty stack above, this
                * ``can't happen''.  */
               assert(compile_stack.avail != 0);
               {
                   /* We don't just want to restore into `regnum', because
                    * later groups should continue to be numbered higher,
                    * as in `(ab)c(de)' -- the second group is #2.  */
                   regnum_t this_group_regnum;

                   compile_stack.avail--;
                   begalt = bufp->buffer + COMPILE_STACK_TOP.begalt_offset;
                   fixup_alt_jump
                       = COMPILE_STACK_TOP.fixup_alt_jump
                       ? bufp->buffer + COMPILE_STACK_TOP.fixup_alt_jump - 1
                       : 0;
                   laststart = bufp->buffer + COMPILE_STACK_TOP.laststart_offset;
                   this_group_regnum = COMPILE_STACK_TOP.regnum;
                   /* If we've reached MAX_REGNUM groups, then this open
                    * won't actually generate any code, so we'll have to
                    * clear pending_exact explicitly.  */
                   pending_exact = 0;

                   /* We're at the end of the group, so now we know how many
                    * groups were inside this one.  */
                   if (this_group_regnum <= MAX_REGNUM) {
                       unsigned char *inner_group_loc
                       = bufp->buffer + COMPILE_STACK_TOP.inner_group_offset;

                       *inner_group_loc = regnum - this_group_regnum;
                       BUF_PUSH_3(stop_memory, this_group_regnum,
                           regnum - this_group_regnum);
                   }
               }
               break;


           case '|':           /* `\|'.  */
               if (syntax & RE_LIMITED_OPS || syntax & RE_NO_BK_VBAR)
                   goto normal_backslash;
             handle_alt:
               if (syntax & RE_LIMITED_OPS)
                   goto normal_char;

               /* Insert before the previous alternative a jump which
                * jumps to this alternative if the former fails.  */
               GET_BUFFER_SPACE(3);
               INSERT_JUMP(on_failure_jump, begalt, b + 6);
               pending_exact = 0;
               b += 3;

               /* The alternative before this one has a jump after it
                * which gets executed if it gets matched.  Adjust that
                * jump so it will jump to this alternative's analogous
                * jump (put in below, which in turn will jump to the next
                * (if any) alternative's such jump, etc.).  The last such
                * jump jumps to the correct final destination.  A picture:
                * _____ _____
                * |   | |   |
                * |   v |   v
                * a | b   | c
                *
                * If we are at `b', then fixup_alt_jump right now points to a
                * three-byte space after `a'.  We'll put in the jump, set
                * fixup_alt_jump to right after `b', and leave behind three
                * bytes which we'll fill in when we get to after `c'.  */

               if (fixup_alt_jump)
                   STORE_JUMP(jump_past_alt, fixup_alt_jump, b);

               /* Mark and leave space for a jump after this alternative,
                * to be filled in later either by next alternative or
                * when know we're at the end of a series of alternatives.  */
               fixup_alt_jump = b;
               GET_BUFFER_SPACE(3);
               b += 3;

               laststart = 0;
               begalt = b;
               break;


           case '{':
               /* If \{ is a literal.  */
               if (!(syntax & RE_INTERVALS)
               /* If we're at `\{' and it's not the open-interval
                * operator.  */
                   || ((syntax & RE_INTERVALS) && (syntax & RE_NO_BK_BRACES))
                   || (p - 2 == pattern && p == pend))
                   goto normal_backslash;

             handle_interval:
               {
                   /* If got here, then the syntax allows intervals.  */

                   /* At least (most) this many matches must be made.  */
                   int lower_bound = -1, upper_bound = -1;

                   beg_interval = p - 1;

                   if (p == pend) {
                       if (syntax & RE_NO_BK_BRACES)
                           goto unfetch_interval;
                       else
                           return REG_EBRACE;
                   }
                   GET_UNSIGNED_NUMBER(lower_bound);

                   if (c == ',') {
                       GET_UNSIGNED_NUMBER(upper_bound);
                       if (upper_bound < 0)
                           upper_bound = RE_DUP_MAX;
                   } else
                       /* Interval such as `{1}' => match exactly once. */
                       upper_bound = lower_bound;

                   if (lower_bound < 0 || upper_bound > RE_DUP_MAX
                       || lower_bound > upper_bound) {
                       if (syntax & RE_NO_BK_BRACES)
                           goto unfetch_interval;
                       else
                           return REG_BADBR;
                   }
                   if (!(syntax & RE_NO_BK_BRACES)) {
                       if (c != '\\')
                           return REG_EBRACE;

                       PATFETCH(c);
                   }
                   if (c != '}') {
                       if (syntax & RE_NO_BK_BRACES)
                           goto unfetch_interval;
                       else
                           return REG_BADBR;
                   }
                   /* We just parsed a valid interval.  */

                   /* If it's invalid to have no preceding re.  */
                   if (!laststart) {
                       if (syntax & RE_CONTEXT_INVALID_OPS)
                           return REG_BADRPT;
                       else if (syntax & RE_CONTEXT_INDEP_OPS)
                           laststart = b;
                       else
                           goto unfetch_interval;
                   }
                   /* If the upper bound is zero, don't want to succeed at
                    * all; jump from `laststart' to `b + 3', which will be
                    * the end of the buffer after we insert the jump.  */
                   if (upper_bound == 0) {
                       GET_BUFFER_SPACE(3);
                       INSERT_JUMP(jump, laststart, b + 3);
                       b += 3;
                   }
                   /* Otherwise, we have a nontrivial interval.  When
                    * we're all done, the pattern will look like:
                    * set_number_at <jump count> <upper bound>
                    * set_number_at <succeed_n count> <lower bound>
                    * succeed_n <after jump addr> <succed_n count>
                    * <body of loop>
                    * jump_n <succeed_n addr> <jump count>
                    * (The upper bound and `jump_n' are omitted if
                    * `upper_bound' is 1, though.)  */
                   else {      /* If the upper bound is > 1, we need to insert
                                * more at the end of the loop.  */
                       unsigned nbytes = 10 + (upper_bound > 1) * 10;

                       GET_BUFFER_SPACE(nbytes);

                       /* Initialize lower bound of the `succeed_n', even
                        * though it will be set during matching by its
                        * attendant `set_number_at' (inserted next),
                        * because `re_compile_fastmap' needs to know.
                        * Jump to the `jump_n' we might insert below.  */
                       INSERT_JUMP2(succeed_n, laststart,
                           b + 5 + (upper_bound > 1) * 5,
                           lower_bound);
                       b += 5;

                       /* Code to initialize the lower bound.  Insert
                        * before the `succeed_n'.  The `5' is the last two
                        * bytes of this `set_number_at', plus 3 bytes of
                        * the following `succeed_n'.  */
                       insert_op2(set_number_at, laststart, 5, lower_bound, b);
                       b += 5;

                       if (upper_bound > 1) {  /* More than one repetition is allowed, so
                                                * append a backward jump to the `succeed_n'
                                                * that starts this interval.
                                                *
                                                * When we've reached this during matching,
                                                * we'll have matched the interval once, so
                                                * jump back only `upper_bound - 1' times.  */
                           STORE_JUMP2(jump_n, b, laststart + 5,
                               upper_bound - 1);
                           b += 5;

                           /* The location we want to set is the second
                            * parameter of the `jump_n'; that is `b-2' as
                            * an absolute address.  `laststart' will be
                            * the `set_number_at' we're about to insert;
                            * `laststart+3' the number to set, the source
                            * for the relative address.  But we are
                            * inserting into the middle of the pattern --
                            * so everything is getting moved up by 5.
                            * Conclusion: (b - 2) - (laststart + 3) + 5,
                            * i.e., b - laststart.
                            *
                            * We insert this at the beginning of the loop
                            * so that if we fail during matching, we'll
                            * reinitialize the bounds.  */
                           insert_op2(set_number_at, laststart, b - laststart,
                               upper_bound - 1, b);
                           b += 5;
                       }
                   }
                   pending_exact = 0;
                   beg_interval = NULL;
               }
               break;

             unfetch_interval:
               /* If an invalid interval, match the characters as literals.  */
               assert(beg_interval);
               p = beg_interval;
               beg_interval = NULL;

               /* normal_char and normal_backslash need `c'.  */
               PATFETCH(c);

               if (!(syntax & RE_NO_BK_BRACES)) {
                   if (p > pattern && p[-1] == '\\')
                       goto normal_backslash;
               }
               goto normal_char;

#ifdef emacs
               /* There is no way to specify the before_dot and after_dot
                * operators.  rms says this is ok.  --karl  */
           case '=':
               BUF_PUSH(at_dot);
               break;

           case 's':
               laststart = b;
               PATFETCH(c);
               BUF_PUSH_2(syntaxspec, syntax_spec_code[c]);
               break;

           case 'S':
               laststart = b;
               PATFETCH(c);
               BUF_PUSH_2(notsyntaxspec, syntax_spec_code[c]);
               break;
#endif /* emacs */


           case 'w':
               laststart = b;
               BUF_PUSH(wordchar);
               break;


           case 'W':
               laststart = b;
               BUF_PUSH(notwordchar);
               break;


           case '<':
               BUF_PUSH(wordbeg);
               break;

           case '>':
               BUF_PUSH(wordend);
               break;

           case 'b':
               BUF_PUSH(wordbound);
               break;

           case 'B':
               BUF_PUSH(notwordbound);
               break;

           case '`':
               BUF_PUSH(begbuf);
               break;

           case '\'':
               BUF_PUSH(endbuf);
               break;

           case '1':
           case '2':
           case '3':
           case '4':
           case '5':
           case '6':
           case '7':
           case '8':
           case '9':
               if (syntax & RE_NO_BK_REFS)
                   goto normal_char;

               c1 = c - '0';

               if (c1 > regnum)
                   return REG_ESUBREG;

               /* Can't back reference to a subexpression if inside of it.  */
               if (group_in_compile_stack(compile_stack, c1))
                   goto normal_char;

               laststart = b;
               BUF_PUSH_2(duplicate, c1);
               break;


           case '+':
           case '?':
               if (syntax & RE_BK_PLUS_QM)
                   goto handle_plus;
               else
                   goto normal_backslash;

           default:
             normal_backslash:
               /* You might think it would be useful for \ to mean
                * not to translate; but if we don't translate it
                * it will never match anything.  */
               c = TRANSLATE(c);
               goto normal_char;
           }
           break;


       default:
           /* Expects the character in `c'.  */
         normal_char:
           /* If no exactn currently being built.  */
           if (!pending_exact

           /* If last exactn not at current position.  */
               || pending_exact + *pending_exact + 1 != b

           /* We have only one byte following the exactn for the count.  */
               || *pending_exact == (1 << BYTEWIDTH) - 1

           /* If followed by a repetition operator.  */
               || *p == '*' || *p == '^'
               || ((syntax & RE_BK_PLUS_QM)
                   ? *p == '\\' && (p[1] == '+' || p[1] == '?')
                   : (*p == '+' || *p == '?'))
               || ((syntax & RE_INTERVALS)
                   && ((syntax & RE_NO_BK_BRACES)
                       ? *p == '{'
                       : (p[0] == '\\' && p[1] == '{')))) {
               /* Start building a new exactn.  */

               laststart = b;

               BUF_PUSH_2(exactn, 0);
               pending_exact = b - 1;
           }
           BUF_PUSH(c);
           (*pending_exact)++;
           break;
       }                       /* switch (c) */
    }                          /* while p != pend */


    /* Through the pattern now.  */

    if (fixup_alt_jump)
       STORE_JUMP(jump_past_alt, fixup_alt_jump, b);

    if (!COMPILE_STACK_EMPTY)
       return REG_EPAREN;

    free(compile_stack.stack);

    /* We have succeeded; set the length of the buffer.  */
    bufp->used = b - bufp->buffer;

#ifdef DEBUG
    if (debug) {
       DEBUG_PRINT1("\nCompiled pattern: ");
       print_compiled_pattern(bufp);
    }
#endif /* DEBUG */

    return REG_NOERROR;
}                              /* regex_compile */

/* Subroutines for `regex_compile'.  */

/* Store OP at LOC followed by two-byte integer parameter ARG.  */

static void
store_op1(re_opcode_t op,unsigned char * loc, int  arg)
{
    *loc = (unsigned char) op;
    STORE_NUMBER(loc + 1, arg);
}


/* Like `store_op1', but for two two-byte parameters ARG1 and ARG2.  */

static void
store_op2(re_opcode_t op, unsigned char *loc, int arg1, int arg2)
{
    *loc = (unsigned char) op;
    STORE_NUMBER(loc + 1, arg1);
    STORE_NUMBER(loc + 3, arg2);
}


/* Copy the bytes from LOC to END to open up three bytes of space at LOC
 * for OP followed by two-byte integer parameter ARG.  */

static void
insert_op1(re_opcode_t  op, unsigned char *loc, int arg, unsigned char * end)
{
    register unsigned char *pfrom = end;
    register unsigned char *pto = end + 3;

    while (pfrom != loc)
       *--pto = *--pfrom;

    store_op1(op, loc, arg);
}


/* Like `insert_op1', but for two two-byte parameters ARG1 and ARG2.  */

static void
insert_op2(re_opcode_t  op, unsigned char *loc, int arg1,int  arg2, unsigned char * end)
{
    register unsigned char *pfrom = end;
    register unsigned char *pto = end + 5;

    while (pfrom != loc)
       *--pto = *--pfrom;

    store_op2(op, loc, arg1, arg2);
}


/* P points to just after a ^ in PATTERN.  Return true if that ^ comes
 * after an alternative or a begin-subexpression.  We assume there is at
 * least one character before the ^.  */

static boolean
at_begline_loc_p(const char *pattern, const char *p, reg_syntax_t syntax)
{
    const char *prev = p - 2;
    boolean prev_prev_backslash = prev > pattern && prev[-1] == '\\';

    return
    /* After a subexpression?  */
       (*prev == '(' && (syntax & RE_NO_BK_PARENS || prev_prev_backslash))
    /* After an alternative?  */
       || (*prev == '|' && (syntax & RE_NO_BK_VBAR || prev_prev_backslash));
}


