/*-
 * Copyright (c) 2014 Pietro Cerutti <gahr@FreeBSD.org>
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek.
 *
 * 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 University 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 REGENTS 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 REGENTS 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.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD: head/lib/libc/string/memcmp.c 251069 2013-05-28 20:57:40Z emaste $");

#include <string.h>

/*
 * Compare memory regions.
 */

int
memcmp(const void *s1, const void *s2, size_t n)
{
	const size_t *p1, *p2;  /* Array traversal sizeof(size_t) bytes at a time */
	const char *c1, *c2;    /* Array traversal 1 byte at a time */

	if (n == 0)
		return (0);

	/* If the two args are aligned, compare them one word at a time. */
	p1 = s1;
	p2 = s2;
	if (((size_t)s1 & (sizeof(size_t) - 1)) == 0 &&
	    ((size_t)s2 & (sizeof(size_t) - 1)) == 0) {
		while (n >= sizeof(size_t) && *p1 == *p2) {
			++p1;
			++p2;
			n -= sizeof(size_t);
		}
		if (n == 0)
			return (0);
	}

	/* Usual byte-by-byte comparison. */
	c1 = (const char *)p1;
	c2 = (const char *)p2;
	while (--n && *c1 == *c2) {
		++c1;
		++c2;
	}
	return (*c1 - *c2);
}