release/src/router/dropbear/libtommath/bn_mp_reduce_2k_setup.c

   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://math.libtomcrypt.com
  16  */
  17
  18 /* determines the setup value */
  19 int 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: /cvs/libtom/libtommath/bn_mp_reduce_2k_setup.c,v $ */
  46 /* $Revision: 1.3 $ */
  47 /* $Date: 2006/03/31 14:18:44 $ */