read/write for basic types

include/sp/protocol/MessageBase.h

@@ -1,5 +1,7 @@
 #pragma once
 
+#include <iosfwd>
+
 namespace sp {
 
 template <typename TMessageID, typename THandler>
@@ -14,6 +16,9 @@ class MessageBase {
 	virtual MessageIdType GetId() const = 0;
 
 	virtual void Dispatch(HandlerType& handler) const = 0;
+
+	virtual void Read(std::istream& a_Is) = 0;
+	virtual void Write(std::ostream& a_Os) const = 0;
 };
 
 }  // namespace sp