gecko-dev/xpcom/glue/nsWeakReference.h

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
*
* The contents of this file are subject to the Mozilla Public
* License Version 1.1 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of
* the License at http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS
* IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
* implied. See the License for the specific language governing
* rights and limitations under the License.
*
* The Original Code is the Mozilla browser.
*
* The Initial Developer of the Original Code is Netscape
* Communications, Inc. Portions created by Netscape are
* Copyright (C) 1999, Mozilla. All Rights Reserved.
*
* Contributor(s):
* Scott Collins <scc@netscape.com>
*/
#ifndef nsWeakReference_h__
#define nsWeakReference_h__
// nsWeakReference.h
#include "nsIWeakReference.h"
class nsWeakReference;
class NS_COM nsSupportsWeakReference : public nsISupportsWeakReference
{
public:
nsSupportsWeakReference()
: mProxy(0)
{
// nothing else to do here
}
inline virtual ~nsSupportsWeakReference();
NS_DECL_NSISUPPORTSWEAKREFERENCE
private:
friend class nsWeakReference;
void
NoticeProxyDestruction()
// ...called (only) by an |nsWeakReference| from _its_ dtor.
{
mProxy = 0;
}
nsWeakReference* mProxy;
protected:
inline void ClearWeakReferences();
PRBool HasWeakReferences() const {return mProxy != 0;}
};
class NS_COM nsWeakReference : public nsIWeakReference
{
public:
// nsISupports...
NS_IMETHOD_(nsrefcnt) AddRef();
NS_IMETHOD_(nsrefcnt) Release();
NS_IMETHOD QueryInterface( const nsIID&, void** );
// nsIWeakReference...
NS_DECL_NSIWEAKREFERENCE
private:
friend class nsSupportsWeakReference;
nsWeakReference( nsSupportsWeakReference* referent )
: mRefCount(0),
mReferent(referent)
// ...I can only be constructed by an |nsSupportsWeakReference|
{
// nothing else to do here
}
virtual ~nsWeakReference()
// ...I will only be destroyed by calling |delete| myself.
{
if ( mReferent )
mReferent->NoticeProxyDestruction();
}
void
NoticeReferentDestruction()
// ...called (only) by an |nsSupportsWeakReference| from _its_ dtor.
{
mReferent = 0;
}
nsrefcnt mRefCount;
nsSupportsWeakReference* mReferent;
};
inline
void
nsSupportsWeakReference::ClearWeakReferences()
/*
Usually being called from |nsSupportsWeakReference::~nsSupportsWeakReference|
will be good enough, but you may have a case where you need to call disconnect
your weak references in an outer destructor (to prevent some client holding a
weak reference from re-entering your destructor).
*/
{
if ( mProxy )
{
mProxy->NoticeReferentDestruction();
mProxy = 0;
}
}
inline
nsSupportsWeakReference::~nsSupportsWeakReference()
{
ClearWeakReferences();
}
#endif