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/*	$OpenBSD: timingsafe_memcmp.c,v 1.2 2015/08/31 02:53:57 guenther Exp $	*/
/*
 * Copyright (c) 2014 Google Inc.
 *
 * Permission to use, copy, modify, and 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 THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR 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.
 */

#include <limits.h>
#include <string.h>

int
timingsafe_memcmp(const void *b1, const void *b2, size_t len)
{
        const unsigned char *p1 = b1, *p2 = b2;
        size_t i;
        int res = 0, done = 0;

        for (i = 0; i < len; i++) {
                /* lt is -1 if p1[i] < p2[i]; else 0. */
                int lt = (p1[i] - p2[i]) >> CHAR_BIT;

                /* gt is -1 if p1[i] > p2[i]; else 0. */
                int gt = (p2[i] - p1[i]) >> CHAR_BIT;

                /* cmp is 1 if p1[i] > p2[i]; -1 if p1[i] < p2[i]; else 0. */
                int cmp = lt - gt;

                /* set res = cmp if !done. */
                res |= cmp & ~done;

                /* set done if p1[i] != p2[i]. */
                done |= lt | gt;
        }

        return (res);
}
22:53:53 -0400'>2019-06-02Add RebornJune McEnroe 2019-05-30Add bit to bin.7June McEnroe 2019-05-30Simplify and build bitJune McEnroe lex is a waste of time. 2019-05-29Add xx -p optionJune McEnroe 2019-05-27Add FrontierJune McEnroe 2019-05-27Break nicks with ZWNJJune McEnroe This should prevent bad wrapping. 2019-05-26Add DawnJune McEnroe 2019-05-20Declare vasprintf(3) for GNUJune McEnroe who the fuck is scraeming "#define _GNU_SOURCE" at my house. show yourself, coward. i will never #define _GNU_SOURCE 2019-05-20Fix comparison warning in ttpreJune McEnroe 2019-05-20Add AuthorityJune McEnroe 2019-05-19Specify precedence of unary versions of operatorsJune McEnroe 2019-05-18Add compound assignment operators to orderJune McEnroe 2019-05-15Support simple assignment in orderJune McEnroe 2019-05-15Implement sizeof in orderJune McEnroe 2019-05-15Add orderJune McEnroe 2019-05-12Add T suffix in bitJune McEnroe 2019-05-10Highlight yacc and lex files as CJune McEnroe Their %-prefixed directives should probably be highlighted Macro. 2019-05-10Use val instead of suboptargJune McEnroe suboptarg doesn't exist in GNU. Hopefully BSD getsubopt also sets val on failure? 2019-05-09Add Parable of the SowerJune McEnroe 2019-05-07Add bit without buildJune McEnroe Need to do some stuff in the Makefile for lex and yacc and generating HTML pages for it. 2019-05-04Fix MANDIR typoJune McEnroe 2019-05-04Move relay to binJune McEnroe