kc3-lang/gnulib/lib/memmem.c

• Show log

  Commit

• Hash : c358da1e
  Author :
  Date : 2008-01-10T12:06:35
  

  Share two-way algorithm.
  
  * lib/str-two-way.h: New file, merged from...
  * lib/memmem.c: ...here...
  * lib/strstr.c: ...and here.
  * modules/memmem (Files): Use it.
  * modules/strstr (Files): Likewise.
  
  Signed-off-by: Eric Blake <ebb9@byu.net>
  

Download

• lib/memmem.c

• /* Copyright (C) 1991,92,93,94,96,97,98,2000,2004,2007,2008 Free Software
     Foundation, Inc.
     This file is part of the GNU C Library.
  
     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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  
  /* This particular implementation was written by Eric Blake, 2008.  */
  
  #ifndef _LIBC
  # include <config.h>
  #endif
  
  /* Specification of memmem.  */
  #include <string.h>
  
  #ifndef _LIBC
  # define __builtin_expect(expr, val)   (expr)
  #endif
  
  #define RETURN_TYPE void *
  #define AVAILABLE(h, h_l, j, n_l) ((j) <= (h_l) - (n_l))
  #include "str-two-way.h"
  
  /* Return the first occurrence of NEEDLE in HAYSTACK.  Return HAYSTACK
     if NEEDLE_LEN is 0, otherwise NULL if NEEDLE is not found in
     HAYSTACK.  */
  void *
  memmem (const void *haystack_start, size_t haystack_len,
  	const void *needle_start, size_t needle_len)
  {
    /* Abstract memory is considered to be an array of 'unsigned char' values,
       not an array of 'char' values.  See ISO C 99 section 6.2.6.1.  */
    const unsigned char *haystack = (const unsigned char *) haystack_start;
    const unsigned char *needle = (const unsigned char *) needle_start;
  
    if (needle_len == 0)
      /* The first occurrence of the empty string is deemed to occur at
         the beginning of the string.  */
      return (void *) haystack;
  
    /* Sanity check, otherwise the loop might search through the whole
       memory.  */
    if (__builtin_expect (haystack_len < needle_len, 0))
      return NULL;
  
    /* Use optimizations in memchr when possible, to reduce the search
       size of haystack using a linear algorithm with a smaller
       coefficient.  However, avoid memchr for long needles, since we
       can often achieve sublinear performance.  */
    if (needle_len < LONG_NEEDLE_THRESHOLD)
      {
        haystack = memchr (haystack, *needle, haystack_len);
        if (!haystack || __builtin_expect (needle_len == 1, 0))
  	return (void *) haystack;
        haystack_len -= haystack - (const unsigned char *) haystack_start;
        if (haystack_len < needle_len)
  	return NULL;
        return two_way_short_needle (haystack, haystack_len, needle, needle_len);
      }
    else
      return two_way_long_needle (haystack, haystack_len, needle, needle_len);
  }
  
  #undef LONG_NEEDLE_THRESHOLD
  

Download