regex.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

/* Extended regular expression matching and search library, version
   0.12.  (Implements POSIX draft P10003.2/D11.2, except for
   internationalization features.)

   Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998 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 02111-1307,
   USA.	 */

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

#undef	_GNU_SOURCE
#define _GNU_SOURCE

#ifdef emacs
/* Converts the pointer to the char to BEG-based offset from the start.	 */
#define PTR_TO_OFFSET(d)						\
	POS_AS_IN_BUFFER (MATCHING_IN_FIRST_STRING			\
			  ? (d) - string1 : (d) - (string2 - size1))
#define POS_AS_IN_BUFFER(p) ((p) + (NILP (re_match_object) || BUFFERP (re_match_object)))
#else
#define PTR_TO_OFFSET(d) 0
#endif

#include "config.h"

/* We need this for `regex.h', and perhaps for the Emacs include files.	 */
#include <sys/types.h>

/* This is for other GNU distributions with internationalized messages.	 */
#if HAVE_LIBINTL_H || defined (_LIBC)
# include <libintl.h>
#else
# define gettext(msgid) (msgid)
#endif

#ifndef gettext_noop
/* This define is so xgettext can find the internationalizable
   strings.  */
#define gettext_noop(String) String
#endif

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

#include "lisp.h"
#include "buffer.h"

/* Make syntax table lookup grant data in gl_state.  */
#define SYNTAX_ENTRY_VIA_PROPERTY

#include "syntax.h"
#include "charset.h"
#include "category.h"

#define malloc xmalloc
#define realloc xrealloc
#define free xfree

#else  /* not emacs */

/* If we are not linking with Emacs proper,
   we can't use the relocating allocator
   even if config.h says that we can.  */
#undef REL_ALLOC

#if defined (STDC_HEADERS) || defined (_LIBC)
#include <stdlib.h>
#else
char *malloc ();
char *realloc ();
#endif

/* When used in Emacs's lib-src, we need to get bzero and bcopy somehow.
   If nothing else has been done, use the method below.	 */
#ifdef INHIBIT_STRING_HEADER
#if !(defined (HAVE_BZERO) && defined (HAVE_BCOPY))
#if !defined (bzero) && !defined (bcopy)
#undef INHIBIT_STRING_HEADER
#endif
#endif
#endif

/* This is the normal way of making sure we have a bcopy and a bzero.
   This is used in most programs--a few other programs avoid this
   by defining INHIBIT_STRING_HEADER.  */
#ifndef INHIBIT_STRING_HEADER
#if defined (HAVE_STRING_H) || defined (STDC_HEADERS) || defined (_LIBC)
#include <string.h>
#ifndef bcmp
#define bcmp(s1, s2, n)	memcmp ((s1), (s2), (n))
#endif
#ifndef bcopy
#define bcopy(s, d, n)	memcpy ((d), (s), (n))
#endif
#ifndef bzero
#define bzero(s, n)	memset ((s), 0, (n))
#endif
#else
#include <strings.h>
#endif
#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 SWITCH_ENUM_BUG
#define SWITCH_ENUM_CAST(x) ((int)(x))
#else
#define SWITCH_ENUM_CAST(x) (x)
#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 ()
{
   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;

   re_syntax_table['_'] = Sword;

   done = 1;
}

#endif /* not SYNTAX_TABLE */

#define SYNTAX(c) re_syntax_table[c]

/* Dummy macros for non-Emacs environments.  */
#define BASE_LEADING_CODE_P(c) (0)
#define WORD_BOUNDARY_P(c1, c2) (0)
#define CHAR_HEAD_P(p) (1)
#define SINGLE_BYTE_CHAR_P(c) (1)
#define SAME_CHARSET_P(c1, c2) (1)
#define MULTIBYTE_FORM_LENGTH(p, s) (1)
#define STRING_CHAR(p, s) (*(p))
#define STRING_CHAR_AND_LENGTH(p, s, actual_len) ((actual_len) = 1, *(p))
#define GET_CHAR_AFTER_2(c, p, str1, end1, str2, end2) \
  (c = ((p) == (end1) ? *(str2) : *(p)))
#define GET_CHAR_BEFORE_2(c, p, str1, end1, str2, end2) \
  (c = ((p) == (str2) ? *((end1) - 1) : *((p) - 1)))
#endif /* not emacs */

/* Get the interface, including the syntax bits.  */
#include "regex.h"

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

/* Jim Meyering writes:

   "... Some ctype macros are valid only for character codes that
   isascii says are ASCII (SGI's IRIX-4.0.5 is one such system --when
   using /bin/cc or gcc but without giving an ansi option).  So, all
   ctype uses should be through macros like ISPRINT...	If
   STDC_HEADERS is defined, then autoconf has verified that the ctype
   macros don't need to be guarded with references to isascii. ...
   Defining isascii to 1 should let any compiler worth its salt
   eliminate the && through constant folding."	*/

#if defined (STDC_HEADERS) || (!defined (isascii) && !defined (HAVE_ISASCII))
#define ISASCII(c) 1
#else
#define ISASCII(c) isascii(c)
#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 (void *)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
#if __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)
#define REGEX_FREE free

#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 */
#if 0 /* It is a bad idea to declare alloca.  We always cast the result.  */
#ifndef _AIX /* Already did AIX, up at the top.	 */
char *alloca ();
#endif /* not _AIX */
#endif
#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),				\
   bcopy (source, destination, osize),					\
   destination)

/* No need to do anything to free, after alloca.  */
#define REGEX_FREE(arg) ((void)0) /* Do nothing!  But inhibit gcc warning.  */

#endif /* not REGEX_MALLOC */

/* Define how to allocate the failure stack.  */

#if defined (REL_ALLOC) && defined (REGEX_MALLOC)

#define REGEX_ALLOCATE_STACK(size)				\
  r_alloc (&failure_stack_ptr, (size))
#define REGEX_REALLOCATE_STACK(source, osize, nsize)		\
  r_re_alloc (&failure_stack_ptr, (nsize))
#define REGEX_FREE_STACK(ptr)					\
  r_alloc_free (&failure_stack_ptr)

#else /* not using relocating allocator */

#ifdef REGEX_MALLOC

#define REGEX_ALLOCATE_STACK malloc
#define REGEX_REALLOCATE_STACK(source, osize, nsize) realloc (source, nsize)
#define REGEX_FREE_STACK free

#else /* not REGEX_MALLOC */

#define REGEX_ALLOCATE_STACK alloca

#define REGEX_REALLOCATE_STACK(source, osize, nsize)			\
   REGEX_REALLOCATE (source, osize, nsize)
/* No need to explicitly free anything.	 */
#define REGEX_FREE_STACK(arg)

#endif /* not REGEX_MALLOC */
#endif /* not using relocating allocator */


/* 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 RETALLOC_IF(addr, n, t) \
  if (addr) RETALLOC((addr), (n), t); else (addr) = TALLOC ((n), 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))

#undef MAX
#undef MIN
#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

static int re_match_2_internal ();

/* 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.  */

typedef enum
{
  no_op = 0,

  /* Succeed right away--no more backtracking.	*/
  succeed,

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

	/* 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.  */