COMBASE.CPP
//==========================================================================;
//
// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY
// KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR
// PURPOSE.
//
// Copyright (c) 1992 - 1997 Microsoft Corporation. All Rights Reserved.
//
//--------------------------------------------------------------------------;
// Base class hierachy for creating COM objects, December 1994
#include <streams.h>
#pragma warning( disable : 4514 ) // Disable warnings re unused inline functions
/* Define the static member variable */
LONG CBaseObject::m_cObjects = 0;
/* Constructor */
CBaseObject::CBaseObject(const TCHAR *pName)
{
/* Increment the number of active objects */
InterlockedIncrement(&m_cObjects);
#ifdef DEBUG
m_dwCookie = DbgRegisterObjectCreation(pName);
#endif
}
HINSTANCEhlibOLEAut32;
/* Destructor */
CBaseObject::~CBaseObject()
{
/* Decrement the number of objects active */
if (InterlockedDecrement(&m_cObjects) == 0) {
if (hlibOLEAut32) {
FreeLibrary(hlibOLEAut32);
hlibOLEAut32 = 0;
}
};
#ifdef DEBUG
DbgRegisterObjectDestruction(m_dwCookie);
#endif
}
static const TCHAR szOle32Aut[] = TEXT("OleAut32.dll");
HINSTANCE LoadOLEAut32()
{
if (hlibOLEAut32 == 0) {
hlibOLEAut32 = LoadLibrary(szOle32Aut);
}
return hlibOLEAut32;
}
/* Constructor */
// We know we use "this" in the initialization list, we also know we don't modify *phr.
#pragma warning( disable : 4355 4100 )
CUnknown::CUnknown(const TCHAR *pName, LPUNKNOWN pUnk)
: CBaseObject(pName)
/* Start the object with a reference count of zero - when the */
/* object is queried for it's first interface this may be */
/* incremented depending on whether or not this object is */
/* currently being aggregated upon */
, m_cRef(0)
/* Set our pointer to our IUnknown interface. */
/* If we have an outer, use its, otherwise use ours. */
/* This pointer effectivly points to the owner of */
/* this object and can be accessed by the GetOwner() method. */
, m_pUnknown( pUnk != 0 ? pUnk : reinterpret_cast<LPUNKNOWN>( static_cast<PNDUNKNOWN>(this) ) )
/* Why the double cast? Well, the inner cast is a type-safe cast */
/* to pointer to a type from which we inherit. The second is */
/* type-unsafe but works because INonDelegatingUnknown "behaves */
/* like" IUnknown. (Only the names on the methods change.) */
{
// Everything we need to do has been done in the initializer list
}
// This does the same as above except it has a useless HRESULT argument
// use the previous constructor, this is just left for compatibility...
CUnknown::CUnknown(TCHAR *pName, LPUNKNOWN pUnk,HRESULT *phr) :
CBaseObject(pName),
m_cRef(0),
m_pUnknown( pUnk != 0 ? pUnk : reinterpret_cast<LPUNKNOWN>( static_cast<PNDUNKNOWN>(this) ) )
{
}
#pragma warning( default : 4355 4100 )
/* QueryInterface */
STDMETHODIMP CUnknown::NonDelegatingQueryInterface(REFIID riid, void ** ppv)
{
CheckPointer(ppv,E_POINTER);
ValidateReadWritePtr(ppv,sizeof(PVOID));
/* We know only about IUnknown */
if (riid == IID_IUnknown) {
GetInterface((LPUNKNOWN) (PNDUNKNOWN) this, ppv);
return NOERROR;
} else {
*ppv = NULL;
return E_NOINTERFACE;
}
}
/* We have to ensure that we DON'T use a max macro, since these will typically */
/* lead to one of the parameters being evaluated twice. Since we are worried */
/* about concurrency, we can't afford to access the m_cRef twice since we can't */
/* afford to run the risk that its value having changed between accesses. */
#ifdef max
#undef max
#endif
template<class T> inline static T max( const T & a, const T & b )
{
return a > b ? a : b;
}
/* AddRef */
STDMETHODIMP_(ULONG) CUnknown::NonDelegatingAddRef()
{
LONG lRef = InterlockedIncrement( &m_cRef );
ASSERT(lRef > 0);
DbgLog((LOG_MEMORY,3,TEXT(" Obj %d ref++ = %d"),
m_dwCookie, m_cRef));
return max(ULONG(m_cRef), 1ul);
}
/* Release */
STDMETHODIMP_(ULONG) CUnknown::NonDelegatingRelease()
{
/* If the reference count drops to zero delete ourselves */
LONG lRef = InterlockedDecrement( &m_cRef );
ASSERT(lRef >= 0);
DbgLog((LOG_MEMORY,3,TEXT(" Object %d ref-- = %d"),
m_dwCookie, m_cRef));
if (lRef == 0) {
// COM rules say we must protect against re-entrancy.
// If we are an aggregator and we hold our own interfaces
// on the aggregatee, the QI for these interfaces will
// addref ourselves. So after doing the QI we must release
// a ref count on ourselves. Then, before releasing the
// private interface, we must addref ourselves. When we do
// this from the destructor here it will result in the ref
// count going to 1 and then back to 0 causing us to
// re-enter the destructor. Hence we add an extra refcount here
// once we know we will delete the object.
// for an example aggregator see filgraph\distrib.cpp.
m_cRef++;
delete this;
return ULONG(0);
} else {
return max(ULONG(m_cRef), 1ul);
}
}
/* Return an interface pointer to a requesting client
performing a thread safe AddRef as necessary */
STDAPI GetInterface(LPUNKNOWN pUnk, void **ppv)
{
CheckPointer(ppv, E_POINTER);
*ppv = pUnk;
pUnk->AddRef();
return NOERROR;
}
/* Compares two interfaces and returns TRUE if they are on the same object */
BOOL WINAPI IsEqualObject(IUnknown *pFirst, IUnknown *pSecond)
{
/* Different objects can't have the same interface pointer for
any interface
*/
if (pFirst == pSecond) {
return TRUE;
}
/* OK - do it the hard way - check if they have the same
IUnknown pointers - a single object can only have one of these
*/
LPUNKNOWN pUnknown1; // Retrieve the IUnknown interface
LPUNKNOWN pUnknown2; // Retrieve the other IUnknown interface
HRESULT hr; // General OLE return code
ASSERT(pFirst);
ASSERT(pSecond);
/* See if the IUnknown pointers match */
hr = pFirst->QueryInterface(IID_IUnknown,(void **) &pUnknown1);
ASSERT(SUCCEEDED(hr));
ASSERT(pUnknown1);
hr = pSecond->QueryInterface(IID_IUnknown,(void **) &pUnknown2);
ASSERT(SUCCEEDED(hr));
ASSERT(pUnknown2);
/* Release the extra interfaces we hold */
pUnknown1->Release();
pUnknown2->Release();
return (pUnknown1 == pUnknown2);
}