windows-server-2003/multimedia/dshow/dmo/dmocom/dmocom.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 - 1998  Microsoft Corporation.  All Rights Reserved.
//
//--------------------------------------------------------------------------;

// Base class hierachy for creating COM objects, December 1994

#include "dmocom.h"


#pragma warning( disable : 4514 )   // Disable warnings re unused inline functions



/* Constructor */

// We know we use "this" in the initialization list, we also know we don't modify *phr.
#pragma warning( disable : 4355 4100 )
CComBase::CComBase(IUnknown* pUnk)
: 
/* 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<IUnknown*>( static_cast<INDUnknown*>(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 INDUnknown "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...
CComBase::CComBase(IUnknown* pUnk,HRESULT *phr) :
    m_cRef(0),
    m_pUnknown( pUnk != 0 ? pUnk : reinterpret_cast<IUnknown*>( static_cast<INDUnknown*>(this) ) )
{
}

#pragma warning( default : 4355 4100 )

/* QueryInterface */

STDMETHODIMP CComBase::NDQueryInterface(REFIID riid, void ** ppv)
{
    CheckPointer(ppv,E_POINTER);
    ValidateReadWritePtr(ppv,sizeof(PVOID));

    /* We know only about IUnknown */

    if (riid == IID_IUnknown) {
        GetInterface((IUnknown*) (INDUnknown*) 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) CComBase::NDAddRef()
{
    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) CComBase::NDRelease()
{
    /* 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(IUnknown* 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
    */
    IUnknown* pUnknown1;     // Retrieve the IUnknown interface
    IUnknown* 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);
}