一个简单的COM程序

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//IUnkown.cpp

#include <iostream.h>

#include <objbase.h>

void trace(const char * msg) {cout << msg << endl ;}

//Interface

interface IX : IUnknown

{

virtual void __stdcall Fx() = 0;

};

interface IY : IUnknown

{

virtual void __stdcall Fy() = 0;

};

interface IZ : IUnknown

{

virtual void __stdcall Fz() = 0;

};

//Forward references for GUIDs

extern const IID IID_IX;

extern const IID IID_IY;

extern const IID IID_IZ;

//Component

class CA : public IX, public IY

{

//IUnknown implementation

virtual HRESULT __stdcall QueryInterface(const IID& iid, void** ppv);

virtual ULONG __stdcall AddRef() {return 0;}

virtual ULONG __stdcall Release() {return 0;}

//Interface IX implementation

virtual void __stdcall Fx() {cout << "Fx" << endl ;}

//Interface IY implementation

virtual void __stdcall Fy() {cout << "Fy" << endl ;}

};

HRESULT __stdcall CA::QueryInterface(const IID& iid, void** ppv)

{

if(iid == IID_IUnknown)

{

trace("QueryInterface:Return pointer to IUnknown.");

*ppv = static_cast< IX* >(this);

}

else if(iid == IID_IX)

{

trace("QueryInterface:Return pointer to IX.");

*ppv = static_cast< IX* >(this);

}

else if(iid == IID_IY)

{

trace("QueryInterface:Return pointer to IY.");

*ppv = static_cast< IY* >(this);

}

else

{

trace("QueryInterface:Interface not supported.");

*ppv = NULL;

return E_NOINTERFACE;

}

reinterpret_cast< IUnknown* >(*ppv)->AddRef();

return S_OK;

}

//Creation function

IUnknown* CreateInstance()

{

IUnknown* pI = static_cast< IX* >(new CA);

pI->AddRef();

return pI;

}

//IIDs

//{32bb8320-b41b-11cf-a6bb-0080c7b2d682}

static const IID IID_IX =

{0x32bb8320, 0xb41b, 0x11cf,

{0xa6, 0xbb, 0x0, 0x80, 0xc7, 0xb2, 0xd6, 0x82}};

//{32bb8321-b41b-11cf-a6bb-0080c7b2d682}

static const IID IID_IY =

{0x32bb8321, 0xb41b, 0x11cf,

{0xa6, 0xbb, 0x0, 0x80, 0xc7, 0xb2, 0xd6, 0x82}};

//{32bb8322-b41b-11cf-a6bb-0080c7b2d682}

static const IID IID_IZ =

{0x32bb8322, 0xb41b, 0x11cf,

{0xa6, 0xbb, 0x0, 0x80, 0xc7, 0xb2, 0xd6, 0x82}};

//Client

int main()

{

HRESULT hr;

trace("Client:Get an IUnknown pointer.");

IUnknown* pIUnknown = CreateInstance();

   trace("Client:Get Interface IUnknown.");

         IUnknown* pIUnknown1 = NULL;

         hr = pIUnknown->QueryInterface(IID_IUnknown,(void**)&pIUnknown1);

trace("Client:Get Interface IX.");

IX* pIX = NULL;

hr = pIUnknown->QueryInterface(IID_IX,(void**)&pIX);

if(SUCCEEDED(hr))

{

trace("Client:Succeeded getting IX.");

pIX->Fx(); //Use interface IX

}

trace("Client:Get Interface IY.");

IY* pIY = NULL;

hr = pIUnknown->QueryInterface(IID_IY,(void**)&pIY);

if(SUCCEEDED(hr))

{

trace("Client:Succeeded getting IY.");

pIY->Fy(); //Use interface IY

}

trace("Client:Get Interface IZ.");

IZ* pIZ = NULL;

hr = pIUnknown->QueryInterface(IID_IZ,(void**)&pIZ);

if(SUCCEEDED(hr))

{

trace("Client:Succeeded getting IZ.");

pIZ->Fz();

}

else

{

trace("Client:Could not get interface IZ.");

}

trace("Client:Get interface IY from interface IX.");

IY* pIYfromIX = NULL;

hr = pIX->QueryInterface(IID_IY, (void**)&pIYfromIX);

if(SUCCEEDED(hr))

{

trace("Client:Succeeded getting IY.");

pIYfromIX->Fy();

}

trace("Client:Get interface IUnknown from IY.");

IUnknown* pIUknownFromIY = NULL;

hr = pIY->QueryInterface(IID_IUnknown, (void**)&pIUknownFromIY);

if(SUCCEEDED(hr))

{

cout << "equal?" ;

if(pIUknownFromIY == pIUnknown)

{

cout << "Yes." << endl;

}

else

{

cout << "No." << endl;

}

//Delete the component

delete pIUnknown;

return 0;

}