| 1 | /* Copyright (C) 1991-2018 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}, @ |
| 21 | size_t @var{haystack_len} const void *@var{needle}, size_t @var{needle_len}) |
| 22 | |
| 23 | Returns a pointer to the first occurrence of @var{needle} (length |
| 24 | @var{needle_len}) in @var{haystack} (length @var{haystack_len}). |
| 25 | Returns @code{NULL} if not found. |
| 26 | |
| 27 | @end deftypefn |
| 28 | |
| 29 | */ |
| 30 | |
| 31 | #ifndef _LIBC |
| 32 | # include <config.h> |
| 33 | #endif |
| 34 | |
| 35 | #include <stddef.h> |
| 36 | #include <string.h> |
| 37 | |
| 38 | #ifndef _LIBC |
| 39 | # define __builtin_expect(expr, val) (expr) |
| 40 | #endif |
| 41 | |
| 42 | #undef memmem |
| 43 | |
| 44 | /* Return the first occurrence of NEEDLE in HAYSTACK. */ |
| 45 | void * |
| 46 | memmem (const void *haystack, size_t haystack_len, const void *needle, |
| 47 | size_t needle_len) |
| 48 | { |
| 49 | const char *begin; |
| 50 | const char *const last_possible |
| 51 | = (const char *) haystack + haystack_len - needle_len; |
| 52 | |
| 53 | if (needle_len == 0) |
| 54 | /* The first occurrence of the empty string is deemed to occur at |
| 55 | the beginning of the string. */ |
| 56 | return (void *) haystack; |
| 57 | |
| 58 | /* Sanity check, otherwise the loop might search through the whole |
| 59 | memory. */ |
| 60 | if (__builtin_expect (haystack_len < needle_len, 0)) |
| 61 | return NULL; |
| 62 | |
| 63 | for (begin = (const char *) haystack; begin <= last_possible; ++begin) |
| 64 | if (begin[0] == ((const char *) needle)[0] && |
| 65 | !memcmp ((const void *) &begin[1], |
| 66 | (const void *) ((const char *) needle + 1), |
| 67 | needle_len - 1)) |
| 68 | return (void *) begin; |
| 69 | |
| 70 | return NULL; |
| 71 | } |