regex.c

早期freebsd实现

/* Extended regular expression matching and search library.
   Copyright (C) 1985, 1989 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 of the License, 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., 675 Mass Ave, Cambridge, MA 02139, USA.  */

/* To test, compile with -Dtest.
 This Dtestable feature turns this into a self-contained program
 which reads a pattern, describes how it compiles,
 then reads a string and searches for it.  */

#ifdef emacs

/* The `emacs' switch turns on certain special matching commands
 that make sense only in emacs. */

#include "config.h"
#include "lisp.h"
#include "buffer.h"
#include "syntax.h"

#else  /* not emacs */

#define bcopy(s,d,n)	memcpy((d),(s),(n))
#define bcmp(s1,s2,n)	memcmp((s1),(s2),(n))
#define bzero(s,n)	memset((s),0,(n))

/* Make alloca work the best possible way.  */
#ifdef __GNUC__
#define alloca __builtin_alloca
#else
#ifdef sparc
#include <alloca.h>
#endif
#endif

/*
 * Define the syntax stuff, so we can do the \<...\> things.
 */

#ifndef Sword /* must be non-zero in some of the tests below... */
#define Sword 1
#endif

#define SYNTAX(c) re_syntax_table[c]

#ifdef SYNTAX_TABLE

char *re_syntax_table;

#else

static char re_syntax_table[256];

static void
init_syntax_once ()
{
   register int c;
   static int done = 0;

   if (done)
     return;

   bzero (re_syntax_table, 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;

   done = 1;
}

#endif /* SYNTAX_TABLE */
#endif /* not emacs */

#include "regex.h"

/* Number of failure points to allocate space for initially,
 when matching.  If this number is exceeded, more space is allocated,
 so it is not a hard limit.  */

#ifndef NFAILURES
#define NFAILURES 80
#endif /* NFAILURES */

/* width of a byte in bits */

#define BYTEWIDTH 8

#ifndef SIGN_EXTEND_CHAR
#define SIGN_EXTEND_CHAR(x) (x)
#endif

static int obscure_syntax = 0;

/* Specify the precise syntax of regexp for compilation.
   This provides for compatibility for various utilities
   which historically have different, incompatible syntaxes.

   The argument SYNTAX is a bit-mask containing the two bits
   RE_NO_BK_PARENS and RE_NO_BK_VBAR.  */

int
re_set_syntax (syntax)
     int syntax;
{
  int ret;

  ret = obscure_syntax;
  obscure_syntax = syntax;
  return ret;
}

/* re_compile_pattern takes a regular-expression string
   and converts it into a buffer full of byte commands for matching.

  PATTERN   is the address of the pattern string
  SIZE      is the length of it.
  BUFP	    is a  struct re_pattern_buffer *  which points to the info
	    on where to store the byte commands.
	    This structure contains a  char *  which points to the
	    actual space, which should have been obtained with malloc.
	    re_compile_pattern may use  realloc  to grow the buffer space.

  The number of bytes of commands can be found out by looking in
  the  struct re_pattern_buffer  that bufp pointed to,
  after re_compile_pattern returns.
*/

#define PATPUSH(ch) (*b++ = (char) (ch))

#define PATFETCH(c) \
 {if (p == pend) goto end_of_pattern; \
  c = * (unsigned char *) p++; \
  if (translate) c = translate[c]; }

#define PATFETCH_RAW(c) \
 {if (p == pend) goto end_of_pattern; \
  c = * (unsigned char *) p++; }

#define PATUNFETCH p--

#define EXTEND_BUFFER \
  { char *old_buffer = bufp->buffer; \
    if (bufp->allocated == (1<<16)) goto too_big; \
    bufp->allocated *= 2; \
    if (bufp->allocated > (1<<16)) bufp->allocated = (1<<16); \
    if (!(bufp->buffer = (char *) realloc (bufp->buffer, bufp->allocated))) \
      goto memory_exhausted; \
    c = bufp->buffer - old_buffer; \
    b += c; \
    if (fixup_jump) \
      fixup_jump += c; \
    if (laststart) \
      laststart += c; \
    begalt += c; \
    if (pending_exact) \
      pending_exact += c; \
  }

static void store_jump (), insert_jump ();

char *
re_compile_pattern (pattern, size, bufp)
     char *pattern;
     int size;
     struct re_pattern_buffer *bufp;
{
  register char *b = bufp->buffer;
  register char *p = pattern;
  char *pend = pattern + size;
  register unsigned c, c1;
  char *p1;
  unsigned char *translate = (unsigned char *) bufp->translate;

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

  /* 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. */

  char *fixup_jump = 0;

