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// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef COMPONENTS_KEYED_SERVICE_CORE_REFCOUNTED_KEYED_SERVICE_H_
#define COMPONENTS_KEYED_SERVICE_CORE_REFCOUNTED_KEYED_SERVICE_H_
#include "base/memory/ref_counted.h"
#include "base/task/sequenced_task_runner.h"
#include "base/task/sequenced_task_runner_helpers.h"
#include "components/keyed_service/core/keyed_service_export.h"
class RefcountedKeyedService;
namespace impl {
struct KEYED_SERVICE_EXPORT RefcountedKeyedServiceTraits {
static void Destruct(const RefcountedKeyedService* obj);
};
} // namespace impl
// Base class for refcounted objects that hang off the BrowserContext.
//
// The two pass shutdown described in KeyedService works a bit differently
// because there could be outstanding references on other threads.
// ShutdownOnUIThread() will be called on the UI thread, and then the
// destructor will run when the last reference is dropped, which may or may not
// be after the corresponding BrowserContext has been destroyed.
//
// Optionally, if you initialize your service with the constructor that takes a
// SequencedTaskRunner, your service will be deleted on that sequence. We
// can't use content::DeleteOnThread<> directly because RefcountedKeyedService
// must not depend on //content.
class KEYED_SERVICE_EXPORT RefcountedKeyedService
: public base::RefCountedThreadSafe<RefcountedKeyedService,
impl::RefcountedKeyedServiceTraits> {
public:
RefcountedKeyedService(const RefcountedKeyedService&) = delete;
RefcountedKeyedService& operator=(const RefcountedKeyedService&) = delete;
// Unlike KeyedService, ShutdownOnUI is not optional. You must do something
// to drop references during the first pass Shutdown() because this is the
// only point where you are guaranteed that something is running on the UI
// thread. The PKSF framework will ensure that this is only called on the UI
// thread; you do not need to check for that yourself.
virtual void ShutdownOnUIThread() = 0;
protected:
// If your service does not need to be deleted on a specific sequence, use the
// default constructor.
RefcountedKeyedService();
// If you need your service to be deleted on a specific sequence (for example,
// you're converting a service that used content::DeleteOnThread<IO>), then
// use this constructor with a reference to the SequencedTaskRunner (e.g., you
// can get it from content::Get(UI|IO)ThreadTaskRunner or
// base::ThreadPool::CreateSequencedTaskRunner).
explicit RefcountedKeyedService(
scoped_refptr<base::SequencedTaskRunner> task_runner);
// The second pass destruction can happen anywhere unless you specify which
// sequence this service must be destroyed on by using the second constructor.
virtual ~RefcountedKeyedService();
private:
friend struct impl::RefcountedKeyedServiceTraits;
friend class base::DeleteHelper<RefcountedKeyedService>;
friend class base::RefCountedThreadSafe<RefcountedKeyedService,
impl::RefcountedKeyedServiceTraits>;
// Do we have to delete this object on a specific sequence?
scoped_refptr<base::SequencedTaskRunner> task_runner_;
};
#endif // COMPONENTS_KEYED_SERVICE_CORE_REFCOUNTED_KEYED_SERVICE_H_
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