1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #ifndef STORAGE_BROWSER_FILEAPI_TASK_RUNNER_BOUND_OBSERVER_LIST_H_
6 #define STORAGE_BROWSER_FILEAPI_TASK_RUNNER_BOUND_OBSERVER_LIST_H_
7
8 #include <map>
9
10 #include "base/basictypes.h"
11 #include "base/bind.h"
12 #include "base/memory/ref_counted.h"
13 #include "base/sequenced_task_runner.h"
14 #include "base/threading/thread.h"
15
16 namespace storage {
17
18 // A wrapper for dispatching method.
19 template <class T, class Method, class Params>
NotifyWrapper(T obj,Method m,const Params & p)20 void NotifyWrapper(T obj, Method m, const Params& p) {
21 DispatchToMethod(base::internal::UnwrapTraits<T>::Unwrap(obj), m, p);
22 }
23
24 // An observer list helper to notify on a given task runner.
25 // Observer pointers (stored as ObserverStoreType) must be kept alive
26 // until this list dispatches all the notifications.
27 //
28 // Unlike regular ObserverList or ObserverListThreadSafe internal observer
29 // list is immutable (though not declared const) and cannot be modified after
30 // constructed.
31 //
32 // It is ok to specify scoped_refptr<Observer> as ObserverStoreType to
33 // explicitly keep references if necessary.
34 template <class Observer, class ObserverStoreType = Observer*>
35 class TaskRunnerBoundObserverList {
36 public:
37 typedef scoped_refptr<base::SequencedTaskRunner> TaskRunnerPtr;
38 typedef std::map<ObserverStoreType, TaskRunnerPtr> ObserversListMap;
39
40 // Creates an empty list.
41 TaskRunnerBoundObserverList<Observer, ObserverStoreType>() {}
42
43 // Creates a new list with given |observers|.
44 explicit TaskRunnerBoundObserverList<Observer, ObserverStoreType>(
45 const ObserversListMap& observers)
observers_(observers)46 : observers_(observers) {}
47
48 virtual ~TaskRunnerBoundObserverList<Observer, ObserverStoreType>() {}
49
50 // Returns a new observer list with given observer.
51 // It is valid to give NULL as |runner_to_notify|, and in that case
52 // notifications are dispatched on the current runner.
53 // Note that this is a const method and does NOT change 'this' observer
54 // list but returns a new list.
AddObserver(Observer * observer,base::SequencedTaskRunner * runner_to_notify)55 TaskRunnerBoundObserverList<Observer, ObserverStoreType> AddObserver(
56 Observer* observer,
57 base::SequencedTaskRunner* runner_to_notify) const {
58 ObserversListMap observers = observers_;
59 observers.insert(std::make_pair(observer, runner_to_notify));
60 return TaskRunnerBoundObserverList<Observer, ObserverStoreType>(observers);
61 }
62
63 // Notify on the task runner that is given to AddObserver.
64 // If we're already on the runner this just dispatches the method.
65 template <class Method, class Params>
Notify(Method method,const Params & params)66 void Notify(Method method, const Params& params) const {
67 COMPILE_ASSERT(
68 (base::internal::ParamsUseScopedRefptrCorrectly<Params>::value),
69 badunboundmethodparams);
70 for (typename ObserversListMap::const_iterator it = observers_.begin();
71 it != observers_.end(); ++it) {
72 if (!it->second.get() || it->second->RunsTasksOnCurrentThread()) {
73 DispatchToMethod(UnwrapTraits::Unwrap(it->first), method, params);
74 continue;
75 }
76 it->second->PostTask(
77 FROM_HERE,
78 base::Bind(&NotifyWrapper<ObserverStoreType, Method, Params>,
79 it->first, method, params));
80 }
81 }
82
83 private:
84 typedef base::internal::UnwrapTraits<ObserverStoreType> UnwrapTraits;
85
86 ObserversListMap observers_;
87 };
88
89 class FileAccessObserver;
90 class FileChangeObserver;
91 class FileUpdateObserver;
92
93 typedef TaskRunnerBoundObserverList<FileAccessObserver> AccessObserverList;
94 typedef TaskRunnerBoundObserverList<FileChangeObserver> ChangeObserverList;
95 typedef TaskRunnerBoundObserverList<FileUpdateObserver> UpdateObserverList;
96
97 } // namespace storage
98
99 #endif // STORAGE_BROWSER_FILEAPI_TASK_RUNNER_BOUND_OBSERVER_LIST_H_
100