search.c 91.2 KB
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/* String search routines for GNU Emacs.
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   Copyright (C) 1985, 1986, 1987, 1993, 1994, 1997, 1998, 1999, 2002, 2003,
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                 2004, 2005, 2006 Free Software Foundation, Inc.
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This file is part of GNU Emacs.

GNU Emacs is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.

GNU Emacs 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 GNU Emacs; see the file COPYING.  If not, write to
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the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301, USA.  */
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#include <config.h>
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#include "lisp.h"
#include "syntax.h"
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#include "category.h"
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#include "buffer.h"
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#include "charset.h"
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#include "region-cache.h"
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#include "commands.h"
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#include "blockinput.h"
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#include "intervals.h"
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#include <sys/types.h>
#include "regex.h"

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#define REGEXP_CACHE_SIZE 20
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/* If the regexp is non-nil, then the buffer contains the compiled form
   of that regexp, suitable for searching.  */
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struct regexp_cache
{
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  struct regexp_cache *next;
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  Lisp_Object regexp, whitespace_regexp;
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  /* Syntax table for which the regexp applies.  We need this because
     of character classes.  */
  Lisp_Object syntax_table;
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  struct re_pattern_buffer buf;
  char fastmap[0400];
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  /* Nonzero means regexp was compiled to do full POSIX backtracking.  */
  char posix;
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};
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/* The instances of that struct.  */
struct regexp_cache searchbufs[REGEXP_CACHE_SIZE];
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/* The head of the linked list; points to the most recently used buffer.  */
struct regexp_cache *searchbuf_head;
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/* Every call to re_match, etc., must pass &search_regs as the regs
   argument unless you can show it is unnecessary (i.e., if re_match
   is certainly going to be called again before region-around-match
   can be called).

   Since the registers are now dynamically allocated, we need to make
   sure not to refer to the Nth register before checking that it has
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   been allocated by checking search_regs.num_regs.

   The regex code keeps track of whether it has allocated the search
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   buffer using bits in the re_pattern_buffer.  This means that whenever
   you compile a new pattern, it completely forgets whether it has
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   allocated any registers, and will allocate new registers the next
   time you call a searching or matching function.  Therefore, we need
   to call re_set_registers after compiling a new pattern or after
   setting the match registers, so that the regex functions will be
   able to free or re-allocate it properly.  */
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static struct re_registers search_regs;

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/* The buffer in which the last search was performed, or
   Qt if the last search was done in a string;
   Qnil if no searching has been done yet.  */
static Lisp_Object last_thing_searched;
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/* error condition signaled when regexp compile_pattern fails */
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Lisp_Object Qinvalid_regexp;

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/* Error condition used for failing searches */
Lisp_Object Qsearch_failed;

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Lisp_Object Vsearch_spaces_regexp;
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static void set_search_regs ();
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static void save_search_regs ();
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static int simple_search ();
static int boyer_moore ();
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static int search_buffer ();
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static void matcher_overflow () NO_RETURN;
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static void
matcher_overflow ()
{
  error ("Stack overflow in regexp matcher");
}

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/* Compile a regexp and signal a Lisp error if anything goes wrong.
   PATTERN is the pattern to compile.
   CP is the place to put the result.
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   TRANSLATE is a translation table for ignoring case, or nil for none.
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   REGP is the structure that says where to store the "register"
   values that will result from matching this pattern.
   If it is 0, we should compile the pattern not to record any
   subexpression bounds.
   POSIX is nonzero if we want full backtracking (POSIX style)
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   for this pattern.  0 means backtrack only enough to get a valid match.
   MULTIBYTE is nonzero if we want to handle multibyte characters in
   PATTERN.  0 means all multibyte characters are recognized just as
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   sequences of binary data.

