Substantially smaller and faster version, from me.
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mycroft
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@ -1,4 +1,5 @@
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/*-
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* Copyright (c) 1994 Charles Hannum.
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* Copyright (c) 1990 The Regents of the University of California.
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* All rights reserved.
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*
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@ -32,15 +33,11 @@
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*
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* from tahoe: in_cksum.c 1.2 86/01/05
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* from: @(#)in_cksum.c 1.3 (Berkeley) 1/19/91
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* $Id: in_cksum.c,v 1.3 1993/05/22 07:59:51 cgd Exp $
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* $Id: in_cksum.c,v 1.4 1994/10/16 15:37:41 mycroft Exp $
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*/
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/*
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* 920724 i386 changes by Bakul Shah <bvs@bitblocks.com>
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*/
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#include "param.h"
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#include "sys/mbuf.h"
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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 Internet Protocol family headers.
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@ -51,49 +48,34 @@
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* This implementation is 386 version.
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*/
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#undef ADDCARRY
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#define ADDCARRY(x) if ((x) > 0xffff) (x) -= 0xffff
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#define REDUCE {sum = (sum & 0xffff) + (sum >> 16); ADDCARRY(sum);}
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#define REDUCE {sum = (sum & 0xffff) + (sum >> 16);}
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#define ADDCARRY {if (sum > 0xffff) sum -= 0xffff;}
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/*
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* Thanks to gcc we don't have to guess
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* which registers contain sum & w.
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*/
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#define CLC asm("clc")
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#define ADD(n) asm("adcl " #n "(%2), %0": "=r"(sum): "0"(sum), "r"(w))
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#define MOP asm("adcl $0, %0": "=r"(sum): "0"(sum))
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#define Asm __asm __volatile
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#define ADD(n) Asm("addl " #n "(%2),%0" : "=r" (sum) : "0" (sum), "r" (w))
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#define ADC(n) Asm("adcl " #n "(%2),%0" : "=r" (sum) : "0" (sum), "r" (w))
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#define MOP Asm("adcl $0,%0" : "=r" (sum) : "0" (sum))
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#define ROL Asm("roll $8,%0" : "=r" (sum) : "0" (sum))
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int
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in_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;
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register u_char *w;
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register unsigned sum = 0;
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register int mlen = 0;
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int byte_swapped = 0;
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union { char c[2]; u_short s; } su;
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for (;m && len; m = m->m_next) {
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for (; m && len; m = m->m_next) {
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if (m->m_len == 0)
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continue;
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w = mtod(m, u_short *);
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if (mlen == -1) {
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/*
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* The first byte of this mbuf is the continuation
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* of a word spanning between this mbuf and the
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* last mbuf.
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*/
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/* su.c[0] is already saved when scanning previous
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* mbuf. sum was REDUCEd when we found mlen == -1
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*/
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su.c[1] = *(u_char *)w;
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sum += su.s;
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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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w = mtod(m, u_char *);
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mlen = m->m_len;
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if (len < mlen)
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mlen = len;
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len -= mlen;
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@ -101,20 +83,36 @@ in_cksum(m, len)
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* Force to long boundary so we do longword aligned
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* memory operations
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*/
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if (3 & (int) w) {
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if ((3 & (int) w) != 0) {
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REDUCE;
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if ((1 & (int) w) && (mlen > 0)) {
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sum <<= 8;
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su.c[0] = *(char *)w;
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w = (u_short *)((char *)w + 1);
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mlen--;
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byte_swapped = 1;
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if ((1 & (int) w) != 0 && mlen >= 1) {
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sum += *w;
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ROL;
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byte_swapped ^= 1;
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w += 1;
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mlen -= 1;
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}
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if ((2 & (int) w) && (mlen >= 2)) {
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sum += *w++;
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if ((2 & (int) w) != 0 && mlen >= 2) {
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sum += *(u_short *)w;
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w += 2;
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mlen -= 2;
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}
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}
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/*
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* Align 4 bytes past a 16-byte cache line boundary.
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*/
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if ((4 & (int) w) == 0 && mlen >= 4) {
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ADD(0);
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MOP;
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w += 4;
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mlen -= 4;
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}
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if ((8 & (int) w) != 0 && mlen >= 8) {
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ADD(0); ADC(4);
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MOP;
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w += 8;
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mlen -= 8;
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}
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/*
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* Do as much of the checksum as possible 32 bits at at time.
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* In fact, this loop is unrolled to make overhead from
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@ -122,56 +120,52 @@ in_cksum(m, len)
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*/
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while ((mlen -= 32) >= 0) {
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/*
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* Clear the carry flag, add with carry 16 words
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* and fold-in last carry by adding a 0 with carry.
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* Add with carry 16 words and fold in the last carry
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* by adding a 0 with carry.
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*
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* We aligned the pointer above so that the out-of-
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* order operations will cause the next cache line to
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* be preloaded while we finish with the current one.
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*/
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CLC;
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ADD(0); ADD(4); ADD(8); ADD(12);
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ADD(16); ADD(20); ADD(24); ADD(28);
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MOP; w += 16;
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ADD(12); ADC(0); ADC(4); ADC(8);
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ADC(28); ADC(16); ADC(20); ADC(24);
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MOP;
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w += 32;
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}
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mlen += 32;
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while ((mlen -= 8) >= 0) {
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CLC;
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ADD(0); ADD(4);
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if (mlen >= 16) {
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ADD(12); ADC(0); ADC(4); ADC(8);
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MOP;
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w += 4;
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w += 16;
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mlen -= 16;
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}
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mlen += 8;
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if (mlen == 0 && byte_swapped == 0)
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continue; /* worth 1% maybe ?? */
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if (mlen >= 8) {
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ADD(0); ADC(4);
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MOP;
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w += 8;
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mlen -= 8;
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}
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if (mlen == 0)
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continue;
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REDUCE;
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while ((mlen -= 2) >= 0) {
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sum += *w++;
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sum += *(u_short *)w;
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w += 2;
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}
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if (mlen == -1) {
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sum += *w;
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ROL;
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byte_swapped ^= 1;
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}
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if (byte_swapped) {
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sum <<= 8;
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byte_swapped = 0;
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if (mlen == -1) {
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su.c[1] = *(char *)w;
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sum += su.s;
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mlen = 0;
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} else
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mlen = -1;
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} else if (mlen == -1)
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/*
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* This mbuf has odd number of bytes.
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* There could be a word split betwen
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* this mbuf and the next mbuf.
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* Save the last byte (to prepend to next mbuf).
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*/
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su.c[0] = *(char *)w;
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}
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if (len)
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printf("cksum: out of data\n");
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if (mlen == -1) {
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/* The last mbuf has odd # of bytes. Follow the
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standard (the odd byte is shifted left by 8 bits) */
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su.c[1] = 0;
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sum += su.s;
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if (byte_swapped) {
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ROL;
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}
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REDUCE;
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return (~sum & 0xffff);
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ADDCARRY;
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return (sum ^ 0xffff);
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}
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