AtlMarshalPtrInProc

Creates a new stream object, writes the CLSID of the proxy to the stream, and marshals the specified interface pointer by writing the data needed to initialize the proxy into the stream.

HRESULT AtlMarshalPtrInProc(
   IUnknown* pUnk,
   const IID& iid,
   IStream** ppStream 
);

Parameters

• pUnk
  [in] A pointer to the interface to be marshaled.

• iid
  [in] The GUID of the interface being marshaled.

• ppStream
  [out] A pointer to the IStream interface on the new stream object used for marshaling.

Return Value

A standard HRESULT value.

Remarks

The MSHLFLAGS_TABLESTRONG flag is set so the pointer can be marshaled to multiple streams. The pointer can also be unmarshaled multiple times.

If marshaling fails, the stream pointer is released.

AtlMarshalPtrInProc can only be used on a pointer to an in-process object.

Example

//marshaling interface from one thread to another

//IStream ptr to hold serialized presentation of interface ptr
IStream* g_pStm;

//forward declaration
DWORD WINAPI ThreadProc(LPVOID lpParameter);

HRESULT WriteInterfacePtrToStream(IMyCircle *pCirc)
{
   //marshal the interface ptr to another thread
   //pCirc has to be pointer to actual object & not a proxy
   HRESULT hr = AtlMarshalPtrInProc(pCirc, IID_IMyCircle, &g_pStm);

   //m_dwThreadID is a DWORD holding thread ID of thread being created.
   CreateThread(NULL, 0, ThreadProc, NULL, 0, &m_dwThreadID);
   return hr;
}

DWORD WINAPI ThreadProc(LPVOID /*lpParameter*/)
{
   // CoInitializeEx is per thread, so initialize COM on this thread
   // (required by AtlUnmarshalPtr)
   HRESULT hr = CoInitializeEx(NULL, COINIT_APARTMENTTHREADED);
   if (SUCCEEDED(hr))
   {
      IMyCircle* pCirc;

      //unmarshal IMyCircle ptr from the stream
      hr = AtlUnmarshalPtr(g_pStm, IID_IMyCircle, (IUnknown**)&pCirc);

      // use IMyCircle ptr to call its methods
      double center;
      pCirc->get_XCenter(&center);

      //release the stream if no other thread requires it 
      //to unmarshal the IMyCircle interface pointer
      hr = AtlFreeMarshalStream(g_pStm);

      CoUninitialize();
   }

   return hr;
}

Requirements

Header: atlbase.h

See Also

Reference

AtlUnmarshalPtr

AtlFreeMarshalStream

MSHLFLAGS

Other Resources

Marshaling Global Functions