pjs/xpcom/base/ClearOnShutdown.h

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set sw=2 ts=8 et ft=cpp : */
/* ***** 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.
*
* The Original Code is Mozilla Code.
*
* The Initial Developer of the Original Code is
* The Mozilla Foundation
* Portions created by the Initial Developer are Copyright (C) 2011
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Justin Lebar <justin.lebar@gmail.com>
*
* Alternatively, the contents of this file may be used under the terms of
* either 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 ***** */
#ifndef mozilla_ClearOnShutdown_h
#include <nsAutoPtr.h>
#include <nsCOMPtr.h>
#include <nsIObserver.h>
#include <nsIObserverService.h>
#include <mozilla/Services.h>
/*
* This header exports one method in the mozilla namespace:
*
* template<class SmartPtr>
* void ClearOnShutdown(SmartPtr *aPtr)
*
* This function takes a pointer to a smart pointer (i.e., nsCOMPtr<T>*,
* nsRefPtr<T>*, or nsAutoPtr<T>*) and nulls the smart pointer on shutdown.
*
* This is useful if you have a global smart pointer object which you don't
* want to "leak" on shutdown.
*
* There is no way to undo a call to ClearOnShutdown, so you can call it only
* on smart pointers which you know will live until the program shuts down.
*/
namespace mozilla {
namespace ClearOnShutdown_Internal {
template<class SmartPtr>
class ShutdownObserver : public nsIObserver
{
public:
ShutdownObserver(SmartPtr *aPtr)
: mPtr(aPtr)
{}
virtual ~ShutdownObserver()
{}
NS_DECL_ISUPPORTS
NS_IMETHOD Observe(nsISupports *aSubject, const char *aTopic,
const PRUnichar *aData)
{
MOZ_ASSERT(strcmp(aTopic, NS_XPCOM_SHUTDOWN_OBSERVER_ID) == 0);
if (mPtr) {
*mPtr = NULL;
}
return NS_OK;
}
private:
SmartPtr *mPtr;
};
// Give the full namespace in the NS_IMPL macros because NS_IMPL_ADDREF/RELEASE
// stringify the class name (using the "#" operator) and use this in
// trace-malloc. If we didn't fully-qualify the class name and someone else
// had a refcounted class named "ShutdownObserver<SmartPtr>" in any namespace,
// trace-malloc would assert (bug 711602).
//
// (Note that because macros happen before templates, trace-malloc sees this
// class name as "ShutdownObserver<SmartPtr>"; therefore, it would also assert
// if ShutdownObserver<T> had a different size than ShutdownObserver<S>.)
template<class SmartPtr>
NS_IMPL_ADDREF(mozilla::ClearOnShutdown_Internal::
ShutdownObserver<SmartPtr>)
template<class SmartPtr>
NS_IMPL_RELEASE(mozilla::ClearOnShutdown_Internal::
ShutdownObserver<SmartPtr>)
template<class SmartPtr>
NS_IMPL_QUERY_INTERFACE1(mozilla::ClearOnShutdown_Internal::
ShutdownObserver<SmartPtr>,
nsIObserver)
} // namespace ClearOnShutdown_Internal
template<class SmartPtr>
void ClearOnShutdown(SmartPtr *aPtr)
{
nsRefPtr<ClearOnShutdown_Internal::ShutdownObserver<SmartPtr> > observer =
new ClearOnShutdown_Internal::ShutdownObserver<SmartPtr>(aPtr);
nsCOMPtr<nsIObserverService> os = services::GetObserverService();
if (!os) {
NS_WARNING("Could not get observer service!");
return;
}
os->AddObserver(observer, NS_XPCOM_SHUTDOWN_OBSERVER_ID, false);
}
} // namespace mozilla
#endif