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// Copyright (c) 2011 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.
#ifndef CHROME_COMMON_PREF_STORE_H_
#define CHROME_COMMON_PREF_STORE_H_
#pragma once
#include <string>
#include "base/basictypes.h"
#include "base/memory/ref_counted.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 PrefStore : public base::RefCounted<PrefStore> {
public:
// Observer interface for monitoring PrefStore.
class Observer {
public:
virtual ~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;
};
// Return values for GetValue().
enum ReadResult {
// Value found and returned.
READ_OK,
// No value present, but skip other pref stores and use default.
READ_USE_DEFAULT,
// No value present.
READ_NO_VALUE,
};
PrefStore() {}
// Add and remove observers.
virtual void AddObserver(Observer* observer) {}
virtual void RemoveObserver(Observer* observer) {}
// 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 READ_OK and if |result|
// is not NULL. Ownership of the |*result| value remains with the PrefStore.
virtual ReadResult GetValue(const std::string& key,
const base::Value** result) const = 0;
protected:
friend class base::RefCounted<PrefStore>;
virtual ~PrefStore() {}
private:
DISALLOW_COPY_AND_ASSIGN(PrefStore);
};
#endif // CHROME_COMMON_PREF_STORE_H_
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