1 /* Copyright (C) 1991,92,93,94,96,97,98,2000 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <http://www.gnu.org/licenses/>. */
17
18 #include <string.h>
19 #include <stddef.h>
20
21 #ifdef __USE_GNU
22
23 /* Return the first occurrence of NEEDLE in HAYSTACK. */
memmem(const void * haystack,size_t haystack_len,const void * needle,size_t needle_len)24 void *memmem (const void *haystack, size_t haystack_len,
25 const void *needle, size_t needle_len)
26 {
27 const char *begin;
28 const char *const last_possible
29 = (const char *) haystack + haystack_len - needle_len;
30
31 if (needle_len == 0)
32 /* The first occurrence of the empty string is deemed to occur at
33 the beginning of the string. */
34 return (void *) haystack;
35
36 /* Sanity check, otherwise the loop might search through the whole
37 memory. */
38 if (__builtin_expect (haystack_len < needle_len, 0))
39 return NULL;
40
41 for (begin = (const char *) haystack; begin <= last_possible; ++begin)
42 if (begin[0] == ((const char *) needle)[0] &&
43 !memcmp ((const void *) &begin[1],
44 (const void *) ((const char *) needle + 1),
45 needle_len - 1))
46 return (void *) begin;
47
48 return NULL;
49 }
50 #endif
51