1 /*
2 * Copyright (C) 2008 The Android Open Source Project
3 * All rights reserved.
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 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in
12 * the documentation and/or other materials provided with the
13 * distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28 /*
29 * This uses the "Not So Naive" algorithm, a very simple but
30 * usually effective algorithm, see:
31 * http://www-igm.univ-mlv.fr/~lecroq/string/
32 */
33 #include <string.h>
34
memmem(const void * haystack,size_t n,const void * needle,size_t m)35 void *memmem(const void *haystack, size_t n, const void *needle, size_t m)
36 {
37 if (m > n || !m || !n)
38 return NULL;
39
40 if (__builtin_expect((m > 1), 1)) {
41 const unsigned char* y = (const unsigned char*) haystack;
42 const unsigned char* x = (const unsigned char*) needle;
43 size_t j = 0;
44 size_t k = 1, l = 2;
45
46 if (x[0] == x[1]) {
47 k = 2;
48 l = 1;
49 }
50 while (j <= n-m) {
51 if (x[1] != y[j+1]) {
52 j += k;
53 } else {
54 if (!memcmp(x+2, y+j+2, m-2) && x[0] == y[j])
55 return (void*) &y[j];
56 j += l;
57 }
58 }
59 } else {
60 /* degenerate case */
61 return memchr(haystack, ((unsigned char*)needle)[0], n);
62 }
63 return NULL;
64 }
65