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/* Copyright (C) 1991-1994, 1996-1998, 2000, 2004, 2007-2023 Free Software
Foundation, Inc.
This file is part of the GNU C Library.
This file 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.
This file 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 this program. If not, see <https://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>
#define RETURN_TYPE void *
#define AVAILABLE(h, h_l, j, n_l) ((j) <= (h_l) - (n_l))
#include "str-two-way.h"
/* 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);
}
#undef LONG_NEEDLE_THRESHOLD
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