crypto/external/bsd/heimdal/dist/lib/hcrypto/libtommath/bn_mp_2expt.c

   1 /*      $NetBSD: bn_mp_2expt.c,v 1.1.1.2 2014/04/24 12:45:31 pettai Exp $       */
   2
   3 #include <tommath.h>
   4 #ifdef BN_MP_2EXPT_C
   5 /* LibTomMath, multiple-precision integer library -- Tom St Denis
   6  *
   7  * LibTomMath is a library that provides multiple-precision
   8  * integer arithmetic as well as number theoretic functionality.
   9  *
  10  * The library was designed directly after the MPI library by
  11  * Michael Fromberger but has been written from scratch with
  12  * additional optimizations in place.
  13  *
  14  * The library is free for all purposes without any express
  15  * guarantee it works.
  16  *
  17  * Tom St Denis, tomstdenis@gmail.com, http://libtom.org
  18  */
  19
  20 /* computes a = 2**b
  21  *
  22  * Simple algorithm which zeroes the int, grows it then just sets one bit
  23  * as required.
  24  */
  25 int
  26 mp_2expt (mp_int * a, int b)
  27 {
  28   int     res;
  29
  30   /* zero a as per default */
  31   mp_zero (a);
  32
  33   /* grow a to accomodate the single bit */
  34   if ((res = mp_grow (a, b / DIGIT_BIT + 1)) != MP_OKAY) {
  35     return res;
  36   }
  37
  38   /* set the used count of where the bit will go */
  39   a->used = b / DIGIT_BIT + 1;
  40
  41   /* put the single bit in its place */
  42   a->dp[b / DIGIT_BIT] = ((mp_digit)1) << (b % DIGIT_BIT);
  43
  44   return MP_OKAY;
  45 }
  46 #endif
  47
  48 /* Source: /cvs/libtom/libtommath/bn_mp_2expt.c,v  */
  49 /* Revision: 1.4  */
  50 /* Date: 2006/12/28 01:25:13  */