view libtommath/bn_mp_reduce_2k_setup.c @ 470:271887c81c07

merge of '9879f7138f243bb2077a06e4c9ea925fa34abe2b' and 'e28650f207028a45182fc2de545b7bd218d13077'
author Matt Johnston <matt@ucc.asn.au>
date Thu, 27 Mar 2008 10:19:36 +0000
parents 5ff8218bcee9
children 60fc6476e044
line wrap: on
line source

#include <tommath.h>
#ifdef BN_MP_REDUCE_2K_SETUP_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, [email protected], http://math.libtomcrypt.com
 */

/* determines the setup value */
int mp_reduce_2k_setup(mp_int *a, mp_digit *d)
{
   int res, p;
   mp_int tmp;
   
   if ((res = mp_init(&tmp)) != MP_OKAY) {
      return res;
   }
   
   p = mp_count_bits(a);
   if ((res = mp_2expt(&tmp, p)) != MP_OKAY) {
      mp_clear(&tmp);
      return res;
   }
   
   if ((res = s_mp_sub(&tmp, a, &tmp)) != MP_OKAY) {
      mp_clear(&tmp);
      return res;
   }
   
   *d = tmp.dp[0];
   mp_clear(&tmp);
   return MP_OKAY;
}
#endif

/* $Source: /cvs/libtom/libtommath/bn_mp_reduce_2k_setup.c,v $ */
/* $Revision: 1.3 $ */
/* $Date: 2006/03/31 14:18:44 $ */