base/prefs/json_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_JSON_PREF_STORE_H_
   6 #define BASE_PREFS_JSON_PREF_STORE_H_
   7
   8 #include <set>
   9 #include <string>
  10
  11 #include "base/basictypes.h"
  12 #include "base/compiler_specific.h"
  13 #include "base/files/file_path.h"
  14 #include "base/files/important_file_writer.h"
  15 #include "base/memory/scoped_ptr.h"
  16 #include "base/message_loop_proxy.h"
  17 #include "base/observer_list.h"
  18 #include "base/prefs/base_prefs_export.h"
  19 #include "base/prefs/persistent_pref_store.h"
  20
  21 namespace base {
  22 class DictionaryValue;
  23 class FilePath;
  24 class SequencedWorkerPool;
  25 class SequencedTaskRunner;
  26 class Value;
  27 }
  28
  29
  30 // A writable PrefStore implementation that is used for user preferences.
  31 class BASE_PREFS_EXPORT JsonPrefStore
  32     : public PersistentPrefStore,
  33       public base::ImportantFileWriter::DataSerializer {
  34  public:
  35   // Returns instance of SequencedTaskRunner which guarantees that file
  36   // operations on the same file will be executed in sequenced order.
  37   static scoped_refptr<base::SequencedTaskRunner> GetTaskRunnerForFile(
  38       const base::FilePath& pref_filename,
  39       base::SequencedWorkerPool* worker_pool);
  40
  41   // |sequenced_task_runner| is must be a shutdown-blocking task runner, ideally
  42   // created by GetTaskRunnerForFile() method above.
  43   JsonPrefStore(const base::FilePath& pref_filename,
  44                 base::SequencedTaskRunner* sequenced_task_runner);
  45
  46   // PrefStore overrides:
  47   virtual bool GetValue(const std::string& key,
  48                         const base::Value** result) const OVERRIDE;
  49   virtual void AddObserver(PrefStore::Observer* observer) OVERRIDE;
  50   virtual void RemoveObserver(PrefStore::Observer* observer) OVERRIDE;
  51   virtual size_t NumberOfObservers() const OVERRIDE;
  52   virtual bool IsInitializationComplete() const OVERRIDE;
  53
  54   // PersistentPrefStore overrides:
  55   virtual bool GetMutableValue(const std::string& key,
  56                                base::Value** result) OVERRIDE;
  57   virtual void SetValue(const std::string& key, base::Value* value) OVERRIDE;
  58   virtual void SetValueSilently(const std::string& key,
  59                                 base::Value* value) OVERRIDE;
  60   virtual void RemoveValue(const std::string& key) OVERRIDE;
  61   virtual void MarkNeedsEmptyValue(const std::string& key) OVERRIDE;
  62   virtual bool ReadOnly() const OVERRIDE;
  63   virtual PrefReadError GetReadError() const OVERRIDE;
  64   virtual PrefReadError ReadPrefs() OVERRIDE;
  65   virtual void ReadPrefsAsync(ReadErrorDelegate* error_delegate) OVERRIDE;
  66   virtual void CommitPendingWrite() OVERRIDE;
  67   virtual void ReportValueChanged(const std::string& key) OVERRIDE;
  68
  69   // This method is called after JSON file has been read. Method takes
  70   // ownership of the |value| pointer. Note, this method is used with
  71   // asynchronous file reading, so class exposes it only for the internal needs.
  72   // (read: do not call it manually).
  73   void OnFileRead(base::Value* value_owned, PrefReadError error, bool no_dir);
  74
  75  private:
  76   virtual ~JsonPrefStore();
  77
  78   // ImportantFileWriter::DataSerializer overrides:
  79   virtual bool SerializeData(std::string* output) OVERRIDE;
  80
  81   base::FilePath path_;
  82   const scoped_refptr<base::SequencedTaskRunner> sequenced_task_runner_;
  83
  84   scoped_ptr<base::DictionaryValue> prefs_;
  85
  86   bool read_only_;
  87
  88   // Helper for safely writing pref data.
  89   base::ImportantFileWriter writer_;
  90
  91   ObserverList<PrefStore::Observer, true> observers_;
  92
  93   scoped_ptr<ReadErrorDelegate> error_delegate_;
  94
  95   bool initialized_;
  96   PrefReadError read_error_;
  97
  98   std::set<std::string> keys_need_empty_value_;
  99
 100   DISALLOW_COPY_AND_ASSIGN(JsonPrefStore);
 101 };
 102
 103 #endif  // BASE_PREFS_JSON_PREF_STORE_H_