1 /* $NetBSD: bn_mp_reduce_2k_setup.c,v 1.1.1.2 2014/04/24 12:45:31 pettai Exp $ */
2
3 #include <tommath.h>
4 #ifdef BN_MP_REDUCE_2K_SETUP_C
5 /* LibTomMath, multiple-precision integer library -- Tom St Denis
6 *
7 * LibTomMath is a library that provides multiple-precision
8 * integer arithmetic as well as number theoretic functionality.
9 *
10 * The library was designed directly after the MPI library by
11 * Michael Fromberger but has been written from scratch with
12 * additional optimizations in place.
13 *
14 * The library is free for all purposes without any express
15 * guarantee it works.
16 *
17 * Tom St Denis, tomstdenis@gmail.com, http://libtom.org
18 */
19
20 /* determines the setup value */
mp_reduce_2k_setup(mp_int * a,mp_digit * d)21 int mp_reduce_2k_setup(mp_int *a, mp_digit *d)
22 {
23 int res, p;
24 mp_int tmp;
25
26 if ((res = mp_init(&tmp)) != MP_OKAY) {
27 return res;
28 }
29
30 p = mp_count_bits(a);
31 if ((res = mp_2expt(&tmp, p)) != MP_OKAY) {
32 mp_clear(&tmp);
33 return res;
34 }
35
36 if ((res = s_mp_sub(&tmp, a, &tmp)) != MP_OKAY) {
37 mp_clear(&tmp);
38 return res;
39 }
40
41 *d = tmp.dp[0];
42 mp_clear(&tmp);
43 return MP_OKAY;
44 }
45 #endif
46
47 /* Source: /cvs/libtom/libtommath/bn_mp_reduce_2k_setup.c,v */
48 /* Revision: 1.4 */
49 /* Date: 2006/12/28 01:25:13 */
50