overlay_persistent_pref_store.h revision ddb351dbec246cf1fab5ec20d2d5520909041de1 
1// Copyright (c) 2011 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 CHROME_BROWSER_PREFS_OVERLAY_PERSISTENT_PREF_STORE_H_
6#define CHROME_BROWSER_PREFS_OVERLAY_PERSISTENT_PREF_STORE_H_
7#pragma once
8
9#include <string>
10
11#include "base/basictypes.h"
12#include "base/memory/ref_counted.h"
13#include "base/observer_list.h"
14#include "chrome/browser/prefs/pref_value_map.h"
15#include "chrome/common/persistent_pref_store.h"
16
17// PersistentPrefStore that directs all write operations into a in-memory
18// PrefValueMap. Read operations are first answered by the PrefValueMap.
19// If the PrefValueMap does not contain a value for the requested key,
20// the look-up is passed on to an underlying PersistentPrefStore |underlay_|.
21class OverlayPersistentPrefStore : public PersistentPrefStore,
22                                   public PrefStore::Observer {
23 public:
24  explicit OverlayPersistentPrefStore(PersistentPrefStore* underlay);
25  virtual ~OverlayPersistentPrefStore();
26
27  // Returns true if a value has been set for the |key| in this
28  // OverlayPersistentPrefStore, i.e. if it potentially overrides a value
29  // from the |underlay_|.
30  virtual bool IsSetInOverlay(const std::string& key) const;
31
32  // Methods of PrefStore.
33  virtual void AddObserver(PrefStore::Observer* observer);
34  virtual void RemoveObserver(PrefStore::Observer* observer);
35  virtual bool IsInitializationComplete() const;
36  virtual ReadResult GetValue(const std::string& key,
37                              const Value** result) const;
38
39  // Methods of PersistentPrefStore.
40  virtual ReadResult GetMutableValue(const std::string& key, Value** result);
41  virtual void SetValue(const std::string& key, Value* value);
42  virtual void SetValueSilently(const std::string& key, Value* value);
43  virtual void RemoveValue(const std::string& key);
44  virtual bool ReadOnly() const;
45  virtual PrefReadError ReadPrefs();
46  virtual bool WritePrefs();
47  virtual void ScheduleWritePrefs();
48  virtual void CommitPendingWrite();
49  virtual void ReportValueChanged(const std::string& key);
50
51 private:
52  // Methods of PrefStore::Observer.
53  virtual void OnPrefValueChanged(const std::string& key);
54  virtual void OnInitializationCompleted();
55
56  ObserverList<PrefStore::Observer, true> observers_;
57  PrefValueMap overlay_;
58  scoped_refptr<PersistentPrefStore> underlay_;
59
60  DISALLOW_COPY_AND_ASSIGN(OverlayPersistentPrefStore);
61};
62
63#endif  // CHROME_BROWSER_PREFS_OVERLAY_PERSISTENT_PREF_STORE_H_
64