COM

CComAutoCriticalSection cs;
DWORD                   dwOwnerThreadId;
ISomeInterface*         pObject = 0;
IStream*                pObjMarshalled = 0;
 
HRESULT RegisterGlobalObject(ISomeInterface* pObj)
{
    if(!cs.Lock()) 
        return E_FAIL;
     
    if(pObject != 0) {
        cs.Unlock();
        return E_UNEXPECTED;
    }
 
    HRESULT hr = CoMarshalInterThreadInterfaceInStream(
        __uuidof(ISomeInterface),
        pObj,
        &pObjMarshalled
    );
 
    if(FAILED(hr)) {
        cs.Unlock();
        return hr;
    }
 
    pObject = pObj;
    dwOwnerThreadId = GetCurrentThreadId();
    cs.Unlock();
 
    return S_OK;
}
  
HRESULT GetGlobalObject(ISomeInterface** ppObj)
{
    if(!ppObj)
        return E_POINTER;

    if(!pObject)
        return E_FAIL;
    
    if(!cs.Lock())
        return E_FAIL;
    
    if(GetCurrentThreadId() == dwOwnerThreadId) {
        *ppObj = pObject;
        (*ppObject)->AddRef();
        cs.Unlock();
        return S_OK;
    }
 
    *ppObj = 0;
 
    LARGE_INTEGER seek;
    seek.QuadPart = 0; 
    HRESULT hr = pObjMarshalled->Seek(seek, STREAM_SEEK_SET, NULL);
    if(FAILED(hr) {
        cs.Unlock();
        return hr;
    }
 
    hr = CoUnmarshalInterface(
        pObjMarshalled, 
        __uuidof(ISomeInterface), 
       (void**)ppObj
    );
 
    cs.Unlock();
    return hr;
}