| lh | 9ed821d | 2023-04-07 01:36:19 -0700 | [diff] [blame^] | 1 | /* Copyright (C) 1991-2015 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 | /* 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 | |
| 27 | #ifndef _LIBC |
| 28 | # define __builtin_expect(expr, val) (expr) |
| 29 | # define __memmem memmem |
| 30 | #endif |
| 31 | |
| 32 | #define RETURN_TYPE void * |
| 33 | #define AVAILABLE(h, h_l, j, n_l) ((j) <= (h_l) - (n_l)) |
| 34 | #include "str-two-way.h" |
| 35 | |
| 36 | #undef memmem |
| 37 | |
| 38 | /* Return the first occurrence of NEEDLE in HAYSTACK. Return HAYSTACK |
| 39 | if NEEDLE_LEN is 0, otherwise NULL if NEEDLE is not found in |
| 40 | HAYSTACK. */ |
| 41 | void * |
| 42 | __memmem (const void *haystack_start, size_t haystack_len, |
| 43 | const void *needle_start, size_t needle_len) |
| 44 | { |
| 45 | /* Abstract memory is considered to be an array of 'unsigned char' values, |
| 46 | not an array of 'char' values. See ISO C 99 section 6.2.6.1. */ |
| 47 | const unsigned char *haystack = (const unsigned char *) haystack_start; |
| 48 | const unsigned char *needle = (const unsigned char *) needle_start; |
| 49 | |
| 50 | if (needle_len == 0) |
| 51 | /* The first occurrence of the empty string is deemed to occur at |
| 52 | the beginning of the string. */ |
| 53 | return (void *) haystack; |
| 54 | |
| 55 | /* Sanity check, otherwise the loop might search through the whole |
| 56 | memory. */ |
| 57 | if (__glibc_unlikely (haystack_len < needle_len)) |
| 58 | return NULL; |
| 59 | |
| 60 | /* Use optimizations in memchr when possible, to reduce the search |
| 61 | size of haystack using a linear algorithm with a smaller |
| 62 | coefficient. However, avoid memchr for long needles, since we |
| 63 | can often achieve sublinear performance. */ |
| 64 | if (needle_len < LONG_NEEDLE_THRESHOLD) |
| 65 | { |
| 66 | haystack = memchr (haystack, *needle, haystack_len); |
| 67 | if (!haystack || __builtin_expect (needle_len == 1, 0)) |
| 68 | return (void *) haystack; |
| 69 | haystack_len -= haystack - (const unsigned char *) haystack_start; |
| 70 | if (haystack_len < needle_len) |
| 71 | return NULL; |
| 72 | return two_way_short_needle (haystack, haystack_len, needle, needle_len); |
| 73 | } |
| 74 | else |
| 75 | return two_way_long_needle (haystack, haystack_len, needle, needle_len); |
| 76 | } |
| 77 | libc_hidden_def (__memmem) |
| 78 | weak_alias (__memmem, memmem) |
| 79 | libc_hidden_weak (memmem) |
| 80 | |
| 81 | #undef LONG_NEEDLE_THRESHOLD |