void fp_mul_2d(fp_int *a, int b, fp_int *c)
{
   fp_digit carry, carrytmp, shift;
   int x;

   /* copy it */
   fp_copy(a, c);

   /* handle whole digits */
   if (b >= DIGIT_BIT) {
      fp_lshd(c, b/DIGIT_BIT);
   }
   b %= DIGIT_BIT;

   /* shift the digits */
   if (b != 0) {
      carry = 0;
      shift = DIGIT_BIT - b;
      for (x = 0; x < c->used; x++) {
          carrytmp = c->dp[x] >> shift;
          c->dp[x] = (c->dp[x] << b) + carry;
          carry = carrytmp;
      }
      /* store last carry if room */
      if (carry && x < FP_SIZE) {
         c->dp[c->used++] = carry;
      }
   }
   fp_clamp(c);
}
void fp_mul_2d(fp_int *a, int b, fp_int *c)
{
   fp_digit carry, carrytmp, shift;
   int x;

    
   fp_copy(a, c);

    
   if (b >= DIGIT_BIT) {
      fp_lshd(c, b/DIGIT_BIT);
   }
   b %= DIGIT_BIT;

    
   if (b != 0) {
      carry = 0;
      shift = DIGIT_BIT - b;
      for (x = 0; x < c->used; x++) {
          carrytmp = c->dp[x] >> shift;
          c->dp[x] = (c->dp[x] << b) + carry;
          carry = carrytmp;
      }
       
      if (carry && x < FP_SIZE) {
         c->dp[c->used++] = carry;
      }
   }
   fp_clamp(c);
}