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comparison libtommath/bn_mp_reduce_2k_l.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
equal deleted inserted replaced
1562:768ebf737aa0 1739:13d834efc376
1 #include <tommath_private.h> 1 #include "tommath_private.h"
2 #ifdef BN_MP_REDUCE_2K_L_C 2 #ifdef BN_MP_REDUCE_2K_L_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 /* reduces a modulo n where n is of the form 2**p - d 6 /* reduces a modulo n where n is of the form 2**p - d
19 This differs from reduce_2k since "d" can be larger 7 This differs from reduce_2k since "d" can be larger
20 than a single digit. 8 than a single digit.
21 */ 9 */
22 int mp_reduce_2k_l(mp_int *a, mp_int *n, mp_int *d) 10 mp_err mp_reduce_2k_l(mp_int *a, const mp_int *n, const mp_int *d)
23 { 11 {
24 mp_int q; 12 mp_int q;
25 int p, res; 13 mp_err err;
14 int p;
26 15
27 if ((res = mp_init(&q)) != MP_OKAY) { 16 if ((err = mp_init(&q)) != MP_OKAY) {
28 return res; 17 return err;
29 } 18 }
30 19
31 p = mp_count_bits(n); 20 p = mp_count_bits(n);
32 top: 21 top:
33 /* q = a/2**p, a = a mod 2**p */ 22 /* q = a/2**p, a = a mod 2**p */
34 if ((res = mp_div_2d(a, p, &q, a)) != MP_OKAY) { 23 if ((err = mp_div_2d(a, p, &q, a)) != MP_OKAY) {
35 goto ERR; 24 goto LBL_ERR;
36 } 25 }
37 26
38 /* q = q * d */ 27 /* q = q * d */
39 if ((res = mp_mul(&q, d, &q)) != MP_OKAY) { 28 if ((err = mp_mul(&q, d, &q)) != MP_OKAY) {
40 goto ERR; 29 goto LBL_ERR;
41 } 30 }
42 31
43 /* a = a + q */ 32 /* a = a + q */
44 if ((res = s_mp_add(a, &q, a)) != MP_OKAY) { 33 if ((err = s_mp_add(a, &q, a)) != MP_OKAY) {
45 goto ERR; 34 goto LBL_ERR;
46 } 35 }
47 36
48 if (mp_cmp_mag(a, n) != MP_LT) { 37 if (mp_cmp_mag(a, n) != MP_LT) {
49 if ((res = s_mp_sub(a, n, a)) != MP_OKAY) { 38 if ((err = s_mp_sub(a, n, a)) != MP_OKAY) {
50 goto ERR; 39 goto LBL_ERR;
51 } 40 }
52 goto top; 41 goto top;
53 } 42 }
54 43
55 ERR: 44 LBL_ERR:
56 mp_clear(&q); 45 mp_clear(&q);
57 return res; 46 return err;
58 } 47 }
59 48
60 #endif 49 #endif
61
62 /* ref: $Format:%D$ */
63 /* git commit: $Format:%H$ */
64 /* commit time: $Format:%ai$ */