gecko-dev/xpcom/glue/nsWeakReference.cpp

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
*
* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* 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.
*
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* The Original Code is the Mozilla browser.
*
* The Initial Developer of the Original Code is
* Netscape Communications, Inc.
* Portions created by the Initial Developer are Copyright (C) 1999
* the Initial Developer. All Rights Reserved.
*
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* Contributor(s):
* Scott Collins <scc@netscape.com>
* Pierre Phaneuf <pp@ludusdesign.com>
*
* Alternatively, the contents of this file may be used under the terms of
* either of the GNU General Public License Version 2 or later (the "GPL"),
* or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
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// nsWeakReference.cpp
#include "mozilla/Attributes.h"
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#include "nsWeakReference.h"
#include "nsCOMPtr.h"
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class nsWeakReference MOZ_FINAL : public nsIWeakReference
{
public:
// nsISupports...
NS_DECL_ISUPPORTS
// nsIWeakReference...
NS_DECL_NSIWEAKREFERENCE
private:
friend class nsSupportsWeakReference;
nsWeakReference( nsSupportsWeakReference* referent )
: mReferent(referent)
// ...I can only be constructed by an |nsSupportsWeakReference|
{
// nothing else to do here
}
~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;
}
nsSupportsWeakReference* mReferent;
};
nsresult
nsQueryReferent::operator()( const nsIID& aIID, void** answer ) const
{
nsresult status;
if ( mWeakPtr )
{
if ( NS_FAILED(status = mWeakPtr->QueryReferent(aIID, answer)) )
*answer = 0;
}
else
status = NS_ERROR_NULL_POINTER;
if ( mErrorPtr )
*mErrorPtr = status;
return status;
}
NS_COM_GLUE nsIWeakReference* // or else |already_AddRefed<nsIWeakReference>|
NS_GetWeakReference( nsISupports* aInstancePtr, nsresult* aErrorPtr )
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{
nsresult status;
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nsIWeakReference* result = nsnull;
if ( aInstancePtr )
{
nsCOMPtr<nsISupportsWeakReference> factoryPtr = do_QueryInterface(aInstancePtr, &status);
NS_ASSERTION(factoryPtr, "Oops! You're asking for a weak reference to an object that doesn't support that.");
if ( factoryPtr )
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{
status = factoryPtr->GetWeakReference(&result);
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}
// else, |status| has already been set by |do_QueryInterface|
}
else
status = NS_ERROR_NULL_POINTER;
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if ( aErrorPtr )
*aErrorPtr = status;
return result;
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}
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NS_COM_GLUE nsresult
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nsSupportsWeakReference::GetWeakReference( nsIWeakReference** aInstancePtr )
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{
if ( !aInstancePtr )
return NS_ERROR_NULL_POINTER;
if ( !mProxy )
mProxy = new nsWeakReference(this);
*aInstancePtr = mProxy;
nsresult status;
if ( !*aInstancePtr )
status = NS_ERROR_OUT_OF_MEMORY;
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else
{
NS_ADDREF(*aInstancePtr);
status = NS_OK;
}
return status;
}
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NS_IMPL_ISUPPORTS1(nsWeakReference, nsIWeakReference)
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NS_IMETHODIMP
nsWeakReference::QueryReferent( const nsIID& aIID, void** aInstancePtr )
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{
return mReferent ? mReferent->QueryInterface(aIID, aInstancePtr) : NS_ERROR_NULL_POINTER;
}
void
nsSupportsWeakReference::ClearWeakReferences()
{
if ( mProxy )
{
mProxy->NoticeReferentDestruction();
mProxy = 0;
}
}