COM 智能指针CComPtr

template <class T>
class CComPtr
{
public:
	typedef T _PtrClass;
	CComPtr()
	{
		p=NULL;
	}
	CComPtr(T* lp)
	{
		if ((p = lp) != NULL)
			p->AddRef();
	}
	CComPtr(const CComPtr<T>& lp)
	{
		if ((p = lp.p) != NULL)
			p->AddRef();
	}
	~CComPtr()
	{
		if (p)
			p->Release();
	}
	void Release()
	{
		IUnknown* pTemp = p;
		if (pTemp)
		{
			p = NULL;
			pTemp->Release();
		}
	}
	operator T*() const
	{
		return (T*)p;
	}
	T& operator*() const
	{
		ATLASSERT(p!=NULL);
		return *p;
	}
	//The assert on operator& usually indicates a bug.  If this is really
	//what is needed, however, take the address of the p member explicitly.
	T** operator&()
	{
		ATLASSERT(p==NULL);
		return &p;
	}
	_NoAddRefReleaseOnCComPtr<T>* operator->() const
	{
		ATLASSERT(p!=NULL);
		return (_NoAddRefReleaseOnCComPtr<T>*)p;
	}
	T* operator=(T* lp)
	{
		return (T*)AtlComPtrAssign((IUnknown**)&p, lp);
	}
	T* operator=(const CComPtr<T>& lp)
	{
		return (T*)AtlComPtrAssign((IUnknown**)&p, lp.p);
	}
	bool operator!() const
	{
		return (p == NULL);
	}
	bool operator<(T* pT) const
	{
		return p < pT;
	}
	bool operator==(T* pT) const
	{
		return p == pT;
	}
	// Compare two objects for equivalence
	bool IsEqualObject(IUnknown* pOther)
	{
		if (p == NULL && pOther == NULL)
			return true; // They are both NULL objects

		if (p == NULL || pOther == NULL)
			return false; // One is NULL the other is not

		CComPtr<IUnknown> punk1;
		CComPtr<IUnknown> punk2;
		p->QueryInterface(IID_IUnknown, (void**)&punk1);
		pOther->QueryInterface(IID_IUnknown, (void**)&punk2);
		return punk1 == punk2;
	}
	void Attach(T* p2)
	{
		if (p)
			p->Release();
		p = p2;
	}
	T* Detach()
	{
		T* pt = p;
		p = NULL;
		return pt;
	}
	HRESULT CopyTo(T** ppT)
	{
		ATLASSERT(ppT != NULL);
		if (ppT == NULL)
			return E_POINTER;
		*ppT = p;
		if (p)
			p->AddRef();
		return S_OK;
	}
	HRESULT SetSite(IUnknown* punkParent)
	{
		return AtlSetChildSite(p, punkParent);
	}
	HRESULT Advise(IUnknown* pUnk, const IID& iid, LPDWORD pdw)
	{
		return AtlAdvise(p, pUnk, iid, pdw);
	}
	HRESULT CoCreateInstance(REFCLSID rclsid, LPUNKNOWN pUnkOuter = NULL, DWORD dwClsContext = CLSCTX_ALL)
	{
		ATLASSERT(p == NULL);
		return ::CoCreateInstance(rclsid, pUnkOuter, dwClsContext, __uuidof(T), (void**)&p);
	}
	HRESULT CoCreateInstance(LPCOLESTR szProgID, LPUNKNOWN pUnkOuter = NULL, DWORD dwClsContext = CLSCTX_ALL)
	{
		CLSID clsid;
		HRESULT hr = CLSIDFromProgID(szProgID, &clsid);
		ATLASSERT(p == NULL);
		if (SUCCEEDED(hr))
			hr = ::CoCreateInstance(clsid, pUnkOuter, dwClsContext, __uuidof(T), (void**)&p);
		return hr;
	}
	template <class Q>
	HRESULT QueryInterface(Q** pp) const
	{
		ATLASSERT(pp != NULL && *pp == NULL);
		return p->QueryInterface(__uuidof(Q), (void**)pp);
	}
	T* p;
};