combase.cpp

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//------------------------------------------------------------------------------
// File: ComBase.cpp
//
// Desc: DirectShow base classes - implements class hierarchy for creating
//       COM objects.
//
// Copyright (c) 1992-2001 Microsoft Corporation.  All rights reserved.
//------------------------------------------------------------------------------


#include "stdafx.h"
#include "combase.h"
#include <assert.h>

#define ASSERT assert

/* Define the static member variable */

/* Constructor */

CBaseObject::CBaseObject(const TCHAR *pName)
{
 /* Increment the number of active objects */
}


/* Destructor */

CBaseObject::~CBaseObject()
{
 /* Decrement the number of objects active */

}
/* 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 */

#define CheckPointer(p,ret) {if((p)==NULL) return (ret);}
#define ValidateReadPtr(p,cb) {if(IsBadReadPtr((PVOID)p,cb) == TRUE) perror("Invalid read pointer");}
#define ValidateWritePtr(p,cb) {if(IsBadWritePtr((PVOID)p,cb) == TRUE) perror("Invalid write pointer");}
#define ValidateReadWritePtr(p,cb) {ValidateReadPtr(p,cb) ValidateWritePtr(p,cb)}

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.        */

template<class T>
inline static T ourmax( const T & a, const T & b )
{
 return a > b ? a : b;
}

/* AddRef */

STDMETHODIMP_(ULONG) CUnknown::NonDelegatingAddRef()
{
 LONG lRef = InterlockedIncrement( (long*)&m_cRef );
 ASSERT(lRef > 0);
 return ourmax(ULONG(m_cRef), 1ul);
}


/* Release */

STDMETHODIMP_(ULONG) CUnknown::NonDelegatingRelease()
{
 /* If the reference count drops to zero delete ourselves */

 LONG lRef = InterlockedDecrement( (long*)&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 ourmax(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);
}