compat/memmem.c

   1 /*      $OpenBSD: memmem.c,v 1.4 2015/08/31 02:53:57 guenther Exp $ */
   2 /*-
   3  * Copyright (c) 2005 Pascal Gloor <pascal.gloor@spale.com>
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. The name of the author may not be used to endorse or promote
  14  *    products derived from this software without specific prior written
  15  *    permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  */
  29
  30 #include <string.h>
  31
  32 #include "compat.h"
  33
  34 /*
  35  * Find the first occurrence of the byte string s in byte string l.
  36  */
  37
  38 void *
  39 memmem(const void *l, size_t l_len, const void *s, size_t s_len)
  40 {
  41         const char *cur, *last;
  42         const char *cl = l;
  43         const char *cs = s;
  44
  45         /* a zero length needle should just return the haystack */
  46         if (s_len == 0)
  47                 return (void *)cl;
  48
  49         /* "s" must be smaller or equal to "l" */
  50         if (l_len < s_len)
  51                 return NULL;
  52
  53         /* special case where s_len == 1 */
  54         if (s_len == 1)
  55                 return memchr(l, *cs, l_len);
  56
  57         /* the last position where its possible to find "s" in "l" */
  58         last = cl + l_len - s_len;
  59
  60         for (cur = cl; cur <= last; cur++)
  61                 if (cur[0] == cs[0] && memcmp(cur, cs, s_len) == 0)
  62                         return (void *)cur;
  63
  64         return NULL;
  65 }