code: @VisibleForTesting
      static double longToDoubleFraction(long value) {
          long shifted = (value >> 12) & MASK;
          return Double.longBitsToDouble(LEADING_BITS + shifted) - 1;
      }
docs: Turns the leading 54 bits of a long into a double between 0 and 1.
  
  @param value The input.