/*-
 * Copyright (c) 1983 The Regents of the University of California.
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. 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.
 */

#ifndef lint
static char sccsid[] = "@(#)cksum.m68000.c	2.4 (Berkeley) 4/20/91";
#endif /* not lint */

#include "../globals.h"
#include <protocols/timed.h>

/* computes the checksum for ip packets for a Motorola 68000 base computer */

in_cksum(w, mlen)
	register u_short *w;
	register int mlen;
{
	register int sum = 0;

	if (mlen > 0) {
		if (((int)w & 1) == 0) {
			sum = ocsum(w, mlen>>1);
			w += mlen>>1;
			if (mlen & 1) {
				sum += *(u_char *)w << 8;
				mlen = -1;
			}
		} else {
			u_short swsum;

			sum = *(u_char *)w << 8;
			mlen--;
			w = (u_short *)(1 + (int)w);
			swsum = ocsum(w, mlen>>1);
			swab((char *)&swsum, (char *)&swsum, sizeof swsum);
			sum += swsum;
			w += mlen>>1;
			if (mlen & 1)
				sum += *(u_char *)w;
		}
	}
	sum = (sum & 0xFFFF) + (sum >> 16);
	sum = (sum & 0xFFFF) + (sum >> 16);
	sum = (~sum) & 0xFFFF;
	return (sum);
}
