Integrating Lua into C++

// ---------------------------------------------------------------------------
// FILE NAME            : LuaThis.h
// ---------------------------------------------------------------------------
// DESCRIPTION :
//
// Controls the "this" table
// 
// ---------------------------------------------------------------------------
// VERSION              : 1.01
// DATE                 : 1-Sep-2005
// AUTHOR               : Richard Shephard
// ---------------------------------------------------------------------------
// LIBRARY INCLUDE FILES
#ifndef __LUA_THIS_H__
#define __LUA_THIS_H__

#include "lualib/luainc.h"
#include "luavirtualmachine.h"

// Sets the "this" global table that scripts use

class CLuaThis
{
public:
   CLuaThis (CLuaVirtualMachine& vm, int iRef) : m_iOldRef (0), m_vm (vm)
   {
      lua_State *state = (lua_State *) vm;
      if (vm.Ok ())
      {
         // Save the old "this" table
         lua_getglobal (state, "this");
         m_iOldRef = luaL_ref (state, LUA_REGISTRYINDEX);

         // replace it with our new one
         lua_rawgeti(state, LUA_REGISTRYINDEX, iRef);
         lua_setglobal (state, "this");
      }
   }

   virtual ~CLuaThis (void)
   {
      lua_State *state = (lua_State *) m_vm;
      if (m_iOldRef > 0 && m_vm.Ok ())
      {
         // Replace the old "this" table
         lua_rawgeti(state, LUA_REGISTRYINDEX, m_iOldRef);
         lua_setglobal (state, "this");
         luaL_unref (state, LUA_REGISTRYINDEX, m_iOldRef);
      }
   }


protected:
   int m_iOldRef;
   CLuaVirtualMachine& m_vm;
};

#endif // __LUA_THIS_H__