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 } 71