text: // 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.
  
  #ifndef BASE_PREFS_PERSISTENT_PREF_STORE_H_
  #define BASE_PREFS_PERSISTENT_PREF_STORE_H_
  
  #include <string>
  
  #include "base/prefs/base_prefs_export.h"
  #include "base/prefs/writeable_pref_store.h"
  
  // This interface is complementary to the PrefStore interface, declaring
  // additional functionality that adds support for setting values and persisting
  // the data to some backing store.
  class BASE_PREFS_EXPORT PersistentPrefStore : public WriteablePrefStore {
   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,
      PREF_READ_ERROR_MAX_ENUM
    };
  
    class ReadErrorDelegate {
     public:
      virtual ~ReadErrorDelegate() {}
  
      virtual void OnError(PrefReadError error) = 0;
    };
  
    // Equivalent to PrefStore::GetValue but returns a mutable value.
    virtual bool GetMutableValue(const std::string& key,
                                 base::Value** result) = 0;
  
    // Triggers a value changed notification. This function needs to be called
    // if one retrieves a list or dictionary with GetMutableValue and change its
    // value. SetValue takes care of notifications itself. Note that
    // ReportValueChanged will trigger notifications even if nothing has changed.
    virtual void ReportValueChanged(const std::string& key) = 0;
  
    // Same as SetValue, but doesn't generate notifications. This is used by
    // PrefService::GetMutableUserPref() in order to put empty entries
    // into the user pref store. Using SetValue is not an option since existing
    // tests rely on the number of notifications generated.
    virtual void SetValueSilently(const std::string& key, base::Value* value) = 0;
  
    // 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() const = 0;
  
    // Gets the read error. Only valid if IsInitializationComplete() returns true.
    virtual PrefReadError GetReadError() const = 0;
  
    // Reads the preferences from disk. Notifies observers via
    // "PrefStore::OnInitializationCompleted" when done.
    virtual PrefReadError ReadPrefs() = 0;
  
    // Reads the preferences from disk asynchronously. Notifies observers via
    // "PrefStore::OnInitializationCompleted" when done. Also it fires
    // |error_delegate| if it is not NULL and reading error has occurred.
    // Owns |error_delegate|.
    virtual void ReadPrefsAsync(ReadErrorDelegate* error_delegate) = 0;
  
    // Lands any pending writes to disk.
    virtual void CommitPendingWrite() = 0;
  
   protected:
    virtual ~PersistentPrefStore() {}
  };
  
  #endif  // BASE_PREFS_PERSISTENT_PREF_STORE_H_
  