comparison libtommath/bn_mp_reduce_2k.c @ 1692:1051e4eea25a

Update LibTomMath to 1.2.0 (#84) * update C files * update other files * update headers * update makefiles * remove mp_set/get_double() * use ltm 1.2.0 API * update ltm_desc * use bundled tommath if system-tommath is too old * XMALLOC etc. were changed to MP_MALLOC etc.
author Steffen Jaeckel <s@jaeckel.eu>
date Tue, 26 May 2020 17:36:47 +0200
parents f52919ffd3b1
children
comparison
equal deleted inserted replaced
1691:2d3745d58843 1692:1051e4eea25a
1 #include "tommath_private.h" 1 #include "tommath_private.h"
2 #ifdef BN_MP_REDUCE_2K_C 2 #ifdef BN_MP_REDUCE_2K_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 * SPDX-License-Identifier: Unlicense
13 */
14 5
15 /* 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 */
16 int mp_reduce_2k(mp_int *a, const mp_int *n, mp_digit d) 7 mp_err mp_reduce_2k(mp_int *a, const mp_int *n, mp_digit d)
17 { 8 {
18 mp_int q; 9 mp_int q;
19 int p, res; 10 mp_err err;
11 int p;
20 12
21 if ((res = mp_init(&q)) != MP_OKAY) { 13 if ((err = mp_init(&q)) != MP_OKAY) {
22 return res; 14 return err;
23 } 15 }
24 16
25 p = mp_count_bits(n); 17 p = mp_count_bits(n);
26 top: 18 top:
27 /* q = a/2**p, a = a mod 2**p */ 19 /* q = a/2**p, a = a mod 2**p */
28 if ((res = mp_div_2d(a, p, &q, a)) != MP_OKAY) { 20 if ((err = mp_div_2d(a, p, &q, a)) != MP_OKAY) {
29 goto LBL_ERR; 21 goto LBL_ERR;
30 } 22 }
31 23
32 if (d != 1u) { 24 if (d != 1u) {
33 /* q = q * d */ 25 /* q = q * d */
34 if ((res = mp_mul_d(&q, d, &q)) != MP_OKAY) { 26 if ((err = mp_mul_d(&q, d, &q)) != MP_OKAY) {
35 goto LBL_ERR; 27 goto LBL_ERR;
36 } 28 }
37 } 29 }
38 30
39 /* a = a + q */ 31 /* a = a + q */
40 if ((res = s_mp_add(a, &q, a)) != MP_OKAY) { 32 if ((err = s_mp_add(a, &q, a)) != MP_OKAY) {
41 goto LBL_ERR; 33 goto LBL_ERR;
42 } 34 }
43 35
44 if (mp_cmp_mag(a, n) != MP_LT) { 36 if (mp_cmp_mag(a, n) != MP_LT) {
45 if ((res = s_mp_sub(a, n, a)) != MP_OKAY) { 37 if ((err = s_mp_sub(a, n, a)) != MP_OKAY) {
46 goto LBL_ERR; 38 goto LBL_ERR;
47 } 39 }
48 goto top; 40 goto top;
49 } 41 }
50 42
51 LBL_ERR: 43 LBL_ERR:
52 mp_clear(&q); 44 mp_clear(&q);
53 return res; 45 return err;
54 } 46 }
55 47
56 #endif 48 #endif
57
58 /* ref: HEAD -> master, tag: v1.1.0 */
59 /* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
60 /* commit time: 2019-01-28 20:32:32 +0100 */