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   The behavior also depends on Vsearch_spaces_regexp.  */
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static void
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compile_pattern_1 (cp, pattern, translate, regp, posix, multibyte)
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     struct regexp_cache *cp;
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     Lisp_Object pattern;
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     Lisp_Object translate;
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     struct re_registers *regp;
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     int posix;
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     int multibyte;
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{
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  unsigned char *raw_pattern;
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  int raw_pattern_size;
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  char *val;
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  reg_syntax_t old;
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  /* MULTIBYTE says whether the text to be searched is multibyte.
     We must convert PATTERN to match that, or we will not really
     find things right.  */

  if (multibyte == STRING_MULTIBYTE (pattern))
    {
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      raw_pattern = (unsigned char *) SDATA (pattern);
      raw_pattern_size = SBYTES (pattern);
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    }
  else if (multibyte)
    {
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      raw_pattern_size = count_size_as_multibyte (SDATA (pattern),
						  SCHARS (pattern));
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      raw_pattern = (unsigned char *) alloca (raw_pattern_size + 1);
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      copy_text (SDATA (pattern), raw_pattern,
		 SCHARS (pattern), 0, 1);
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    }
  else
    {
      /* Converting multibyte to single-byte.

	 ??? Perhaps this conversion should be done in a special way
	 by subtracting nonascii-insert-offset from each non-ASCII char,
	 so that only the multibyte chars which really correspond to
	 the chosen single-byte character set can possibly match.  */
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      raw_pattern_size = SCHARS (pattern);
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      raw_pattern = (unsigned char *) alloca (raw_pattern_size + 1);
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      copy_text (SDATA (pattern), raw_pattern,
		 SBYTES (pattern), 1, 0);
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    }

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  cp->regexp = Qnil;
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  cp->buf.translate = (! NILP (translate) ? translate : make_number (0));
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  cp->posix = posix;
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  cp->buf.multibyte = multibyte;
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  cp->whitespace_regexp = Vsearch_spaces_regexp;
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  cp->syntax_table = current_buffer->syntax_table;
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  /* Doing BLOCK_INPUT here has the effect that
     the debugger won't run if an error occurs.
     Why is BLOCK_INPUT needed here?  */
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  BLOCK_INPUT;
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  old = re_set_syntax (RE_SYNTAX_EMACS
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		       | (posix ? 0 : RE_NO_POSIX_BACKTRACKING));
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  re_set_whitespace_regexp (NILP (Vsearch_spaces_regexp) ? NULL
			    : SDATA (Vsearch_spaces_regexp));
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  val = (char *) re_compile_pattern ((char *)raw_pattern,
				     raw_pattern_size, &cp->buf);
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  re_set_whitespace_regexp (NULL);

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  re_set_syntax (old);
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  UNBLOCK_INPUT;
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  if (val)
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    xsignal1 (Qinvalid_regexp, build_string (val));
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  cp->regexp = Fcopy_sequence (pattern);
}

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/* Shrink each compiled regexp buffer in the cache
   to the size actually used right now.
   This is called from garbage collection.  */

void
shrink_regexp_cache ()
{
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  struct regexp_cache *cp;
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  for (cp = searchbuf_head; cp != 0; cp = cp->next)
    {
      cp->buf.allocated = cp->buf.used;
      cp->buf.buffer
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	= (unsigned char *) xrealloc (cp->buf.buffer, cp->buf.used);
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    }
}

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/* Clear the regexp cache.
   There is no danger of memory leak here because re_compile_pattern
   automagically manages the memory in each re_pattern_buffer struct,
   based on its `allocated' and `buffer' values.  */
void
clear_regexp_cache ()
{
  int i;

  for (i = 0; i < REGEXP_CACHE_SIZE; ++i)
    searchbufs[i].regexp = Qnil;
}

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/* Compile a regexp if necessary, but first check to see if there's one in
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   the cache.
   PATTERN is the pattern to compile.
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   TRANSLATE is a translation table for ignoring case, or nil for none.
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   REGP is the structure that says where to store the "register"
   values that will result from matching this pattern.
   If it is 0, we should compile the pattern not to record any
   subexpression bounds.
   POSIX is nonzero if we want full backtracking (POSIX style)
   for this pattern.  0 means backtrack only enough to get a valid match.  */
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struct re_pattern_buffer *
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compile_pattern (pattern, regp, translate, posix, multibyte)
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     Lisp_Object pattern;
     struct re_registers *regp;
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     Lisp_Object translate;
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     int posix, multibyte;
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{
  struct regexp_cache *cp, **cpp;