/* The dual of at_begline_loc_p.  This one is for $.  We assume there is
 * at least one character after the $, i.e., `P < PEND'.  */

static boolean
at_endline_loc_p(const char *p, const char * pend, int syntax)
{
    const char *next = p;
    boolean next_backslash = *next == '\\';
    const char *next_next = p + 1 < pend ? p + 1 : NULL;

    return
    /* Before a subexpression?  */
       (syntax & RE_NO_BK_PARENS ? *next == ')'
       : next_backslash && next_next && *next_next == ')')
    /* Before an alternative?  */
       || (syntax & RE_NO_BK_VBAR ? *next == '|'
       : next_backslash && next_next && *next_next == '|');
}


/* Returns true if REGNUM is in one of COMPILE_STACK's elements and
 * false if it's not.  */

static boolean
group_in_compile_stack(compile_stack_type  compile_stack,regnum_t  regnum)
{
    int this_element;

    for (this_element = compile_stack.avail - 1;
       this_element >= 0;
       this_element--)
       if (compile_stack.stack[this_element].regnum == regnum)
           return true;

    return false;
}


/* Read the ending character of a range (in a bracket expression) from the
 * uncompiled pattern *P_PTR (which ends at PEND).  We assume the
 * starting character is in `P[-2]'.  (`P[-1]' is the character `-'.)
 * Then we set the translation of all bits between the starting and
 * ending characters (inclusive) in the compiled pattern B.
 *
 * Return an error code.
 *
 * We use these short variable names so we can use the same macros as
 * `regex_compile' itself.  */

static reg_errcode_t
compile_range(const char **p_ptr, char *pend, char *  translate, reg_syntax_t  syntax, unsigned char * b)
{
    unsigned this_char;

    const char *p = *p_ptr;
    int range_start, range_end;

    if (p == pend)
       return REG_ERANGE;

    /* Even though the pattern is a signed `char *', we need to fetch
     * with unsigned char *'s; if the high bit of the pattern character
     * is set, the range endpoints will be negative if we fetch using a
     * signed char *.
     *
     * We also want to fetch the endpoints without translating them; the
     * appropriate translation is done in the bit-setting loop below.  */
    range_start = ((unsigned char *) p)[-2];
    range_end = ((unsigned char *) p)[0];

    /* Have to increment the pointer into the pattern string, so the
     * caller isn't still at the ending character.  */
    (*p_ptr)++;

    /* If the start is after the end, the range is empty.  */
    if (range_start > range_end)
       return syntax & RE_NO_EMPTY_RANGES ? REG_ERANGE : REG_NOERROR;

    /* Here we see why `this_char' has to be larger than an `unsigned
     * char' -- the range is inclusive, so if `range_end' == 0xff
     * (assuming 8-bit characters), we would otherwise go into an infinite
     * loop, since all characters <= 0xff.  */
    for (this_char = range_start; this_char <= range_end; this_char++) {
       SET_LIST_BIT(TRANSLATE(this_char));
    }

    return REG_NOERROR;
}

/* Failure stack declarations and macros; both re_compile_fastmap and
 * re_match_2 use a failure stack.  These have to be macros because of
 * REGEX_ALLOCATE.  */


/* Number of failure points for which to initially allocate space
 * when matching.  If this number is exceeded, we allocate more
 * space, so it is not a hard limit.  */
#ifndef INIT_FAILURE_ALLOC
#define INIT_FAILURE_ALLOC 5
#endif

/* Roughly the maximum number of failure points on the stack.  Would be
 * exactly that if always used MAX_FAILURE_SPACE each time we failed.
 * This is a variable only so users of regex can assign to it; we never
 * change it ourselves.  */
int re_max_failures = 2000;

typedef const unsigned char *fail_stack_elt_t;

typedef struct {
    fail_stack_elt_t *stack;
    unsigned size;
    unsigned avail;            /* Offset of next open position.  */
} fail_stack_type;

#define FAIL_STACK_EMPTY()     (fail_stack.avail == 0)
#define FAIL_STACK_PTR_EMPTY() (fail_stack_ptr->avail == 0)
#define FAIL_STACK_FULL()      (fail_stack.avail == fail_stack.size)
#define FAIL_STACK_TOP()       (fail_stack.stack[fail_stack.avail])


/* Initialize `fail_stack'.  Do `return -2' if the alloc fails.  */

#define INIT_FAIL_STACK()                                              \
  do {                                                                 \
    fail_stack.stack = (fail_stack_elt_t *)                            \
      REGEX_ALLOCATE (INIT_FAILURE_ALLOC * sizeof (fail_stack_elt_t)); \
                                                                       \
    if (fail_stack.stack == NULL)                                      \
      return -2;                                                       \
                                                                       \
    fail_stack.size = INIT_FAILURE_ALLOC;                              \
    fail_stack.avail = 0;                                              \
  } while (0)


/* Double the size of FAIL_STACK, up to approximately `re_max_failures' items.
 *
 * Return 1 if succeeds, and 0 if either ran out of memory
 * allocating space for it or it was already too large.
 *
 * REGEX_REALLOCATE requires `destination' be declared.   */

#define DOUBLE_FAIL_STACK(fail_stack)                                  \
  ((fail_stack).size > re_max_failures * MAX_FAILURE_ITEMS             \
   ? 0                                                                 \
   : ((fail_stack).stack = (fail_stack_elt_t *)                                \
        REGEX_REALLOCATE ((fail_stack).stack,                          \
          (fail_stack).size * sizeof (fail_stack_elt_t),               \
          ((fail_stack).size << 1) * sizeof (fail_stack_elt_t)),       \
                                                                       \
      (fail_stack).stack == NULL                                       \
      ? 0                                                              \
      : ((fail_stack).size <<= 1,                                      \
         1)))


/* Push PATTERN_OP on FAIL_STACK.
 *
 * Return 1 if was able to do so and 0 if ran out of memory allocating
 * space to do so.  */
#define PUSH_PATTERN_OP(pattern_op, fail_stack)                                \
  ((FAIL_STACK_FULL ()                                                 \
    && !DOUBLE_FAIL_STACK (fail_stack))                                        \
    ? 0                                                                        \
    : ((fail_stack).stack[(fail_stack).avail++] = pattern_op,          \
       1))

/* This pushes an item onto the failure stack.  Must be a four-byte
 * value.  Assumes the variable `fail_stack'.  Probably should only
 * be called from within `PUSH_FAILURE_POINT'.  */
#define PUSH_FAILURE_ITEM(item)                                                \
  fail_stack.stack[fail_stack.avail++] = (fail_stack_elt_t) item

/* The complement operation.  Assumes `fail_stack' is nonempty.  */
#define POP_FAILURE_ITEM() fail_stack.stack[--fail_stack.avail]

/* Used to omit pushing failure point id's when we're not debugging.  */
#ifdef DEBUG
#define DEBUG_PUSH PUSH_FAILURE_ITEM
#define DEBUG_POP(item_addr) *(item_addr) = POP_FAILURE_ITEM ()
#else
#define DEBUG_PUSH(item)
#define DEBUG_POP(item_addr)
#endif


/* Push the information about the state we will need
 * if we ever fail back to it.
 *
 * Requires variables fail_stack, regstart, regend, reg_info, and
 * num_regs be declared.  DOUBLE_FAIL_STACK requires `destination' be
 * declared.
 *
 * Does `return FAILURE_CODE' if runs out of memory.  */

#define PUSH_FAILURE_POINT(pattern_place, string_place, failure_code)  \
  do {                                                                 \
    char *destination;                                                 \
    /* Must be int, so when we don't save any registers, the arithmetic        \
       of 0 + -1 isn't done as unsigned.  */                           \
    int this_reg;                                                      \
                                                                       \
    DEBUG_STATEMENT (failure_id++);                                    \
    DEBUG_STATEMENT (nfailure_points_pushed++);                                \
    DEBUG_PRINT2 ("\nPUSH_FAILURE_POINT #%u:\n", failure_id);          \
    DEBUG_PRINT2 ("  Before push, next avail: %d\n", (fail_stack).avail);\
    DEBUG_PRINT2 ("                     size: %d\n", (fail_stack).size);\
                                                                       \
    DEBUG_PRINT2 ("  slots needed: %d\n", NUM_FAILURE_ITEMS);          \
    DEBUG_PRINT2 ("     available: %d\n", REMAINING_AVAIL_SLOTS);      \
                                                                       \
    /* Ensure we have enough space allocated for what we will push.  */        \
    while (REMAINING_AVAIL_SLOTS < NUM_FAILURE_ITEMS)                  \
      {                                                                        \
        if (!DOUBLE_FAIL_STACK (fail_stack))                   \
          return failure_code;                                         \
                                                                       \
        DEBUG_PRINT2 ("\n  Doubled stack; size now: %d\n",             \
                      (fail_stack).size);                              \
        DEBUG_PRINT2 ("  slots available: %d\n", REMAINING_AVAIL_SLOTS);\
      }                                                                        \
                                                                       \
    /* Push the info, starting with the registers.  */                 \
    DEBUG_PRINT1 ("\n");                                               \
                                                                       \
    for (this_reg = lowest_active_reg; this_reg <= highest_active_reg; \
         this_reg++)                                                   \
      {                                                                        \
       DEBUG_PRINT2 ("  Pushing reg: %d\n", this_reg);                 \
        DEBUG_STATEMENT (num_regs_pushed++);                           \
                                                                       \
       DEBUG_PRINT2 ("    start: 0x%x\n", regstart[this_reg]);         \
        PUSH_FAILURE_ITEM (regstart[this_reg]);                                \
                                                                        \
       DEBUG_PRINT2 ("    end: 0x%x\n", regend[this_reg]);             \
        PUSH_FAILURE_ITEM (regend[this_reg]);                          \
                                                                       \
       DEBUG_PRINT2 ("    info: 0x%x\n      ", reg_info[this_reg]);    \
        DEBUG_PRINT2 (" match_null=%d",                                        \
                      REG_MATCH_NULL_STRING_P (reg_info[this_reg]));   \
        DEBUG_PRINT2 (" active=%d", IS_ACTIVE (reg_info[this_reg]));   \
        DEBUG_PRINT2 (" matched_something=%d",                         \
                      MATCHED_SOMETHING (reg_info[this_reg]));         \
        DEBUG_PRINT2 (" ever_matched=%d",                              \
                      EVER_MATCHED_SOMETHING (reg_info[this_reg]));    \
       DEBUG_PRINT1 ("\n");                                            \
        PUSH_FAILURE_ITEM (reg_info[this_reg].word);                   \
      }                                                                        \
                                                                       \
    DEBUG_PRINT2 ("  Pushing  low active reg: %d\n", lowest_active_reg);\
    PUSH_FAILURE_ITEM (lowest_active_reg);                             \
                                                                       \
    DEBUG_PRINT2 ("  Pushing high active reg: %d\n", highest_active_reg);\
    PUSH_FAILURE_ITEM (highest_active_reg);                            \
                                                                       \
    DEBUG_PRINT2 ("  Pushing pattern 0x%x: ", pattern_place);          \
    DEBUG_PRINT_COMPILED_PATTERN (bufp, pattern_place, pend);          \
    PUSH_FAILURE_ITEM (pattern_place);                                 \
                                                                       \
    DEBUG_PRINT2 ("  Pushing string 0x%x: `", string_place);           \
    DEBUG_PRINT_DOUBLE_STRING (string_place, string1, size1, string2,   \
                                size2);                                \
    DEBUG_PRINT1 ("'\n");                                              \
    PUSH_FAILURE_ITEM (string_place);                                  \
                                                                       \
    DEBUG_PRINT2 ("  Pushing failure id: %u\n", failure_id);           \
    DEBUG_PUSH (failure_id);                                           \
  } while (0)

/* This is the number of items that are pushed and popped on the stack
 * for each register.  */
#define NUM_REG_ITEMS  3

/* Individual items aside from the registers.  */
#ifdef DEBUG
#define NUM_NONREG_ITEMS 5     /* Includes failure point id.  */
#else
#define NUM_NONREG_ITEMS 4
#endif

/* We push at most this many items on the stack.  */
#define MAX_FAILURE_ITEMS ((num_regs - 1) * NUM_REG_ITEMS + NUM_NONREG_ITEMS)

/* We actually push this many items.  */
#define NUM_FAILURE_ITEMS                                              \
  ((highest_active_reg - lowest_active_reg + 1) * NUM_REG_ITEMS        \
    + NUM_NONREG_ITEMS)

/* How many items can still be added to the stack without overflowing it.  */
#define REMAINING_AVAIL_SLOTS ((fail_stack).size - (fail_stack).avail)


/* Pops what PUSH_FAIL_STACK pushes.
 *
 * We restore into the parameters, all of which should be lvalues:
 * STR -- the saved data position.
 * PAT -- the saved pattern position.
 * LOW_REG, HIGH_REG -- the highest and lowest active registers.
 * REGSTART, REGEND -- arrays of string positions.
 * REG_INFO -- array of information about each subexpression.
 *
 * Also assumes the variables `fail_stack' and (if debugging), `bufp',
 * `pend', `string1', `size1', `string2', and `size2'.  */