  /* address of start of the most recently finished expression.
    This tells postfix * where to find the start of its operand. */

  char *laststart = 0;

  /* In processing a repeat, 1 means zero matches is allowed */

  char zero_times_ok;

  /* In processing a repeat, 1 means many matches is allowed */

  char many_times_ok;

  /* address of beginning of regexp, or inside of last \( */

  char *begalt = b;

  /* Stack of information saved by \( and restored by \).
     Four stack elements are pushed by each \(:
       First, the value of b.
       Second, the value of fixup_jump.
       Third, the value of regnum.
       Fourth, the value of begalt.  */

  int stackb[40];
  int *stackp = stackb;
  int *stacke = stackb + 40;
  int *stackt;

  /* Counts \('s as they are encountered.  Remembered for the matching \),
     where it becomes the "register number" to put in the stop_memory command */

  int regnum = 1;

  bufp->fastmap_accurate = 0;

#ifndef emacs
#ifndef SYNTAX_TABLE
  /*
   * Initialize the syntax table.
   */
   init_syntax_once();
#endif
#endif

  if (bufp->allocated == 0)
    {
      bufp->allocated = 28;
      if (bufp->buffer)
	/* EXTEND_BUFFER loses when bufp->allocated is 0 */
	bufp->buffer = (char *) realloc (bufp->buffer, 28);
      else
	/* Caller did not allocate a buffer.  Do it for him */
	bufp->buffer = (char *) malloc (28);
      if (!bufp->buffer) goto memory_exhausted;
      begalt = b = bufp->buffer;
    }

  while (p != pend)
    {
      if (b - bufp->buffer > bufp->allocated - 10)
	/* Note that EXTEND_BUFFER clobbers c */
	EXTEND_BUFFER;

      PATFETCH (c);

      switch (c)
	{
	case '$':
	  if (obscure_syntax & RE_TIGHT_VBAR)
	    {
	      if (! (obscure_syntax & RE_CONTEXT_INDEP_OPS) && p != pend)
		goto normal_char;
	      /* Make operand of last vbar end before this `$'.  */
	      if (fixup_jump)
		store_jump (fixup_jump, jump, b);
	      fixup_jump = 0;
	      PATPUSH (endline);
	      break;
	    }

	  /* $ means succeed if at end of line, but only in special contexts.
	    If randomly in the middle of a pattern, it is a normal character. */
	  if (p == pend || *p == '\n'
	      || (obscure_syntax & RE_CONTEXT_INDEP_OPS)
	      || (obscure_syntax & RE_NO_BK_PARENS
		  ? *p == ')'
		  : *p == '\\' && p[1] == ')')
	      || (obscure_syntax & RE_NO_BK_VBAR
		  ? *p == '|'
		  : *p == '\\' && p[1] == '|'))
	    {
	      PATPUSH (endline);
	      break;
	    }
	  goto normal_char;

	case '^':
	  /* ^ means succeed if at beg of line, but only if no preceding pattern. */

	  if (laststart && p[-2] != '\n'
	      && ! (obscure_syntax & RE_CONTEXT_INDEP_OPS))
	    goto normal_char;
	  if (obscure_syntax & RE_TIGHT_VBAR)
	    {
	      if (p != pattern + 1
		  && ! (obscure_syntax & RE_CONTEXT_INDEP_OPS))
		goto normal_char;
	      PATPUSH (begline);
	      begalt = b;
	    }
	  else
	    PATPUSH (begline);
	  break;

	case '+':
	case '?':
	  if (obscure_syntax & RE_BK_PLUS_QM)
	    goto normal_char;
	handle_plus:
	case '*':
	  /* If there is no previous pattern, char not special. */
	  if (!laststart && ! (obscure_syntax & RE_CONTEXT_INDEP_OPS))
	    goto normal_char;
	  /* If there is a sequence of repetition chars,
	     collapse it down to equivalent to just one.  */
	  zero_times_ok = 0;
	  many_times_ok = 0;
	  while (1)
	    {
	      zero_times_ok |= c != '+';
	      many_times_ok |= c != '?';
	      if (p == pend)
		break;
	      PATFETCH (c);
	      if (c == '*')
		;
	      else if (!(obscure_syntax & RE_BK_PLUS_QM)
		       && (c == '+' || c == '?'))
		;
	      else if ((obscure_syntax & RE_BK_PLUS_QM)
		       && c == '\\')
		{
		  int c1;
		  PATFETCH (c1);
		  if (!(c1 == '+' || c1 == '?'))
		    {
		      PATUNFETCH;
		      PATUNFETCH;
		      break;
		    }
		  c = c1;
		}
	      else
		{
		  PATUNFETCH;
		  break;
		}
	    }

