libs/libtommath/bn_mp_set_int.c

   1 #include <tommath.h>
   2 #ifdef BN_MP_SET_INT_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 /* set a 32-bit const */
  19 int mp_set_int (mp_int * a, unsigned long b)
  20 {
  21   int     x, res;
  22
  23   mp_zero (a);
  24
  25   /* set four bits at a time */
  26   for (x = 0; x < 8; x++) {
  27     /* shift the number up four bits */
  28     if ((res = mp_mul_2d (a, 4, a)) != MP_OKAY) {
  29       return res;
  30     }
  31
  32     /* OR in the top four bits of the source */
  33     a->dp[0] |= (b >> 28) & 15;
  34
  35     /* shift the source up to the next four bits */
  36     b <<= 4;
  37
  38     /* ensure that digits are not clamped off */
  39     a->used += 1;
  40   }
  41   mp_clamp (a);
  42   return MP_OKAY;
  43 }
  44 #endif
  45
  46 /* $Source: /cvs/libtom/libtommath/bn_mp_set_int.c,v $ */
  47 /* $Revision: 1.4 $ */
  48 /* $Date: 2006/12/28 01:25:13 $ */