annotate bn_mp_lcm.c @ 1:22d5cf7d4b1a libtommath

Renaming branch
author Matt Johnston <matt@ucc.asn.au>
date Mon, 31 May 2004 18:23:46 +0000
parents
children d29b64170cf0
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
1
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
1 /* LibTomMath, multiple-precision integer library -- Tom St Denis
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
2 *
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
3 * LibTomMath is a library that provides multiple-precision
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
4 * integer arithmetic as well as number theoretic functionality.
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
5 *
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
6 * The library was designed directly after the MPI library by
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
7 * Michael Fromberger but has been written from scratch with
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
8 * additional optimizations in place.
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
9 *
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
10 * The library is free for all purposes without any express
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
11 * guarantee it works.
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
12 *
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
13 * Tom St Denis, [email protected], http://math.libtomcrypt.org
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
14 */
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
15 #include <tommath.h>
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
16
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
17 /* computes least common multiple as |a*b|/(a, b) */
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
18 int mp_lcm (mp_int * a, mp_int * b, mp_int * c)
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
19 {
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
20 int res;
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
21 mp_int t1, t2;
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
22
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
23
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
24 if ((res = mp_init_multi (&t1, &t2, NULL)) != MP_OKAY) {
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
25 return res;
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
26 }
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
27
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
28 /* t1 = get the GCD of the two inputs */
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
29 if ((res = mp_gcd (a, b, &t1)) != MP_OKAY) {
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
30 goto __T;
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
31 }
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
32
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
33 /* divide the smallest by the GCD */
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
34 if (mp_cmp_mag(a, b) == MP_LT) {
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
35 /* store quotient in t2 such that t2 * b is the LCM */
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
36 if ((res = mp_div(a, &t1, &t2, NULL)) != MP_OKAY) {
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
37 goto __T;
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
38 }
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
39 res = mp_mul(b, &t2, c);
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
40 } else {
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
41 /* store quotient in t2 such that t2 * a is the LCM */
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
42 if ((res = mp_div(b, &t1, &t2, NULL)) != MP_OKAY) {
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
43 goto __T;
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
44 }
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
45 res = mp_mul(a, &t2, c);
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
46 }
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
47
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
48 /* fix the sign to positive */
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
49 c->sign = MP_ZPOS;
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
50
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
51 __T:
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
52 mp_clear_multi (&t1, &t2, NULL);
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
53 return res;
22d5cf7d4b1a Renaming branch
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
54 }