base/prefs/persistent_pref_store.h

   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/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 PrefStore {
  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 order here as it will change the server's meaning
  21   // of the histogram.
  22   enum PrefReadError {
  23     PREF_READ_ERROR_NONE = 0,
  24     PREF_READ_ERROR_JSON_PARSE,
  25     PREF_READ_ERROR_JSON_TYPE,
  26     PREF_READ_ERROR_ACCESS_DENIED,
  27     PREF_READ_ERROR_FILE_OTHER,
  28     PREF_READ_ERROR_FILE_LOCKED,
  29     PREF_READ_ERROR_NO_FILE,
  30     PREF_READ_ERROR_JSON_REPEAT,
  31     PREF_READ_ERROR_OTHER,
  32     PREF_READ_ERROR_FILE_NOT_SPECIFIED,
  33     PREF_READ_ERROR_MAX_ENUM
  34   };
  35
  36   class ReadErrorDelegate {
  37    public:
  38     virtual ~ReadErrorDelegate() {}
  39
  40     virtual void OnError(PrefReadError error) = 0;
  41   };
  42
  43   // Equivalent to PrefStore::GetValue but returns a mutable value.
  44   virtual bool GetMutableValue(const std::string& key,
  45                                base::Value** result) = 0;
  46
  47   // Triggers a value changed notification. This function needs to be called
  48   // if one retrieves a list or dictionary with GetMutableValue and change its
  49   // value. SetValue takes care of notifications itself. Note that
  50   // ReportValueChanged will trigger notifications even if nothing has changed.
  51   virtual void ReportValueChanged(const std::string& key) = 0;
  52
  53   // Sets a |value| for |key| in the store. Assumes ownership of |value|, which
  54   // must be non-NULL.
  55   virtual void SetValue(const std::string& key, base::Value* value) = 0;
  56
  57   // Same as SetValue, but doesn't generate notifications. This is used by
  58   // PrefService::GetMutableUserPref() in order to put empty entries
  59   // into the user pref store. Using SetValue is not an option since existing
  60   // tests rely on the number of notifications generated.
  61   virtual void SetValueSilently(const std::string& key, base::Value* value) = 0;
  62
  63   // Removes the value for |key|.
  64   virtual void RemoveValue(const std::string& key) = 0;
  65
  66   // Marks that the |key| with empty ListValue/DictionaryValue needs to be
  67   // persisted.
  68   virtual void MarkNeedsEmptyValue(const std::string& key) = 0;
  69
  70   // Whether the store is in a pseudo-read-only mode where changes are not
  71   // actually persisted to disk.  This happens in some cases when there are
  72   // read errors during startup.
  73   virtual bool ReadOnly() const = 0;
  74
  75   // Gets the read error. Only valid if IsInitializationComplete() returns true.
  76   virtual PrefReadError GetReadError() const = 0;
  77
  78   // Reads the preferences from disk. Notifies observers via
  79   // "PrefStore::OnInitializationCompleted" when done.
  80   virtual PrefReadError ReadPrefs() = 0;
  81
  82   // Reads the preferences from disk asynchronously. Notifies observers via
  83   // "PrefStore::OnInitializationCompleted" when done. Also it fires
  84   // |error_delegate| if it is not NULL and reading error has occurred.
  85   // Owns |error_delegate|.
  86   virtual void ReadPrefsAsync(ReadErrorDelegate* error_delegate) = 0;
  87
  88   // Lands any pending writes to disk.
  89   virtual void CommitPendingWrite() = 0;
  90
  91  protected:
  92   virtual ~PersistentPrefStore() {}
  93 };
  94
  95 #endif  // BASE_PREFS_PERSISTENT_PREF_STORE_H_