33 lines
737 B
C
33 lines
737 B
C
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/* $NetBSD: consttime_memequal.c,v 1.4 2013/08/28 19:31:14 riastradh Exp $ */
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#if !defined(_KERNEL) && !defined(_STANDALONE)
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#include "namespace.h"
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#include <string.h>
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#ifdef __weak_alias
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__weak_alias(consttime_memequal,_consttime_memequal)
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#endif
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#else
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#include <lib/libkern/libkern.h>
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#endif
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int
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consttime_memequal(const void *b1, const void *b2, size_t len)
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{
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const char *c1 = b1, *c2 = b2;
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int res = 0;
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while (len --)
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res |= *c1++ ^ *c2++;
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/*
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* If the compiler for your favourite architecture generates a
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* conditional branch for `!res', it will be a data-dependent
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* branch, in which case this should be replaced by
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*
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* return (1 - (1 & ((res - 1) >> 8)));
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*
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* or rewritten in assembly.
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*/
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return !res;
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}
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