#define POP_FAILURE_POINT(str, pat, low_reg, high_reg, regstart, regend, reg_info)\
{                                                                      \
  DEBUG_STATEMENT (fail_stack_elt_t failure_id;)                       \
  int this_reg;                                                                \
  const unsigned char *string_temp;                                    \
                                                                       \
  assert (!FAIL_STACK_EMPTY ());                                       \
                                                                       \
  /* Remove failure points and point to how many regs pushed.  */      \
  DEBUG_PRINT1 ("POP_FAILURE_POINT:\n");                               \
  DEBUG_PRINT2 ("  Before pop, next avail: %d\n", fail_stack.avail);   \
  DEBUG_PRINT2 ("                    size: %d\n", fail_stack.size);    \
                                                                       \
  assert (fail_stack.avail >= NUM_NONREG_ITEMS);                       \
                                                                       \
  DEBUG_POP (&failure_id);                                             \
  DEBUG_PRINT2 ("  Popping failure id: %u\n", failure_id);             \
                                                                       \
  /* If the saved string location is NULL, it came from an             \
     on_failure_keep_string_jump opcode, and we want to throw away the \
     saved NULL, thus retaining our current position in the string.  */        \
  string_temp = POP_FAILURE_ITEM ();                                   \
  if (string_temp != NULL)                                             \
    str = (const char *) string_temp;                                  \
                                                                       \
  DEBUG_PRINT2 ("  Popping string 0x%x: `", str);                      \
  DEBUG_PRINT_DOUBLE_STRING (str, string1, size1, string2, size2);     \
  DEBUG_PRINT1 ("'\n");                                                        \
                                                                       \
  pat = (unsigned char *) POP_FAILURE_ITEM ();                         \
  DEBUG_PRINT2 ("  Popping pattern 0x%x: ", pat);                      \
  DEBUG_PRINT_COMPILED_PATTERN (bufp, pat, pend);                      \
                                                                       \
  /* Restore register info.  */                                                \
  high_reg = (unsigned long) POP_FAILURE_ITEM ();                      \
  DEBUG_PRINT2 ("  Popping high active reg: %d\n", high_reg);          \
                                                                       \
  low_reg = (unsigned long) POP_FAILURE_ITEM ();                       \
  DEBUG_PRINT2 ("  Popping  low active reg: %d\n", low_reg);           \
                                                                       \
  for (this_reg = high_reg; this_reg >= low_reg; this_reg--)           \
    {                                                                  \
      DEBUG_PRINT2 ("    Popping reg: %d\n", this_reg);                        \
                                                                       \
      reg_info[this_reg].word = POP_FAILURE_ITEM ();                   \
      DEBUG_PRINT2 ("      info: 0x%x\n", reg_info[this_reg]);         \
                                                                       \
      regend[this_reg] = (const char *) POP_FAILURE_ITEM ();           \
      DEBUG_PRINT2 ("      end: 0x%x\n", regend[this_reg]);            \
                                                                       \
      regstart[this_reg] = (const char *) POP_FAILURE_ITEM ();         \
      DEBUG_PRINT2 ("      start: 0x%x\n", regstart[this_reg]);                \
    }                                                                  \
                                                                       \
  DEBUG_STATEMENT (nfailure_points_popped++);                          \
}                              /* POP_FAILURE_POINT */

/* re_compile_fastmap computes a ``fastmap'' for the compiled pattern in
 * BUFP.  A fastmap records which of the (1 << BYTEWIDTH) possible
 * characters can start a string that matches the pattern.  This fastmap
 * is used by re_search to skip quickly over impossible starting points.
 *
 * The caller must supply the address of a (1 << BYTEWIDTH)-byte data
 * area as BUFP->fastmap.
 *
 * We set the `fastmap', `fastmap_accurate', and `can_be_null' fields in
 * the pattern buffer.
 *
 * Returns 0 if we succeed, -2 if an internal error.   */

int
re_compile_fastmap(struct re_pattern_buffer *bufp)
{
    int j, k;
    fail_stack_type fail_stack;
#ifndef REGEX_MALLOC
    char *destination;
#endif
    /* We don't push any register information onto the failure stack.  */
    unsigned num_regs = 0;

    register char *fastmap = bufp->fastmap;
    unsigned char *pattern = bufp->buffer;
    unsigned long size = bufp->used;
    const unsigned char *p = pattern;
    register unsigned char *pend = pattern + size;

    /* Assume that each path through the pattern can be null until
     * proven otherwise.  We set this false at the bottom of switch
     * statement, to which we get only if a particular path doesn't
     * match the empty string.  */
    boolean path_can_be_null = true;

    /* We aren't doing a `succeed_n' to begin with.  */
    boolean succeed_n_p = false;

    assert(fastmap != NULL && p != NULL);

    INIT_FAIL_STACK();
    memset(fastmap, 0, 1 << BYTEWIDTH);                /* Assume nothing's valid.  */
    bufp->fastmap_accurate = 1;        /* It will be when we're done.  */
    bufp->can_be_null = 0;

    while (p != pend || !FAIL_STACK_EMPTY()) {
       if (p == pend) {
           bufp->can_be_null |= path_can_be_null;

           /* Reset for next path.  */
           path_can_be_null = true;

           p = fail_stack.stack[--fail_stack.avail];
       }
       /* We should never be about to go beyond the end of the pattern.  */
       assert(p < pend);

#ifdef SWITCH_ENUM_BUG
       switch ((int) ((re_opcode_t) * p++))
#else
       switch ((re_opcode_t) * p++)
#endif
       {

           /* I guess the idea here is to simply not bother with a fastmap
            * if a backreference is used, since it's too hard to figure out
            * the fastmap for the corresponding group.  Setting
            * `can_be_null' stops `re_search_2' from using the fastmap, so
            * that is all we do.  */
       case duplicate:
           bufp->can_be_null = 1;
           return 0;


           /* Following are the cases which match a character.  These end
            * with `break'.  */

       case exactn:
           fastmap[p[1]] = 1;
           break;


       case charset:
           for (j = *p++ * BYTEWIDTH - 1; j >= 0; j--)
               if (p[j / BYTEWIDTH] & (1 << (j % BYTEWIDTH)))
                   fastmap[j] = 1;
           break;


       case charset_not:
           /* Chars beyond end of map must be allowed.  */
           for (j = *p * BYTEWIDTH; j < (1 << BYTEWIDTH); j++)
               fastmap[j] = 1;

           for (j = *p++ * BYTEWIDTH - 1; j >= 0; j--)
               if (!(p[j / BYTEWIDTH] & (1 << (j % BYTEWIDTH))))
                   fastmap[j] = 1;
           break;


       case wordchar:
           for (j = 0; j < (1 << BYTEWIDTH); j++)
               if (SYNTAX(j) == Sword)
                   fastmap[j] = 1;
           break;


       case notwordchar:
           for (j = 0; j < (1 << BYTEWIDTH); j++)
               if (SYNTAX(j) != Sword)
                   fastmap[j] = 1;
           break;


       case anychar:
           /* `.' matches anything ...  */
           for (j = 0; j < (1 << BYTEWIDTH); j++)
               fastmap[j] = 1;

           /* ... except perhaps newline.  */
           if (!(bufp->syntax & RE_DOT_NEWLINE))
               fastmap['\n'] = 0;

           /* Return if we have already set `can_be_null'; if we have,
            * then the fastmap is irrelevant.  Something's wrong here.  */
           else if (bufp->can_be_null)
               return 0;

           /* Otherwise, have to check alternative paths.  */
           break;


#ifdef emacs
       case syntaxspec:
           k = *p++;
           for (j = 0; j < (1 << BYTEWIDTH); j++)
               if (SYNTAX(j) == (enum syntaxcode) k)
                   fastmap[j] = 1;
           break;


       case notsyntaxspec:
           k = *p++;
           for (j = 0; j < (1 << BYTEWIDTH); j++)
               if (SYNTAX(j) != (enum syntaxcode) k)
                   fastmap[j] = 1;
           break;


           /* All cases after this match the empty string.  These end with
            * `continue'.  */


       case before_dot:
       case at_dot:
       case after_dot:
           continue;
#endif /* not emacs */


       case no_op:
       case begline:
       case endline:
       case begbuf:
       case endbuf:
       case wordbound:
       case notwordbound:
       case wordbeg:
       case wordend:
       case push_dummy_failure:
           continue;


       case jump_n:
       case pop_failure_jump:
       case maybe_pop_jump:
       case jump:
       case jump_past_alt:
       case dummy_failure_jump:
           EXTRACT_NUMBER_AND_INCR(j, p);
           p += j;
           if (j > 0)
               continue;

           /* Jump backward implies we just went through the body of a
            * loop and matched nothing.  Opcode jumped to should be
            * `on_failure_jump' or `succeed_n'.  Just treat it like an
            * ordinary jump.  For a * loop, it has pushed its failure
            * point already; if so, discard that as redundant.  */
           if ((re_opcode_t) * p != on_failure_jump
               && (re_opcode_t) * p != succeed_n)
               continue;

           p++;
           EXTRACT_NUMBER_AND_INCR(j, p);
           p += j;

           /* If what's on the stack is where we are now, pop it.  */
           if (!FAIL_STACK_EMPTY()
               && fail_stack.stack[fail_stack.avail - 1] == p)
               fail_stack.avail--;

           continue;


       case on_failure_jump:
       case on_failure_keep_string_jump:
         handle_on_failure_jump:
           EXTRACT_NUMBER_AND_INCR(j, p);

           /* For some patterns, e.g., `(a?)?', `p+j' here points to the
            * end of the pattern.  We don't want to push such a point,
            * since when we restore it above, entering the switch will
            * increment `p' past the end of the pattern.  We don't need
            * to push such a point since we obviously won't find any more
            * fastmap entries beyond `pend'.  Such a pattern can match
            * the null string, though.  */
           if (p + j < pend) {
               if (!PUSH_PATTERN_OP(p + j, fail_stack))
                   return -2;
           } else
               bufp->can_be_null = 1;

           if (succeed_n_p) {
               EXTRACT_NUMBER_AND_INCR(k, p);  /* Skip the n.  */
               succeed_n_p = false;
           }
           continue;


       case succeed_n:
           /* Get to the number of times to succeed.  */
           p += 2;

           /* Increment p past the n for when k != 0.  */
           EXTRACT_NUMBER_AND_INCR(k, p);
           if (k == 0) {
               p -= 4;
               succeed_n_p = true;     /* Spaghetti code alert.  */
               goto handle_on_failure_jump;
           }
           continue;


       case set_number_at:
           p += 4;
           continue;


       case start_memory:
       case stop_memory:
           p += 2;
           continue;


       default:
           abort();            /* We have listed all the cases.  */
       }                       /* switch *p++ */

       /* Getting here means we have found the possible starting
        * characters for one path of the pattern -- and that the empty
        * string does not match.  We need not follow this path further.
        * Instead, look at the next alternative (remembered on the
        * stack), or quit if no more.  The test at the top of the loop
        * does these things.  */
       path_can_be_null = false;
       p = pend;
    }                          /* while p */

    /* Set `can_be_null' for the last path (also the first path, if the
     * pattern is empty).  */
    bufp->can_be_null |= path_can_be_null;
    return 0;
}                              /* re_compile_fastmap */

/* Set REGS to hold NUM_REGS registers, storing them in STARTS and
 * ENDS.  Subsequent matches using PATTERN_BUFFER and REGS will use
 * this memory for recording register information.  STARTS and ENDS
 * must be allocated using the malloc library routine, and must each
 * be at least NUM_REGS * sizeof (regoff_t) bytes long.
 *
 * If NUM_REGS == 0, then subsequent matches should allocate their own
 * register data.
 *
 * Unless this function is called, the first search or match using
 * PATTERN_BUFFER will allocate its own register data, without
 * freeing the old data.  */

void
re_set_registers(struct re_pattern_buffer *bufp, struct re_registers * regs,
                 unsigned  num_regs, regoff_t *starts, regoff_t * ends)
{
    if (num_regs) {
       bufp->regs_allocated = REGS_REALLOCATE;
       regs->num_regs = num_regs;
       regs->start = starts;
       regs->end = ends;
    } else {
       bufp->regs_allocated = REGS_UNALLOCATED;
       regs->num_regs = 0;
       regs->start = regs->end = (regoff_t) 0;
    }
}

/* Searching routines.  */

/* Like re_search_2, below, but only one string is specified, and
 * doesn't let you say where to stop matching. */

int
re_search(struct re_pattern_buffer *bufp, const char *string,
        int size,int  startpos,int  range, struct re_registers * regs)
{
    return re_search_2(bufp, NULL, 0, string, size, startpos, range,
       regs, size);
}


/* Using the compiled pattern in BUFP->buffer, first tries to match the
 * virtual concatenation of STRING1 and STRING2, starting first at index
 * STARTPOS, then at STARTPOS + 1, and so on.
 *
 * STRING1 and STRING2 have length SIZE1 and SIZE2, respectively.
 *
 * RANGE is how far to scan while trying to match.  RANGE = 0 means try
 * only at STARTPOS; in general, the last start tried is STARTPOS +
 * RANGE.
 *
 * In REGS, return the indices of the virtual concatenation of STRING1
 * and STRING2 that matched the entire BUFP->buffer and its contained
 * subexpressions.
 *
 * Do not consider matching one past the index STOP in the virtual
 * concatenation of STRING1 and STRING2.
 *
 * We return either the position in the strings at which the match was
 * found, -1 if no match, or -2 if error (such as failure
 * stack overflow).  */

int
re_search_2(struct re_pattern_buffer *bufp, const char * string1, int size1,
            const char *string2, int size2, int startpos, int range,
            struct re_registers * regs, int stop)
{
    int val;
    register char *fastmap = bufp->fastmap;
    register char *translate = bufp->translate;
    int total_size = size1 + size2;
    int endpos = startpos + range;

