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1 | /* Copyright (C) 1991,92,93,94,96,97,98,2000,2004,2007 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}, size_t @var{haystack_len} const void *@var{needle}, size_t @var{needle_len}) | |
21 | ||
22 | Returns a pointer to the first occurrence of @var{needle} (length | |
23 | @var{needle_len}) in @var{haystack} (length @var{haystack_len}). | |
24 | Returns @code{NULL} if not found. | |
25 | ||
26 | @end deftypefn | |
27 | ||
28 | */ | |
29 | ||
30 | #ifndef _LIBC | |
31 | # include <config.h> | |
32 | #endif | |
33 | ||
34 | #include <stddef.h> | |
35 | #include <string.h> | |
36 | ||
37 | #ifndef _LIBC | |
38 | # define __builtin_expect(expr, val) (expr) | |
39 | #endif | |
40 | ||
41 | #undef memmem | |
42 | ||
43 | /* Return the first occurrence of NEEDLE in HAYSTACK. */ | |
44 | void * | |
45 | memmem (const void *haystack, size_t haystack_len, const void *needle, | |
46 | size_t needle_len) | |
47 | { | |
48 | const char *begin; | |
49 | const char *const last_possible | |
50 | = (const char *) haystack + haystack_len - needle_len; | |
51 | ||
52 | if (needle_len == 0) | |
53 | /* The first occurrence of the empty string is deemed to occur at | |
54 | the beginning of the string. */ | |
55 | return (void *) haystack; | |
56 | ||
57 | /* Sanity check, otherwise the loop might search through the whole | |
58 | memory. */ | |
59 | if (__builtin_expect (haystack_len < needle_len, 0)) | |
60 | return NULL; | |
61 | ||
62 | for (begin = (const char *) haystack; begin <= last_possible; ++begin) | |
63 | if (begin[0] == ((const char *) needle)[0] && | |
64 | !memcmp ((const void *) &begin[1], | |
65 | (const void *) ((const char *) needle + 1), | |
66 | needle_len - 1)) | |
67 | return (void *) begin; | |
68 | ||
69 | return NULL; | |
70 | } |