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comparison libtommath/bn_mp_lcm.c @ 284:eed26cff980b

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propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583) to branch 'au.asn.ucc.matt.dropbear' (head fff0894a0399405a9410ea1c6d118f342cf2aa64)
author Matt Johnston <matt@ucc.asn.au>
date Wed, 08 Mar 2006 13:23:49 +0000
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children 5ff8218bcee9
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283:bd240aa12ba7 284:eed26cff980b
1 #include <tommath.h>
2 #ifdef BN_MP_LCM_C
3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
4 *
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://math.libtomcrypt.org
16 */
17
18 /* computes least common multiple as |a*b|/(a, b) */
19 int mp_lcm (mp_int * a, mp_int * b, mp_int * c)
20 {
21 int res;
22 mp_int t1, t2;
23
24
25 if ((res = mp_init_multi (&t1, &t2, NULL)) != MP_OKAY) {
26 return res;
27 }
28
29 /* t1 = get the GCD of the two inputs */
30 if ((res = mp_gcd (a, b, &t1)) != MP_OKAY) {
31 goto LBL_T;
32 }
33
34 /* divide the smallest by the GCD */
35 if (mp_cmp_mag(a, b) == MP_LT) {
36 /* store quotient in t2 such that t2 * b is the LCM */
37 if ((res = mp_div(a, &t1, &t2, NULL)) != MP_OKAY) {
38 goto LBL_T;
39 }
40 res = mp_mul(b, &t2, c);
41 } else {
42 /* store quotient in t2 such that t2 * a is the LCM */
43 if ((res = mp_div(b, &t1, &t2, NULL)) != MP_OKAY) {
44 goto LBL_T;
45 }
46 res = mp_mul(a, &t2, c);
47 }
48
49 /* fix the sign to positive */
50 c->sign = MP_ZPOS;
51
52 LBL_T:
53 mp_clear_multi (&t1, &t2, NULL);
54 return res;
55 }
56 #endif