    /* Check for out-of-range STARTPOS.  */
    if (startpos < 0 || startpos > total_size)
       return -1;

    /* Fix up RANGE if it might eventually take us outside
     * the virtual concatenation of STRING1 and STRING2.  */
    if (endpos < -1)
       range = -1 - startpos;
    else if (endpos > total_size)
       range = total_size - startpos;

    /* If the search isn't to be a backwards one, don't waste time in a
     * search for a pattern that must be anchored.  */
    if (bufp->used > 0 && (re_opcode_t) bufp->buffer[0] == begbuf && range > 0) {
       if (startpos > 0)
           return -1;
       else
           range = 1;
    }
    /* Update the fastmap now if not correct already.  */
    if (fastmap && !bufp->fastmap_accurate)
       if (re_compile_fastmap(bufp) == -2)
           return -2;

    /* Loop through the string, looking for a place to start matching.  */
    for (;;) {
       /* If a fastmap is supplied, skip quickly over characters that
        * cannot be the start of a match.  If the pattern can match the
        * null string, however, we don't need to skip characters; we want
        * the first null string.  */
       if (fastmap && startpos < total_size && !bufp->can_be_null) {
           if (range > 0) {    /* Searching forwards.  */
               register const char *d;
               register int lim = 0;
               int irange = range;

               if (startpos < size1 && startpos + range >= size1)
                   lim = range - (size1 - startpos);

               d = (startpos >= size1 ? string2 - size1 : string1) + startpos;

               /* Written out as an if-else to avoid testing `translate'
                * inside the loop.  */
               if (translate)
                   while (range > lim
                       && !fastmap[(unsigned char)
                           translate[(unsigned char) *d++]])
                       range--;
               else
                   while (range > lim && !fastmap[(unsigned char) *d++])
                       range--;

               startpos += irange - range;
           } else {            /* Searching backwards.  */
               register char c = (size1 == 0 || startpos >= size1
                   ? string2[startpos - size1]
                   : string1[startpos]);

               if (!fastmap[(unsigned char) TRANSLATE(c)])
                   goto advance;
           }
       }
       /* If can't match the null string, and that's all we have left, fail.  */
       if (range >= 0 && startpos == total_size && fastmap
           && !bufp->can_be_null)
           return -1;

       val = re_match_2(bufp, string1, size1, string2, size2,
           startpos, regs, stop);
       if (val >= 0)
           return startpos;

       if (val == -2)
           return -2;

      advance:
       if (!range)
           break;
       else if (range > 0) {
           range--;
           startpos++;
       } else {
           range++;
           startpos--;
       }
    }
    return -1;
}                              /* re_search_2 */

/* Declarations and macros for re_match_2.  */

static int
bcmp_translate(unsigned char *s1, unsigned char *s2, register int len, char *translate);



/* Structure for per-register (a.k.a. per-group) information.
 * This must not be longer than one word, because we push this value
 * onto the failure stack.  Other register information, such as the
 * starting and ending positions (which are addresses), and the list of
 * inner groups (which is a bits list) are maintained in separate
 * variables.
 *
 * We are making a (strictly speaking) nonportable assumption here: that
 * the compiler will pack our bit fields into something that fits into
 * the type of `word', i.e., is something that fits into one item on the
 * failure stack.  */
typedef union {
    fail_stack_elt_t word;
    struct {
       /* This field is one if this group can match the empty string,
        * zero if not.  If not yet determined,  `MATCH_NULL_UNSET_VALUE'.  */
#define MATCH_NULL_UNSET_VALUE 3
       unsigned match_null_string_p:2;
       unsigned is_active:1;
       unsigned matched_something:1;
       unsigned ever_matched_something:1;
    } bits;
} register_info_type;


static boolean
alt_match_null_string_p(unsigned char *p, unsigned char *end, register_info_type * reg_info);
static boolean
common_op_match_null_string_p(unsigned char **p, unsigned char *end, register_info_type * reg_info);
static boolean
group_match_null_string_p(unsigned char **p, unsigned char *end, register_info_type *reg_info);

#define REG_MATCH_NULL_STRING_P(R)  ((R).bits.match_null_string_p)
#define IS_ACTIVE(R)  ((R).bits.is_active)
#define MATCHED_SOMETHING(R)  ((R).bits.matched_something)
#define EVER_MATCHED_SOMETHING(R)  ((R).bits.ever_matched_something)


/* Call this when have matched a real character; it sets `matched' flags
 * for the subexpressions which we are currently inside.  Also records
 * that those subexprs have matched.  */
#define SET_REGS_MATCHED()                                             \
  do                                                                   \
    {                                                                  \
      unsigned r;                                                      \
      for (r = lowest_active_reg; r <= highest_active_reg; r++)                \
        {                                                              \
          MATCHED_SOMETHING (reg_info[r])                              \
            = EVER_MATCHED_SOMETHING (reg_info[r])                     \
            = 1;                                                       \
        }                                                              \
    }                                                                  \
  while (0)


/* This converts PTR, a pointer into one of the search strings `string1'
 * and `string2' into an offset from the beginning of that string.  */
#define POINTER_TO_OFFSET(ptr)                                         \
  (FIRST_STRING_P (ptr) ? (ptr) - string1 : (ptr) - string2 + size1)

/* Registers are set to a sentinel when they haven't yet matched.  */
#define REG_UNSET_VALUE ((char *) -1)
#define REG_UNSET(e) ((e) == REG_UNSET_VALUE)


/* Macros for dealing with the split strings in re_match_2.  */

#define MATCHING_IN_FIRST_STRING  (dend == end_match_1)

/* Call before fetching a character with *d.  This switches over to
 * string2 if necessary.  */
#define PREFETCH()                                                     \
  while (d == dend)                                                    \
    {                                                                  \
      /* End of string2 => fail.  */                                   \
      if (dend == end_match_2)                                                 \
        goto fail;                                                     \
      /* End of string1 => advance to string2.  */                     \
      d = string2;                                                     \
      dend = end_match_2;                                              \
    }


/* Test if at very beginning or at very end of the virtual concatenation
 * of `string1' and `string2'.  If only one string, it's `string2'.  */
#define AT_STRINGS_BEG(d) ((d) == (size1 ? string1 : string2) || !size2)
#define AT_STRINGS_END(d) ((d) == end2)


/* Test if D points to a character which is word-constituent.  We have
 * two special cases to check for: if past the end of string1, look at
 * the first character in string2; and if before the beginning of
 * string2, look at the last character in string1.  */
#define WORDCHAR_P(d)                                                  \
  (SYNTAX ((d) == end1 ? *string2                                      \
           : (d) == string2 - 1 ? *(end1 - 1) : *(d))                  \
   == Sword)

/* Test if the character before D and the one at D differ with respect
 * to being word-constituent.  */
#define AT_WORD_BOUNDARY(d)                                            \
  (AT_STRINGS_BEG (d) || AT_STRINGS_END (d)                            \
   || WORDCHAR_P (d - 1) != WORDCHAR_P (d))


/* Free everything we malloc.  */
#ifdef REGEX_MALLOC
#define FREE_VAR(var) if (var) free (var); var = NULL
#define FREE_VARIABLES()                                               \
  do {                                                                 \
    FREE_VAR (fail_stack.stack);                                       \
    FREE_VAR (regstart);                                               \
    FREE_VAR (regend);                                                 \
    FREE_VAR (old_regstart);                                           \
    FREE_VAR (old_regend);                                             \
    FREE_VAR (best_regstart);                                          \
    FREE_VAR (best_regend);                                            \
    FREE_VAR (reg_info);                                               \
    FREE_VAR (reg_dummy);                                              \
    FREE_VAR (reg_info_dummy);                                         \
  } while (0)
#else /* not REGEX_MALLOC */
/* Some MIPS systems (at least) want this to free alloca'd storage.  */
#define FREE_VARIABLES() alloca (0)
#endif /* not REGEX_MALLOC */


/* These values must meet several constraints.  They must not be valid
 * register values; since we have a limit of 255 registers (because
 * we use only one byte in the pattern for the register number), we can
 * use numbers larger than 255.  They must differ by 1, because of
 * NUM_FAILURE_ITEMS above.  And the value for the lowest register must
 * be larger than the value for the highest register, so we do not try
 * to actually save any registers when none are active.  */
#define NO_HIGHEST_ACTIVE_REG (1 << BYTEWIDTH)
#define NO_LOWEST_ACTIVE_REG (NO_HIGHEST_ACTIVE_REG + 1)

/* Matching routines.  */

#ifndef emacs                  /* Emacs never uses this.  */
/* re_match is like re_match_2 except it takes only a single string.  */

int
re_match(struct re_pattern_buffer *bufp, const char *string, int size, int pos, struct re_registers * regs)
{
    return re_match_2(bufp, NULL, 0, string, size, pos, regs, size);
}
#endif /* not emacs */


/* re_match_2 matches the compiled pattern in BUFP against the
 * the (virtual) concatenation of STRING1 and STRING2 (of length SIZE1
 * and SIZE2, respectively).  We start matching at POS, and stop
 * matching at STOP.
 *
 * If REGS is non-null and the `no_sub' field of BUFP is nonzero, we
 * store offsets for the substring each group matched in REGS.  See the
 * documentation for exactly how many groups we fill.
 *
 * We return -1 if no match, -2 if an internal error (such as the
 * failure stack overflowing).  Otherwise, we return the length of the
 * matched substring.  */

int
re_match_2(struct re_pattern_buffer * bufp,const char * string1, int size1,
           const char *string2, int size2, int pos,struct re_registers * regs, int stop)

{
    /* General temporaries.  */
    int mcnt;
    unsigned char *p1;

    /* Just past the end of the corresponding string.  */
    const char *end1, *end2;

    /* Pointers into string1 and string2, just past the last characters in
     * each to consider matching.  */
    const char *end_match_1, *end_match_2;

    /* Where we are in the data, and the end of the current string.  */
    const char *d, *dend;

    /* Where we are in the pattern, and the end of the pattern.  */
    unsigned char *p = bufp->buffer;
    register unsigned char *pend = p + bufp->used;

    /* We use this to map every character in the string.  */
    char *translate = bufp->translate;

    /* Failure point stack.  Each place that can handle a failure further
     * down the line pushes a failure point on this stack.  It consists of
     * restart, regend, and reg_info for all registers corresponding to
     * the subexpressions we're currently inside, plus the number of such
     * registers, and, finally, two char *'s.  The first char * is where
     * to resume scanning the pattern; the second one is where to resume
     * scanning the strings.  If the latter is zero, the failure point is
     * a ``dummy''; if a failure happens and the failure point is a dummy,
     * it gets discarded and the next next one is tried.  */
    fail_stack_type fail_stack;
#ifdef DEBUG
    static unsigned failure_id = 0;
    unsigned nfailure_points_pushed = 0, nfailure_points_popped = 0;
#endif

    /* We fill all the registers internally, independent of what we
     * return, for use in backreferences.  The number here includes
     * an element for register zero.  */
    unsigned num_regs = bufp->re_nsub + 1;

    /* The currently active registers.  */
    unsigned long lowest_active_reg = NO_LOWEST_ACTIVE_REG;
    unsigned long highest_active_reg = NO_HIGHEST_ACTIVE_REG;

    /* Information on the contents of registers. These are pointers into
     * the input strings; they record just what was matched (on this
     * attempt) by a subexpression part of the pattern, that is, the
     * regnum-th regstart pointer points to where in the pattern we began
     * matching and the regnum-th regend points to right after where we
     * stopped matching the regnum-th subexpression.  (The zeroth register
     * keeps track of what the whole pattern matches.)  */
    const char **regstart = NULL, **regend = NULL;

    /* If a group that's operated upon by a repetition operator fails to
     * match anything, then the register for its start will need to be
     * restored because it will have been set to wherever in the string we
     * are when we last see its open-group operator.  Similarly for a
     * register's end.  */
    const char **old_regstart = NULL, **old_regend = NULL;

    /* The is_active field of reg_info helps us keep track of which (possibly
     * nested) subexpressions we are currently in. The matched_something
     * field of reg_info[reg_num] helps us tell whether or not we have
     * matched any of the pattern so far this time through the reg_num-th
     * subexpression.  These two fields get reset each time through any
     * loop their register is in.  */
    register_info_type *reg_info = NULL;

    /* The following record the register info as found in the above
     * variables when we find a match better than any we've seen before.
     * This happens as we backtrack through the failure points, which in
     * turn happens only if we have not yet matched the entire string. */
    unsigned best_regs_set = false;
    const char **best_regstart = NULL, **best_regend = NULL;

    /* Logically, this is `best_regend[0]'.  But we don't want to have to
     * allocate space for that if we're not allocating space for anything
     * else (see below).  Also, we never need info about register 0 for
     * any of the other register vectors, and it seems rather a kludge to
     * treat `best_regend' differently than the rest.  So we keep track of
     * the end of the best match so far in a separate variable.  We
     * initialize this to NULL so that when we backtrack the first time
     * and need to test it, it's not garbage.  */
    const char *match_end = NULL;

    /* Used when we pop values we don't care about.  */
    const char **reg_dummy = NULL;
    register_info_type *reg_info_dummy = NULL;

#ifdef DEBUG
    /* Counts the total number of registers pushed.  */
    unsigned num_regs_pushed = 0;
#endif

    DEBUG_PRINT1("\n\nEntering re_match_2.\n");

    INIT_FAIL_STACK();

