1#include <tommath.h>
2#ifdef BN_MP_REDUCE_2K_SETUP_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, tomstdenis@gmail.com, http://libtom.org
16 */
17
18/* determines the setup value */
19int mp_reduce_2k_setup(mp_int *a, mp_digit *d)
20{
21   int res, p;
22   mp_int tmp;
23
24   if ((res = mp_init(&tmp)) != MP_OKAY) {
25      return res;
26   }
27
28   p = mp_count_bits(a);
29   if ((res = mp_2expt(&tmp, p)) != MP_OKAY) {
30      mp_clear(&tmp);
31      return res;
32   }
33
34   if ((res = s_mp_sub(&tmp, a, &tmp)) != MP_OKAY) {
35      mp_clear(&tmp);
36      return res;
37   }
38
39   *d = tmp.dp[0];
40   mp_clear(&tmp);
41   return MP_OKAY;
42}
43#endif
44
45/* $Source$ */
46/* $Revision$ */
47/* $Date$ */
48