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comparison libtommath/bn_mp_cnt_lsb.c @ 1739:13d834efc376 fuzz

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merge from main
author Matt Johnston <matt@ucc.asn.au>
date Thu, 15 Oct 2020 19:55:15 +0800
parents 1051e4eea25a
children
comparison
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1562:768ebf737aa0 1739:13d834efc376
1 #include <tommath_private.h> 1 #include "tommath_private.h"
2 #ifdef BN_MP_CNT_LSB_C 2 #ifdef BN_MP_CNT_LSB_C
3 /* LibTomMath, multiple-precision integer library -- Tom St Denis 3 /* LibTomMath, multiple-precision integer library -- Tom St Denis */
4 * 4 /* SPDX-License-Identifier: Unlicense */
5 * LibTomMath is a library that provides multiple-precision
6 * integer arithmetic as well as number theoretic functionality.
7 *
8 * The library was designed directly after the MPI library by
9 * Michael Fromberger but has been written from scratch with
10 * additional optimizations in place.
11 *
12 * The library is free for all purposes without any express
13 * guarantee it works.
14 *
15 * Tom St Denis, [email protected], http://libtom.org
16 */
17 5
18 static const int lnz[16] = { 6 static const int lnz[16] = {
19 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0 7 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0
20 }; 8 };
21 9
22 /* Counts the number of lsbs which are zero before the first zero bit */ 10 /* Counts the number of lsbs which are zero before the first zero bit */
23 int mp_cnt_lsb(mp_int *a) 11 int mp_cnt_lsb(const mp_int *a)
24 { 12 {
25 int x; 13 int x;
26 mp_digit q, qq; 14 mp_digit q, qq;
27 15
28 /* easy out */ 16 /* easy out */
29 if (mp_iszero(a) == MP_YES) { 17 if (MP_IS_ZERO(a)) {
30 return 0; 18 return 0;
31 } 19 }
32 20
33 /* scan lower digits until non-zero */ 21 /* scan lower digits until non-zero */
34 for (x = 0; (x < a->used) && (a->dp[x] == 0); x++) {} 22 for (x = 0; (x < a->used) && (a->dp[x] == 0u); x++) {}
35 q = a->dp[x]; 23 q = a->dp[x];
36 x *= DIGIT_BIT; 24 x *= MP_DIGIT_BIT;
37 25
38 /* now scan this digit until a 1 is found */ 26 /* now scan this digit until a 1 is found */
39 if ((q & 1) == 0) { 27 if ((q & 1u) == 0u) {
40 do { 28 do {
41 qq = q & 15; 29 qq = q & 15u;
42 x += lnz[qq]; 30 x += lnz[qq];
43 q >>= 4; 31 q >>= 4;
44 } while (qq == 0); 32 } while (qq == 0u);
45 } 33 }
46 return x; 34 return x;
47 } 35 }
48 36
49 #endif 37 #endif
50
51 /* ref: $Format:%D$ */
52 /* git commit: $Format:%H$ */
53 /* commit time: $Format:%ai$ */