1/* $openbsd: memmem.c,v 1.4 2015/08/31 02:53:57 guenther exp $ */
 2
 3/*
 4 * copyright (c) 2005 pascal gloor <pascal.gloor@spale.com>
 5 *
 6 * redistribution and use in source and binary forms, with or without
 7 * modification, are permitted provided that the following conditions
 8 * are met:
 9 * 1. redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer
11 * 2. redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution
14 * 3. the name of the author may not be used to endorse or promote
15 * products derived from this software without specific prior written
16 * permission
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR a PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE
29 */
30
31#include <string.h>
32
33#include "../util.h"
34
35/*
36 * find the first occurrence of the byte string s in byte string l
37 */
38
39void *
40memmem(const void *l, size_t l_len, const void *s, size_t s_len)
41{
42  const char *cur, *last;
43  const char *cl = l;
44  const char *cs = s;
45
46  /* a zero length needle should just return the haystack */
47  if (s_len == 0)
48    return (void *)cl;
49
50  /* "s" must be smaller or equal to "l" */
51  if (l_len < s_len)
52    return NULL;
53
54  /* special case where s_len == 1 */
55  if (s_len == 1)
56    return memchr(l, *cs, l_len);
57
58  /* the last position where its possible to find "s" in "l" */
59  last = cl + l_len - s_len;
60
61  for (cur = cl; cur <= last; cur++)
62    if (cur[0] == cs[0] && memcmp(cur, cs, s_len) == 0)
63      return (void *)cur;
64
65  return NULL;
66}