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}