1 /* $NetBSD: memmem.c,v 1.2 2008/04/28 20:23:00 martin Exp $ */
2
3 /*-
4 * Copyright (c) 2005 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Perry E. Metzger of Metzger, Dowdeswell & Co. LLC.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32 #include <sys/cdefs.h>
33 #if defined(LIBC_SCCS) && !defined(lint)
34 __RCSID("$NetBSD: memmem.c,v 1.2 2008/04/28 20:23:00 martin Exp $");
35 #endif /* LIBC_SCCS and not lint */
36
37 #if !defined(_KERNEL) && !defined(_STANDALONE)
38 #include <assert.h>
39 #include <string.h>
40 #else
41 #include <lib/libkern/libkern.h>
42 #define _DIAGASSERT(x) (void)0
43 #define NULL ((void *)0)
44 #endif
45
46 void *
memmem(const void * block,size_t blen,const void * pat,size_t plen)47 memmem(const void *block, size_t blen, const void *pat, size_t plen)
48 {
49 const unsigned char *bp, *pp, *endp;
50
51 _DIAGASSERT(block != NULL);
52 _DIAGASSERT(pat != NULL);
53
54 /*
55 * Following the precedent in ststr(3) and glibc, a zero
56 * length pattern matches the start of block.
57 */
58 if (plen == 0)
59 return __UNCONST(block);
60
61 if (blen < plen)
62 return NULL;
63
64 bp = block;
65 pp = pat;
66 endp = bp + (blen - plen) + 1;
67
68 /*
69 * As a cheezy optimization, check that the first chars are
70 * the same before calling memcmp. Really we should use bm(3)
71 * to speed this up if blen is large enough.
72 */
73 while (bp < endp) {
74 if ((*bp == *pp) && (memcmp(bp, pp, plen) == 0))
75 return __UNCONST(bp);
76 bp++;
77 }
78
79 return NULL;
80 }
81