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WebSVN – planix.SVN – Blame – /os/branches/feature_posix/sys/src/libsec/port/tsmemcmp.c – Rev 33

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26 7u83 1 
#include "os.h"
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#include <libsec.h>
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/*
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 * timing safe memcmp()
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 */
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int
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tsmemcmp(void *a1, void *a2, ulong n)
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{
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	int lt, gt, c1, c2, r, m;
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	uchar *s1, *s2;
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	r = m = 0;
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	s1 = a1;
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	s2 = a2;
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	while(n--){
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		c1 = *s1++;
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		c2 = *s2++;
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		lt = (c1 - c2) >> 8;
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		gt = (c2 - c1) >> 8;
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		r |= (lt - gt) & ~m;
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		m |= lt | gt;
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	}
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	return r;
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}