Torque2D/engine/source/messaging/message.h

//-----------------------------------------------------------------------------
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/*
** Alive and Ticking
** (c) Copyright 2006 Burnt Wasp
**     All Rights Reserved.
**
** Filename:    messageQueue.h
** Author:      Tom Bampton
** Created:     19/8/2006
** Purpose:
**   Message
**
*/

#include "sim/simBase.h"
#include "network/netConnection.h"

#ifndef _MESSAGE_H_
#define _MESSAGE_H_

// Forward Refs
class MessageQueue;

/// @addtogroup msgsys Message System
///
/// Most of the message system docs are currently just stubs and will
/// be fleshed out soon.
///
// @{

//////////////////////////////////////////////////////////////////////////
// Message Base Class
//////////////////////////////////////////////////////////////////////////

//////////////////////////////////////////////////////////////////////////
/// @brief Base class for messages
/// 
/// Message is the base class for C++ defined messages, and may also be used
/// in script for script defined messages if no C++ subclass is appropriate.
///
/// Messages are reference counted and will be automatically deleted when
/// their reference count reaches zero. When you dispatch a message, a
/// reference will be added before the dispatch and freed after the dispatch.
/// This allows for temporary messages with no additional code. If you want
/// to keep the message around, for example to dispatch it to multiple
/// queues, call addReference() before dispatching it and freeReference()
/// when you are done with it. Never delete a Message object directly
/// unless addReference() has not been called or the message has not been
/// dispatched.
///
/// Message IDs are pooled similarly to datablocks, with the exception that
/// IDs are reused. If you keep a message for longer than a single dispatch,
/// then you should ensure that you clear any script variables that refer
/// to it after the last freeReference(). If you don't, then it is probable
/// that the object ID will become valid again in the future and could cause
/// hard to track down bugs.
///
/// Messages have a unique type to simplify message handling code. For object
/// messages, the type is defined as either the script defined class name
/// or the C++ class name if no script class was defined. The message type
/// may be obtained through the getType() method.
///
/// By convention, any data for the message is held in script accessible
/// fields. Messages that need to be handled in C++ as well as script
/// provide the relevant data through persistent fields in a subclass of
/// Message to provide best performance on the C++ side. Script defined
/// messages usually their through dynamic fields, and may be accessed in 
/// C++ using the SimObject::getDataField() method.
//////////////////////////////////////////////////////////////////////////
class Message : public SimObject
{
   typedef SimObject Parent;

private:
   /// Current reference count
   S32 mRefCount;

public:
   Message();
   DECLARE_CONOBJECT(Message);

   //////////////////////////////////////////////////////////////////////////
   /// @brief Obtain next available #SimObjectId for messages
   ///
   /// This is used in combination with the newmsg script operator to provide
   /// ID pooling for messages and works similarly to datablock IDs.
   ///
   /// By default, the 64 IDs following the datablock IDs are used for messages.
   /// As message objects generally have a short life time this prevents them
   /// from eating object IDs as if they haven't eaten for a year.
   ///
   /// Note that unlike SimObjects and datablocks, Messages IDs are re-used.
   /// If you store a message object in script and do not clear the variable
   /// containing the object ID after freeing the message, it is probable that
   /// the object ID will become valid again.
   /// 
   /// @return Next available SimObjectId
   //////////////////////////////////////////////////////////////////////////
   static SimObjectId getNextMessageID();


   //////////////////////////////////////////////////////////////////////////
   /// @brief Get the type of the message
   ///
   /// The message type is either the script class name or the C++ class name
   /// if it has not been overridden in script. This allows easy identification
   /// of message types with minimum effort.
   /// 
   /// @return Type of message
   //////////////////////////////////////////////////////////////////////////
   const char *getType();

   //////////////////////////////////////////////////////////////////////////
   /// @brief Add a reference to the reference count of this message
   ///
   /// Use freeReference() to free the reference when you are done with it.
   /// 
   /// @see freeReference()
   //////////////////////////////////////////////////////////////////////////
   void addReference();

   //////////////////////////////////////////////////////////////////////////
   /// @brief Free a reference to this message
   /// 
   /// @see addReference()
   //////////////////////////////////////////////////////////////////////////
   void freeReference();
};

// @}

#endif // _MESSAGE_H_