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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <string>
#include "base/basictypes.h"
#include "base/memory/ref_counted.h"
#include "base/prefs/base_prefs_export.h"
namespace base {
class Value;
// This is an abstract interface for reading and writing from/to a persistent
// preference store, used by PrefService. An implementation using a JSON file
// can be found in JsonPrefStore, while an implementation without any backing
// store for testing can be found in TestingPrefStore. Furthermore, there is
// CommandLinePrefStore, which bridges command line options to preferences and
// ConfigurationPolicyPrefStore, which is used for hooking up configuration
// policy with the preference subsystem.
class BASE_PREFS_EXPORT PrefStore : public base::RefCounted<PrefStore> {
// Observer interface for monitoring PrefStore.
class BASE_PREFS_EXPORT Observer {
// Called when the value for the given |key| in the store changes.
virtual void OnPrefValueChanged(const std::string& key) = 0;
// Notification about the PrefStore being fully initialized.
virtual void OnInitializationCompleted(bool succeeded) = 0;
virtual ~Observer() {}
PrefStore() {}
// Add and remove observers.
virtual void AddObserver(Observer* observer) {}
virtual void RemoveObserver(Observer* observer) {}
virtual size_t NumberOfObservers() const;
// Whether the store has completed all asynchronous initialization.
virtual bool IsInitializationComplete() const;
// Get the value for a given preference |key| and stores it in |*result|.
// |*result| is only modified if the return value is true and if |result|
// is not NULL. Ownership of the |*result| value remains with the PrefStore.
virtual bool GetValue(const std::string& key,
const base::Value** result) const = 0;
friend class base::RefCounted<PrefStore>;
virtual ~PrefStore() {}