  for (cpp = &searchbuf_head; ; cpp = &cp->next)
    {
      cp = *cpp;
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      /* Entries are initialized to nil, and may be set to nil by
	 compile_pattern_1 if the pattern isn't valid.  Don't apply
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	 string accessors in those cases.  However, compile_pattern_1
	 is only applied to the cache entry we pick here to reuse.  So
	 nil should never appear before a non-nil entry.  */
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      if (NILP (cp->regexp))
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	goto compile_it;
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      if (SCHARS (cp->regexp) == SCHARS (pattern)
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	  && STRING_MULTIBYTE (cp->regexp) == STRING_MULTIBYTE (pattern)
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	  && !NILP (Fstring_equal (cp->regexp, pattern))
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	  && EQ (cp->buf.translate, (! NILP (translate) ? translate : make_number (0)))
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	  && cp->posix == posix
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	  && cp->buf.multibyte == multibyte
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	  /* TODO: Strictly speaking, we only need to match syntax
	     tables when a character class like [[:space:]] occurs in
	     the pattern. -- cyd*/
	  && EQ (cp->syntax_table, current_buffer->syntax_table)
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	  && !NILP (Fequal (cp->whitespace_regexp, Vsearch_spaces_regexp)))
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	break;

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      /* If we're at the end of the cache, compile into the nil cell
	 we found, or the last (least recently used) cell with a
	 string value.  */
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      if (cp->next == 0)
	{
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	compile_it:
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	  compile_pattern_1 (cp, pattern, translate, regp, posix, multibyte);
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	  break;
	}
    }

  /* When we get here, cp (aka *cpp) contains the compiled pattern,
     either because we found it in the cache or because we just compiled it.
     Move it to the front of the queue to mark it as most recently used.  */
  *cpp = cp->next;
  cp->next = searchbuf_head;
  searchbuf_head = cp;
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  /* Advise the searching functions about the space we have allocated
     for register data.  */
  if (regp)
    re_set_registers (&cp->buf, regp, regp->num_regs, regp->start, regp->end);

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  return &cp->buf;
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}


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static Lisp_Object
looking_at_1 (string, posix)
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     Lisp_Object string;
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     int posix;
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{
  Lisp_Object val;
  unsigned char *p1, *p2;
  int s1, s2;
  register int i;
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  struct re_pattern_buffer *bufp;
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  if (running_asynch_code)
    save_search_regs ();

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  /* This is so set_image_of_range_1 in regex.c can find the EQV table.  */
  XCHAR_TABLE (current_buffer->case_canon_table)->extras[2]
    = current_buffer->case_eqv_table;

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  CHECK_STRING (string);
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  bufp = compile_pattern (string, &search_regs,
			  (!NILP (current_buffer->case_fold_search)
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			   ? current_buffer->case_canon_table : Qnil),
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			  posix,
			  !NILP (current_buffer->enable_multibyte_characters));
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  immediate_quit = 1;
  QUIT;			/* Do a pending quit right away, to avoid paradoxical behavior */

  /* Get pointers and sizes of the two strings
     that make up the visible portion of the buffer. */

  p1 = BEGV_ADDR;
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  s1 = GPT_BYTE - BEGV_BYTE;
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  p2 = GAP_END_ADDR;
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  s2 = ZV_BYTE - GPT_BYTE;
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  if (s1 < 0)
    {
      p2 = p1;
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      s2 = ZV_BYTE - BEGV_BYTE;
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      s1 = 0;
    }
  if (s2 < 0)
    {
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      s1 = ZV_BYTE - BEGV_BYTE;
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      s2 = 0;
    }
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  re_match_object = Qnil;
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  i = re_match_2 (bufp, (char *) p1, s1, (char *) p2, s2,
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		  PT_BYTE - BEGV_BYTE, &search_regs,
		  ZV_BYTE - BEGV_BYTE);
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  immediate_quit = 0;
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  if (i == -2)
    matcher_overflow ();

  val = (0 <= i ? Qt : Qnil);
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  if (i >= 0)
    for (i = 0; i < search_regs.num_regs; i++)
      if (search_regs.start[i] >= 0)
	{
	  search_regs.start[i]
	    = BYTE_TO_CHAR (search_regs.start[i] + BEGV_BYTE);
	  search_regs.end[i]
	    = BYTE_TO_CHAR (search_regs.end[i] + BEGV_BYTE);
	}
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  XSETBUFFER (last_thing_searched, current_buffer);
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  return val;
}

