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 BASE_PREFS_OVERLAY_USER_PREF_STORE_H_
6#define BASE_PREFS_OVERLAY_USER_PREF_STORE_H_
7
8#include <map>
9#include <string>
10
11#include "base/basictypes.h"
12#include "base/memory/ref_counted.h"
13#include "base/observer_list.h"
14#include "base/prefs/base_prefs_export.h"
15#include "base/prefs/persistent_pref_store.h"
16#include "base/prefs/pref_value_map.h"
17
18// PersistentPrefStore that directs all write operations into an in-memory
19// PrefValueMap. Read operations are first answered by the PrefValueMap.
20// If the PrefValueMap does not contain a value for the requested key,
21// the look-up is passed on to an underlying PersistentPrefStore |underlay_|.
22class BASE_PREFS_EXPORT OverlayUserPrefStore : public PersistentPrefStore,
23                                               public PrefStore::Observer {
24 public:
25  explicit OverlayUserPrefStore(PersistentPrefStore* underlay);
26
27  // Returns true if a value has been set for the |key| in this
28  // OverlayUserPrefStore, 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) OVERRIDE;
34  virtual void RemoveObserver(PrefStore::Observer* observer) OVERRIDE;
35  virtual bool HasObservers() const OVERRIDE;
36  virtual bool IsInitializationComplete() const OVERRIDE;
37  virtual bool GetValue(const std::string& key,
38                        const base::Value** result) const OVERRIDE;
39
40  // Methods of PersistentPrefStore.
41  virtual bool GetMutableValue(const std::string& key,
42                               base::Value** result) OVERRIDE;
43  virtual void SetValue(const std::string& key, base::Value* value) OVERRIDE;
44  virtual void SetValueSilently(const std::string& key,
45                                base::Value* value) OVERRIDE;
46  virtual void RemoveValue(const std::string& key) OVERRIDE;
47  virtual bool ReadOnly() const OVERRIDE;
48  virtual PrefReadError GetReadError() const OVERRIDE;
49  virtual PrefReadError ReadPrefs() OVERRIDE;
50  virtual void ReadPrefsAsync(ReadErrorDelegate* delegate) OVERRIDE;
51  virtual void CommitPendingWrite() OVERRIDE;
52  virtual void ReportValueChanged(const std::string& key) OVERRIDE;
53
54  // Methods of PrefStore::Observer.
55  virtual void OnPrefValueChanged(const std::string& key) OVERRIDE;
56  virtual void OnInitializationCompleted(bool succeeded) OVERRIDE;
57
58  void RegisterOverlayPref(const std::string& key);
59  void RegisterOverlayPref(const std::string& overlay_key,
60                           const std::string& underlay_key);
61
62 protected:
63  virtual ~OverlayUserPrefStore();
64
65 private:
66  typedef std::map<std::string, std::string> NamesMap;
67
68  const std::string& GetOverlayKey(const std::string& underlay_key) const;
69  const std::string& GetUnderlayKey(const std::string& overlay_key) const;
70
71  // Returns true if |key| corresponds to a preference that shall be stored in
72  // an in-memory PrefStore that is not persisted to disk.
73  bool ShallBeStoredInOverlay(const std::string& key) const;
74
75  ObserverList<PrefStore::Observer, true> observers_;
76  PrefValueMap overlay_;
77  scoped_refptr<PersistentPrefStore> underlay_;
78  NamesMap overlay_to_underlay_names_map_;
79  NamesMap underlay_to_overlay_names_map_;
80
81  DISALLOW_COPY_AND_ASSIGN(OverlayUserPrefStore);
82};
83
84#endif  // BASE_PREFS_OVERLAY_USER_PREF_STORE_H_
85