    /* Do not bother to initialize all the register variables if there are
     * no groups in the pattern, as it takes a fair amount of time.  If
     * there are groups, we include space for register 0 (the whole
     * pattern), even though we never use it, since it simplifies the
     * array indexing.  We should fix this.  */
    if (bufp->re_nsub) {
       regstart = REGEX_TALLOC(num_regs, const char *);
       regend = REGEX_TALLOC(num_regs, const char *);
       old_regstart = REGEX_TALLOC(num_regs, const char *);
       old_regend = REGEX_TALLOC(num_regs, const char *);
       best_regstart = REGEX_TALLOC(num_regs, const char *);
       best_regend = REGEX_TALLOC(num_regs, const char *);
       reg_info = REGEX_TALLOC(num_regs, register_info_type);
       reg_dummy = REGEX_TALLOC(num_regs, const char *);
       reg_info_dummy = REGEX_TALLOC(num_regs, register_info_type);

       if (!(regstart && regend && old_regstart && old_regend && reg_info
               && best_regstart && best_regend && reg_dummy && reg_info_dummy)) {
           FREE_VARIABLES();
           return -2;
       }
    }
#ifdef REGEX_MALLOC
    else {
       /* We must initialize all our variables to NULL, so that
        * `FREE_VARIABLES' doesn't try to free them.  */
       regstart = regend = old_regstart = old_regend = best_regstart
           = best_regend = reg_dummy = NULL;
       reg_info = reg_info_dummy = (register_info_type *) NULL;
    }
#endif /* REGEX_MALLOC */

    /* The starting position is bogus.  */
    if (pos < 0 || pos > size1 + size2) {
       FREE_VARIABLES();
       return -1;
    }
    /* Initialize subexpression text positions to -1 to mark ones that no
     * start_memory/stop_memory has been seen for. Also initialize the
     * register information struct.  */
    for (mcnt = 1; mcnt < num_regs; mcnt++) {
       regstart[mcnt] = regend[mcnt]
           = old_regstart[mcnt] = old_regend[mcnt] = REG_UNSET_VALUE;

       REG_MATCH_NULL_STRING_P(reg_info[mcnt]) = MATCH_NULL_UNSET_VALUE;
       IS_ACTIVE(reg_info[mcnt]) = 0;
       MATCHED_SOMETHING(reg_info[mcnt]) = 0;
       EVER_MATCHED_SOMETHING(reg_info[mcnt]) = 0;
    }

    /* We move `string1' into `string2' if the latter's empty -- but not if
     * `string1' is null.  */
    if (size2 == 0 && string1 != NULL) {
       string2 = string1;
       size2 = size1;
       string1 = 0;
       size1 = 0;
    }
    end1 = string1 + size1;
    end2 = string2 + size2;

    /* Compute where to stop matching, within the two strings.  */
    if (stop <= size1) {
       end_match_1 = string1 + stop;
       end_match_2 = string2;
    } else {
       end_match_1 = end1;
       end_match_2 = string2 + stop - size1;
    }

    /* `p' scans through the pattern as `d' scans through the data.
     * `dend' is the end of the input string that `d' points within.  `d'
     * is advanced into the following input string whenever necessary, but
     * this happens before fetching; therefore, at the beginning of the
     * loop, `d' can be pointing at the end of a string, but it cannot
     * equal `string2'.  */
    if (size1 > 0 && pos <= size1) {
       d = string1 + pos;
       dend = end_match_1;
    } else {
       d = string2 + pos - size1;
       dend = end_match_2;
    }

    DEBUG_PRINT1("The compiled pattern is: ");
    DEBUG_PRINT_COMPILED_PATTERN(bufp, p, pend);
    DEBUG_PRINT1("The string to match is: `");
    DEBUG_PRINT_DOUBLE_STRING(d, string1, size1, string2, size2);
    DEBUG_PRINT1("'\n");

    /* This loops over pattern commands.  It exits by returning from the
     * function if the match is complete, or it drops through if the match
     * fails at this starting point in the input data.  */
    for (;;) {
       DEBUG_PRINT2("\n0x%x: ", p);

       if (p == pend) {        /* End of pattern means we might have succeeded.  */
           DEBUG_PRINT1("end of pattern ... ");

           /* If we haven't matched the entire string, and we want the
            * longest match, try backtracking.  */
           if (d != end_match_2) {
               DEBUG_PRINT1("backtracking.\n");

               if (!FAIL_STACK_EMPTY()) {      /* More failure points to try.  */
                   boolean same_str_p = (FIRST_STRING_P(match_end)
                       == MATCHING_IN_FIRST_STRING);

                   /* If exceeds best match so far, save it.  */
                   if (!best_regs_set
                       || (same_str_p && d > match_end)
                       || (!same_str_p && !MATCHING_IN_FIRST_STRING)) {
                       best_regs_set = true;
                       match_end = d;

                       DEBUG_PRINT1("\nSAVING match as best so far.\n");

                       for (mcnt = 1; mcnt < num_regs; mcnt++) {
                           best_regstart[mcnt] = regstart[mcnt];
                           best_regend[mcnt] = regend[mcnt];
                       }
                   }
                   goto fail;
               }
               /* If no failure points, don't restore garbage.  */
               else if (best_regs_set) {
                 restore_best_regs:
                   /* Restore best match.  It may happen that `dend ==
                    * end_match_1' while the restored d is in string2.
                    * For example, the pattern `x.*y.*z' against the
                    * strings `x-' and `y-z-', if the two strings are
                    * not consecutive in memory.  */
                   DEBUG_PRINT1("Restoring best registers.\n");

                   d = match_end;
                   dend = ((d >= string1 && d <= end1)
                       ? end_match_1 : end_match_2);

                   for (mcnt = 1; mcnt < num_regs; mcnt++) {
                       regstart[mcnt] = best_regstart[mcnt];
                       regend[mcnt] = best_regend[mcnt];
                   }
               }
           }                   /* d != end_match_2 */
           DEBUG_PRINT1("Accepting match.\n");

           /* If caller wants register contents data back, do it.  */
           if (regs && !bufp->no_sub) {
               /* Have the register data arrays been allocated?  */
               if (bufp->regs_allocated == REGS_UNALLOCATED) {         /* No.  So allocate them with malloc.  We need one
                                                                        * extra element beyond `num_regs' for the `-1' marker
                                                                        * GNU code uses.  */
                   regs->num_regs = MAX(RE_NREGS, num_regs + 1);
                   regs->start = TALLOC(regs->num_regs, regoff_t);
                   regs->end = TALLOC(regs->num_regs, regoff_t);
                   if (regs->start == NULL || regs->end == NULL)
                       return -2;
                   bufp->regs_allocated = REGS_REALLOCATE;
               } else if (bufp->regs_allocated == REGS_REALLOCATE) {   /* Yes.  If we need more elements than were already
                                                                        * allocated, reallocate them.  If we need fewer, just
                                                                        * leave it alone.  */
                   if (regs->num_regs < num_regs + 1) {
                       regs->num_regs = num_regs + 1;
                       RETALLOC(regs->start, regs->num_regs, regoff_t);
                       RETALLOC(regs->end, regs->num_regs, regoff_t);
                       if (regs->start == NULL || regs->end == NULL)
                           return -2;
                   }
               } else
                   assert(bufp->regs_allocated == REGS_FIXED);

               /* Convert the pointer data in `regstart' and `regend' to
                * indices.  Register zero has to be set differently,
                * since we haven't kept track of any info for it.  */
               if (regs->num_regs > 0) {
                   regs->start[0] = pos;
                   regs->end[0] = (MATCHING_IN_FIRST_STRING ? d - string1
                       : d - string2 + size1);
               }
               /* Go through the first `min (num_regs, regs->num_regs)'
                * registers, since that is all we initialized.  */
               for (mcnt = 1; mcnt < MIN(num_regs, regs->num_regs); mcnt++) {
                   if (REG_UNSET(regstart[mcnt]) || REG_UNSET(regend[mcnt]))
                       regs->start[mcnt] = regs->end[mcnt] = -1;
                   else {
                       regs->start[mcnt] = POINTER_TO_OFFSET(regstart[mcnt]);
                       regs->end[mcnt] = POINTER_TO_OFFSET(regend[mcnt]);
                   }
               }

               /* If the regs structure we return has more elements than
                * were in the pattern, set the extra elements to -1.  If
                * we (re)allocated the registers, this is the case,
                * because we always allocate enough to have at least one
                * -1 at the end.  */
               for (mcnt = num_regs; mcnt < regs->num_regs; mcnt++)
                   regs->start[mcnt] = regs->end[mcnt] = -1;
           }                   /* regs && !bufp->no_sub */
           FREE_VARIABLES();
           DEBUG_PRINT4("%u failure points pushed, %u popped (%u remain).\n",
               nfailure_points_pushed, nfailure_points_popped,
               nfailure_points_pushed - nfailure_points_popped);
           DEBUG_PRINT2("%u registers pushed.\n", num_regs_pushed);

           mcnt = d - pos - (MATCHING_IN_FIRST_STRING
               ? string1
               : string2 - size1);

           DEBUG_PRINT2("Returning %d from re_match_2.\n", mcnt);

           return mcnt;
       }
       /* Otherwise match next pattern command.  */
#ifdef SWITCH_ENUM_BUG
       switch ((int) ((re_opcode_t) * p++))
#else
       switch ((re_opcode_t) * p++)
#endif
       {
           /* Ignore these.  Used to ignore the n of succeed_n's which
            * currently have n == 0.  */
       case no_op:
           DEBUG_PRINT1("EXECUTING no_op.\n");
           break;


           /* Match the next n pattern characters exactly.  The following
            * byte in the pattern defines n, and the n bytes after that
            * are the characters to match.  */
       case exactn:
           mcnt = *p++;
           DEBUG_PRINT2("EXECUTING exactn %d.\n", mcnt);

           /* This is written out as an if-else so we don't waste time
            * testing `translate' inside the loop.  */
           if (translate) {
               do {
                   PREFETCH();
                   if (translate[(unsigned char) *d++] != (char) *p++)
                       goto fail;
               }
               while (--mcnt);
           } else {
               do {
                   PREFETCH();
                   if (*d++ != (char) *p++)
                       goto fail;
               }
               while (--mcnt);
           }
           SET_REGS_MATCHED();
           break;


           /* Match any character except possibly a newline or a null.  */
       case anychar:
           DEBUG_PRINT1("EXECUTING anychar.\n");

           PREFETCH();

           if ((!(bufp->syntax & RE_DOT_NEWLINE) && TRANSLATE(*d) == '\n')
               || (bufp->syntax & RE_DOT_NOT_NULL && TRANSLATE(*d) == '\000'))
               goto fail;

           SET_REGS_MATCHED();
           DEBUG_PRINT2("  Matched `%d'.\n", *d);
           d++;
           break;


       case charset:
       case charset_not:
           {
               register unsigned char c;
               boolean not = (re_opcode_t) * (p - 1) == charset_not;

               DEBUG_PRINT2("EXECUTING charset%s.\n", not ? "_not" : "");

               PREFETCH();
               c = TRANSLATE(*d);      /* The character to match.  */

               /* Cast to `unsigned' instead of `unsigned char' in case the
                * bit list is a full 32 bytes long.  */
               if (c < (unsigned) (*p * BYTEWIDTH)
                   && p[1 + c / BYTEWIDTH] & (1 << (c % BYTEWIDTH)))
                   not = !not;

               p += 1 + *p;

               if (!not)
                   goto fail;

               SET_REGS_MATCHED();
               d++;
               break;
           }


           /* The beginning of a group is represented by start_memory.
            * The arguments are the register number in the next byte, and the
            * number of groups inner to this one in the next.  The text
            * matched within the group is recorded (in the internal
            * registers data structure) under the register number.  */
       case start_memory:
           DEBUG_PRINT3("EXECUTING start_memory %d (%d):\n", *p, p[1]);

           /* Find out if this group can match the empty string.  */
           p1 = p;             /* To send to group_match_null_string_p.  */

           if (REG_MATCH_NULL_STRING_P(reg_info[*p]) == MATCH_NULL_UNSET_VALUE)
               REG_MATCH_NULL_STRING_P(reg_info[*p])
                   = group_match_null_string_p(&p1, pend, reg_info);

           /* Save the position in the string where we were the last time
            * we were at this open-group operator in case the group is
            * operated upon by a repetition operator, e.g., with `(a*)*b'
            * against `ab'; then we want to ignore where we are now in
            * the string in case this attempt to match fails.  */
           old_regstart[*p] = REG_MATCH_NULL_STRING_P(reg_info[*p])
               ? REG_UNSET(regstart[*p]) ? d : regstart[*p]
               : regstart[*p];
           DEBUG_PRINT2("  old_regstart: %d\n",
               POINTER_TO_OFFSET(old_regstart[*p]));

           regstart[*p] = d;
           DEBUG_PRINT2("  regstart: %d\n", POINTER_TO_OFFSET(regstart[*p]));

           IS_ACTIVE(reg_info[*p]) = 1;
           MATCHED_SOMETHING(reg_info[*p]) = 0;

           /* This is the new highest active register.  */
           highest_active_reg = *p;

           /* If nothing was active before, this is the new lowest active
            * register.  */
           if (lowest_active_reg == NO_LOWEST_ACTIVE_REG)
               lowest_active_reg = *p;

           /* Move past the register number and inner group count.  */
           p += 2;
           break;


           /* The stop_memory opcode represents the end of a group.  Its
            * arguments are the same as start_memory's: the register
            * number, and the number of inner groups.  */
       case stop_memory:
           DEBUG_PRINT3("EXECUTING stop_memory %d (%d):\n", *p, p[1]);

