mirror of
https://git.savannah.gnu.org/git/emacs.git
synced 2024-12-02 08:22:22 +00:00
72 lines
2.7 KiB
C
72 lines
2.7 KiB
C
/* Copyright (C) 1991-1994, 1996-1998, 2000, 2004, 2007-2022 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
|