BSD 4_3_Reno release

[unix-history] / usr / src / sys / hp300 / ns_cksum.c

/*
* Copyright (c) 1985, 1986 Regents of the University of California.
* All rights reserved.
*
* Redistribution is only permitted until one year after the first shipment
* of 4.4BSD by the Regents.  Otherwise, 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.
*
*      @(#)ns_cksum.c  7.1 (Berkeley) 5/8/90
*/

#include "types.h"
#include "mbuf.h"


/*
* Checksum routine for Network Systems Protocol Packets (SUN Version).
*
* This routine is very heavily used in the network
* code and should be modified for each CPU to be as fast as possible.
*/

u_short
ns_cksum(m, len)
       register struct mbuf *m;
       register int len;
{
       register u_short *w;            /* on sun, known to be a4 */
       register int sum = 0;           /* on sun, known to be d6 */
       register int low = 0;           /* on sun, known to be d5 */
       register int mlen = low;        /* want 0, shuts lint up about low */
       register int zero = mlen;       /* handy for fold */
       register int sumH = mlen;       /* handy for fold2 */
#undef ADD
#define ADD asm("addw a4@+,d6; addxw d3,d6; rolw #1,d6")
#define FOLD asm("movw d6,d5; swap d6; addw d6,d5; addxw d3,d5;  movl d5,d6");
#define ADDH asm("movb a4@+,d5; addl d5,d2; addl d2,d2")
#define ADDL asm("movb a4@+,d5; addl d5,d6; addl d6,d6")
#define FOLDH asm("movw d2,d5; swap d2; addw d2,d5; addxw d3,d5; movl d5,d2");

       for (;;) {
               /*
                * Each trip around loop adds in
                * word from one mbuf segment.
                */
               w = mtod(m, u_short *);
               if (mlen == -1) {
                       /*
                        * There is a byte left from the last segment;
                        * ones-complement add it into the checksum.
                        */
                       low = *(u_char *)w;
                       asm("addw d5,d6; addxw d3,d6; rolw #1,d6");
                       w = (u_short *)((char *)w + 1);
                       mlen = m->m_len - 1;
                       len--;
               } else
                       mlen = m->m_len;
               m = m->m_next;
               if (len < mlen)
                       mlen = len;
               len -= mlen;
               /*
                *
                * We can do a 16 bit ones complement sum using
                * 32 bit arithmetic registers for adding,
                * with carries from the low added
                * into the high (by normal carry-chaining)
                * so long as we fold back before 16 carries have occured.
                *
                */
#ifndef OKTOODDWORD
               if (((int) w & 1)==0) goto easycase;
               while ((mlen -= 32) >= 0) {
                       ADDH; ADDL; ADDH; ADDL; ADDH; ADDL; ADDH; ADDL;
                       ADDH; ADDL; ADDH; ADDL; ADDH; ADDL; ADDH; ADDL;
                       FOLD;
                       FOLDH;
                       ADDH; ADDL; ADDH; ADDL; ADDH; ADDL; ADDH; ADDL;
                       ADDH; ADDL; ADDH; ADDL; ADDH; ADDL; ADDH; ADDL;
                       FOLD;
                       FOLDH;
               }
               mlen += 32;
               while ((mlen -= 8) >= 0) {
                       ADDH; ADDL; ADDH; ADDL; ADDH; ADDL; ADDH; ADDL;
                       FOLD;
                       FOLDH;
               }
               mlen += 8;
               while ((mlen -= 2) >= 0) {
                       ADDH; ADDL;
               }
               FOLDH;
               sum = (sumH << 8) + sum;
               FOLD;
               sumH = 0;
               goto commoncase;
easycase:
#endif
               /* In this sequence there will be no carries out of
                * the lower 16 bits.
                */
               while ((mlen -= 32) >= 0) {
                       ADD; ADD; ADD; ADD; ADD; ADD; ADD; ADD;
                       ADD; ADD; ADD; ADD; ADD; ADD; ADD; ADD;
               }
               mlen += 32;
               while ((mlen -= 8) >= 0) {
                       ADD; ADD; ADD; ADD;
               }
               mlen += 8;
               while ((mlen -= 2) >= 0) {
                       ADD;
               }
commoncase:
               if (mlen == -1) {
                       /*sum += *(u_char *)w << 8; FOLD*/
                       low = *(u_char *)w << 8;
                       asm("addw d5,d6; addxw d3,d6");
               }
               if (len == 0) 
                       break;
               /*
                * Locate the next block with some data.
                * If there is a word split across a boundary we
                * will wrap to the top with mlen == -1 and
                * then add it in shifted appropriately.
                */
               for (;;) {
                       if (m == 0) {
                               printf("idpcksum: out of data\n");
                               goto done;
                       }
                       if (m->m_len)
                               break;
                       m = m->m_next;
               }
       }
done:
       /*
        * sum has already been kept to low sixteen bits.
        * just examine result and exit.
        */
       
       if(sum==0xffff) sum = 0;
       return (sum);
}