libs/libtommath/bn_mp_get_int.c

   1 #include <tommath.h>
   2 #ifdef BN_MP_GET_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 /* get the lower 32-bits of an mp_int */
  19 unsigned long mp_get_int(mp_int * a)
  20 {
  21   int i;
  22   unsigned long res;
  23
  24   if (a->used == 0) {
  25      return 0;
  26   }
  27
  28   /* get number of digits of the lsb we have to read */
  29   i = MIN(a->used,(int)((sizeof(unsigned long)*CHAR_BIT+DIGIT_BIT-1)/DIGIT_BIT))-1;
  30
  31   /* get most significant digit of result */
  32   res = DIGIT(a,i);
  33
  34   while (--i >= 0) {
  35     res = (res << DIGIT_BIT) | DIGIT(a,i);
  36   }
  37
  38   /* force result to 32-bits always so it is consistent on non 32-bit platforms */
  39   return res & 0xFFFFFFFFUL;
  40 }
  41 #endif
  42
  43 /* $Source: /cvs/libtom/libtommath/bn_mp_get_int.c,v $ */
  44 /* $Revision: 1.4 $ */
  45 /* $Date: 2006/12/28 01:25:13 $ */