| /* Copyright (C) 1991-2014 Free Software Foundation, Inc. |
| This file is part of the GNU C Library. |
| |
| The GNU C Library is free software; you can redistribute it and/or |
| modify it under the terms of the GNU Lesser General Public |
| License as published by the Free Software Foundation; either |
| version 2.1 of the License, or (at your option) any later version. |
| |
| The GNU C Library is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| Lesser General Public License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public |
| License along with the GNU C Library; if not, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| /* This particular implementation was written by Eric Blake, 2008. */ |
| |
| #ifndef _LIBC |
| # include <config.h> |
| #endif |
| |
| /* Specification of memmem. */ |
| #include <string.h> |
| |
| #ifndef _LIBC |
| # define __builtin_expect(expr, val) (expr) |
| #endif |
| |
| #define RETURN_TYPE void * |
| #define AVAILABLE(h, h_l, j, n_l) ((j) <= (h_l) - (n_l)) |
| #include "str-two-way.h" |
| |
| #undef memmem |
| |
| /* Return the first occurrence of NEEDLE in HAYSTACK. Return HAYSTACK |
| if NEEDLE_LEN is 0, otherwise NULL if NEEDLE is not found in |
| HAYSTACK. */ |
| void * |
| memmem (const void *haystack_start, size_t haystack_len, |
| const void *needle_start, size_t needle_len) |
| { |
| /* Abstract memory is considered to be an array of 'unsigned char' values, |
| not an array of 'char' values. See ISO C 99 section 6.2.6.1. */ |
| const unsigned char *haystack = (const unsigned char *) haystack_start; |
| const unsigned char *needle = (const unsigned char *) needle_start; |
| |
| if (needle_len == 0) |
| /* The first occurrence of the empty string is deemed to occur at |
| the beginning of the string. */ |
| return (void *) haystack; |
| |
| /* Sanity check, otherwise the loop might search through the whole |
| memory. */ |
| if (__builtin_expect (haystack_len < needle_len, 0)) |
| return NULL; |
| |
| /* Use optimizations in memchr when possible, to reduce the search |
| size of haystack using a linear algorithm with a smaller |
| coefficient. However, avoid memchr for long needles, since we |
| can often achieve sublinear performance. */ |
| if (needle_len < LONG_NEEDLE_THRESHOLD) |
| { |
| haystack = memchr (haystack, *needle, haystack_len); |
| if (!haystack || __builtin_expect (needle_len == 1, 0)) |
| return (void *) haystack; |
| haystack_len -= haystack - (const unsigned char *) haystack_start; |
| if (haystack_len < needle_len) |
| return NULL; |
| return two_way_short_needle (haystack, haystack_len, needle, needle_len); |
| } |
| else |
| return two_way_long_needle (haystack, haystack_len, needle, needle_len); |
| } |
| libc_hidden_def (memmem) |
| |
| #undef LONG_NEEDLE_THRESHOLD |