           /* We need to save the string position the last time we were at
            * this close-group operator in case the group is operated
            * upon by a repetition operator, e.g., with `((a*)*(b*)*)*'
            * against `aba'; then we want to ignore where we are now in
            * the string in case this attempt to match fails.  */
           old_regend[*p] = REG_MATCH_NULL_STRING_P(reg_info[*p])
               ? REG_UNSET(regend[*p]) ? d : regend[*p]
               : regend[*p];
           DEBUG_PRINT2("      old_regend: %d\n",
               POINTER_TO_OFFSET(old_regend[*p]));

           regend[*p] = d;
           DEBUG_PRINT2("      regend: %d\n", POINTER_TO_OFFSET(regend[*p]));

           /* This register isn't active anymore.  */
           IS_ACTIVE(reg_info[*p]) = 0;

           /* If this was the only register active, nothing is active
            * anymore.  */
           if (lowest_active_reg == highest_active_reg) {
               lowest_active_reg = NO_LOWEST_ACTIVE_REG;
               highest_active_reg = NO_HIGHEST_ACTIVE_REG;
           } else {            /* We must scan for the new highest active register, since
                                * it isn't necessarily one less than now: consider
                                * (a(b)c(d(e)f)g).  When group 3 ends, after the f), the
                                * new highest active register is 1.  */
               unsigned char r = *p - 1;
               while (r > 0 && !IS_ACTIVE(reg_info[r]))
                   r--;

               /* If we end up at register zero, that means that we saved
                * the registers as the result of an `on_failure_jump', not
                * a `start_memory', and we jumped to past the innermost
                * `stop_memory'.  For example, in ((.)*) we save
                * registers 1 and 2 as a result of the *, but when we pop
                * back to the second ), we are at the stop_memory 1.
                * Thus, nothing is active.  */
               if (r == 0) {
                   lowest_active_reg = NO_LOWEST_ACTIVE_REG;
                   highest_active_reg = NO_HIGHEST_ACTIVE_REG;
               } else
                   highest_active_reg = r;
           }

           /* If just failed to match something this time around with a
            * group that's operated on by a repetition operator, try to
            * force exit from the ``loop'', and restore the register
            * information for this group that we had before trying this
            * last match.  */
           if ((!MATCHED_SOMETHING(reg_info[*p])
                   || (re_opcode_t) p[-3] == start_memory)
               && (p + 2) < pend) {
               boolean is_a_jump_n = false;

               p1 = p + 2;
               mcnt = 0;
               switch ((re_opcode_t) * p1++) {
               case jump_n:
                   is_a_jump_n = true;
               case pop_failure_jump:
               case maybe_pop_jump:
               case jump:
               case dummy_failure_jump:
                   EXTRACT_NUMBER_AND_INCR(mcnt, p1);
                   if (is_a_jump_n)
                       p1 += 2;
                   break;

               default:
                   /* do nothing */ ;
               }
               p1 += mcnt;

               /* If the next operation is a jump backwards in the pattern
                * to an on_failure_jump right before the start_memory
                * corresponding to this stop_memory, exit from the loop
                * by forcing a failure after pushing on the stack the
                * on_failure_jump's jump in the pattern, and d.  */
               if (mcnt < 0 && (re_opcode_t) * p1 == on_failure_jump
                   && (re_opcode_t) p1[3] == start_memory && p1[4] == *p) {
                   /* If this group ever matched anything, then restore
                    * what its registers were before trying this last
                    * failed match, e.g., with `(a*)*b' against `ab' for
                    * regstart[1], and, e.g., with `((a*)*(b*)*)*'
                    * against `aba' for regend[3].
                    *
                    * Also restore the registers for inner groups for,
                    * e.g., `((a*)(b*))*' against `aba' (register 3 would
                    * otherwise get trashed).  */

                   if (EVER_MATCHED_SOMETHING(reg_info[*p])) {
                       unsigned r;

                       EVER_MATCHED_SOMETHING(reg_info[*p]) = 0;

                       /* Restore this and inner groups' (if any) registers.  */
                       for (r = *p; r < *p + *(p + 1); r++) {
                           regstart[r] = old_regstart[r];

                           /* xx why this test?  */
                           if ((long) old_regend[r] >= (long) regstart[r])
                               regend[r] = old_regend[r];
                       }
                   }
                   p1++;
                   EXTRACT_NUMBER_AND_INCR(mcnt, p1);
                   PUSH_FAILURE_POINT(p1 + mcnt, d, -2);

                   goto fail;
               }
           }
           /* Move past the register number and the inner group count.  */
           p += 2;
           break;


           /* \<digit> has been turned into a `duplicate' command which is
            * followed by the numeric value of <digit> as the register number.  */
       case duplicate:
           {
               register const char *d2, *dend2;
               int regno = *p++;       /* Get which register to match against.  */
               DEBUG_PRINT2("EXECUTING duplicate %d.\n", regno);

               /* Can't back reference a group which we've never matched.  */
               if (REG_UNSET(regstart[regno]) || REG_UNSET(regend[regno]))
                   goto fail;

               /* Where in input to try to start matching.  */
               d2 = regstart[regno];

               /* Where to stop matching; if both the place to start and
                * the place to stop matching are in the same string, then
                * set to the place to stop, otherwise, for now have to use
                * the end of the first string.  */

               dend2 = ((FIRST_STRING_P(regstart[regno])
                       == FIRST_STRING_P(regend[regno]))
                   ? regend[regno] : end_match_1);
               for (;;) {
                   /* If necessary, advance to next segment in register
                    * contents.  */
                   while (d2 == dend2) {
                       if (dend2 == end_match_2)
                           break;
                       if (dend2 == regend[regno])
                           break;

                       /* End of string1 => advance to string2. */
                       d2 = string2;
                       dend2 = regend[regno];
                   }
                   /* At end of register contents => success */
                   if (d2 == dend2)
                       break;

                   /* If necessary, advance to next segment in data.  */
                   PREFETCH();

                   /* How many characters left in this segment to match.  */
                   mcnt = dend - d;

                   /* Want how many consecutive characters we can match in
                    * one shot, so, if necessary, adjust the count.  */
                   if (mcnt > dend2 - d2)
                       mcnt = dend2 - d2;

                   /* Compare that many; failure if mismatch, else move
                    * past them.  */
                   if (translate
                       ? bcmp_translate((unsigned char*)d, (unsigned char*) d2, mcnt, translate)
                       : memcmp(d, d2, mcnt))
                       goto fail;
                   d += mcnt, d2 += mcnt;
               }
           }
           break;


           /* begline matches the empty string at the beginning of the string
            * (unless `not_bol' is set in `bufp'), and, if
            * `newline_anchor' is set, after newlines.  */
       case begline:
           DEBUG_PRINT1("EXECUTING begline.\n");

           if (AT_STRINGS_BEG(d)) {
               if (!bufp->not_bol)
                   break;
           } else if (d[-1] == '\n' && bufp->newline_anchor) {
               break;
           }
           /* In all other cases, we fail.  */
           goto fail;


           /* endline is the dual of begline.  */
       case endline:
           DEBUG_PRINT1("EXECUTING endline.\n");

           if (AT_STRINGS_END(d)) {
               if (!bufp->not_eol)
                   break;
           }
           /* We have to ``prefetch'' the next character.  */
           else if ((d == end1 ? *string2 : *d) == '\n'
               && bufp->newline_anchor) {
               break;
           }
           goto fail;


           /* Match at the very beginning of the data.  */
       case begbuf:
           DEBUG_PRINT1("EXECUTING begbuf.\n");
           if (AT_STRINGS_BEG(d))
               break;
           goto fail;


           /* Match at the very end of the data.  */
       case endbuf:
           DEBUG_PRINT1("EXECUTING endbuf.\n");
           if (AT_STRINGS_END(d))
               break;
           goto fail;


           /* on_failure_keep_string_jump is used to optimize `.*\n'.  It
            * pushes NULL as the value for the string on the stack.  Then
            * `pop_failure_point' will keep the current value for the
            * string, instead of restoring it.  To see why, consider
            * matching `foo\nbar' against `.*\n'.  The .* matches the foo;
            * then the . fails against the \n.  But the next thing we want
            * to do is match the \n against the \n; if we restored the
            * string value, we would be back at the foo.
            *
            * Because this is used only in specific cases, we don't need to
            * check all the things that `on_failure_jump' does, to make
            * sure the right things get saved on the stack.  Hence we don't
            * share its code.  The only reason to push anything on the
            * stack at all is that otherwise we would have to change
            * `anychar's code to do something besides goto fail in this
            * case; that seems worse than this.  */
       case on_failure_keep_string_jump:
           DEBUG_PRINT1("EXECUTING on_failure_keep_string_jump");

           EXTRACT_NUMBER_AND_INCR(mcnt, p);
           DEBUG_PRINT3(" %d (to 0x%x):\n", mcnt, p + mcnt);

           PUSH_FAILURE_POINT(p + mcnt, NULL, -2);
           break;


           /* Uses of on_failure_jump:
            *
            * Each alternative starts with an on_failure_jump that points
            * to the beginning of the next alternative.  Each alternative
            * except the last ends with a jump that in effect jumps past
            * the rest of the alternatives.  (They really jump to the
            * ending jump of the following alternative, because tensioning
            * these jumps is a hassle.)
            *
            * Repeats start with an on_failure_jump that points past both
            * the repetition text and either the following jump or
            * pop_failure_jump back to this on_failure_jump.  */
       case on_failure_jump:
         on_failure:
           DEBUG_PRINT1("EXECUTING on_failure_jump");

           EXTRACT_NUMBER_AND_INCR(mcnt, p);
           DEBUG_PRINT3(" %d (to 0x%x)", mcnt, p + mcnt);

           /* If this on_failure_jump comes right before a group (i.e.,
            * the original * applied to a group), save the information
            * for that group and all inner ones, so that if we fail back
            * to this point, the group's information will be correct.
            * For example, in \(a*\)*\1, we need the preceding group,
            * and in \(\(a*\)b*\)\2, we need the inner group.  */

           /* We can't use `p' to check ahead because we push
            * a failure point to `p + mcnt' after we do this.  */
           p1 = p;

           /* We need to skip no_op's before we look for the
            * start_memory in case this on_failure_jump is happening as
            * the result of a completed succeed_n, as in \(a\)\{1,3\}b\1
            * against aba.  */
           while (p1 < pend && (re_opcode_t) * p1 == no_op)
               p1++;

           if (p1 < pend && (re_opcode_t) * p1 == start_memory) {
               /* We have a new highest active register now.  This will
                * get reset at the start_memory we are about to get to,
                * but we will have saved all the registers relevant to
                * this repetition op, as described above.  */
               highest_active_reg = *(p1 + 1) + *(p1 + 2);
               if (lowest_active_reg == NO_LOWEST_ACTIVE_REG)
                   lowest_active_reg = *(p1 + 1);
           }
           DEBUG_PRINT1(":\n");
           PUSH_FAILURE_POINT(p + mcnt, d, -2);
           break;


           /* A smart repeat ends with `maybe_pop_jump'.
            * We change it to either `pop_failure_jump' or `jump'.  */
       case maybe_pop_jump:
           EXTRACT_NUMBER_AND_INCR(mcnt, p);
           DEBUG_PRINT2("EXECUTING maybe_pop_jump %d.\n", mcnt);
           {
               register unsigned char *p2 = p;

               /* Compare the beginning of the repeat with what in the
                * pattern follows its end. If we can establish that there
                * is nothing that they would both match, i.e., that we
                * would have to backtrack because of (as in, e.g., `a*a')
                * then we can change to pop_failure_jump, because we'll
                * never have to backtrack.
                *
                * This is not true in the case of alternatives: in
                * `(a|ab)*' we do need to backtrack to the `ab' alternative
                * (e.g., if the string was `ab').  But instead of trying to
                * detect that here, the alternative has put on a dummy
                * failure point which is what we will end up popping.  */

               /* Skip over open/close-group commands.  */
               while (p2 + 2 < pend
                   && ((re_opcode_t) * p2 == stop_memory
                       || (re_opcode_t) * p2 == start_memory))
                   p2 += 3;    /* Skip over args, too.  */

               /* If we're at the end of the pattern, we can change.  */
               if (p2 == pend) {
                   /* Consider what happens when matching ":\(.*\)"
                    * against ":/".  I don't really understand this code
                    * yet.  */
                   p[-3] = (unsigned char) pop_failure_jump;
                   DEBUG_PRINT1
                       ("  End of pattern: change to `pop_failure_jump'.\n");
               } else if ((re_opcode_t) * p2 == exactn
                   || (bufp->newline_anchor && (re_opcode_t) * p2 == endline)) {
                   register unsigned char c
                   = *p2 == (unsigned char) endline ? '\n' : p2[2];
                   p1 = p + mcnt;

                   /* p1[0] ... p1[2] are the `on_failure_jump' corresponding
                    * to the `maybe_finalize_jump' of this case.  Examine what
                    * follows.  */
                   if ((re_opcode_t) p1[3] == exactn && p1[5] != c) {
                       p[-3] = (unsigned char) pop_failure_jump;
                       DEBUG_PRINT3("  %c != %c => pop_failure_jump.\n",
                           c, p1[5]);
                   } else if ((re_opcode_t) p1[3] == charset
                       || (re_opcode_t) p1[3] == charset_not) {
                       int not = (re_opcode_t) p1[3] == charset_not;

                       if (c < (unsigned char) (p1[4] * BYTEWIDTH)
                           && p1[5 + c / BYTEWIDTH] & (1 << (c % BYTEWIDTH)))
                           not = !not;

