fix issue 7

rdpy/network/type.py

@@ -463,7 +463,8 @@ class CompositeType(Type):
                 if not self._readLen is None and readLen > self._readLen.value:
                     #roll back
                     s.pos -= sizeof(self.__dict__[name])
-                    #and notify
+                    #and notify if not optional
+                    if not self.__dict__[name]._optional:
                         raise InvalidSize("Impossible to read type %s : read length is too small"%(self.__class__))
                 
             except Exception as e: