1 /* Copyright (C) 1991,92,93,94,96,97,98,2000,2004,2007,2011 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 2, or (at your option)
7 any later version.
8
9 This program 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
12 GNU General Public License for more details.
13
14 You should have received a copy of the GNU General Public License along
15 with this program; if not, write to the Free Software Foundation,
16 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
17
18 /*
19
20 @deftypefn Supplemental void* memmem (const void *@var{haystack}, @
21 size_t @var{haystack_len} const void *@var{needle}, size_t @var{needle_len})
22
23 Returns a pointer to the first occurrence of @var{needle} (length
24 @var{needle_len}) in @var{haystack} (length @var{haystack_len}).
25 Returns @code{NULL} if not found.
26
27 @end deftypefn
28
29 */
30
31 #ifndef _LIBC
32 # include <config.h>
33 #endif
34
35 #include <stddef.h>
36 #include <string.h>
37
38 #ifndef _LIBC
39 # define __builtin_expect(expr, val) (expr)
40 #endif
41
42 #undef memmem
43
44 /* Return the first occurrence of NEEDLE in HAYSTACK. */
45 void *
memmem(const void * haystack,size_t haystack_len,const void * needle,size_t needle_len)46 memmem (const void *haystack, size_t haystack_len, const void *needle,
47 size_t needle_len)
48 {
49 const char *begin;
50 const char *const last_possible
51 = (const char *) haystack + haystack_len - needle_len;
52
53 if (needle_len == 0)
54 /* The first occurrence of the empty string is deemed to occur at
55 the beginning of the string. */
56 return (void *) haystack;
57
58 /* Sanity check, otherwise the loop might search through the whole
59 memory. */
60 if (__builtin_expect (haystack_len < needle_len, 0))
61 return NULL;
62
63 for (begin = (const char *) haystack; begin <= last_possible; ++begin)
64 if (begin[0] == ((const char *) needle)[0] &&
65 !memcmp ((const void *) &begin[1],
66 (const void *) ((const char *) needle + 1),
67 needle_len - 1))
68 return (void *) begin;
69
70 return NULL;
71 }
72