IUnknown

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  void GetObject([out] IUnknown **ppUnk);

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  void UseObject([in] IUnknown *pUnk);

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 void GetAndUse(/* [out] */ IUnknown ** ppUnkOut)  {      IUnknown *pUnk1 = 0, *pUnk2 = 0;      *ppUnkOut =0;                                      // R3        // get pointers to one (or two) objects        //         (   )        GetObject(&pUnk1);                               //A2      GetObject(&pUnk2);                               //A1         // set pUnk2 to point to first object        //   pUnk2,                if (pUnk2) pUnk2->Release():                          //R1     if (pUnk2 = pUnk1) pUnk2->AddRef():                   //A1       // pass pUnk2 to some other function        //   pUnk2  -              UseObject(pUnk2);                                   //S1       // return pUnk2 to caller using ppUnkOut parameter        //   pUnk2    ,          //   ppUnkOut      if (*ppUnkOut = pUnk2) (*ppUnkOut)->AddRef();     // A2        // falling out of scope so clean up        //                    if (pUnk1) pUnkl->Release();                         //R2      if (pUnk2) pUnk2->Release();                         //R2  }

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 inline void SafeRelease(IUnknown * &rpUnk)  {      if (rpUnk) {          rpUnk->Release();          rpUnk = 0;        // rpUnk passed by reference        // rpUnk,          }  }

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