Home | History | Annotate | Download | only in common 
      1 // Copyright (c) 2011 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_COMMON_PREF_STORE_H_
      6 #define CHROME_COMMON_PREF_STORE_H_
      7 #pragma once
      8 
      9 #include <string>
     10 
     11 #include "base/basictypes.h"
     12 #include "base/memory/ref_counted.h"
     13 
     14 class Value;
     15 
     16 // This is an abstract interface for reading and writing from/to a persistent
     17 // preference store, used by PrefService. An implementation using a JSON file
     18 // can be found in JsonPrefStore, while an implementation without any backing
     19 // store for testing can be found in TestingPrefStore. Furthermore, there is
     20 // CommandLinePrefStore, which bridges command line options to preferences and
     21 // ConfigurationPolicyPrefStore, which is used for hooking up configuration
     22 // policy with the preference subsystem.
     23 class PrefStore : public base::RefCounted<PrefStore> {
     24  public:
     25   // Observer interface for monitoring PrefStore.
     26   class Observer {
     27    public:
     28     virtual ~Observer() {}
     29 
     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() = 0;
     34   };
     35 
     36   // Return values for GetValue().
     37   enum ReadResult {
     38     // Value found and returned.
     39     READ_OK,
     40     // No value present, but skip other pref stores and use default.
     41     READ_USE_DEFAULT,
     42     // No value present.
     43     READ_NO_VALUE,
     44   };
     45 
     46   PrefStore() {}
     47 
     48   // Add and remove observers.
     49   virtual void AddObserver(Observer* observer) {}
     50   virtual void RemoveObserver(Observer* observer) {}
     51 
     52   // Whether the store has completed all asynchronous initialization.
     53   virtual bool IsInitializationComplete() const;
     54 
     55   // Get the value for a given preference |key| and stores it in |result|.
     56   // |result| is only modified if the return value is READ_OK. Ownership of the
     57   // |result| value remains with the PrefStore.
     58   virtual ReadResult GetValue(const std::string& key,
     59                               const Value** result) const = 0;
     60 
     61  protected:
     62   friend class base::RefCounted<PrefStore>;
     63   virtual ~PrefStore() {}
     64 
     65  private:
     66   DISALLOW_COPY_AND_ASSIGN(PrefStore);
     67 };
     68 
     69 #endif  // CHROME_COMMON_PREF_STORE_H_
     70