关于com中的CComPtr
这篇文章讲COM的，比较好，里面提到了关于CComPtr的一些知识，很值得一看http://www.360doc.com/content/09/0713/10/168576_4247483.shtml
===========================================
关于CComPtr的基类的源代码：看了多多少少有点理解，其实和stl或者boost的智能指针还是有点相似，
因为这里传入的是一些com，不需要类CComPtrBase去计数了，仅仅是做好本次的addref和release就OK了。
template <class T> class CComPtrBase { protected: CComPtrBase() throw() { p = NULL; } CComPtrBase(_In_ int nNull) throw() { ATLASSERT(nNull == 0); (void)nNull; p = NULL; } CComPtrBase(_In_opt_ T* lp) throw() { p = lp; if (p != NULL) p->AddRef(); } public: typedef T _PtrClass; ~CComPtrBase() throw() { if (p) p->Release(); } operator T*() const throw() { return p; } T& operator*() const { ATLENSURE(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&() throw() { ATLASSERT(p==NULL); return &p; } _NoAddRefReleaseOnCComPtr<T>* operator->() const throw() { ATLASSERT(p!=NULL); return (_NoAddRefReleaseOnCComPtr<T>*)p; } bool operator!() const throw() { return (p == NULL); } bool operator<(_In_opt_ T* pT) const throw() { return p < pT; } bool operator!=(_In_opt_ T* pT) const { return !operator==(pT); } bool operator==(_In_opt_ T* pT) const throw() { return p == pT; } // Release the interface and set to NULL void Release() throw() { T* pTemp = p; if (pTemp) { p = NULL; pTemp->Release(); } } // Compare two objects for equivalence bool IsEqualObject(_In_opt_ IUnknown* pOther) throw() { 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(__uuidof(IUnknown), (void**)&punk1); pOther->QueryInterface(__uuidof(IUnknown), (void**)&punk2); return punk1 == punk2; } // Attach to an existing interface (does not AddRef) void Attach(_In_opt_ T* p2) throw() { if (p) p->Release(); p = p2; } // Detach the interface (does not Release) T* Detach() throw() { T* pt = p; p = NULL; return pt; } _Check_return_ HRESULT CopyTo(_Deref_out_opt_ T** ppT) throw() { ATLASSERT(ppT != NULL); if (ppT == NULL) return E_POINTER; *ppT = p; if (p) p->AddRef(); return S_OK; } _Check_return_ HRESULT SetSite(_In_opt_ IUnknown* punkParent) throw() { return AtlSetChildSite(p, punkParent); } _Check_return_ HRESULT Advise(_In_ IUnknown* pUnk, _In_ const IID& iid, _Out_ LPDWORD pdw) throw() { return AtlAdvise(p, pUnk, iid, pdw); } _Check_return_ HRESULT CoCreateInstance(_In_ REFCLSID rclsid, _In_opt_ LPUNKNOWN pUnkOuter = NULL, _In_ DWORD dwClsContext = CLSCTX_ALL) throw() { ATLASSERT(p == NULL); return ::CoCreateInstance(rclsid, pUnkOuter, dwClsContext, __uuidof(T), (void**)&p); } _Check_return_ HRESULT CoCreateInstance(_In_ LPCOLESTR szProgID, _In_opt_ LPUNKNOWN pUnkOuter = NULL, _In_ DWORD dwClsContext = CLSCTX_ALL) throw() { 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> _Check_return_ HRESULT QueryInterface(_Deref_out_opt_ Q** pp) const throw() { ATLASSERT(pp != NULL); return p->QueryInterface(__uuidof(Q), (void**)pp); } T* p; };
这个将原理的，http://blog.csdn.net/bjwdxs/archive/2008/02/15/2096995.aspx