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DEFUN ("looking-at", Flooking_at, Slooking_at, 1, 1, 0,
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       doc: /* Return t if text after point matches regular expression REGEXP.
This function modifies the match data that `match-beginning',
`match-end' and `match-data' access; save and restore the match
data if you want to preserve them.  */)
     (regexp)
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     Lisp_Object regexp;
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{
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  return looking_at_1 (regexp, 0);
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}

DEFUN ("posix-looking-at", Fposix_looking_at, Sposix_looking_at, 1, 1, 0,
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       doc: /* Return t if text after point matches regular expression REGEXP.
Find the longest match, in accord with Posix regular expression rules.
This function modifies the match data that `match-beginning',
`match-end' and `match-data' access; save and restore the match
data if you want to preserve them.  */)
     (regexp)
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     Lisp_Object regexp;
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{
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  return looking_at_1 (regexp, 1);
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}

static Lisp_Object
string_match_1 (regexp, string, start, posix)
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     Lisp_Object regexp, string, start;
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     int posix;
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{
  int val;
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  struct re_pattern_buffer *bufp;
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  int pos, pos_byte;
  int i;
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  if (running_asynch_code)
    save_search_regs ();

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  CHECK_STRING (regexp);
  CHECK_STRING (string);
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  if (NILP (start))
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    pos = 0, pos_byte = 0;
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  else
    {
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      int len = SCHARS (string);
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      CHECK_NUMBER (start);
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      pos = XINT (start);
      if (pos < 0 && -pos <= len)
	pos = len + pos;
      else if (0 > pos || pos > len)
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	args_out_of_range (string, start);
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      pos_byte = string_char_to_byte (string, pos);
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    }

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  /* This is so set_image_of_range_1 in regex.c can find the EQV table.  */
  XCHAR_TABLE (current_buffer->case_canon_table)->extras[2]
    = current_buffer->case_eqv_table;

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  bufp = compile_pattern (regexp, &search_regs,
			  (!NILP (current_buffer->case_fold_search)
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			   ? current_buffer->case_canon_table : Qnil),
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			  posix,
			  STRING_MULTIBYTE (string));
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  immediate_quit = 1;
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  re_match_object = string;
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  val = re_search (bufp, (char *) SDATA (string),
		   SBYTES (string), pos_byte,
		   SBYTES (string) - pos_byte,
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		   &search_regs);
  immediate_quit = 0;
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  last_thing_searched = Qt;
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  if (val == -2)
    matcher_overflow ();
  if (val < 0) return Qnil;
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  for (i = 0; i < search_regs.num_regs; i++)
    if (search_regs.start[i] >= 0)
      {
	search_regs.start[i]
	  = string_byte_to_char (string, search_regs.start[i]);
	search_regs.end[i]
	  = string_byte_to_char (string, search_regs.end[i]);
      }

  return make_number (string_byte_to_char (string, val));
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}
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DEFUN ("string-match", Fstring_match, Sstring_match, 2, 3, 0,
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       doc: /* Return index of start of first match for REGEXP in STRING, or nil.
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Matching ignores case if `case-fold-search' is non-nil.
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If third arg START is non-nil, start search at that index in STRING.
For index of first char beyond the match, do (match-end 0).
`match-end' and `match-beginning' also give indices of substrings
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matched by parenthesis constructs in the pattern.

You can use the function `match-string' to extract the substrings
matched by the parenthesis constructions in REGEXP. */)
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     (regexp, string, start)
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     Lisp_Object regexp, string, start;
{
  return string_match_1 (regexp, string, start, 0);
}

DEFUN ("posix-string-match", Fposix_string_match, Sposix_string_match, 2, 3, 0,
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       doc: /* Return index of start of first match for REGEXP in STRING, or nil.
Find the longest match, in accord with Posix regular expression rules.
Case is ignored if `case-fold-search' is non-nil in the current buffer.
If third arg START is non-nil, start search at that index in STRING.
For index of first char beyond the match, do (match-end 0).
`match-end' and `match-beginning' also give indices of substrings
matched by parenthesis constructs in the pattern.  */)
     (regexp, string, start)
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     Lisp_Object regexp, string, start;
{
  return string_match_1 (regexp, string, start, 1);
}

