base/prefs/overlay_user_pref_store.h

   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_|.
  22 class 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 size_t NumberOfObservers() 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 void MarkNeedsEmptyValue(const std::string& key) OVERRIDE;
  48   virtual bool ReadOnly() const OVERRIDE;
  49   virtual PrefReadError GetReadError() const OVERRIDE;
  50   virtual PrefReadError ReadPrefs() OVERRIDE;
  51   virtual void ReadPrefsAsync(ReadErrorDelegate* delegate) OVERRIDE;
  52   virtual void CommitPendingWrite() OVERRIDE;
  53   virtual void ReportValueChanged(const std::string& key) OVERRIDE;
  54
  55   // Methods of PrefStore::Observer.
  56   virtual void OnPrefValueChanged(const std::string& key) OVERRIDE;
  57   virtual void OnInitializationCompleted(bool succeeded) OVERRIDE;
  58
  59   void RegisterOverlayPref(const std::string& key);
  60   void RegisterOverlayPref(const std::string& overlay_key,
  61                            const std::string& underlay_key);
  62
  63  protected:
  64   virtual ~OverlayUserPrefStore();
  65
  66  private:
  67   typedef std::map<std::string, std::string> NamesMap;
  68
  69   const std::string& GetOverlayKey(const std::string& underlay_key) const;
  70   const std::string& GetUnderlayKey(const std::string& overlay_key) const;
  71
  72   // Returns true if |key| corresponds to a preference that shall be stored in
  73   // an in-memory PrefStore that is not persisted to disk.
  74   bool ShallBeStoredInOverlay(const std::string& key) const;
  75
  76   ObserverList<PrefStore::Observer, true> observers_;
  77   PrefValueMap overlay_;
  78   scoped_refptr<PersistentPrefStore> underlay_;
  79   NamesMap overlay_to_underlay_names_map_;
  80   NamesMap underlay_to_overlay_names_map_;
  81
  82   DISALLOW_COPY_AND_ASSIGN(OverlayUserPrefStore);
  83 };
  84
  85 #endif  // BASE_PREFS_OVERLAY_USER_PREF_STORE_H_