GCC Code Coverage Report
Directory: ./ Exec Total Coverage
File: lib/libc/string/timingsafe_memcmp.c Lines: 0 7 0.0 %
Date: 2017-11-07 Branches: 0 2 0.0 %

Line Branch Exec Source
1
/*	$OpenBSD: timingsafe_memcmp.c,v 1.2 2015/08/31 02:53:57 guenther Exp $	*/
2
/*
3
 * Copyright (c) 2014 Google Inc.
4
 *
5
 * Permission to use, copy, modify, and distribute this software for any
6
 * purpose with or without fee is hereby granted, provided that the above
7
 * copyright notice and this permission notice appear in all copies.
8
 *
9
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16
 */
17
18
#include <limits.h>
19
#include <string.h>
20
21
int
22
timingsafe_memcmp(const void *b1, const void *b2, size_t len)
23
{
24
        const unsigned char *p1 = b1, *p2 = b2;
25
        size_t i;
26
        int res = 0, done = 0;
27
28
        for (i = 0; i < len; i++) {
29
                /* lt is -1 if p1[i] < p2[i]; else 0. */
30
                int lt = (p1[i] - p2[i]) >> CHAR_BIT;
31
32
                /* gt is -1 if p1[i] > p2[i]; else 0. */
33
                int gt = (p2[i] - p1[i]) >> CHAR_BIT;
34
35
                /* cmp is 1 if p1[i] > p2[i]; -1 if p1[i] < p2[i]; else 0. */
36
                int cmp = lt - gt;
37
38
                /* set res = cmp if !done. */
39
                res |= cmp & ~done;
40
41
                /* set done if p1[i] != p2[i]. */
42
                done |= lt | gt;
43
        }
44
45
        return (res);
46
}
47
DEF_WEAK(timingsafe_memcmp);