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/* Copyright (C) 1991-2024 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;
}
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