void fp_mul_d(fp_int *a, fp_digit b, fp_int *c)
{
   fp_word  w;
   int      x, oldused;

   oldused = c->used;
   c->used = a->used;
   c->sign = a->sign;
   w       = 0;
   for (x = 0; x < a->used; x++) {
       w         = ((fp_word)a->dp[x]) * ((fp_word)b) + w;
       c->dp[x]  = (fp_digit)w;
       w         = w >> DIGIT_BIT;
   }
   if (w != 0 && (a->used != FP_SIZE)) {
      c->dp[c->used++] = (fp_digit) w;
      ++x;
   }

   /* zero any excess digits on the destination that we didn't write to */
   /* also checking FP_SIZE here for static analysis */
   for (; x < oldused && x < FP_SIZE; x++) {
      c->dp[x] = 0;
   }
   fp_clamp(c);
}
void fp_mul_d(fp_int *a, fp_digit b, fp_int *c)
{
   fp_word  w;
   int      x, oldused;

   oldused = c->used;
   c->used = a->used;
   c->sign = a->sign;
   w       = 0;
   for (x = 0; x < a->used; x++) {
       w         = ((fp_word)a->dp[x]) * ((fp_word)b) + w;
       c->dp[x]  = (fp_digit)w;
       w         = w >> DIGIT_BIT;
   }
   if (w != 0 && (a->used != FP_SIZE)) {
      c->dp[c->used++] = (fp_digit) w;
      ++x;
   }

    
    
   for (; x < oldused && x < FP_SIZE; x++) {
      c->dp[x] = 0;
   }
   fp_clamp(c);
}