memmem.c revision 149466 
1/*-
2 * Copyright (c) 2005 Pascal Gloor <pascal.gloor@spale.com>
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 * 3. The name of the author may not be used to endorse or promote
13 *    products derived from this software without specific prior written
14 *    permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29#include <sys/cdefs.h>
30__FBSDID("$FreeBSD: head/lib/libc/string/memmem.c 149466 2005-08-25 18:26:58Z andre $");
31
32#include <string.h>
33
34/*
35 * Find the first occurrence of the byte string s in byte string l.
36 */
37
38void *
39memmem(l, l_len, s, s_len)
40	const void *l; size_t l_len;
41	const void *s; size_t s_len;
42{
43	register char *cur, *last;
44	const char *cl = (const char *)l;
45	const char *cs = (const char *)s;
46
47	/* we need something to compare */
48	if (l_len == 0 || s_len == 0)
49		return NULL;
50
51	/* "s" must be smaller or equal to "l" */
52	if (l_len < s_len)
53		return NULL;
54
55	/* special case where s_len == 1 */
56	if (s_len == 1)
57		return memchr(l, (int)*cs, l_len);
58
59	/* the last position where its possible to find "s" in "l" */
60	last = (char *)cl + l_len - s_len;
61
62	for (cur = (char *)cl; cur <= last; cur++)
63		if (cur[0] == cs[0] && memcmp(cur, cs, s_len) == 0)
64			return cur;
65
66	return NULL;
67}
68