//Sets a = b / c, where a and c are digits.
//Lengths: b[2].
//Assumes b[1] < c and HIGH_HALF (c) > 0. For efficiency, c should be normalized.
void NN_DigitDiv (NN_DIGIT *a, NN_DIGIT b[2], NN_DIGIT c)
{
  NN_DIGIT t_h, t_l, u, v, aHigh, aLow;

  t_l = b[0];
  t_h = b[1];

  //Underestimate high half of quotient and subtract.
  if ((c >> 16) == 0x0000ffff) aHigh = (t_h >> 16);
                          else aHigh = ((t_h / ((c >> 16) + 1)) & 0x0000ffff);
  u = aHigh * (c & 0x0000ffff);
  v = aHigh * (c >> 16);
  if ((u << 16) > t_l) t_h--;
  t_l -= (u << 16);
  t_h -= (u >> 16);
  t_h -= v;

  //Correct estimate.
  while ((t_h > (c >> 16)) || ((t_h == (c >> 16)) && (t_l >= (c << 16)))){
    if ((c << 16) > t_l) t_h--;
    t_l -= (c << 16);
    t_h -= (c >> 16);
    aHigh = ((aHigh + 1) & 0x0000ffff);
                                                                         }
  //Underestimate low half of quotient and subtract.
  if ((c >> 16) == 0x0000ffff) aLow = (t_h & 0x0000ffff);
  else aLow = ((((t_h << 16) + (t_l >> 16)) / ((c >> 16) + 1)) & 0x0000ffff);
  u = aLow * (c & 0x0000ffff);
  v = aLow * (c >> 16);
  if (u > t_l) t_h--;
  t_l -= u;
  if ((v << 16) > t_l) t_h--;
  t_l -= (v << 16);
  t_h -= (v >> 16);

  //Correct estimate.
  while ((t_h > 0) || ((t_h == 0) && t_l >= c)) {if (c > t_l) t_h--;
                                                 t_l -= c;
                                                 aLow = ((aLow + 1) & 0x0000ffff);
                                                }
  *a = ((aHigh << 16) + aLow);
}