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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef STORAGE_BROWSER_FILEAPI_TASK_RUNNER_BOUND_OBSERVER_LIST_H_
#define STORAGE_BROWSER_FILEAPI_TASK_RUNNER_BOUND_OBSERVER_LIST_H_
#include <map>
#include "base/bind.h"
#include "base/memory/ref_counted.h"
#include "base/sequenced_task_runner.h"
#include "base/threading/thread.h"
#include "base/tuple.h"
namespace storage {
// A wrapper for dispatching method.
template <class T, class Method, class Params>
void NotifyWrapper(T obj, Method m, const Params& p) {
base::DispatchToMethod(obj, m, p);
}
// An observer list helper to notify on a given task runner.
// Observer pointers (stored as ObserverStoreType) must be kept alive
// until this list dispatches all the notifications.
//
// Unlike regular ObserverList or ObserverListThreadSafe internal observer
// list is immutable (though not declared const) and cannot be modified after
// constructed.
//
// It is ok to specify scoped_refptr<Observer> as ObserverStoreType to
// explicitly keep references if necessary.
template <class Observer, class ObserverStoreType = Observer*>
class TaskRunnerBoundObserverList {
public:
typedef scoped_refptr<base::SequencedTaskRunner> TaskRunnerPtr;
typedef std::map<ObserverStoreType, TaskRunnerPtr> ObserversListMap;
// Creates an empty list.
TaskRunnerBoundObserverList<Observer, ObserverStoreType>() {}
// Creates a new list with given |observers|.
explicit TaskRunnerBoundObserverList<Observer, ObserverStoreType>(
const ObserversListMap& observers)
: observers_(observers) {}
virtual ~TaskRunnerBoundObserverList<Observer, ObserverStoreType>() {}
// Returns a new observer list with given observer.
// It is valid to give NULL as |runner_to_notify|, and in that case
// notifications are dispatched on the current runner.
// Note that this is a const method and does NOT change 'this' observer
// list but returns a new list.
TaskRunnerBoundObserverList<Observer, ObserverStoreType> AddObserver(
Observer* observer,
base::SequencedTaskRunner* runner_to_notify) const {
ObserversListMap observers = observers_;
observers.insert(std::make_pair(observer, runner_to_notify));
return TaskRunnerBoundObserverList<Observer, ObserverStoreType>(observers);
}
// Notify on the task runner that is given to AddObserver.
// If we're already on the runner this just dispatches the method.
template <class Method, class Params>
void Notify(Method method, const Params& params) const {
static_assert(
(base::internal::ParamsUseScopedRefptrCorrectly<Params>::value),
"bad unbound method params");
for (typename ObserversListMap::const_iterator it = observers_.begin();
it != observers_.end(); ++it) {
if (!it->second.get() || it->second->RunsTasksOnCurrentThread()) {
base::DispatchToMethod(it->first, method, params);
continue;
}
it->second->PostTask(
FROM_HERE,
base::Bind(&NotifyWrapper<ObserverStoreType, Method, Params>,
it->first, method, params));
}
}
private:
ObserversListMap observers_;
};
class FileAccessObserver;
class FileChangeObserver;
class FileUpdateObserver;
typedef TaskRunnerBoundObserverList<FileAccessObserver> AccessObserverList;
typedef TaskRunnerBoundObserverList<FileChangeObserver> ChangeObserverList;
typedef TaskRunnerBoundObserverList<FileUpdateObserver> UpdateObserverList;
} // namespace storage
#endif // STORAGE_BROWSER_FILEAPI_TASK_RUNNER_BOUND_OBSERVER_LIST_H_