《COM技术内幕》代码之 引用计数的实现，AddRef,Release

#include <iostream>#include <atlbase.h>using namespace std;interface IX : public IUnknown{virtual void _stdcall Fx() = 0;};interface IY : public IUnknown{virtual void _stdcall Fy() = 0;};interface IZ : public IUnknown{virtual void _stdcall Fz() = 0;};static const IID IID_IX = {0xec53e1de, 0x37d, 0x48f5, {0xa1, 0xee, 0x2d, 0xf5, 0xa5, 0xde, 0xf3, 0x49}}; // {EC53E1DE-037D-48f5-A1EE-2DF5A5DEF349}static const IID IID_IY = {0x4c510b77, 0xc63a, 0x4e0f, {0xa2, 0x45, 0x7b, 0x21, 0x23, 0x12, 0x23, 0xe7}};// {4C510B77-C63A-4e0f-A245-7B21231223E7}static const IID IID_IZ = {0xefb1f8d4, 0x674e, 0x4123, {0xa9, 0x19, 0x3c, 0x72, 0xee, 0xe8, 0x1d, 0x92}};// {EFB1F8D4-674E-4123-A919-3C72EEE81D92}class CA : public IX,public IY{public:CA() : m_cRef(0) { }virtual ~CA(){ }public:virtual HRESULT _stdcall QueryInterface(REFIID riid, __RPC__deref_out void **ppvObject);virtual ULONG _stdcall AddRef();virtual ULONG _stdcall Release();virtual void _stdcall Fx() { cout<<"CA::Fx"<<endl; }virtual void _stdcall Fy() { cout<<"CA::Fy"<<endl; }private:LONG m_cRef;};HRESULT _stdcall CA::QueryInterface(REFIID riid, __RPC__deref_out void **ppvObject){if(IID_IX == riid){*ppvObject = static_cast<IX*>(this);}else if(IID_IY == riid){*ppvObject = static_cast<IY*>(this);}else if(IID_IUnknown == riid){*ppvObject = static_cast<IX*>(this);}else{ *ppvObject = NULL;return E_NOINTERFACE;}reinterpret_cast<IUnknown*>(*ppvObject)->AddRef(); //对应 这五个地方需要对应起来 return S_OK;}ULONG _stdcall CA::AddRef(){InterlockedIncrement(&m_cRef);return m_cRef;}ULONG _stdcall CA::Release(){if(InterlockedDecrement(&m_cRef) == 0){delete this; //下面标记的3个Release 缺少一个则执行不到这return 0;}return m_cRef;}IUnknown* CreateInstance(){IUnknown *pIUnk = static_cast<IX*>(new CA); pIUnk->AddRef(); //对应 这五个地方需要对应起来 return pIUnk;}void _tmain(int argc,_TCHAR*argv[]){IUnknown *pIUnk = CreateInstance();IX *pIX = NULL;HRESULT hr = pIUnk->QueryInterface(IID_IX,(void**)&pIX);if(SUCCEEDED(hr)){pIX->Fx();pIX->Release(); //对应 这五个地方需要对应起来 }IY *pIY = NULL;hr = pIUnk->QueryInterface(IID_IY,(void**)&pIY);if(SUCCEEDED(hr)){pIY->Fy();pIY->Release(); //对应 这五个地方需要对应起来 }IZ *pIZ = NULL; //没有执行到AddRef，故不需要释放hr = pIUnk->QueryInterface(IID_IZ,(void**)&pIZ);if(SUCCEEDED(hr)){cout<<"found pIZ"<<endl;pIZ->Release();}pIUnk->Release(); //对应 这五个地方需要对应起来 }