blob: d4932ae1d58f070f7f17673a4982a30680180fcf [file] [log] [blame]
// SPDX-License-Identifier: BSD-3-Clause
/*
* Copyright (c) 1994-2009 Red Hat, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* 3. Neither the name of the copyright holder nor the names of its
* contributors may be used to endorse or promote products derived from this
* software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/*
FUNCTION
<<memcmp>>---compare two memory areas
INDEX
memcmp
ANSI_SYNOPSIS
#include <string.h>
int memcmp(const void *<[s1]>, const void *<[s2]>, size_t <[n]>);
TRAD_SYNOPSIS
#include <string.h>
int memcmp(<[s1]>, <[s2]>, <[n]>)
void *<[s1]>;
void *<[s2]>;
size_t <[n]>;
DESCRIPTION
This function compares not more than <[n]> characters of the
object pointed to by <[s1]> with the object pointed to by <[s2]>.
RETURNS
The function returns an integer greater than, equal to or
less than zero according to whether the object pointed to by
<[s1]> is greater than, equal to or less than the object
pointed to by <[s2]>.
PORTABILITY
<<memcmp>> is ANSI C.
<<memcmp>> requires no supporting OS subroutines.
QUICKREF
memcmp ansi pure
*/
#include "_ansi.h"
#include <string.h>
/* Nonzero if either X or Y is not aligned on a "long" boundary. */
#define UNALIGNED(X, Y) \
(((long)X & (sizeof(long) - 1)) | ((long)Y & (sizeof(long) - 1)))
/* How many bytes are copied each iteration of the word copy loop. */
#define LBLOCKSIZE (sizeof(long))
/* Threshhold for punting to the byte copier. */
#define TOO_SMALL(LEN) ((LEN) < LBLOCKSIZE)
int
_DEFUN(memcmp, (m1, m2, n), _CONST _PTR m1 _AND _CONST _PTR m2 _AND size_t n)
{
#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
unsigned char *s1 = (unsigned char *)m1;
unsigned char *s2 = (unsigned char *)m2;
while (n--) {
if (*s1 != *s2)
return *s1 - *s2;
s1++;
s2++;
}
return 0;
#else
unsigned char *s1 = (unsigned char *)m1;
unsigned char *s2 = (unsigned char *)m2;
unsigned long *a1;
unsigned long *a2;
/* If the size is too small, or either pointer is unaligned,
then we punt to the byte compare loop. Hopefully this will
not turn up in inner loops. */
if (!TOO_SMALL(n) && !UNALIGNED(s1, s2)) {
/*
* Otherwise, load and compare the blocks of memory one word at
* a time.
*/
a1 = (unsigned long *)s1;
a2 = (unsigned long *)s2;
while (n >= LBLOCKSIZE) {
if (*a1 != *a2)
break;
a1++;
a2++;
n -= LBLOCKSIZE;
}
/* check m mod LBLOCKSIZE remaining characters */
s1 = (unsigned char *)a1;
s2 = (unsigned char *)a2;
}
while (n--) {
if (*s1 != *s2)
return *s1 - *s2;
s1++;
s2++;
}
return 0;
#endif /* not PREFER_SIZE_OVER_SPEED */
}