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/* Match REGEXP against STRING, searching all of STRING,
   and return the index of the match, or negative on failure.
   This does not clobber the match data.  */

int
fast_string_match (regexp, string)
     Lisp_Object regexp, string;
{
  int val;
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  struct re_pattern_buffer *bufp;
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  bufp = compile_pattern (regexp, 0, Qnil,
			  0, STRING_MULTIBYTE (string));
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  immediate_quit = 1;
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  re_match_object = string;
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  val = re_search (bufp, (char *) SDATA (string),
		   SBYTES (string), 0,
		   SBYTES (string), 0);
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  immediate_quit = 0;
  return val;
}
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/* Match REGEXP against STRING, searching all of STRING ignoring case,
   and return the index of the match, or negative on failure.
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   This does not clobber the match data.
   We assume that STRING contains single-byte characters.  */
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extern Lisp_Object Vascii_downcase_table;

int
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fast_c_string_match_ignore_case (regexp, string)
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     Lisp_Object regexp;
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     const char *string;
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{
  int val;
  struct re_pattern_buffer *bufp;
  int len = strlen (string);

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  regexp = string_make_unibyte (regexp);
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  re_match_object = Qt;
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  bufp = compile_pattern (regexp, 0,
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			  Vascii_canon_table, 0,
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			  0);
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  immediate_quit = 1;
  val = re_search (bufp, string, len, 0, len, 0);
  immediate_quit = 0;
  return val;
}
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/* Like fast_string_match but ignore case.  */

int
fast_string_match_ignore_case (regexp, string)
     Lisp_Object regexp, string;
{
  int val;
  struct re_pattern_buffer *bufp;

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  bufp = compile_pattern (regexp, 0, Vascii_canon_table,
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			  0, STRING_MULTIBYTE (string));
  immediate_quit = 1;
  re_match_object = string;

  val = re_search (bufp, (char *) SDATA (string),
		   SBYTES (string), 0,
		   SBYTES (string), 0);
  immediate_quit = 0;
  return val;
}
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/* The newline cache: remembering which sections of text have no newlines.  */

/* If the user has requested newline caching, make sure it's on.
   Otherwise, make sure it's off.
   This is our cheezy way of associating an action with the change of
   state of a buffer-local variable.  */
static void
newline_cache_on_off (buf)
     struct buffer *buf;
{
  if (NILP (buf->cache_long_line_scans))
    {
      /* It should be off.  */
      if (buf->newline_cache)
        {
          free_region_cache (buf->newline_cache);
          buf->newline_cache = 0;
        }
    }
  else
    {
      /* It should be on.  */
      if (buf->newline_cache == 0)
        buf->newline_cache = new_region_cache ();
    }
}


/* Search for COUNT instances of the character TARGET between START and END.

   If COUNT is positive, search forwards; END must be >= START.
   If COUNT is negative, search backwards for the -COUNTth instance;
      END must be <= START.
   If COUNT is zero, do anything you please; run rogue, for all I care.

   If END is zero, use BEGV or ZV instead, as appropriate for the
   direction indicated by COUNT.
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   If we find COUNT instances, set *SHORTAGE to zero, and return the
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   position past the COUNTth match.  Note that for reverse motion
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   this is not the same as the usual convention for Emacs motion commands.
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   If we don't find COUNT instances before reaching END, set *SHORTAGE
   to the number of TARGETs left unfound, and return END.
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   If ALLOW_QUIT is non-zero, set immediate_quit.  That's good to do
   except when inside redisplay.  */

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int
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scan_buffer (target, start, end, count, shortage, allow_quit)
     register int target;
     int start, end;
     int count;
     int *shortage;
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     int allow_quit;
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{
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  struct region_cache *newline_cache;
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  int direction;
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  if (count > 0)
    {
      direction = 1;
      if (! end) end = ZV;
    }
  else
    {
      direction = -1;
      if (! end) end = BEGV;
    }
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  newline_cache_on_off (current_buffer);
  newline_cache = current_buffer->newline_cache;
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  if (shortage != 0)
    *shortage = 0;