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

	  /* Now we know whether 0 matches is allowed,
	     and whether 2 or more matches is allowed.  */
	  if (many_times_ok)
	    {
	      /* If more than one repetition is allowed,
		 put in a backward jump at the end.  */
	      store_jump (b, maybe_finalize_jump, laststart - 3);
	      b += 3;
	    }
	  insert_jump (on_failure_jump, laststart, b + 3, b);
	  pending_exact = 0;
	  b += 3;
	  if (!zero_times_ok)
	    {
	      /* At least one repetition required: insert before the loop
		 a skip over the initial on-failure-jump instruction */
	      insert_jump (dummy_failure_jump, laststart, laststart + 6, b);
	      b += 3;
	    }
	  break;

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

	case '[':
	  while (b - bufp->buffer
		 > bufp->allocated - 3 - (1 << BYTEWIDTH) / BYTEWIDTH)
	    /* Note that EXTEND_BUFFER clobbers c */
	    EXTEND_BUFFER;

	  laststart = b;
	  if (*p == '^')
	    PATPUSH (charset_not), p++;
	  else
	    PATPUSH (charset);
	  p1 = p;

	  PATPUSH ((1 << BYTEWIDTH) / BYTEWIDTH);
	  /* Clear the whole map */
	  bzero (b, (1 << BYTEWIDTH) / BYTEWIDTH);
	  /* Read in characters and ranges, setting map bits */
	  while (1)
	    {
	      PATFETCH (c);
	      if (c == ']' && p != p1 + 1) break;
	      if (*p == '-' && p[1] != ']')
		{
		  PATFETCH (c1);
		  PATFETCH (c1);
		  while (c <= c1)
		    b[c / BYTEWIDTH] |= 1 << (c % BYTEWIDTH), c++;
		}
	      else
		{
		  b[c / BYTEWIDTH] |= 1 << (c % BYTEWIDTH);
		}
	    }
	  /* Discard any bitmap bytes that are all 0 at the end of the map.
	     Decrement the map-length byte too. */
	  while ((int) b[-1] > 0 && b[b[-1] - 1] == 0)
	    b[-1]--;
	  b += b[-1];
	  break;

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

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

	case '\n':
	  if (! (obscure_syntax & RE_NEWLINE_OR))
	    goto normal_char;
	  else
	    goto handle_bar;

	case '|':
	  if (! (obscure_syntax & RE_NO_BK_VBAR))
	    goto normal_char;
	  else
	    goto handle_bar;

        case '\\':
	  if (p == pend) goto invalid_pattern;
	  PATFETCH_RAW (c);
	  switch (c)
	    {
	    case '(':
	      if (obscure_syntax & RE_NO_BK_PARENS)
		goto normal_backsl;
	    handle_open:
	      if (stackp == stacke) goto nesting_too_deep;
	      if (regnum < RE_NREGS)
	        {
		  PATPUSH (start_memory);
		  PATPUSH (regnum);
	        }
	      *stackp++ = b - bufp->buffer;
	      *stackp++ = fixup_jump ? fixup_jump - bufp->buffer + 1 : 0;
	      *stackp++ = regnum++;
	      *stackp++ = begalt - bufp->buffer;
	      fixup_jump = 0;
	      laststart = 0;
	      begalt = b;
	      break;

	    case ')':
	      if (obscure_syntax & RE_NO_BK_PARENS)
		goto normal_backsl;
	    handle_close:
	      if (stackp == stackb) goto unmatched_close;
	      begalt = *--stackp + bufp->buffer;
	      if (fixup_jump)
		store_jump (fixup_jump, jump, b);
	      if (stackp[-1] < RE_NREGS)
		{
		  PATPUSH (stop_memory);
		  PATPUSH (stackp[-1]);
		}
	      stackp -= 2;
	      fixup_jump = 0;
	      if (*stackp)
		fixup_jump = *stackp + bufp->buffer - 1;
	      laststart = *--stackp + bufp->buffer;
	      break;

	    case '|':
	      if (obscure_syntax & RE_NO_BK_VBAR)
		goto normal_backsl;
	    handle_bar:
	      insert_jump (on_failure_jump, begalt, b + 6, b);
	      pending_exact = 0;
	      b += 3;
	      if (fixup_jump)
		store_jump (fixup_jump, jump, b);
	      fixup_jump = b;
	      b += 3;
	      laststart = 0;
	      begalt = b;
	      break;

#ifdef emacs
	    case '=':
	      PATPUSH (at_dot);
	      break;

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

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

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

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

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

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

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

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

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

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

	    case '1':
	    case '2':
	    case '3':
	    case '4':
	    case '5':