                       /* `not' is equal to 1 if c would match, which means
                        * that we can't change to pop_failure_jump.  */
                       if (!not) {
                           p[-3] = (unsigned char) pop_failure_jump;
                           DEBUG_PRINT1("  No match => pop_failure_jump.\n");
                       }
                   }
               }
           }
           p -= 2;             /* Point at relative address again.  */
           if ((re_opcode_t) p[-1] != pop_failure_jump) {
               p[-1] = (unsigned char) jump;
               DEBUG_PRINT1("  Match => jump.\n");
               goto unconditional_jump;
           }
           /* Note fall through.  */


           /* The end of a simple repeat has a pop_failure_jump back to
            * its matching on_failure_jump, where the latter will push a
            * failure point.  The pop_failure_jump takes off failure
            * points put on by this pop_failure_jump's matching
            * on_failure_jump; we got through the pattern to here from the
            * matching on_failure_jump, so didn't fail.  */
       case pop_failure_jump:
           {
               /* We need to pass separate storage for the lowest and
                * highest registers, even though we don't care about the
                * actual values.  Otherwise, we will restore only one
                * register from the stack, since lowest will == highest in
                * `pop_failure_point'.  */
               unsigned long dummy_low_reg, dummy_high_reg;
               unsigned char *pdummy;
               const char *sdummy;

               DEBUG_PRINT1("EXECUTING pop_failure_jump.\n");
               POP_FAILURE_POINT(sdummy, pdummy,
                   dummy_low_reg, dummy_high_reg,
                   reg_dummy, reg_dummy, reg_info_dummy);
           }
           /* Note fall through.  */


           /* Unconditionally jump (without popping any failure points).  */
       case jump:
         unconditional_jump:
           EXTRACT_NUMBER_AND_INCR(mcnt, p);   /* Get the amount to jump.  */
           DEBUG_PRINT2("EXECUTING jump %d ", mcnt);
           p += mcnt;          /* Do the jump.  */
           DEBUG_PRINT2("(to 0x%x).\n", p);
           break;


           /* We need this opcode so we can detect where alternatives end
            * in `group_match_null_string_p' et al.  */
       case jump_past_alt:
           DEBUG_PRINT1("EXECUTING jump_past_alt.\n");
           goto unconditional_jump;


           /* Normally, the on_failure_jump pushes a failure point, which
            * then gets popped at pop_failure_jump.  We will end up at
            * pop_failure_jump, also, and with a pattern of, say, `a+', we
            * are skipping over the on_failure_jump, so we have to push
            * something meaningless for pop_failure_jump to pop.  */
       case dummy_failure_jump:
           DEBUG_PRINT1("EXECUTING dummy_failure_jump.\n");
           /* It doesn't matter what we push for the string here.  What
            * the code at `fail' tests is the value for the pattern.  */
           PUSH_FAILURE_POINT(0, 0, -2);
           goto unconditional_jump;


           /* At the end of an alternative, we need to push a dummy failure
            * point in case we are followed by a `pop_failure_jump', because
            * we don't want the failure point for the alternative to be
            * popped.  For example, matching `(a|ab)*' against `aab'
            * requires that we match the `ab' alternative.  */
       case push_dummy_failure:
           DEBUG_PRINT1("EXECUTING push_dummy_failure.\n");
           /* See comments just above at `dummy_failure_jump' about the
            * two zeroes.  */
           PUSH_FAILURE_POINT(0, 0, -2);
           break;

           /* Have to succeed matching what follows at least n times.
            * After that, handle like `on_failure_jump'.  */
       case succeed_n:
           EXTRACT_NUMBER(mcnt, p + 2);
           DEBUG_PRINT2("EXECUTING succeed_n %d.\n", mcnt);

           assert(mcnt >= 0);
           /* Originally, this is how many times we HAVE to succeed.  */
           if (mcnt > 0) {
               mcnt--;
               p += 2;
               STORE_NUMBER_AND_INCR(p, mcnt);
               DEBUG_PRINT3("  Setting 0x%x to %d.\n", p, mcnt);
           } else if (mcnt == 0) {
               DEBUG_PRINT2("  Setting two bytes from 0x%x to no_op.\n", p + 2);
               p[2] = (unsigned char) no_op;
               p[3] = (unsigned char) no_op;
               goto on_failure;
           }
           break;

       case jump_n:
           EXTRACT_NUMBER(mcnt, p + 2);
           DEBUG_PRINT2("EXECUTING jump_n %d.\n", mcnt);

           /* Originally, this is how many times we CAN jump.  */
           if (mcnt) {
               mcnt--;
               STORE_NUMBER(p + 2, mcnt);
               goto unconditional_jump;
           }
           /* If don't have to jump any more, skip over the rest of command.  */
           else
               p += 4;
           break;

       case set_number_at:
           {
               DEBUG_PRINT1("EXECUTING set_number_at.\n");

               EXTRACT_NUMBER_AND_INCR(mcnt, p);
               p1 = p + mcnt;
               EXTRACT_NUMBER_AND_INCR(mcnt, p);
               DEBUG_PRINT3("  Setting 0x%x to %d.\n", p1, mcnt);
               STORE_NUMBER(p1, mcnt);
               break;
           }

       case wordbound:
           DEBUG_PRINT1("EXECUTING wordbound.\n");
           if (AT_WORD_BOUNDARY(d))
               break;
           goto fail;

       case notwordbound:
           DEBUG_PRINT1("EXECUTING notwordbound.\n");
           if (AT_WORD_BOUNDARY(d))
               goto fail;
           break;

       case wordbeg:
           DEBUG_PRINT1("EXECUTING wordbeg.\n");
           if (WORDCHAR_P(d) && (AT_STRINGS_BEG(d) || !WORDCHAR_P(d - 1)))
               break;
           goto fail;

       case wordend:
           DEBUG_PRINT1("EXECUTING wordend.\n");
           if (!AT_STRINGS_BEG(d) && WORDCHAR_P(d - 1)
               && (!WORDCHAR_P(d) || AT_STRINGS_END(d)))
               break;
           goto fail;

#ifdef emacs
#ifdef emacs19
       case before_dot:
           DEBUG_PRINT1("EXECUTING before_dot.\n");
           if (PTR_CHAR_POS((unsigned char *) d) >= point)
               goto fail;
           break;

       case at_dot:
           DEBUG_PRINT1("EXECUTING at_dot.\n");
           if (PTR_CHAR_POS((unsigned char *) d) != point)
               goto fail;
           break;

       case after_dot:
           DEBUG_PRINT1("EXECUTING after_dot.\n");
           if (PTR_CHAR_POS((unsigned char *) d) <= point)
               goto fail;
           break;
#else /* not emacs19 */
       case at_dot:
           DEBUG_PRINT1("EXECUTING at_dot.\n");
           if (PTR_CHAR_POS((unsigned char *) d) + 1 != point)
               goto fail;
           break;
#endif /* not emacs19 */

       case syntaxspec:
           DEBUG_PRINT2("EXECUTING syntaxspec %d.\n", mcnt);
           mcnt = *p++;
           goto matchsyntax;

       case wordchar:
           DEBUG_PRINT1("EXECUTING Emacs wordchar.\n");
           mcnt = (int) Sword;
         matchsyntax:
           PREFETCH();
           if (SYNTAX(*d++) != (enum syntaxcode) mcnt)
               goto fail;
           SET_REGS_MATCHED();
           break;

       case notsyntaxspec:
           DEBUG_PRINT2("EXECUTING notsyntaxspec %d.\n", mcnt);
           mcnt = *p++;
           goto matchnotsyntax;

       case notwordchar:
           DEBUG_PRINT1("EXECUTING Emacs notwordchar.\n");
           mcnt = (int) Sword;
         matchnotsyntax:
           PREFETCH();
           if (SYNTAX(*d++) == (enum syntaxcode) mcnt)
               goto fail;
           SET_REGS_MATCHED();
           break;

#else /* not emacs */
       case wordchar:
           DEBUG_PRINT1("EXECUTING non-Emacs wordchar.\n");
           PREFETCH();
           if (!WORDCHAR_P(d))
               goto fail;
           SET_REGS_MATCHED();
           d++;
           break;

       case notwordchar:
           DEBUG_PRINT1("EXECUTING non-Emacs notwordchar.\n");
           PREFETCH();
           if (WORDCHAR_P(d))
               goto fail;
           SET_REGS_MATCHED();
           d++;
           break;
#endif /* not emacs */

       default:
           abort();
       }
       continue;               /* Successfully executed one pattern command; keep going.  */


       /* We goto here if a matching operation fails. */
      fail:
       if (!FAIL_STACK_EMPTY()) {      /* A restart point is known.  Restore to that state.  */
           DEBUG_PRINT1("\nFAIL:\n");
           POP_FAILURE_POINT(d, p,
               lowest_active_reg, highest_active_reg,
               regstart, regend, reg_info);

           /* If this failure point is a dummy, try the next one.  */
           if (!p)
               goto fail;

           /* If we failed to the end of the pattern, don't examine *p.  */
           assert(p <= pend);
           if (p < pend) {
               boolean is_a_jump_n = false;

               /* If failed to a backwards jump that's part of a repetition
                * loop, need to pop this failure point and use the next one.  */
               switch ((re_opcode_t) * p) {
               case jump_n:
                   is_a_jump_n = true;
               case maybe_pop_jump:
               case pop_failure_jump:
               case jump:
                   p1 = p + 1;
                   EXTRACT_NUMBER_AND_INCR(mcnt, p1);
                   p1 += mcnt;

                   if ((is_a_jump_n && (re_opcode_t) * p1 == succeed_n)
                       || (!is_a_jump_n
                           && (re_opcode_t) * p1 == on_failure_jump))
                       goto fail;
                   break;
               default:
                   /* do nothing */ ;
               }
           }
           if (d >= string1 && d <= end1)
               dend = end_match_1;
       } else
           break;              /* Matching at this starting point really fails.  */
    }                          /* for (;;) */

    if (best_regs_set)
       goto restore_best_regs;

    FREE_VARIABLES();

    return -1;                 /* Failure to match.  */
}                              /* re_match_2 */

/* Subroutine definitions for re_match_2.  */


/* We are passed P pointing to a register number after a start_memory.
 *
 * Return true if the pattern up to the corresponding stop_memory can
 * match the empty string, and false otherwise.
 *
 * If we find the matching stop_memory, sets P to point to one past its number.
 * Otherwise, sets P to an undefined byte less than or equal to END.
 *
 * We don't handle duplicates properly (yet).  */

static boolean
group_match_null_string_p(unsigned char **p, unsigned char *end, register_info_type *reg_info)
{
    int mcnt;
    /* Point to after the args to the start_memory.  */
    unsigned char *p1 = *p + 2;

    while (p1 < end) {
       /* Skip over opcodes that can match nothing, and return true or
        * false, as appropriate, when we get to one that can't, or to the
        * matching stop_memory.  */

       switch ((re_opcode_t) * p1) {
           /* Could be either a loop or a series of alternatives.  */
       case on_failure_jump:
           p1++;
           EXTRACT_NUMBER_AND_INCR(mcnt, p1);

           /* If the next operation is not a jump backwards in the
            * pattern.  */

           if (mcnt >= 0) {
               /* Go through the on_failure_jumps of the alternatives,
                * seeing if any of the alternatives cannot match nothing.
                * The last alternative starts with only a jump,
                * whereas the rest start with on_failure_jump and end
                * with a jump, e.g., here is the pattern for `a|b|c':
                *
                * /on_failure_jump/0/6/exactn/1/a/jump_past_alt/0/6
                * /on_failure_jump/0/6/exactn/1/b/jump_past_alt/0/3
                * /exactn/1/c
                *
                * So, we have to first go through the first (n-1)
                * alternatives and then deal with the last one separately.  */


               /* Deal with the first (n-1) alternatives, which start
                * with an on_failure_jump (see above) that jumps to right
                * past a jump_past_alt.  */

               while ((re_opcode_t) p1[mcnt - 3] == jump_past_alt) {
                   /* `mcnt' holds how many bytes long the alternative
                    * is, including the ending `jump_past_alt' and
                    * its number.  */

                   if (!alt_match_null_string_p(p1, p1 + mcnt - 3,
                           reg_info))
                       return false;

                   /* Move to right after this alternative, including the
                    * jump_past_alt.  */
                   p1 += mcnt;

                   /* Break if it's the beginning of an n-th alternative
                    * that doesn't begin with an on_failure_jump.  */
                   if ((re_opcode_t) * p1 != on_failure_jump)
                       break;

                   /* Still have to check that it's not an n-th
                    * alternative that starts with an on_failure_jump.  */
                   p1++;
                   EXTRACT_NUMBER_AND_INCR(mcnt, p1);
                   if ((re_opcode_t) p1[mcnt - 3] != jump_past_alt) {
                       /* Get to the beginning of the n-th alternative.  */
                       p1 -= 3;
                       break;
                   }
               }