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  immediate_quit = allow_quit;
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  if (count > 0)
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    while (start != end)
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      {
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        /* Our innermost scanning loop is very simple; it doesn't know
           about gaps, buffer ends, or the newline cache.  ceiling is
           the position of the last character before the next such
           obstacle --- the last character the dumb search loop should
           examine.  */
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	int ceiling_byte = CHAR_TO_BYTE (end) - 1;
	int start_byte = CHAR_TO_BYTE (start);
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	int tem;
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        /* If we're looking for a newline, consult the newline cache
           to see where we can avoid some scanning.  */
        if (target == '\n' && newline_cache)
          {
            int next_change;
            immediate_quit = 0;
            while (region_cache_forward
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                   (current_buffer, newline_cache, start_byte, &next_change))
              start_byte = next_change;
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            immediate_quit = allow_quit;
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            /* START should never be after END.  */
            if (start_byte > ceiling_byte)
              start_byte = ceiling_byte;
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            /* Now the text after start is an unknown region, and
               next_change is the position of the next known region. */
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            ceiling_byte = min (next_change - 1, ceiling_byte);
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          }

        /* The dumb loop can only scan text stored in contiguous
           bytes. BUFFER_CEILING_OF returns the last character
           position that is contiguous, so the ceiling is the
           position after that.  */
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	tem = BUFFER_CEILING_OF (start_byte);
	ceiling_byte = min (tem, ceiling_byte);
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        {
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          /* The termination address of the dumb loop.  */
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          register unsigned char *ceiling_addr
	    = BYTE_POS_ADDR (ceiling_byte) + 1;
          register unsigned char *cursor
	    = BYTE_POS_ADDR (start_byte);
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          unsigned char *base = cursor;

          while (cursor < ceiling_addr)
            {
              unsigned char *scan_start = cursor;

              /* The dumb loop.  */
              while (*cursor != target && ++cursor < ceiling_addr)
                ;

              /* If we're looking for newlines, cache the fact that
                 the region from start to cursor is free of them. */
              if (target == '\n' && newline_cache)
                know_region_cache (current_buffer, newline_cache,
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                                   start_byte + scan_start - base,
                                   start_byte + cursor - base);
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              /* Did we find the target character?  */
              if (cursor < ceiling_addr)
                {
                  if (--count == 0)
                    {
                      immediate_quit = 0;
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                      return BYTE_TO_CHAR (start_byte + cursor - base + 1);
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                    }
                  cursor++;
                }
            }

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          start = BYTE_TO_CHAR (start_byte + cursor - base);
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        }
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      }
  else
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    while (start > end)
      {
        /* The last character to check before the next obstacle.  */
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	int ceiling_byte = CHAR_TO_BYTE (end);
	int start_byte = CHAR_TO_BYTE (start);
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	int tem;
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        /* Consult the newline cache, if appropriate.  */
        if (target == '\n' && newline_cache)
          {
            int next_change;
            immediate_quit = 0;
            while (region_cache_backward
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                   (current_buffer, newline_cache, start_byte, &next_change))
              start_byte = next_change;
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            immediate_quit = allow_quit;
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            /* Start should never be at or before end.  */
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            if (start_byte <= ceiling_byte)
              start_byte = ceiling_byte + 1;
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            /* Now the text before start is an unknown region, and
               next_change is the position of the next known region. */
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            ceiling_byte = max (next_change, ceiling_byte);
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          }

        /* Stop scanning before the gap.  */
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	tem = BUFFER_FLOOR_OF (start_byte - 1);
	ceiling_byte = max (tem, ceiling_byte);
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        {
          /* The termination address of the dumb loop.  */
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          register unsigned char *ceiling_addr = BYTE_POS_ADDR (ceiling_byte);
          register unsigned char *cursor = BYTE_POS_ADDR (start_byte - 1);
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          unsigned char *base = cursor;

          while (cursor >= ceiling_addr)
            {
              unsigned char *scan_start = cursor;

              while (*cursor != target && --cursor >= ceiling_addr)
                ;

