*/
      sqrt0 = sqrtApproxWithDoubles(x.shiftRight(shift)).shiftLeft(shift >> 1);
    }
    BigInteger sqrt1 = sqrt0.add(x.divide(sqrt0)).shiftRight(1);
    if (sqrt0.equals(sqrt1)) {
      return sqrt0;
    }
    do {
      sqrt0 = sqrt1;
      sqrt1 = sqrt0.add(x.divide(sqrt0)).shiftRight(1);
    } while (sqrt1.compareTo(sqrt0) < 0);
    return sqrt0;
  }

     *
     * It helps to consider the real number signif = absX * 2^(SIGNIFICAND_BITS - exponent).
     */
    int shift = exponent - SIGNIFICAND_BITS - 1;
    long twiceSignifFloor = absX.shiftRight(shift).longValue();
    long signifFloor = twiceSignifFloor >> 1;
    signifFloor &= SIGNIFICAND_MASK; // remove the implied bit

    /*

                .multiply(BigInteger.valueOf(10000L));

        byte[] data = new byte[8];
        long low = filetime.longValue();
        long high = filetime.shiftRight(32).longValue();

        // write little-endian
        data[0] = (byte) (low);
        data[1] = (byte) (low >> 8);
        data[2] = (byte) (low >> 16);
        data[3] = (byte) (low >> 24);