Understanding The COM Single-Threaded Apartment Part 1

#include "refcountobj.h"





CReferenceCountedObject::CReferenceCountedObject() :
	m_cRef(1)
{
  // Increment the global count of objects.
  InterlockedIncrement(&g_lObjsInUse);
}





CReferenceCountedObject::~CReferenceCountedObject()
{
  // Decrement the global count of objects.
  InterlockedDecrement(&g_lObjsInUse);

  CClassFactory::AttemptToTerminateServer();
}





STDMETHODIMP CReferenceCountedObject::QueryInterface(REFIID riid, void** ppvObject)
{
  if (riid == IID_IUnknown)
  {
	*ppvObject = (IUnknown*)this;
	AddRef();
	return S_OK;
  }
  
  return E_NOINTERFACE;
}





STDMETHODIMP_(ULONG) CReferenceCountedObject::AddRef()
{
  InterlockedIncrement(&m_cRef);
  
  return m_cRef;
}





STDMETHODIMP_(ULONG) CReferenceCountedObject::Release()
{
  InterlockedDecrement(&m_cRef);
  
  if (m_cRef == 0)
  {
 	delete this;
	return 0;
  }
  
  return m_cRef;
}





CClassFactory::CClassFactory() :
	m_cRef(1)
{
}





CClassFactory::~CClassFactory()
{
}





STDMETHODIMP CClassFactory::QueryInterface(REFIID riid, void** ppvObject)
{
  if (riid == IID_IUnknown)
  {
    CReferenceCountedObject* pCReferenceCountedObject = (CReferenceCountedObject*)this;

	*ppvObject = (IUnknown*)pCReferenceCountedObject;
	((CReferenceCountedObject*)this) -> AddRef();
	return S_OK;
  }

  if (riid == IID_IClassFactory)
  {
    *ppvObject = (IClassFactory*)this;
	((CReferenceCountedObject*)this) -> AddRef();
	return S_OK;
  }

  *ppvObject = NULL;
  
  return E_NOINTERFACE;
}





STDMETHODIMP_(ULONG) CClassFactory::AddRef()
{
  InterlockedIncrement(&m_cRef);
  
  return m_cRef;
}





STDMETHODIMP_(ULONG) CClassFactory::Release()
{
  InterlockedDecrement(&m_cRef);
  
  if (m_cRef == 0)
  {
 	delete this;
	return 0;
  }
  
  return m_cRef;
}





// IClassFactory method.
STDMETHODIMP CClassFactory::CreateInstance
(
  IUnknown __RPC_FAR *pUnkOuter,
  REFIID riid,
  void __RPC_FAR *__RPC_FAR *ppvObject
)
{
  return E_NOTIMPL;
}





// IClassFactory method.
STDMETHODIMP CClassFactory::LockServer
(
  BOOL fLock
)
{
  if (fLock) 
  {
    ::InterlockedIncrement(&g_lServerLocks) ; 
  }
  else
  {
	::InterlockedDecrement(&g_lServerLocks) ;
  }
  // If this is an out-of-proc server, check to see
  // whether we should shut down.
  AttemptToTerminateServer() ;  //@local

  return S_OK ;
}





// Shut down the application.
void CClassFactory::AttemptToTerminateServer()
{
  if ((g_lObjsInUse > 0) || (g_lServerLocks > 0))
  {
  }
  else
  {
	::PostThreadMessage(g_dwMainThreadID, WM_QUIT, 0, 0);
  }
}