              /* If we're looking for newlines, cache the fact that
                 the region from after the cursor to start is free of them.  */
              if (target == '\n' && newline_cache)
                know_region_cache (current_buffer, newline_cache,
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                                   start_byte + cursor - base,
                                   start_byte + scan_start - base);
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              /* Did we find the target character?  */
              if (cursor >= ceiling_addr)
                {
                  if (++count >= 0)
                    {
                      immediate_quit = 0;
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                      return BYTE_TO_CHAR (start_byte + cursor - base);
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                    }
                  cursor--;
                }
            }

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	  start = BYTE_TO_CHAR (start_byte + cursor - base);
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        }
      }

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  immediate_quit = 0;
  if (shortage != 0)
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    *shortage = count * direction;
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  return start;
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}
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/* Search for COUNT instances of a line boundary, which means either a
   newline or (if selective display enabled) a carriage return.
   Start at START.  If COUNT is negative, search backwards.

   We report the resulting position by calling TEMP_SET_PT_BOTH.

   If we find COUNT instances. we position after (always after,
   even if scanning backwards) the COUNTth match, and return 0.

   If we don't find COUNT instances before reaching the end of the
   buffer (or the beginning, if scanning backwards), we return
   the number of line boundaries left unfound, and position at
   the limit we bumped up against.

   If ALLOW_QUIT is non-zero, set immediate_quit.  That's good to do
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   except in special cases.  */
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int
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scan_newline (start, start_byte, limit, limit_byte, count, allow_quit)
     int start, start_byte;
     int limit, limit_byte;
     register int count;
     int allow_quit;
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{
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  int direction = ((count > 0) ? 1 : -1);

  register unsigned char *cursor;
  unsigned char *base;

  register int ceiling;
  register unsigned char *ceiling_addr;

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  int old_immediate_quit = immediate_quit;

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  /* The code that follows is like scan_buffer
     but checks for either newline or carriage return.  */

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  if (allow_quit)
    immediate_quit++;
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  start_byte = CHAR_TO_BYTE (start);

  if (count > 0)
    {
      while (start_byte < limit_byte)
	{
	  ceiling =  BUFFER_CEILING_OF (start_byte);
	  ceiling = min (limit_byte - 1, ceiling);
	  ceiling_addr = BYTE_POS_ADDR (ceiling) + 1;
	  base = (cursor = BYTE_POS_ADDR (start_byte));
	  while (1)
	    {
	      while (*cursor != '\n' && ++cursor != ceiling_addr)
		;

	      if (cursor != ceiling_addr)
		{
		  if (--count == 0)
		    {
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		      immediate_quit = old_immediate_quit;
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		      start_byte = start_byte + cursor - base + 1;
		      start = BYTE_TO_CHAR (start_byte);
		      TEMP_SET_PT_BOTH (start, start_byte);
		      return 0;
		    }
		  else
		    if (++cursor == ceiling_addr)
		      break;
		}
	      else
		break;
	    }
	  start_byte += cursor - base;
	}
    }
  else
    {
      while (start_byte > limit_byte)
	{
	  ceiling = BUFFER_FLOOR_OF (start_byte - 1);
	  ceiling = max (limit_byte, ceiling);
	  ceiling_addr = BYTE_POS_ADDR (ceiling) - 1;
	  base = (cursor = BYTE_POS_ADDR (start_byte - 1) + 1);
	  while (1)
	    {
	      while (--cursor != ceiling_addr && *cursor != '\n')
		;

	      if (cursor != ceiling_addr)
		{
		  if (++count == 0)
		    {
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		      immediate_quit = old_immediate_quit;
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		      /* Return the position AFTER the match we found.  */
		      start_byte = start_byte + cursor - base + 1;
		      start = BYTE_TO_CHAR (start_byte);
		      TEMP_SET_PT_BOTH (start, start_byte);
		      return 0;
		    }
		}
	      else
		break;
	    }
	  /* Here we add 1 to compensate for the last decrement
	     of CURSOR, which took it past the valid range.  */
	  start_byte += cursor - base + 1;
	}
    }

  TEMP_SET_PT_BOTH (limit, limit_byte);
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  immediate_quit = old_immediate_quit;
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  return count * direction;
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}

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int
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find_next_newline_no_quit (from, cnt)
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     register int from, cnt;
{
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  return scan_buffer ('\n', from, 0, cnt, (int *) 0, 0);
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}

