luaReference.h

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/*******************************************************************************
** Copyright (c) 2025 MAK Technologies
** All rights reserved.
*******************************************************************************/
 
//! \file luaReference.h
//! \ingroup vreUtil
//! \brief Provides a reference counting mechanism for Lua objects
//!
//! This file defines the DtLuaReference class which manages references to Lua objects
//! through the Lua registry. It automatically handles reference counting to ensure
//! proper cleanup of Lua objects when they are no longer needed.
 
#pragma once
 
#include "vreUtil/export.h"
 
struct lua_State;
 
namespace makVre
{
//! \brief Manages references to Lua objects through the Lua registry
//!
//! This class creates and manages references to Lua objects in the Lua registry.
//! It provides reference counting to ensure objects are properly cleaned up when
//! they are no longer needed by any C++ code.
class UTIL_DLL DtLuaReference
{
public:
   //! \brief Constructor that creates a reference to a Lua object
   //! \param s The Lua state containing the object
   //! \param index Index of the object on the Lua stack to reference
   //!
   //! Creates a new reference to the Lua object at the given stack index
   //! and stores it in the Lua registry.
   DtLuaReference(lua_State& s, int index);
 
   //! \brief Destructor
   //!
   //! Removes the reference from the Lua registry if this is the last
   //! C++ object referring to it.
   ~DtLuaReference();
 
   //! \brief Gets the Lua registry reference value
   //! \return The reference value in the Lua registry
   int value() { return myRef; }
 
   //! \brief Increments the reference count
   //!
   //! Called when another C++ object starts using this reference.
   void inc() { myRefCount++; }
 
   //! \brief Decrements the reference count
   //!
   //! Called when a C++ object stops using this reference.
   //! If the reference count reaches zero, the Lua reference is released.
   void dec();
 
private:
   //! \brief Copy constructor (private, not implemented)
   //!
   //! References should not be copied directly; instead, increment the reference count.
   DtLuaReference(const DtLuaReference& src);
 
   //! \brief Assignment operator (private, not implemented)
   //!
   //! References should not be assigned directly; instead, use reference counting.
   const DtLuaReference& operator=(const DtLuaReference& src);
 
   //! \brief Reference to the Lua state
   lua_State& myState;
 
   //! \brief Number of C++ objects using this reference
   int myRefCount;
 
   //! \brief The actual reference value in the Lua registry
   int myRef;
};
 
 
} // namespace makVre