usr/src/usr.sbin/timed/timed/cksum.vax.c

/*
 * Copyright (c) 1983 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted provided
 * that: (1) source distributions retain this entire copyright notice and
 * comment, and (2) distributions including binaries display the following
 * acknowledgement:  ``This product includes software developed by the
 * University of California, Berkeley and its contributors'' in the
 * documentation or other materials provided with the distribution and in
 * all advertising materials mentioning features or use of this software.
 * 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 ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#ifndef lint
static char sccsid[] = "@(#)cksum.vax.c 1.5 (Berkeley) 6/1/90";
#endif /* not lint */

#include <sys/types.h>

#define ADD     asm("adwc (r9)+,r8;");

/* computes the checksum for ip packets for the VAX */

in_cksum(addr, len)
u_short *addr;
int len;
{
        register int nleft = len;       /* on vax, (user mode), r11 */
#ifndef lint
        register int xxx;               /* on vax, (user mode), r10 */
#endif not lint
        register u_short *w = addr;     /* on vax, known to be r9 */
        register int sum = 0;           /* on vax, known to be r8 */

        if (((int)w&0x2) && nleft >= 2) {
                sum += *w++;
                nleft -= 2;
        }
        while ((nleft -= 32) >= 0) {
                asm("clrl r0");         /* clears carry */
                ADD; ADD; ADD; ADD; ADD; ADD; ADD; ADD;
                asm("adwc $0,r8");
        }
        nleft += 32;
        while ((nleft -= 8) >= 0) {
                asm("clrl r0");
                ADD; ADD;
                asm("adwc $0,r8");
        }
        nleft += 8;
        { asm("ashl $-16,r8,r0; addw2 r0,r8");
          asm("adwc $0,r8; movzwl r8,r8"); }
        while ((nleft -= 2) >= 0) {
                asm("movzwl (r9)+,r0; addl2 r0,r8");
        }
        if (nleft == -1) {
                sum += *(u_char *)w;
        }

        { asm("ashl $-16,r8,r0; addw2 r0,r8; adwc $0,r8");
          asm("mcoml r8,r8; movzwl r8,r8"); }
        return (sum);
}