/* Like find_next_newline, but returns position before the newline,
   not after, and only search up to TO.  This isn't just
   find_next_newline (...)-1, because you might hit TO.  */
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int
find_before_next_newline (from, to, cnt)
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     int from, to, cnt;
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{
  int shortage;
  int pos = scan_buffer ('\n', from, to, cnt, &shortage, 1);

  if (shortage == 0)
    pos--;
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  return pos;
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}

/* Subroutines of Lisp buffer search functions. */

static Lisp_Object
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search_command (string, bound, noerror, count, direction, RE, posix)
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     Lisp_Object string, bound, noerror, count;
     int direction;
     int RE;
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     int posix;
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{
  register int np;
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  int lim, lim_byte;
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  int n = direction;

  if (!NILP (count))
    {
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      CHECK_NUMBER (count);
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      n *= XINT (count);
    }

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  CHECK_STRING (string);
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  if (NILP (bound))
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    {
      if (n > 0)
	lim = ZV, lim_byte = ZV_BYTE;
      else
	lim = BEGV, lim_byte = BEGV_BYTE;
    }
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  else
    {
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      CHECK_NUMBER_COERCE_MARKER (bound);
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      lim = XINT (bound);
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      if (n > 0 ? lim < PT : lim > PT)
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	error ("Invalid search bound (wrong side of point)");
      if (lim > ZV)
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	lim = ZV, lim_byte = ZV_BYTE;
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      else if (lim < BEGV)
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	lim = BEGV, lim_byte = BEGV_BYTE;
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      else
	lim_byte = CHAR_TO_BYTE (lim);
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    }

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  /* This is so set_image_of_range_1 in regex.c can find the EQV table.  */
  XCHAR_TABLE (current_buffer->case_canon_table)->extras[2]
    = current_buffer->case_eqv_table;

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  np = search_buffer (string, PT, PT_BYTE, lim, lim_byte, n, RE,
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		      (!NILP (current_buffer->case_fold_search)
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		       ? current_buffer->case_canon_table
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		       : Qnil),
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		      (!NILP (current_buffer->case_fold_search)
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		       ? current_buffer->case_eqv_table
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		       : Qnil),
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		      posix);
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  if (np <= 0)
    {
      if (NILP (noerror))
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	xsignal1 (Qsearch_failed, string);

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      if (!EQ (noerror, Qt))
	{
	  if (lim < BEGV || lim > ZV)
	    abort ();
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	  SET_PT_BOTH (lim, lim_byte);
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	  return Qnil;
#if 0 /* This would be clean, but maybe programs depend on
	 a value of nil here.  */
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	  np = lim;
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#endif
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	}
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      else
	return Qnil;
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    }

  if (np < BEGV || np > ZV)
    abort ();

  SET_PT (np);

  return make_number (np);
}

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/* Return 1 if REGEXP it matches just one constant string.  */

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static int
trivial_regexp_p (regexp)
     Lisp_Object regexp;
{
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  int len = SBYTES (regexp);
  unsigned char *s = SDATA (regexp);
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  while (--len >= 0)
    {
      switch (*s++)
	{
	case '.': case '*': case '+': case '?': case '[': case '^': case '$':
	  return 0;
	case '\\':
	  if (--len < 0)
	    return 0;
	  switch (*s++)
	    {
	    case '|': case '(': case ')': case '`': case '\'': case 'b':
	    case 'B': case '<': case '>': case 'w': case 'W': case 's':
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	    case 'S': case '=': case '{': case '}': case '_':
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	    case 'c': case 'C':	/* for categoryspec and notcategoryspec */
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	    case '1': case '2': case '3': case '4': case '5':
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	    case '6': case '7': case '8': case '9':
	      return 0;
	    }
	}
    }
  return 1;
}

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/* Search for the n'th occurrence of STRING in the current buffer,
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   starting at position POS and stopping at position LIM,
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   treating STRING as a literal string if RE is false or as
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   a regular expression if RE is true.

   If N is positive, searching is forward and LIM must be greater than POS.
   If N is negative, searching is backward and LIM must be less than POS.

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   Returns -x if x occurrences remain to be found (x > 0),
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   or else the position at the beginning of the Nth occurrence
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