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#define _GNU_SOURCE
31#include <string.h>
32
33/*
34 * Find the first occurrence of the byte string s in byte string l.
35 */
36
37void *
38memmem(const void *l, size_t l_len, const void *s, size_t s_len)
39{
40	const char *cur, *last;
41	const char *cl = l;
42	const char *cs = s;
43
44	/* a zero length needle should just return the haystack */
45	if (s_len == 0)
46		return (void *)cl;
47
48	/* "s" must be smaller or equal to "l" */
49	if (l_len < s_len)
50		return NULL;
51
52	/* special case where s_len == 1 */
53	if (s_len == 1)
54		return memchr(l, *cs, l_len);
55
56	/* the last position where its possible to find "s" in "l" */
57	last = cl + l_len - s_len;
58
59	for (cur = cl; cur <= last; cur++)
60		if (cur[0] == cs[0] && memcmp(cur, cs, s_len) == 0)
61			return (void *)cur;
62
63	return NULL;
64}
65