《COM技术内幕》笔记(二）-白红宇

//AddRef和Release的实现

#include <iostream>

using namespace std;

#include <objbase.h>

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

// Forward references for GUIDs

extern const IID IID_IX ;

extern const IID IID_IY ;

extern const IID IID_IZ ;

// Interfaces

interface IX : IUnknown

{

virtual void __stdcall Fx() = 0 ;

} ;

interface IY : IUnknown

{

virtual void __stdcall Fy() = 0 ;

} ;

interface IZ : IUnknown

{

virtual void __stdcall Fz() = 0 ;

} ;

// Component

class CA : public IX,

public IY

{

// IUnknown implementation

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

virtual ULONG __stdcall AddRef() ;

virtual ULONG __stdcall Release() ;

// Interface IX implementation

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

// Interface IY implementation

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

public:

// Constructor

CA() : m_cRef(0) {}

// Destructor

~CA() { trace("CA: Destroy self.") ;}

private:

long m_cRef;

} ;

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

{

if (iid == IID_IUnknown)

{

trace("CA QI: Return pointer to IUnknown.") ;

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

}

else if (iid == IID_IX)

{

trace("CA QI: Return pointer to IX.") ;

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

}

else if (iid == IID_IY)

{

trace("CA QI: Return pointer to IY.") ;

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

}

else

{

trace("CA QI: Interface not supported.") ;

*ppv = NULL ;

return E_NOINTERFACE;

}

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

return S_OK ;

}

ULONG __stdcall CA::AddRef()

{

cout << "CA: AddRef = " << m_cRef+1 << '.' << endl ;

return InterlockedIncrement(&m_cRef) ;

}

ULONG __stdcall CA::Release()

{

cout << "CA: Release = " << m_cRef-1 << '.' << endl ;

if (InterlockedDecrement(&m_cRef) == 0)

{

delete this ;

return 0 ;

}

return m_cRef ;

}

// 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 IX.") ;

IX* pIX = NULL ;

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

if (SUCCEEDED(hr))

{

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

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

pIX->Release() ;

}

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.

pIY->Release() ;

}

trace("Client: Ask for an unsupported interface.") ;

IZ* pIZ = NULL ;

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

if (SUCCEEDED(hr))

{

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

pIZ->Fz() ;

pIZ->Release() ;

}

else

{

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

}

trace("Client: Release IUnknown interface.") ;

pIUnknown->Release() ;

system("pause");

return 0;

}

本文转自Phinecos(洞庭散人)博客园博客，原文链接：http://www.cnblogs.com/phinecos/archive/2008/04/18/1159407.html，如需转载请自行联系原作者