chrome/browser/prefs/tracked/segregated_pref_store.h

   1 // Copyright 2014 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_TRACKED_SEGREGATED_PREF_STORE_H_
   6 #define CHROME_BROWSER_PREFS_TRACKED_SEGREGATED_PREF_STORE_H_
   7
   8 #include <set>
   9 #include <string>
  10
  11 #include "base/compiler_specific.h"
  12 #include "base/macros.h"
  13 #include "base/memory/ref_counted.h"
  14 #include "base/memory/scoped_ptr.h"
  15 #include "base/observer_list.h"
  16 #include "base/prefs/persistent_pref_store.h"
  17
  18 // Provides a unified PersistentPrefStore implementation that splits its storage
  19 // and retrieval between two underlying PersistentPrefStore instances: a set of
  20 // preference names is used to partition the preferences.
  21 //
  22 // Combines properties of the two stores as follows:
  23 //   * The unified read error will be:
  24 //                           Selected Store Error
  25 //    Default Store Error | NO_ERROR      | NO_FILE       | other selected |
  26 //               NO_ERROR | NO_ERROR      | NO_ERROR      | other selected |
  27 //               NO_FILE  | NO_FILE       | NO_FILE       | NO_FILE        |
  28 //          other default | other default | other default | other default  |
  29 //   * The unified initialization success, initialization completion, and
  30 //     read-only state are the boolean OR of the underlying stores' properties.
  31 class SegregatedPrefStore : public PersistentPrefStore {
  32  public:
  33   // Creates an instance that delegates to |selected_pref_store| for the
  34   // preferences named in |selected_pref_names| and to |default_pref_store|
  35   // for all others. If an unselected preference is present in
  36   // |selected_pref_store| (i.e. because it was previously selected) it will
  37   // be migrated back to |default_pref_store| upon access via a non-const
  38   // method.
  39   // |on_initialization| will be invoked when both stores have been initialized,
  40   // before observers of the SegregatedPrefStore store are notified.
  41   SegregatedPrefStore(
  42       const scoped_refptr<PersistentPrefStore>& default_pref_store,
  43       const scoped_refptr<PersistentPrefStore>& selected_pref_store,
  44       const std::set<std::string>& selected_pref_names);
  45
  46   // PrefStore implementation
  47   virtual void AddObserver(Observer* observer) OVERRIDE;
  48   virtual void RemoveObserver(Observer* observer) OVERRIDE;
  49   virtual bool HasObservers() const OVERRIDE;
  50   virtual bool IsInitializationComplete() const OVERRIDE;
  51   virtual bool GetValue(const std::string& key,
  52                         const base::Value** result) const OVERRIDE;
  53
  54   // WriteablePrefStore implementation
  55   virtual void SetValue(const std::string& key, base::Value* value) OVERRIDE;
  56   virtual void RemoveValue(const std::string& key) OVERRIDE;
  57
  58   // PersistentPrefStore implementation
  59   virtual bool GetMutableValue(const std::string& key,
  60                                base::Value** result) OVERRIDE;
  61   virtual void ReportValueChanged(const std::string& key) OVERRIDE;
  62   virtual void SetValueSilently(const std::string& key,
  63                                 base::Value* value) OVERRIDE;
  64   virtual bool ReadOnly() const OVERRIDE;
  65   virtual PrefReadError GetReadError() const OVERRIDE;
  66   virtual PrefReadError ReadPrefs() OVERRIDE;
  67   virtual void ReadPrefsAsync(ReadErrorDelegate* error_delegate) OVERRIDE;
  68   virtual void CommitPendingWrite() OVERRIDE;
  69
  70  private:
  71   // Aggregates events from the underlying stores and synthesizes external
  72   // events via |on_initialization|, |read_error_delegate_|, and |observers_|.
  73   class AggregatingObserver : public PrefStore::Observer {
  74    public:
  75     explicit AggregatingObserver(SegregatedPrefStore* outer);
  76
  77     // PrefStore::Observer implementation
  78     virtual void OnPrefValueChanged(const std::string& key) OVERRIDE;
  79     virtual void OnInitializationCompleted(bool succeeded) OVERRIDE;
  80
  81    private:
  82     SegregatedPrefStore* outer_;
  83     int failed_sub_initializations_;
  84     int successful_sub_initializations_;
  85
  86     DISALLOW_COPY_AND_ASSIGN(AggregatingObserver);
  87   };
  88
  89   virtual ~SegregatedPrefStore();
  90
  91   // Returns |selected_pref_store| if |key| is selected and |default_pref_store|
  92   // otherwise.
  93   PersistentPrefStore* StoreForKey(const std::string& key);
  94   const PersistentPrefStore* StoreForKey(const std::string& key) const;
  95
  96   scoped_refptr<PersistentPrefStore> default_pref_store_;
  97   scoped_refptr<PersistentPrefStore> selected_pref_store_;
  98   std::set<std::string> selected_preference_names_;
  99
 100   scoped_ptr<PersistentPrefStore::ReadErrorDelegate> read_error_delegate_;
 101   ObserverList<PrefStore::Observer, true> observers_;
 102   AggregatingObserver aggregating_observer_;
 103
 104   DISALLOW_COPY_AND_ASSIGN(SegregatedPrefStore);
 105 };
 106
 107 #endif  // CHROME_BROWSER_PREFS_TRACKED_SEGREGATED_PREF_STORE_H_