mirror of
https://gcc.gnu.org/git/gcc.git
synced 2024-11-24 19:33:59 +08:00
72 lines
2.1 KiB
C
72 lines
2.1 KiB
C
/* Copyright (C) 1991-2022 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
|
|
This program is free software; you can redistribute it and/or modify
|
|
it under the terms of the GNU General Public License as published by
|
|
the Free Software Foundation; either version 2, or (at your option)
|
|
any later version.
|
|
|
|
This program 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 General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License along
|
|
with this program; if not, write to the Free Software Foundation,
|
|
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
|
|
|
|
/*
|
|
|
|
@deftypefn Supplemental void* memmem (const void *@var{haystack}, @
|
|
size_t @var{haystack_len} const void *@var{needle}, size_t @var{needle_len})
|
|
|
|
Returns a pointer to the first occurrence of @var{needle} (length
|
|
@var{needle_len}) in @var{haystack} (length @var{haystack_len}).
|
|
Returns @code{NULL} if not found.
|
|
|
|
@end deftypefn
|
|
|
|
*/
|
|
|
|
#ifndef _LIBC
|
|
# include <config.h>
|
|
#endif
|
|
|
|
#include <stddef.h>
|
|
#include <string.h>
|
|
|
|
#ifndef _LIBC
|
|
# define __builtin_expect(expr, val) (expr)
|
|
#endif
|
|
|
|
#undef memmem
|
|
|
|
/* Return the first occurrence of NEEDLE in HAYSTACK. */
|
|
void *
|
|
memmem (const void *haystack, size_t haystack_len, const void *needle,
|
|
size_t needle_len)
|
|
{
|
|
const char *begin;
|
|
const char *const last_possible
|
|
= (const char *) haystack + haystack_len - needle_len;
|
|
|
|
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;
|
|
|
|
for (begin = (const char *) haystack; begin <= last_possible; ++begin)
|
|
if (begin[0] == ((const char *) needle)[0] &&
|
|
!memcmp ((const void *) &begin[1],
|
|
(const void *) ((const char *) needle + 1),
|
|
needle_len - 1))
|
|
return (void *) begin;
|
|
|
|
return NULL;
|
|
}
|