ProtocolCF.h

#ifndef PASSTHROUGHAPP_PROTOCOLCF_H
#define PASSTHROUGHAPP_PROTOCOLCF_H

#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000

namespace PassthroughAPP
{

namespace Detail
{
// A bit of template metaprogramming allows to avoid requiring
// the protocol class to either derive from CComCoClass or explicitly
// specify DECLARE_*AGGREGATABLE macro. If the class does it, the declared
// behavior is used, otherwise the default behavior is as if
// DECLARE_AGGREGATABLE is specified

// If T has a typedef _CreatorClass, Derived would pick it from its base.
// If T does not define _CreatorClass, the definition is picked from the next
// enclosing scope, which is ChooseCreatorClass::_CreatorClass, or Default
template <typename T, typename Default>
struct ChooseCreatorClass
{
	typedef Default _CreatorClass;
	struct Derived : private T
	{
		typedef _CreatorClass CreatorClass;
	};
	typedef typename Derived::CreatorClass CreatorClass;
};

} // end namespace PassthroughAPP::Detail

class ATL_NO_VTABLE CComClassFactoryProtocol :
	public CComClassFactory
{
	typedef CComClassFactory BaseClass;
public:
	STDMETHODIMP CreateInstance(IUnknown* punkOuter, REFIID riid,
		void** ppvObj);

	HRESULT CreateInstanceTarget(IUnknown** ppTargetProtocol);

	HRESULT GetTargetClassFactory(IClassFactory** ppCF);
	HRESULT SetTargetClassFactory(IClassFactory* pCF);
	HRESULT SetTargetCLSID(REFCLSID clsid, DWORD clsContext = CLSCTX_ALL);

	void FinalRelease();
private:
	CComPtr<IClassFactory> m_spTargetCF;
};

template <class Factory, class Protocol,
	class FactoryComObject = CComObjectNoLock<Factory> >
struct CMetaFactory
{
	typedef
		CComCreator2<CComCreator<CComObject<Protocol> >,
			CComCreator<CComAggObject<Protocol> > >
	DefaultCreatorClass;

	typedef typename
		Detail::ChooseCreatorClass<Protocol, DefaultCreatorClass>::CreatorClass
			CreatorClass;

	// returns a non-AddRef'ed pointer to FactoryComObject, already initialized
	// with Protocol's creator function, via ppObj [out] parameter
	static HRESULT CreateInstance(Factory** ppObj);

	static HRESULT CreateInstance(IClassFactory* pTargetCF,
		IClassFactory** ppCF);
	static HRESULT CreateInstance(REFCLSID clsidTarget, IClassFactory** ppCF);
};

} // end namespace PassthroughAPP

#include "ProtocolCF.inl"

#endif // PASSTHROUGHAPP_PROTOCOLCF_H