78 lines
1.6 KiB
C
78 lines
1.6 KiB
C
/*
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* This file is part of the UCB release of Plan 9. It is subject to the license
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* terms in the LICENSE file found in the top-level directory of this
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* distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No
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* part of the UCB release of Plan 9, including this file, may be copied,
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* modified, propagated, or distributed except according to the terms contained
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* in the LICENSE file.
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*/
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#include <u.h>
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#include <libc.h>
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#include <ip.h>
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static int16_t endian = 1;
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static uint8_t* aendian = (uint8_t*)&endian;
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#define LITTLE *aendian
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uint16_t
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ptclbsum(uint8_t *addr, int len)
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{
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uint32_t losum, hisum, mdsum, x;
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uint32_t t1, t2;
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losum = 0;
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hisum = 0;
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mdsum = 0;
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x = 0;
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if((uintptr_t)addr & 1) {
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if(len) {
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hisum += addr[0];
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len--;
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addr++;
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}
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x = 1;
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}
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while(len >= 16) {
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t1 = *(uint16_t*)(addr+0);
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t2 = *(uint16_t*)(addr+2); mdsum += t1;
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t1 = *(uint16_t*)(addr+4); mdsum += t2;
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t2 = *(uint16_t*)(addr+6); mdsum += t1;
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t1 = *(uint16_t*)(addr+8); mdsum += t2;
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t2 = *(uint16_t*)(addr+10); mdsum += t1;
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t1 = *(uint16_t*)(addr+12); mdsum += t2;
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t2 = *(uint16_t*)(addr+14); mdsum += t1;
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mdsum += t2;
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len -= 16;
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addr += 16;
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}
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while(len >= 2) {
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mdsum += *(uint16_t*)addr;
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len -= 2;
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addr += 2;
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}
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if(x) {
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if(len)
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losum += addr[0];
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if(LITTLE)
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losum += mdsum;
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else
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hisum += mdsum;
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} else {
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if(len)
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hisum += addr[0];
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if(LITTLE)
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hisum += mdsum;
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else
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losum += mdsum;
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}
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losum += hisum >> 8;
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losum += (hisum & 0xff) << 8;
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while(hisum = losum>>16)
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losum = hisum + (losum & 0xffff);
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return losum & 0xffff;
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}
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