Machine-optimized version of ns_cksum.c.
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/* $NetBSD: ns_cksum.c,v 1.1 1996/03/03 11:54:37 ragge Exp $ */
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/*
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* Copyright (c) 1985, 1986 Regents of the University of California.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)ns_cksum.c 7.6 (Berkeley) 12/16/90
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*/
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#include <sys/param.h>
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#include <sys/mbuf.h>
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/*
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* Checksum routine for Network Systems Protocol Packets (VAX Version).
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*
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* This routine is very heavily used in the network
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* code and should be modified for each CPU to be as fast as possible.
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*/
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u_short
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ns_cksum(m, len)
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register struct mbuf *m;
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register int len;
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{
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register u_short *w asm("r9"); /* on vax, known to be r9 */
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register int sum asm("r8"); /* on vax, known to be r8 */
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register int low asm("r7"); /* on vax, known to be r7 */
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register int mlen; /* want 0, shuts lint up about low */
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sum = 0;
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low = 0;
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mlen = 0;
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for (;;) {
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/*
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* Each trip around loop adds in
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* word from one mbuf segment.
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*/
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w = mtod(m, u_short *);
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if (mlen == -1) {
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/*
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* There is a byte left from the last segment;
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* add it into the checksum. Don't have to worry
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* about a carry-out here because we make sure
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* that high part of (32 bit) sum is small below.
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*/
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sum += *(u_char *)w << 8;
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sum += sum;
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w = (u_short *)((char *)w + 1);
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mlen = m->m_len - 1;
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len--;
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} else
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mlen = m->m_len;
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m = m->m_next;
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if (len < mlen)
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mlen = len;
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len -= mlen;
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/*
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* Force to long boundary so we do longword aligned
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* memory operations. It is too hard to do byte
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* adjustment, do only word adjustment.
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*/
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if (((int)w&0x2) && mlen >= 2) {
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sum += *w++;
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sum += sum;
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mlen -= 2;
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}
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/*
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*
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* We can do a 16 bit ones complement sum using
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* 32 bit arithmetic registers for adding,
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* with carries from the low added
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* into the high (by normal carry-chaining)
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* so long as we fold back before 16 carries have occured.
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*
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*/
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while ((mlen -= 32) >= 0) {
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/*asm("bicpsw $1"); clears carry */
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#undef ADD
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#define ADD asm("movw (r9)+,r7; addl2 r7,r8; addl2 r8,r8")
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#define FOLD { asm("ashl $-16,r8,r0; addw2 r0,r8; adwc $0,r8; movzwl r8,r8"); }
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FOLD;
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ADD; ADD; ADD; ADD; ADD; ADD; ADD; ADD;
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FOLD;
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ADD; ADD; ADD; ADD; ADD; ADD; ADD; ADD;
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}
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mlen += 32;
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while ((mlen -= 8) >= 0) {
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/*asm("bicpsw $1"); clears carry */
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FOLD;
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ADD; ADD; ADD; ADD;
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}
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mlen += 8;
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/*
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* Now eliminate the possibility of carry-out's by
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* folding back to a 16 bit number (adding high and
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* low parts together.) Then mop up trailing words
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* and maybe an odd byte.
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*/
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FOLD;
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while ((mlen -= 2) >= 0) {
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ADD;
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}
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if (mlen == -1) {
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sum += *(u_char *)w;
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}
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if (len == 0)
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break;
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/*
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* Locate the next block with some data.
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* If there is a word split across a boundary we
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* will wrap to the top with mlen == -1 and
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* then add it in shifted appropriately.
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*/
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for (;;) {
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if (m == 0) {
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printf("idpcksum: out of data\n");
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goto done;
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}
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if (m->m_len)
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break;
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m = m->m_next;
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}
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}
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done:
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/*
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* Add together high and low parts of sum
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* and carry to get cksum.
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* Have to be careful to not drop the last
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* carry here.
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*/
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FOLD;
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if(sum==0xffff) sum = 0;
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return (sum);
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}
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