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   void AddObserver(PrefStore::Observer* observer) override;
  34   void RemoveObserver(PrefStore::Observer* observer) override;
  35   bool HasObservers() const override;
  36   bool IsInitializationComplete() const override;
  37   bool GetValue(const std::string& key,
  38                 const base::Value** result) const override;
  39
  40   // Methods of PersistentPrefStore.
  41   bool GetMutableValue(const std::string& key, base::Value** result) override;
  42   void SetValue(const std::string& key, base::Value* value) override;
  43   void SetValueSilently(const std::string& key, base::Value* value) override;
  44   void RemoveValue(const std::string& key) override;
  45   bool ReadOnly() const override;
  46   PrefReadError GetReadError() const override;
  47   PrefReadError ReadPrefs() override;
  48   void ReadPrefsAsync(ReadErrorDelegate* delegate) override;
  49   void CommitPendingWrite() override;
  50   void ReportValueChanged(const std::string& key) override;
  51
  52   // Methods of PrefStore::Observer.
  53   void OnPrefValueChanged(const std::string& key) override;
  54   void OnInitializationCompleted(bool succeeded) override;
  55
  56   void RegisterOverlayPref(const std::string& key);
  57   void RegisterOverlayPref(const std::string& overlay_key,
  58                            const std::string& underlay_key);
  59
  60  protected:
  61   ~OverlayUserPrefStore() override;
  62
  63  private:
  64   typedef std::map<std::string, std::string> NamesMap;
  65
  66   const std::string& GetOverlayKey(const std::string& underlay_key) const;
  67   const std::string& GetUnderlayKey(const std::string& overlay_key) const;
  68
  69   // Returns true if |key| corresponds to a preference that shall be stored in
  70   // an in-memory PrefStore that is not persisted to disk.
  71   bool ShallBeStoredInOverlay(const std::string& key) const;
  72
  73   ObserverList<PrefStore::Observer, true> observers_;
  74   PrefValueMap overlay_;
  75   scoped_refptr<PersistentPrefStore> underlay_;
  76   NamesMap overlay_to_underlay_names_map_;
  77   NamesMap underlay_to_overlay_names_map_;
  78
  79   DISALLOW_COPY_AND_ASSIGN(OverlayUserPrefStore);
  80 };
  81
  82 #endif  // BASE_PREFS_OVERLAY_USER_PREF_STORE_H_