Source code
Revision control
Copy as Markdown
Other Tools
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this file,
* You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef mozilla_StaticBackgroundTaskQueue_h
#define mozilla_StaticBackgroundTaskQueue_h
#include "mozilla/Attributes.h"
#include "mozilla/Mutex.h"
#include "mozilla/NeverDestroyed.h"
#include "mozilla/StaticString.h"
#include "nsCOMPtr.h"
#include "nsITargetShutdownTask.h"
namespace mozilla {
/**
* Helper class for declaring a process-lifetime shared background task queue in
* a thread-safe manner.
*
* This type is intended to be used as a static-local class, and will construct
* the task queue when first accessed. The queue will automatically be cleaned
* up during XPCOM shutdown, after which point Get() will return nullptr.
*
* This queue will run on the generic background task queue, and is created
* using NS_CreateBackgroundTaskQueue.
*
* Example Usage:
*
* static already_AddRefed<nsISerialEventTarget> FooBarQueue() {
* static StaticBackgroundTaskQueue sQueue("FooBar");
* return sQueue.Get();
* }
*/
class MOZ_STATIC_LOCAL_CLASS StaticBackgroundTaskQueue final {
public:
explicit StaticBackgroundTaskQueue(StaticString aName);
already_AddRefed<nsISerialEventTarget> Get();
private:
// Inner Impl type. This is wrapped in NeverDestroyed<...> to avoid
// introducing static destructors, and uses fake refcounting for the
// nsITargetShutdownTask implementation.
struct Impl final : public nsITargetShutdownTask {
explicit Impl(StaticString aName);
// nsISupports (fake refcounting, always static)
NS_IMETHOD QueryInterface(REFNSIID aIID, void** aInstancePtr) override;
NS_IMETHOD_(MozExternalRefCountType) AddRef() override { return 2; }
NS_IMETHOD_(MozExternalRefCountType) Release() override { return 2; }
// nsITargetShutdownTask
void TargetShutdown() override;
OffTheBooksMutex mMutex;
nsCOMPtr<nsISerialEventTarget> mQueue MOZ_GUARDED_BY(mMutex);
};
NeverDestroyed<Impl> mImpl;
};
} // namespace mozilla
#endif // mozilla_StaticBackgroundTaskQueue_h