[unix-history] / usr / src / sys / vax / vax / in_cksum.c

/* in_cksum.c 1.3 81/10/18 */

#include <sys/types.h>
#include "../bbnnet/net.h"
#include "../bbnnet/count.h"

/*
* Network primitives; this file varies per-cpu,
* and the code here is for VAX only.
*/

/*
* Checksum routine for TCP/IP headers.  This
* is very heavily used in the network
* code and should be rewritten for each CPU
* to be as fast as possible.
*/
cksum(m, len)
       register struct mbuf *m;
       register int len;
{
       register u_short *w;            /* known to be r9 */
       register int sum = 0;           /* known to be r8 */
       register int mlen = 0;
COUNT(CKSUM);

       for (;;) {
               w = (u_short *)((int)m + m->m_off);
               if (mlen == -1) {
                       sum += *(u_char *)w << 8;
                       w = (unsigned 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;
               while ((mlen -= 32) >= 0) {
#define ADD             asm("movzwl (r9)+,r0; addl2 r0,r8");
                       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;
               }
               if (mlen == -1)
                       sum += *(u_char *)w;
               if (len == 0)
                       break;
               for (;;) {
                       if (m == 0) {
                               printf("cksum: out of data");
                               goto done;
                       }
                       if (m->m_len)
                               break;
                       m = m->m_next;
               }
       }
done:
       return(~(sum + (sum >> 16)) & 0xffff);
}

/*
* These routines are implemented as inline expansions
* and are mentioned here for reference only
*
*      htons and ntohs         do byte reverse of a 16 bit integer
*      htonl and ntohl         do byte reverse of a 32 bit integer
*/