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// Copyright (c) 2010 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
class DictionaryValue;
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 (currently used for testing) can be found in |DummyPrefStore|.
class PrefStore {
public:
// Unique integer code for each type of error so we can report them
// distinctly in a histogram.
// NOTE: Don't change the order here as it will change the server's meaning
// of the histogram.
enum PrefReadError {
PREF_READ_ERROR_NONE = 0,
PREF_READ_ERROR_JSON_PARSE,
PREF_READ_ERROR_JSON_TYPE,
PREF_READ_ERROR_ACCESS_DENIED,
PREF_READ_ERROR_FILE_OTHER,
PREF_READ_ERROR_FILE_LOCKED,
PREF_READ_ERROR_NO_FILE,
PREF_READ_ERROR_JSON_REPEAT,
PREF_READ_ERROR_OTHER,
PREF_READ_ERROR_FILE_NOT_SPECIFIED
};
// To require that the default value be used for a preference, a
// PrefStore can set the value in its own prefs dictionary to the
// sentinel Value returned by this function.
// TODO(danno): Instead of having a sentinel value, pref stores
// should return a richer set of information from the property
// accessor methods to indicate that the default should be used.
static Value* CreateUseDefaultSentinelValue();
// Returns true if a value is the special sentinel value created by
// CreateUseDefaultSentinelValue.
static bool IsUseDefaultSentinelValue(Value* value);
virtual ~PrefStore() { }
// Whether the store is in a pseudo-read-only mode where changes are not
// actually persisted to disk. This happens in some cases when there are
// read errors during startup.
virtual bool ReadOnly() { return true; }
// TODO(danno): PrefValueStore shouldn't allow direct access to the
// DictionaryValue. Instead, it should have getters that return a
// richer set of information for a pref, including if the store
// wants to return the default value for a preference.
virtual DictionaryValue* prefs() const = 0;
virtual PrefReadError ReadPrefs() = 0;
virtual bool WritePrefs() { return true; }
virtual void ScheduleWritePrefs() { }
};
#endif // CHROME_COMMON_PREF_STORE_H_
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