xref: /freebsd/sys/libkern/memmem.c (revision e0c4386e7e71d93b0edc0c8fa156263fc4a8b0b6)
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 #include <sys/libkern.h>
31 #include <sys/param.h>
32 
33 void *
34 memmem(const void *l, size_t l_len, const void *s, size_t s_len)
35 {
36         char *cur, *last;
37         const char *cl = (const char *)l;
38         const char *cs = (const char *)s;
39 
40         /* we need something to compare */
41         if (l_len == 0 || s_len == 0)
42                 return NULL;
43 
44         /* "s" must be smaller or equal to "l" */
45         if (l_len < s_len)
46                 return NULL;
47 
48         /* special case where s_len == 1 */
49         if (s_len == 1)
50                 return memchr(l, (int)*cs, l_len);
51 
52         /* the last position where its possible to find "s" in "l" */
53         last = __DECONST(char *, cl) + l_len - s_len;
54 
55         for (cur = __DECONST(char *, cl); cur <= last; cur++)
56                 if (cur[0] == cs[0] && memcmp(cur, cs, s_len) == 0)
57                         return cur;
58 
59         return NULL;
60 }
61