'Decode bytes into an L{_OPTVariableOption} instance.
@type strio: L{file}
@param strio: Bytes will be read from this file until the full
L{_OPTVariableOption} is decoded.
@type length: L{int} or L{None}
@param length: Not used.'

def decode(self, strio, length=None):

    l = struct.calcsize(self._fmt)
    buff = readPrecisely(strio, l)
    (self.code, length) = struct.unpack(self._fmt, buff)
    self.data = readPrecisely(strio, length)
