1 /*	$NetBSD: bn_mp_reduce_2k_setup.c,v 1.1.1.1 2011/04/13 18:14:54 elric 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 */
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