docs: protected void fillArray(final short[] array) {
      int pos = 0;
      int base = 0;
      for (int k = 0; k < bitmap.length; ++k) {
        long bitset = bitmap[k];
        while (bitset != 0) {
          array[pos++] = (short) (base + numberOfTrailingZeros(bitset));
          bitset &= (bitset - 1);
        }
        base += 64;
      }
    }