static final int EXPONENT_BIAS = 1023;

  /** The implicit 1 bit that is omitted in significands of normal doubles. */
  static final long IMPLICIT_BIT = SIGNIFICAND_MASK + 1;

  static long getSignificand(double d) {
    checkArgument(isFinite(d), "not a normal value");
    int exponent = getExponent(d);
    long bits = doubleToRawLongBits(d);
    bits &= SIGNIFICAND_MASK;

          }
          // halfway between the representable values; do the half-whatever logic
          switch (mode) {
            case HALF_EVEN:
              return ((DoubleUtils.getSignificand(roundFloorAsDouble) & 1L) == 0)
                  ? roundFloorAsDouble
                  : roundCeilingAsDouble;
            case HALF_DOWN:
              return (x >= 0) ? roundFloorAsDouble : roundCeilingAsDouble;