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      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_PREF_STORE_H_
      6 #define BASE_PREFS_PREF_STORE_H_
      7 
      8 #include <string>
      9 
     10 #include "base/basictypes.h"
     11 #include "base/memory/ref_counted.h"
     12 #include "base/prefs/base_prefs_export.h"
     13 
     14 namespace base {
     15 class Value;
     16 }
     17 
     18 // This is an abstract interface for reading and writing from/to a persistent
     19 // preference store, used by PrefService. An implementation using a JSON file
     20 // can be found in JsonPrefStore, while an implementation without any backing
     21 // store for testing can be found in TestingPrefStore. Furthermore, there is
     22 // CommandLinePrefStore, which bridges command line options to preferences and
     23 // ConfigurationPolicyPrefStore, which is used for hooking up configuration
     24 // policy with the preference subsystem.
     25 class BASE_PREFS_EXPORT PrefStore : public base::RefCounted<PrefStore> {
     26  public:
     27   // Observer interface for monitoring PrefStore.
     28   class BASE_PREFS_EXPORT Observer {
     29    public:
     30     // Called when the value for the given |key| in the store changes.
     31     virtual void OnPrefValueChanged(const std::string& key) = 0;
     32     // Notification about the PrefStore being fully initialized.
     33     virtual void OnInitializationCompleted(bool succeeded) = 0;
     34 
     35    protected:
     36     virtual ~Observer() {}
     37   };
     38 
     39   PrefStore() {}
     40 
     41   // Add and remove observers.
     42   virtual void AddObserver(Observer* observer) {}
     43   virtual void RemoveObserver(Observer* observer) {}
     44   virtual bool HasObservers() const;
     45 
     46   // Whether the store has completed all asynchronous initialization.
     47   virtual bool IsInitializationComplete() const;
     48 
     49   // Get the value for a given preference |key| and stores it in |*result|.
     50   // |*result| is only modified if the return value is true and if |result|
     51   // is not NULL. Ownership of the |*result| value remains with the PrefStore.
     52   virtual bool GetValue(const std::string& key,
     53                         const base::Value** result) const = 0;
     54 
     55  protected:
     56   friend class base::RefCounted<PrefStore>;
     57   virtual ~PrefStore() {}
     58 
     59  private:
     60   DISALLOW_COPY_AND_ASSIGN(PrefStore);
     61 };
     62 
     63 #endif  // BASE_PREFS_PREF_STORE_H_
     64