xref: /freebsd/sys/libkern/memmem.c (revision 27ecc2adbc0b52765d647326836e7314264bcc59)
1*27ecc2adSBenno Rice /*-
2*27ecc2adSBenno Rice  * Copyright (c) 2005 Pascal Gloor <pascal.gloor@spale.com>
3*27ecc2adSBenno Rice  *
4*27ecc2adSBenno Rice  * Redistribution and use in source and binary forms, with or without
5*27ecc2adSBenno Rice  * modification, are permitted provided that the following conditions
6*27ecc2adSBenno Rice  * are met:
7*27ecc2adSBenno Rice  * 1. Redistributions of source code must retain the above copyright
8*27ecc2adSBenno Rice  *    notice, this list of conditions and the following disclaimer.
9*27ecc2adSBenno Rice  * 2. Redistributions in binary form must reproduce the above copyright
10*27ecc2adSBenno Rice  *    notice, this list of conditions and the following disclaimer in the
11*27ecc2adSBenno Rice  *    documentation and/or other materials provided with the distribution.
12*27ecc2adSBenno Rice  * 3. The name of the author may not be used to endorse or promote
13*27ecc2adSBenno Rice  *    products derived from this software without specific prior written
14*27ecc2adSBenno Rice  *    permission.
15*27ecc2adSBenno Rice  *
16*27ecc2adSBenno Rice  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17*27ecc2adSBenno Rice  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18*27ecc2adSBenno Rice  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19*27ecc2adSBenno Rice  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20*27ecc2adSBenno Rice  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21*27ecc2adSBenno Rice  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22*27ecc2adSBenno Rice  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23*27ecc2adSBenno Rice  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24*27ecc2adSBenno Rice  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25*27ecc2adSBenno Rice  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26*27ecc2adSBenno Rice  * SUCH DAMAGE.
27*27ecc2adSBenno Rice  */
28*27ecc2adSBenno Rice 
29*27ecc2adSBenno Rice #include <sys/cdefs.h>
30*27ecc2adSBenno Rice __FBSDID("$FreeBSD$");
31*27ecc2adSBenno Rice 
32*27ecc2adSBenno Rice #include <sys/libkern.h>
33*27ecc2adSBenno Rice #include <sys/param.h>
34*27ecc2adSBenno Rice 
35*27ecc2adSBenno Rice void *
36*27ecc2adSBenno Rice memmem(const void *l, size_t l_len, const void *s, size_t s_len)
37*27ecc2adSBenno Rice {
38*27ecc2adSBenno Rice         register char *cur, *last;
39*27ecc2adSBenno Rice         const char *cl = (const char *)l;
40*27ecc2adSBenno Rice         const char *cs = (const char *)s;
41*27ecc2adSBenno Rice 
42*27ecc2adSBenno Rice         /* we need something to compare */
43*27ecc2adSBenno Rice         if (l_len == 0 || s_len == 0)
44*27ecc2adSBenno Rice                 return NULL;
45*27ecc2adSBenno Rice 
46*27ecc2adSBenno Rice         /* "s" must be smaller or equal to "l" */
47*27ecc2adSBenno Rice         if (l_len < s_len)
48*27ecc2adSBenno Rice                 return NULL;
49*27ecc2adSBenno Rice 
50*27ecc2adSBenno Rice         /* special case where s_len == 1 */
51*27ecc2adSBenno Rice         if (s_len == 1)
52*27ecc2adSBenno Rice                 return memchr(l, (int)*cs, l_len);
53*27ecc2adSBenno Rice 
54*27ecc2adSBenno Rice         /* the last position where its possible to find "s" in "l" */
55*27ecc2adSBenno Rice         last = (char *)cl + l_len - s_len;
56*27ecc2adSBenno Rice 
57*27ecc2adSBenno Rice         for (cur = (char *)cl; cur <= last; cur++)
58*27ecc2adSBenno Rice                 if (cur[0] == cs[0] && memcmp(cur, cs, s_len) == 0)
59*27ecc2adSBenno Rice                         return cur;
60*27ecc2adSBenno Rice 
61*27ecc2adSBenno Rice         return NULL;
62*27ecc2adSBenno Rice }
63