Mercurial > dropbear

comparison tomsfastmath/src/numtheory/fp_gcd.c @ 643:a362b62d38b2 dropbear-tfm

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Add tomsfastmath from git rev bfa4582842bc3bab42e4be4aed5703437049502a with Makefile.in renamed
author Matt Johnston <matt@ucc.asn.au>
date Wed, 23 Nov 2011 18:10:20 +0700
parents
children
comparison
equal deleted inserted replaced
642:33fd2f3499d2 643:a362b62d38b2
1 /* TomsFastMath, a fast ISO C bignum library.
2 *
3 * This project is meant to fill in where LibTomMath
4 * falls short. That is speed ;-)
5 *
6 * This project is public domain and free for all purposes.
7 *
8 * Tom St Denis, [email protected]
9 */
10 #include <tfm.h>
11
12 /* c = (a, b) */
13 void fp_gcd(fp_int *a, fp_int *b, fp_int *c)
14 {
15 fp_int u, v, r;
16
17 /* either zero than gcd is the largest */
18 if (fp_iszero (a) == 1 && fp_iszero (b) == 0) {
19 fp_abs (b, c);
20 return;
21 }
22 if (fp_iszero (a) == 0 && fp_iszero (b) == 1) {
23 fp_abs (a, c);
24 return;
25 }
26
27 /* optimized. At this point if a == 0 then
28 * b must equal zero too
29 */
30 if (fp_iszero (a) == 1) {
31 fp_zero(c);
32 return;
33 }
34
35 /* sort inputs */
36 if (fp_cmp_mag(a, b) != FP_LT) {
37 fp_init_copy(&u, a);
38 fp_init_copy(&v, b);
39 } else {
40 fp_init_copy(&u, b);
41 fp_init_copy(&v, a);
42 }
43
44 fp_zero(&r);
45 while (fp_iszero(&v) == FP_NO) {
46 fp_mod(&u, &v, &r);
47 fp_copy(&v, &u);
48 fp_copy(&r, &v);
49 }
50 fp_copy(&u, c);
51 }
52
53 /* $Source$ */
54 /* $Revision$ */
55 /* $Date$ */