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c0c3707f | 1 | /* Copyright (C) 1991-1994, 1996-1998, 2000, 2004, 2007-2019 Free Software |
770d76d7 | 2 | Foundation, Inc. |
f6ea5628 DJ |
3 | This file is part of the GNU C Library. |
4 | ||
5 | This program is free software; you can redistribute it and/or modify | |
6 | it under the terms of the GNU General Public License as published by | |
4c38e0a4 | 7 | the Free Software Foundation; either version 3, or (at your option) |
f6ea5628 DJ |
8 | any later version. |
9 | ||
10 | This program is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
13 | GNU General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU General Public License along | |
c0c3707f | 16 | with this program; if not, see <https://www.gnu.org/licenses/>. */ |
f6ea5628 DJ |
17 | |
18 | /* This particular implementation was written by Eric Blake, 2008. */ | |
19 | ||
20 | #ifndef _LIBC | |
21 | # include <config.h> | |
22 | #endif | |
23 | ||
24 | /* Specification of memmem. */ | |
25 | #include <string.h> | |
26 | ||
f6ea5628 DJ |
27 | #define RETURN_TYPE void * |
28 | #define AVAILABLE(h, h_l, j, n_l) ((j) <= (h_l) - (n_l)) | |
29 | #include "str-two-way.h" | |
30 | ||
31 | /* Return the first occurrence of NEEDLE in HAYSTACK. Return HAYSTACK | |
32 | if NEEDLE_LEN is 0, otherwise NULL if NEEDLE is not found in | |
33 | HAYSTACK. */ | |
34 | void * | |
35 | memmem (const void *haystack_start, size_t haystack_len, | |
f434ba03 | 36 | const void *needle_start, size_t needle_len) |
f6ea5628 DJ |
37 | { |
38 | /* Abstract memory is considered to be an array of 'unsigned char' values, | |
39 | not an array of 'char' values. See ISO C 99 section 6.2.6.1. */ | |
40 | const unsigned char *haystack = (const unsigned char *) haystack_start; | |
41 | const unsigned char *needle = (const unsigned char *) needle_start; | |
42 | ||
43 | if (needle_len == 0) | |
44 | /* The first occurrence of the empty string is deemed to occur at | |
45 | the beginning of the string. */ | |
46 | return (void *) haystack; | |
47 | ||
48 | /* Sanity check, otherwise the loop might search through the whole | |
49 | memory. */ | |
50 | if (__builtin_expect (haystack_len < needle_len, 0)) | |
51 | return NULL; | |
52 | ||
53 | /* Use optimizations in memchr when possible, to reduce the search | |
54 | size of haystack using a linear algorithm with a smaller | |
55 | coefficient. However, avoid memchr for long needles, since we | |
56 | can often achieve sublinear performance. */ | |
57 | if (needle_len < LONG_NEEDLE_THRESHOLD) | |
58 | { | |
59 | haystack = memchr (haystack, *needle, haystack_len); | |
60 | if (!haystack || __builtin_expect (needle_len == 1, 0)) | |
f434ba03 | 61 | return (void *) haystack; |
f6ea5628 DJ |
62 | haystack_len -= haystack - (const unsigned char *) haystack_start; |
63 | if (haystack_len < needle_len) | |
f434ba03 | 64 | return NULL; |
f6ea5628 DJ |
65 | return two_way_short_needle (haystack, haystack_len, needle, needle_len); |
66 | } | |
67 | else | |
68 | return two_way_long_needle (haystack, haystack_len, needle, needle_len); | |
69 | } | |
70 | ||
71 | #undef LONG_NEEDLE_THRESHOLD |