Mercurial > dropbear

comparison libtommath/bn_mp_gcd.c @ 1733:d529a52b2f7c coverity coverity

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
merge coverity from main
author Matt Johnston <matt@ucc.asn.au>
date Fri, 26 Jun 2020 21:07:34 +0800
parents 1051e4eea25a
children
comparison
equal deleted inserted replaced
1643:b59623a64678 1733:d529a52b2f7c
1 #include <tommath_private.h> 1 #include "tommath_private.h"
2 #ifdef BN_MP_GCD_C 2 #ifdef BN_MP_GCD_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 /* Greatest Common Divisor using the binary method */ 6 /* Greatest Common Divisor using the binary method */
19 int mp_gcd (mp_int * a, mp_int * b, mp_int * c) 7 mp_err mp_gcd(const mp_int *a, const mp_int *b, mp_int *c)
20 { 8 {
21 mp_int u, v; 9 mp_int u, v;
22 int k, u_lsb, v_lsb, res; 10 int k, u_lsb, v_lsb;
11 mp_err err;
23 12
24 /* either zero than gcd is the largest */ 13 /* either zero than gcd is the largest */
25 if (mp_iszero (a) == MP_YES) { 14 if (MP_IS_ZERO(a)) {
26 return mp_abs (b, c); 15 return mp_abs(b, c);
27 } 16 }
28 if (mp_iszero (b) == MP_YES) { 17 if (MP_IS_ZERO(b)) {
29 return mp_abs (a, c); 18 return mp_abs(a, c);
30 } 19 }
31 20
32 /* get copies of a and b we can modify */ 21 /* get copies of a and b we can modify */
33 if ((res = mp_init_copy (&u, a)) != MP_OKAY) { 22 if ((err = mp_init_copy(&u, a)) != MP_OKAY) {
34 return res; 23 return err;
35 } 24 }
36 25
37 if ((res = mp_init_copy (&v, b)) != MP_OKAY) { 26 if ((err = mp_init_copy(&v, b)) != MP_OKAY) {
38 goto LBL_U; 27 goto LBL_U;
39 } 28 }
40 29
41 /* must be positive for the remainder of the algorithm */ 30 /* must be positive for the remainder of the algorithm */
42 u.sign = v.sign = MP_ZPOS; 31 u.sign = v.sign = MP_ZPOS;
43 32
44 /* B1. Find the common power of two for u and v */ 33 /* B1. Find the common power of two for u and v */
45 u_lsb = mp_cnt_lsb(&u); 34 u_lsb = mp_cnt_lsb(&u);
46 v_lsb = mp_cnt_lsb(&v); 35 v_lsb = mp_cnt_lsb(&v);
47 k = MIN(u_lsb, v_lsb); 36 k = MP_MIN(u_lsb, v_lsb);
48 37
49 if (k > 0) { 38 if (k > 0) {
50 /* divide the power of two out */ 39 /* divide the power of two out */
51 if ((res = mp_div_2d(&u, k, &u, NULL)) != MP_OKAY) { 40 if ((err = mp_div_2d(&u, k, &u, NULL)) != MP_OKAY) {
52 goto LBL_V; 41 goto LBL_V;
53 } 42 }
54 43
55 if ((res = mp_div_2d(&v, k, &v, NULL)) != MP_OKAY) { 44 if ((err = mp_div_2d(&v, k, &v, NULL)) != MP_OKAY) {
56 goto LBL_V; 45 goto LBL_V;
57 } 46 }
58 } 47 }
59 48
60 /* divide any remaining factors of two out */ 49 /* divide any remaining factors of two out */
61 if (u_lsb != k) { 50 if (u_lsb != k) {
62 if ((res = mp_div_2d(&u, u_lsb - k, &u, NULL)) != MP_OKAY) { 51 if ((err = mp_div_2d(&u, u_lsb - k, &u, NULL)) != MP_OKAY) {
63 goto LBL_V; 52 goto LBL_V;
64 } 53 }
65 } 54 }
66 55
67 if (v_lsb != k) { 56 if (v_lsb != k) {
68 if ((res = mp_div_2d(&v, v_lsb - k, &v, NULL)) != MP_OKAY) { 57 if ((err = mp_div_2d(&v, v_lsb - k, &v, NULL)) != MP_OKAY) {
69 goto LBL_V; 58 goto LBL_V;
70 } 59 }
71 } 60 }
72 61
73 while (mp_iszero(&v) == MP_NO) { 62 while (!MP_IS_ZERO(&v)) {
74 /* make sure v is the largest */ 63 /* make sure v is the largest */
75 if (mp_cmp_mag(&u, &v) == MP_GT) { 64 if (mp_cmp_mag(&u, &v) == MP_GT) {
76 /* swap u and v to make sure v is >= u */ 65 /* swap u and v to make sure v is >= u */
77 mp_exch(&u, &v); 66 mp_exch(&u, &v);
78 } 67 }
79
80 /* subtract smallest from largest */
81 if ((res = s_mp_sub(&v, &u, &v)) != MP_OKAY) {
82 goto LBL_V;
83 }
84
85 /* Divide out all factors of two */
86 if ((res = mp_div_2d(&v, mp_cnt_lsb(&v), &v, NULL)) != MP_OKAY) {
87 goto LBL_V;
88 }
89 }
90 68
91 /* multiply by 2**k which we divided out at the beginning */ 69 /* subtract smallest from largest */
92 if ((res = mp_mul_2d (&u, k, c)) != MP_OKAY) { 70 if ((err = s_mp_sub(&v, &u, &v)) != MP_OKAY) {
93 goto LBL_V; 71 goto LBL_V;
94 } 72 }
95 c->sign = MP_ZPOS; 73
96 res = MP_OKAY; 74 /* Divide out all factors of two */
97 LBL_V:mp_clear (&u); 75 if ((err = mp_div_2d(&v, mp_cnt_lsb(&v), &v, NULL)) != MP_OKAY) {
98 LBL_U:mp_clear (&v); 76 goto LBL_V;
99 return res; 77 }
78 }
79
80 /* multiply by 2**k which we divided out at the beginning */
81 if ((err = mp_mul_2d(&u, k, c)) != MP_OKAY) {
82 goto LBL_V;
83 }
84 c->sign = MP_ZPOS;
85 err = MP_OKAY;
86 LBL_V:
87 mp_clear(&u);
88 LBL_U:
89 mp_clear(&v);
90 return err;
100 } 91 }
101 #endif 92 #endif
102
103 /* ref: $Format:%D$ */
104 /* git commit: $Format:%H$ */
105 /* commit time: $Format:%ai$ */