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Dynamic binding of an Interface from a Dynamic loaded DLL

Dynamic binding of an Interface from a Dynamic loaded DLL

class IRenderer
{
public:
	virtual ~IRenderer( ) { }

	virtual int Init( int ) = 0; 
};

 
//DLL Header:  DllName.h


#ifdef DLLNAME_EXPORTS 
# define CLASS_DECLSPEC __declspec(dllexport) 
#else 
# define CLASS_DECLSPEC __declspec(dllimport) 
#endif

#include "RendererInterface.h"

template<class T>
class TSingleton
{
private:
	static T* object;
	static int refcount;
public:
	TSingleton( ) { if( !refcount++ ) object = new T; }
	~TSingleton( ) { if( !--refcount ) { delete object; object = NULL; } }
	const T& GetObject( ) { return *object; }
	static void* operator new( size_t ) { return NULL; }
	static void* operator new[]( size_t ) { return NULL; }
	static const int& RefCount( ) { return refcount; }
};

template<class T>T* TSingleton<T>::object = NULL;
template<class T>int TSingleton<T>::refcount = 0;

class CD3d : public IRenderer
{
public:
	virtual 	~CD3d( ) { }
	virtual int	Init( int );
  
};

int CD3d::Init( int i )
{
	return ++i;
}
 

//DLL Source:  DllName.cpp

static bool wasCreated = false;
extern "C" 
{	
	CLASS_DECLSPEC IRenderer* __cdecl CreateInstance( )
	{
		static TSingleton<CD3d> d3d; 		
		wasCreated = true;		
		return const_cast<CD3d*>( &d3d.GetObject( ) );
	}
 			
	CLASS_DECLSPEC IRenderer* __cdecl GetInstance( ) 
	{ 
		assert( false !=  wasCreated ); 
		TSingleton<CD3d> d3d; 
		return const_cast<CD3d*>( &d3d.GetObject( ) );  
	} 
}

BOOL APIENTRY DllMain( HANDLE hModule, DWORD ul_reason_for_call, LPVOID lpReserved )
{
	switch (ul_reason_for_call)
	{
	case DLL_PROCESS_ATTACH:
		break; 
	case DLL_THREAD_ATTACH: 
		break; 
	case DLL_THREAD_DETACH: 
		break; 
	case DLL_PROCESS_DETACH: 
		break; 
	} 
	return TRUE; 
} 
 

//Application SceneGraph Header:  sg.h


class CSceneGraph
{
private:
	typedef IRenderer* (__cdecl * funcCreateInstance)( );
	IRenderer* iRen;
	HMODULE hMod;
	funcCreateInstance CreateInstance;
public:
	CSceneGraph( )
	{
		hMod = LoadLibrary( "dllname.dll" );
		
		CreateInstance = reinterpret_cast<funcCreateInstance>( GetProcAddress( hMod, "CreateInstance" ) );
		iRen = CreateInstance( );
		//i should return 1 if binding worked
		int i =	iRen->Init( 0 );
	}

	~CSceneGraph( )
	{
		FreeLibrary( hMod )
	}
}