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kc3-lang/libtommath/bn_mp_div_2.c

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  • Author : Tom St Denis
    Date : 2003-02-28 16:08:34
    Hash : 57354e11
    Message : added libtommath-0.12

  • bn_mp_div_2.c
  • /* LibTomMath, multiple-precision integer library -- Tom St Denis
     *
     * LibTomMath is library that provides for multiple-precision
     * integer arithmetic as well as number theoretic functionality.
     *
     * The library is 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, tomstdenis@iahu.ca, http://libtommath.iahu.ca
     */
    #include <tommath.h>
    
    /* b = a/2 */
    int
    mp_div_2 (mp_int * a, mp_int * b)
    {
      mp_digit  r, rr;
      int       x, res;
    
    
      /* copy */
      if ((res = mp_copy (a, b)) != MP_OKAY) {
        return res;
      }
    
      r = 0;
      for (x = b->used - 1; x >= 0; x--) {
        rr = b->dp[x] & 1;
        b->dp[x] = (b->dp[x] >> 1) | (r << (DIGIT_BIT - 1));
        r = rr;
      }
      mp_clamp (b);
      return MP_OKAY;
    }