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