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#include <machine/rtems-bsd-user-space.h>
/*
* Copyright (C) 2004-2007, 2011, 2012 Internet Systems Consortium, Inc. ("ISC")
* Copyright (C) 1999-2001, 2003 Internet Software Consortium.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
* REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
* INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
* LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
* OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
* PERFORMANCE OF THIS SOFTWARE.
*/
/* $Id$ */
/*! \file */
#include <config.h>
#include <limits.h>
#include <isc/string.h>
/* Making a portable memcmp that has no internal branches and loops always
* once for every byte without early-out shortcut has a few challenges.
*
* Inspired by 'timingsafe_memcmp()' from the BSD system and
* https://github.com/libressl-portable/openbsd/blob/master/src/lib/libc/string/timingsafe_memcmp.c
*
* Sadly, that one is not portable C: It makes assumptions on the representation
* of negative integers and assumes sign-preserving right-shift of negative
* signed values. This is a rewrite from scratch that should not suffer from
* such issues.
*
* 2015-12-12, J. Perlinger (perlinger-at-ntp-dot-org)
*/
int
isc_tsmemcmp(const void *p1, const void *p2, size_t nb) {
const unsigned char *ucp1 = p1;
const unsigned char *ucp2 = p2;
unsigned int isLT = 0u;
unsigned int isGT = 0u;
volatile unsigned int mask = (1u << CHAR_BIT);
for (/*NOP*/; 0 != nb; --nb, ++ucp1, ++ucp2) {
isLT |= mask &
((unsigned int)*ucp1 - (unsigned int)*ucp2);
isGT |= mask &
((unsigned int)*ucp2 - (unsigned int)*ucp1);
mask &= ~(isLT | isGT);
}
return (int)(isGT >> CHAR_BIT) - (int)(isLT >> CHAR_BIT);
}
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