Implementation of leveldb-backed PrefStore

chrome/browser/prefs/leveldb_pref_store.h

+// 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 CHROME_BROWSER_PREFS_LEVELDB_PREF_STORE_H_
+#define CHROME_BROWSER_PREFS_LEVELDB_PREF_STORE_H_
+
+#include <set>
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "base/files/file_path.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/message_loop/message_loop_proxy.h"
+#include "base/observer_list.h"
+#include "base/prefs/persistent_pref_store.h"
+#include "base/prefs/pref_value_map.h"
+#include "base/timer/timer.h"
+
+namespace base {
+class DictionaryValue;
+class SequencedTaskRunner;
+class Value;
+}
+
+namespace leveldb {
+class DB;
+}
+
+// A writable PrefStore implementation that is used for user preferences.
+class LevelDBPrefStore : public PersistentPrefStore {
+ public:
+  // |sequenced_task_runner| is must be a shutdown-blocking task runner, ideally
+  // created by GetTaskRunnerForFile() method above.
+  LevelDBPrefStore(const base::FilePath& pref_filename,
+                   base::SequencedTaskRunner* sequenced_task_runner);
+
+  // PrefStore overrides:
+  virtual bool GetValue(const std::string& key,
+                        const base::Value** result) const OVERRIDE;
+  virtual void AddObserver(PrefStore::Observer* observer) OVERRIDE;
+  virtual void RemoveObserver(PrefStore::Observer* observer) OVERRIDE;
+  virtual bool HasObservers() const OVERRIDE;
+  virtual bool IsInitializationComplete() const OVERRIDE;
+
+  // PersistentPrefStore overrides:
+  virtual bool GetMutableValue(const std::string& key,
+                               base::Value** result) OVERRIDE;
+  // Takes ownership of value.
+  virtual void SetValue(const std::string& key, base::Value* value) OVERRIDE;
+  virtual void SetValueSilently(const std::string& key,
+                                base::Value* value) OVERRIDE;
+  virtual void RemoveValue(const std::string& key) OVERRIDE;
+  virtual bool ReadOnly() const OVERRIDE;
+  virtual PrefReadError GetReadError() const OVERRIDE;
+  virtual PrefReadError ReadPrefs() OVERRIDE;
+  virtual void ReadPrefsAsync(ReadErrorDelegate* error_delegate) OVERRIDE;
+  virtual void CommitPendingWrite() OVERRIDE;
+  virtual void ReportValueChanged(const std::string& key) OVERRIDE;
+
+ private:
+  struct ReadingResults;
+  class FileThreadSerializer;
+
+  virtual ~LevelDBPrefStore();
+
+  static scoped_ptr<ReadingResults> DoReading(const base::FilePath& path);
+  static void OpenDB(const base::FilePath& path,
+                     ReadingResults* reading_results);
+  void OnStorageRead(scoped_ptr<ReadingResults> reading_results);
+
+  void PersistFromUIThread();
+  void RemoveFromUIThread(const std::string& key);
+  void ScheduleWrite();
+
+  void SetValueInternal(const std::string& key,
+                        base::Value* value,
+                        bool notify);
+  void NotifyObservers(const std::string& key);
+  void MarkForInsertion(const std::string& key, const std::string& value);
+  void MarkForDeletion(const std::string& key);
+
+  base::FilePath path_;
+
+  const scoped_refptr<base::SequencedTaskRunner> sequenced_task_runner_;
+  const scoped_refptr<base::SequencedTaskRunner> original_task_runner_;
+
+  PrefValueMap prefs_;
+
+  bool read_only_;
+
+  ObserverList<PrefStore::Observer, true> observers_;
+
+  scoped_ptr<ReadErrorDelegate> error_delegate_;
+
+  bool initialized_;
+  PrefReadError read_error_;
+
+  // This object is created on the UI thread right after preferences are loaded
+  // from disk. A message to delete it is sent to the FILE thread by
+  // ~LevelDBPrefStore.
+  scoped_ptr<FileThreadSerializer> serializer_;
+
+  // Changes are accumulated in |keys_to_delete_| and |keys_to_set_| and are
+  // stored in the database according to |timer_|.
+  std::set<std::string> keys_to_delete_;
+  std::map<std::string, std::string> keys_to_set_;
+  base::OneShotTimer<LevelDBPrefStore> timer_;
+
+  base::WeakPtrFactory<LevelDBPrefStore> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(LevelDBPrefStore);
+};
+
+#endif  // CHROME_BROWSER_PREFS_LEVELDB_PREF_STORE_H_