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      1 // Copyright (c) 2012 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 BASE_PREFS_PERSISTENT_PREF_STORE_H_
      6 #define BASE_PREFS_PERSISTENT_PREF_STORE_H_
      7 
      8 #include <string>
      9 
     10 #include "base/prefs/base_prefs_export.h"
     11 #include "base/prefs/writeable_pref_store.h"
     12 
     13 // This interface is complementary to the PrefStore interface, declaring
     14 // additional functionality that adds support for setting values and persisting
     15 // the data to some backing store.
     16 class BASE_PREFS_EXPORT PersistentPrefStore : public WriteablePrefStore {
     17  public:
     18   // Unique integer code for each type of error so we can report them
     19   // distinctly in a histogram.
     20   // NOTE: Don't change the explicit values of the enums as it will change the
     21   // server's meaning of the histogram.
     22   enum PrefReadError {
     23     PREF_READ_ERROR_NONE = 0,
     24     PREF_READ_ERROR_JSON_PARSE = 1,
     25     PREF_READ_ERROR_JSON_TYPE = 2,
     26     PREF_READ_ERROR_ACCESS_DENIED = 3,
     27     PREF_READ_ERROR_FILE_OTHER = 4,
     28     PREF_READ_ERROR_FILE_LOCKED = 5,
     29     PREF_READ_ERROR_NO_FILE = 6,
     30     PREF_READ_ERROR_JSON_REPEAT = 7,
     31     // PREF_READ_ERROR_OTHER = 8,  // Deprecated.
     32     PREF_READ_ERROR_FILE_NOT_SPECIFIED = 9,
     33     // Indicates that ReadPrefs() couldn't complete synchronously and is waiting
     34     // for an asynchronous task to complete first.
     35     PREF_READ_ERROR_ASYNCHRONOUS_TASK_INCOMPLETE = 10,
     36     PREF_READ_ERROR_MAX_ENUM
     37   };
     38 
     39   class ReadErrorDelegate {
     40    public:
     41     virtual ~ReadErrorDelegate() {}
     42 
     43     virtual void OnError(PrefReadError error) = 0;
     44   };
     45 
     46   // Whether the store is in a pseudo-read-only mode where changes are not
     47   // actually persisted to disk.  This happens in some cases when there are
     48   // read errors during startup.
     49   virtual bool ReadOnly() const = 0;
     50 
     51   // Gets the read error. Only valid if IsInitializationComplete() returns true.
     52   virtual PrefReadError GetReadError() const = 0;
     53 
     54   // Reads the preferences from disk. Notifies observers via
     55   // "PrefStore::OnInitializationCompleted" when done.
     56   virtual PrefReadError ReadPrefs() = 0;
     57 
     58   // Reads the preferences from disk asynchronously. Notifies observers via
     59   // "PrefStore::OnInitializationCompleted" when done. Also it fires
     60   // |error_delegate| if it is not NULL and reading error has occurred.
     61   // Owns |error_delegate|.
     62   virtual void ReadPrefsAsync(ReadErrorDelegate* error_delegate) = 0;
     63 
     64   // Lands any pending writes to disk.
     65   virtual void CommitPendingWrite() = 0;
     66 
     67   // Schedule a write if there is any lossy data pending. Unlike
     68   // CommitPendingWrite() this does not immediately sync to disk, instead it
     69   // triggers an eventual write if there is lossy data pending and if there
     70   // isn't one scheduled already.
     71   virtual void SchedulePendingLossyWrites() = 0;
     72 
     73  protected:
     74   ~PersistentPrefStore() override {}
     75 };
     76 
     77 #endif  // BASE_PREFS_PERSISTENT_PREF_STORE_H_
     78