code: public static Double decodeDoubleObjDesc(byte[] src, int srcOffset)
          throws CorruptEncodingException
      {
          long bits = DataDecoder.decodeDoubleBits(src, srcOffset);
          if (bits >= 0) {
              bits ^= 0x7fffffffffffffffL;
          }
          return bits == 0x7fffffffffffffffL ? null : Double.longBitsToDouble(bits);
      }
docs: Decodes a Double object from exactly 8 bytes.
  
  @param src source of encoded bytes
  @param srcOffset offset into source array
  @return Double object or null