               /* Deal with the last alternative: go back and get number
                * of the `jump_past_alt' just before it.  `mcnt' contains
                * the length of the alternative.  */
               EXTRACT_NUMBER(mcnt, p1 - 2);

               if (!alt_match_null_string_p(p1, p1 + mcnt, reg_info))
                   return false;

               p1 += mcnt;     /* Get past the n-th alternative.  */
           }                   /* if mcnt > 0 */
           break;


       case stop_memory:
           assert(p1[1] == **p);
           *p = p1 + 2;
           return true;


       default:
           if (!common_op_match_null_string_p(&p1, end, reg_info))
               return false;
       }
    }                          /* while p1 < end */

    return false;
}                              /* group_match_null_string_p */


/* Similar to group_match_null_string_p, but doesn't deal with alternatives:
 * It expects P to be the first byte of a single alternative and END one
 * byte past the last. The alternative can contain groups.  */

static boolean
alt_match_null_string_p(unsigned char *p, unsigned char *end, register_info_type * reg_info)
{
    int mcnt;
    unsigned char *p1 = p;

    while (p1 < end) {
       /* Skip over opcodes that can match nothing, and break when we get
        * to one that can't.  */

       switch ((re_opcode_t) * p1) {
           /* It's a loop.  */
       case on_failure_jump:
           p1++;
           EXTRACT_NUMBER_AND_INCR(mcnt, p1);
           p1 += mcnt;
           break;

       default:
           if (!common_op_match_null_string_p(&p1, end, reg_info))
               return false;
       }
    }                          /* while p1 < end */

    return true;
}                              /* alt_match_null_string_p */


/* Deals with the ops common to group_match_null_string_p and
 * alt_match_null_string_p.
 *
 * Sets P to one after the op and its arguments, if any.  */

static boolean
common_op_match_null_string_p(unsigned char **p, unsigned char *end, register_info_type * reg_info)
{
    int mcnt;
    boolean ret;
    int reg_no;
    unsigned char *p1 = *p;

    switch ((re_opcode_t) * p1++) {
    case no_op:
    case begline:
    case endline:
    case begbuf:
    case endbuf:
    case wordbeg:
    case wordend:
    case wordbound:
    case notwordbound:
#ifdef emacs
    case before_dot:
    case at_dot:
    case after_dot:
#endif
       break;

    case start_memory:
       reg_no = *p1;
       assert(reg_no > 0 && reg_no <= MAX_REGNUM);
       ret = group_match_null_string_p(&p1, end, reg_info);

       /* Have to set this here in case we're checking a group which
        * contains a group and a back reference to it.  */

       if (REG_MATCH_NULL_STRING_P(reg_info[reg_no]) == MATCH_NULL_UNSET_VALUE)
           REG_MATCH_NULL_STRING_P(reg_info[reg_no]) = ret;

       if (!ret)
           return false;
       break;

       /* If this is an optimized succeed_n for zero times, make the jump.  */
    case jump:
       EXTRACT_NUMBER_AND_INCR(mcnt, p1);
       if (mcnt >= 0)
           p1 += mcnt;
       else
           return false;
       break;

    case succeed_n:
       /* Get to the number of times to succeed.  */
       p1 += 2;
       EXTRACT_NUMBER_AND_INCR(mcnt, p1);

       if (mcnt == 0) {
           p1 -= 4;
           EXTRACT_NUMBER_AND_INCR(mcnt, p1);
           p1 += mcnt;
       } else
           return false;
       break;

    case duplicate:
       if (!REG_MATCH_NULL_STRING_P(reg_info[*p1]))
           return false;
       break;

    case set_number_at:
       p1 += 4;

    default:
       /* All other opcodes mean we cannot match the empty string.  */
       return false;
    }

    *p = p1;
    return true;
}                              /* common_op_match_null_string_p */


/* Return zero if TRANSLATE[S1] and TRANSLATE[S2] are identical for LEN
 * bytes; nonzero otherwise.  */

static int
bcmp_translate(unsigned char *s1, unsigned char *s2, register int len, char *translate)
{
    register unsigned char *p1 = s1, *p2 = s2;
    while (len) {
       if (translate[*p1++] != translate[*p2++])
           return 1;
       len--;
    }
    return 0;
}

/* Entry points for GNU code.  */

/* re_compile_pattern is the GNU regular expression compiler: it
 * compiles PATTERN (of length SIZE) and puts the result in BUFP.
 * Returns 0 if the pattern was valid, otherwise an error string.
 *
 * Assumes the `allocated' (and perhaps `buffer') and `translate' fields
 * are set in BUFP on entry.
 *
 * We call regex_compile to do the actual compilation.  */

const char *
re_compile_pattern(const char *pattern, int length,struct re_pattern_buffer * bufp)
{
    reg_errcode_t ret;

    /* GNU code is written to assume at least RE_NREGS registers will be set
     * (and at least one extra will be -1).  */
    bufp->regs_allocated = REGS_UNALLOCATED;

    /* And GNU code determines whether or not to get register information
     * by passing null for the REGS argument to re_match, etc., not by
     * setting no_sub.  */
    bufp->no_sub = 0;

    /* Match anchors at newline.  */
    bufp->newline_anchor = 1;

    ret = regex_compile(pattern, length, re_syntax_options, bufp);

    return re_error_msg[(int) ret];
}

/* Entry points compatible with 4.2 BSD regex library.  We don't define
 * them if this is an Emacs or POSIX compilation.  */

#if !defined (emacs) && !defined (_POSIX_SOURCE)

/* BSD has one and only one pattern buffer.  */
static struct re_pattern_buffer re_comp_buf;

char *
re_comp(const char *s)
{
    reg_errcode_t ret;

    if (!s) {
       if (!re_comp_buf.buffer)
           return "No previous regular expression";
       return 0;
    }
    if (!re_comp_buf.buffer) {
       re_comp_buf.buffer = (unsigned char *) malloc(200);
       if (re_comp_buf.buffer == NULL)
           return "Memory exhausted";
       re_comp_buf.allocated = 200;

       re_comp_buf.fastmap = (char *) malloc(1 << BYTEWIDTH);
       if (re_comp_buf.fastmap == NULL)
           return "Memory exhausted";
    }
    /* Since `re_exec' always passes NULL for the `regs' argument, we
     * don't need to initialize the pattern buffer fields which affect it.  */

    /* Match anchors at newlines.  */
    re_comp_buf.newline_anchor = 1;

    ret = regex_compile(s, strlen(s), re_syntax_options, &re_comp_buf);

    /* Yes, we're discarding `const' here.  */
    return (char *) re_error_msg[(int) ret];
}


int
re_exec(const char *s)
{
    const int len = strlen(s);
    return
       0 <= re_search(&re_comp_buf, s, len, 0, len, (struct re_registers *) 0);
}

#endif /* not emacs and not _POSIX_SOURCE */

/* POSIX.2 functions.  Don't define these for Emacs.  */

#ifndef emacs

/* regcomp takes a regular expression as a string and compiles it.
 *
 * PREG is a regex_t *.  We do not expect any fields to be initialized,
 * since POSIX says we shouldn't.  Thus, we set
 *
 * `buffer' to the compiled pattern;
 * `used' to the length of the compiled pattern;
 * `syntax' to RE_SYNTAX_POSIX_EXTENDED if the
 * REG_EXTENDED bit in CFLAGS is set; otherwise, to
 * RE_SYNTAX_POSIX_BASIC;
 * `newline_anchor' to REG_NEWLINE being set in CFLAGS;
 * `fastmap' and `fastmap_accurate' to zero;
 * `re_nsub' to the number of subexpressions in PATTERN.
 *
 * PATTERN is the address of the pattern string.
 *
 * CFLAGS is a series of bits which affect compilation.
 *
 * If REG_EXTENDED is set, we use POSIX extended syntax; otherwise, we
 * use POSIX basic syntax.
 *
 * If REG_NEWLINE is set, then . and [^...] don't match newline.
 * Also, regexec will try a match beginning after every newline.
 *
 * If REG_ICASE is set, then we considers upper- and lowercase
 * versions of letters to be equivalent when matching.
 *
 * If REG_NOSUB is set, then when PREG is passed to regexec, that
 * routine will report only success or failure, and nothing about the
 * registers.
 *
 * It returns 0 if it succeeds, nonzero if it doesn't.  (See regex.h for
 * the return codes and their meanings.)  */

int
regcomp(regex_t *preg, const char *pattern, int cflags)
{
    reg_errcode_t ret;
    unsigned syntax
    = (cflags & REG_EXTENDED) ?
    RE_SYNTAX_POSIX_EXTENDED : RE_SYNTAX_POSIX_BASIC;

    /* regex_compile will allocate the space for the compiled pattern.  */
    preg->buffer = 0;
    preg->allocated = 0;

    /* Don't bother to use a fastmap when searching.  This simplifies the
     * REG_NEWLINE case: if we used a fastmap, we'd have to put all the
     * characters after newlines into the fastmap.  This way, we just try
     * every character.  */
    preg->fastmap = 0;

    if (cflags & REG_ICASE) {
       unsigned i;

       preg->translate = (char *) malloc(CHAR_SET_SIZE);
       if (preg->translate == NULL)
           return (int) REG_ESPACE;

       /* Map uppercase characters to corresponding lowercase ones.  */
       for (i = 0; i < CHAR_SET_SIZE; i++)
           preg->translate[i] = ISUPPER(i) ? tolower(i) : i;
    } else
       preg->translate = NULL;

    /* If REG_NEWLINE is set, newlines are treated differently.  */
    if (cflags & REG_NEWLINE) {        /* REG_NEWLINE implies neither . nor [^...] match newline.  */
       syntax &= ~RE_DOT_NEWLINE;
       syntax |= RE_HAT_LISTS_NOT_NEWLINE;
       /* It also changes the matching behavior.  */
       preg->newline_anchor = 1;
    } else
       preg->newline_anchor = 0;

    preg->no_sub = !!(cflags & REG_NOSUB);

    /* POSIX says a null character in the pattern terminates it, so we
     * can use strlen here in compiling the pattern.  */
    ret = regex_compile(pattern, strlen(pattern), syntax, preg);

    /* POSIX doesn't distinguish between an unmatched open-group and an
     * unmatched close-group: both are REG_EPAREN.  */
    if (ret == REG_ERPAREN)
       ret = REG_EPAREN;

    return (int) ret;
}


/* regexec searches for a given pattern, specified by PREG, in the
 * string STRING.
 *
 * If NMATCH is zero or REG_NOSUB was set in the cflags argument to
 * `regcomp', we ignore PMATCH.  Otherwise, we assume PMATCH has at
 * least NMATCH elements, and we set them to the offsets of the
 * corresponding matched substrings.
 *
 * EFLAGS specifies `execution flags' which affect matching: if
 * REG_NOTBOL is set, then ^ does not match at the beginning of the
 * string; if REG_NOTEOL is set, then $ does not match at the end.
 *
 * We return 0 if we find a match and REG_NOMATCH if not.  */

int
regexec(const regex_t *preg,const char * string,size_t  nmatch, regmatch_t pmatch[], int eflags)
{
    int ret;
    struct re_registers regs;
    regex_t private_preg;
    int len = strlen(string);
    boolean want_reg_info = !preg->no_sub && nmatch > 0;

    private_preg = *preg;

    private_preg.not_bol = !!(eflags & REG_NOTBOL);
    private_preg.not_eol = !!(eflags & REG_NOTEOL);

    /* The user has told us exactly how many registers to return
     * information about, via `nmatch'.  We have to pass that on to the
     * matching routines.  */
    private_preg.regs_allocated = REGS_FIXED;

    if (want_reg_info) {
       regs.num_regs = nmatch;
       regs.start = TALLOC(nmatch, regoff_t);
       regs.end = TALLOC(nmatch, regoff_t);
       if (regs.start == NULL || regs.end == NULL)
           return (int) REG_NOMATCH;
    }
    /* Perform the searching operation.  */
    ret = re_search(&private_preg, string, len,
       /* start: */ 0, /* range: */ len,
       want_reg_info ? &regs : (struct re_registers *) 0);

    /* Copy the register information to the POSIX structure.  */
    if (want_reg_info) {
       if (ret >= 0) {
           unsigned r;

           for (r = 0; r < nmatch; r++) {
               pmatch[r].rm_so = regs.start[r];
               pmatch[r].rm_eo = regs.end[r];
           }
       }
       /* If we needed the temporary register info, free the space now.  */
       free(regs.start);
       free(regs.end);
    }
    /* We want zero return to mean success, unlike `re_search'.  */
    return ret >= 0 ? (int) REG_NOERROR : (int) REG_NOMATCH;
}


/* Returns a message corresponding to an error code, ERRCODE, returned
 * from either regcomp or regexec.   We don't use PREG here.  */

size_t
regerror(int errcode, const regex_t * preg,char * errbuf, size_t  errbuf_size)
{
    const char *msg;
    size_t msg_size;

    if (errcode < 0
       || errcode >= (sizeof(re_error_msg) / sizeof(re_error_msg[0])))
       /* Only error codes returned by the rest of the code should be passed
        * to this routine.  If we are given anything else, or if other regex
        * code generates an invalid error code, then the program has a bug.
        * Dump core so we can fix it.  */
       abort();

    msg = re_error_msg[errcode];

    /* POSIX doesn't require that we do anything in this case, but why
     * not be nice.  */
    if (!msg)
       msg = "Success";

    msg_size = strlen(msg) + 1;        /* Includes the null.  */

    if (errbuf_size != 0) {
       if (msg_size > errbuf_size) {
           strncpy(errbuf, msg, errbuf_size - 1);
           errbuf[errbuf_size - 1] = 0;
       } else
           strcpy(errbuf, msg);
    }
    return msg_size;
}


/* Free dynamically allocated space used by PREG.  */

void
regfree(regex_t * preg)
{
    if (preg->buffer != NULL)
       free(preg->buffer);
    preg->buffer = NULL;

    preg->allocated = 0;
    preg->used = 0;

    if (preg->fastmap != NULL)
       free(preg->fastmap);
    preg->fastmap = NULL;
    preg->fastmap_accurate = 0;

    if (preg->translate != NULL)
       free(preg->translate);
    preg->translate = NULL;
}

#endif /* not emacs  */

/*
 * Local variables:
 * make-backup-files: t
 * version-control: t
 * trim-versions-without-asking: nil
 * End:
 */

