summaryrefslogtreecommitdiffstats
path: root/libtommath/bn_mp_mod.c
blob: 9f70026372929d6e3dd55bfe7fc419934116d20b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
#include <tommath.h>
#ifdef BN_MP_MOD_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis
 *
 * LibTomMath is a library that provides multiple-precision
 * integer arithmetic as well as number theoretic functionality.
 *
 * The library was designed directly after the MPI library by
 * Michael Fromberger but has been written from scratch with
 * additional optimizations in place.
 *
 * The library is free for all purposes without any express
 * guarantee it works.
 *
 * Tom St Denis, tomstdenis@gmail.com, http://libtom.org
 */

/* c = a mod b, 0 <= c < b */
int mp_mod(mp_int * a, mp_int * b, mp_int * c)
{
	mp_int t;
	int res;

	if ((res = mp_init(&t)) != MP_OKAY) {
		return res;
	}

	if ((res = mp_div(a, b, NULL, &t)) != MP_OKAY) {
		mp_clear(&t);
		return res;
	}

	if (t.sign != b->sign) {
		res = mp_add(b, &t, c);
	} else {
		res = MP_OKAY;
		mp_exch(&t, c);
	}

	mp_clear(&t);
	return res;
}
#endif

/* $Source: /cvs/libtom/libtommath/bn_mp_mod.c,v $ */
/* $Revision: 1.4 $ */
/* $Date: 2006/12/28 01:25:13 $ */