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comparison libtommath/bn_mp_sub.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_SUB_C 2 #ifdef BN_MP_SUB_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 /* high level subtraction (handles signs) */ 6 /* high level subtraction (handles signs) */
19 int 7 mp_err mp_sub(const mp_int *a, const mp_int *b, mp_int *c)
20 mp_sub (mp_int * a, mp_int * b, mp_int * c)
21 { 8 {
22 int sa, sb, res; 9 mp_sign sa = a->sign, sb = b->sign;
10 mp_err err;
23 11
24 sa = a->sign; 12 if (sa != sb) {
25 sb = b->sign; 13 /* subtract a negative from a positive, OR */
26 14 /* subtract a positive from a negative. */
27 if (sa != sb) { 15 /* In either case, ADD their magnitudes, */
28 /* subtract a negative from a positive, OR */ 16 /* and use the sign of the first number. */
29 /* subtract a positive from a negative. */
30 /* In either case, ADD their magnitudes, */
31 /* and use the sign of the first number. */
32 c->sign = sa;
33 res = s_mp_add (a, b, c);
34 } else {
35 /* subtract a positive from a positive, OR */
36 /* subtract a negative from a negative. */
37 /* First, take the difference between their */
38 /* magnitudes, then... */
39 if (mp_cmp_mag (a, b) != MP_LT) {
40 /* Copy the sign from the first */
41 c->sign = sa; 17 c->sign = sa;
42 /* The first has a larger or equal magnitude */ 18 err = s_mp_add(a, b, c);
43 res = s_mp_sub (a, b, c); 19 } else {
44 } else { 20 /* subtract a positive from a positive, OR */
45 /* The result has the *opposite* sign from */ 21 /* subtract a negative from a negative. */
46 /* the first number. */ 22 /* First, take the difference between their */
47 c->sign = (sa == MP_ZPOS) ? MP_NEG : MP_ZPOS; 23 /* magnitudes, then... */
48 /* The second has a larger magnitude */ 24 if (mp_cmp_mag(a, b) != MP_LT) {
49 res = s_mp_sub (b, a, c); 25 /* Copy the sign from the first */
50 } 26 c->sign = sa;
51 } 27 /* The first has a larger or equal magnitude */
52 return res; 28 err = s_mp_sub(a, b, c);
29 } else {
30 /* The result has the *opposite* sign from */
31 /* the first number. */
32 c->sign = (sa == MP_ZPOS) ? MP_NEG : MP_ZPOS;
33 /* The second has a larger magnitude */
34 err = s_mp_sub(b, a, c);
35 }
36 }
37 return err;
53 } 38 }
54 39
55 #endif 40 #endif
56
57 /* ref: $Format:%D$ */
58 /* git commit: $Format:%H$ */
59 /* commit time: $Format:%ai$ */