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comparison libtommath/bn_mp_mod_2d.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
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1562:768ebf737aa0 1739:13d834efc376
1 #include <tommath_private.h> 1 #include "tommath_private.h"
2 #ifdef BN_MP_MOD_2D_C 2 #ifdef BN_MP_MOD_2D_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 /* calc a value mod 2**b */ 6 /* calc a value mod 2**b */
19 int 7 mp_err mp_mod_2d(const mp_int *a, int b, mp_int *c)
20 mp_mod_2d (mp_int * a, int b, mp_int * c)
21 { 8 {
22 int x, res; 9 int x;
10 mp_err err;
23 11
24 /* if b is <= 0 then zero the int */ 12 /* if b is <= 0 then zero the int */
25 if (b <= 0) { 13 if (b <= 0) {
26 mp_zero (c); 14 mp_zero(c);
27 return MP_OKAY; 15 return MP_OKAY;
28 } 16 }
29 17
30 /* if the modulus is larger than the value than return */ 18 /* if the modulus is larger than the value than return */
31 if (b >= (int) (a->used * DIGIT_BIT)) { 19 if (b >= (a->used * MP_DIGIT_BIT)) {
32 res = mp_copy (a, c); 20 return mp_copy(a, c);
33 return res; 21 }
34 }
35 22
36 /* copy */ 23 /* copy */
37 if ((res = mp_copy (a, c)) != MP_OKAY) { 24 if ((err = mp_copy(a, c)) != MP_OKAY) {
38 return res; 25 return err;
39 } 26 }
40 27
41 /* zero digits above the last digit of the modulus */ 28 /* zero digits above the last digit of the modulus */
42 for (x = (b / DIGIT_BIT) + (((b % DIGIT_BIT) == 0) ? 0 : 1); x < c->used; x++) { 29 x = (b / MP_DIGIT_BIT) + (((b % MP_DIGIT_BIT) == 0) ? 0 : 1);
43 c->dp[x] = 0; 30 MP_ZERO_DIGITS(c->dp + x, c->used - x);
44 } 31
45 /* clear the digit that is not completely outside/inside the modulus */ 32 /* clear the digit that is not completely outside/inside the modulus */
46 c->dp[b / DIGIT_BIT] &= 33 c->dp[b / MP_DIGIT_BIT] &=
47 (mp_digit) ((((mp_digit) 1) << (((mp_digit) b) % DIGIT_BIT)) - ((mp_digit) 1)); 34 ((mp_digit)1 << (mp_digit)(b % MP_DIGIT_BIT)) - (mp_digit)1;
48 mp_clamp (c); 35 mp_clamp(c);
49 return MP_OKAY; 36 return MP_OKAY;
50 } 37 }
51 #endif 38 #endif
52
53 /* ref: $Format:%D$ */
54 /* git commit: $Format:%H$ */
55 /* commit time: $Format:%ai$ */