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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	short	endian	= 1;
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static	uchar*	aendian	= (uchar*)&endian;
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#define	LITTLE	*aendian
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ushort
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ptclbsum(uchar *addr, int len)
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{
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	ulong losum, hisum, mdsum, x;
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	ulong 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)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 = *(ushort*)(addr+0);
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		t2 = *(ushort*)(addr+2);	mdsum += t1;
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		t1 = *(ushort*)(addr+4);	mdsum += t2;
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		t2 = *(ushort*)(addr+6);	mdsum += t1;
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		t1 = *(ushort*)(addr+8);	mdsum += t2;
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		t2 = *(ushort*)(addr+10);	mdsum += t1;
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		t1 = *(ushort*)(addr+12);	mdsum += t2;
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		t2 = *(ushort*)(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 += *(ushort*)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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}