Implementation of leveldb-backed PrefStore

base/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 BASE_PREFS_JSON_PREF_STORE_H_
 #define BASE_PREFS_JSON_PREF_STORE_H_
 
 #include <set>
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/files/file_path.h"
-#include "base/files/important_file_writer.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop_proxy.h"
 #include "base/observer_list.h"
-#include "base/prefs/base_prefs_export.h"
 #include "base/prefs/persistent_pref_store.h"
-
-class PrefFilter;
+#include "base/prefs/pref_value_map.h"
+#include "base/timer/timer.h"
 
 namespace base {
 class DictionaryValue;
-class FilePath;
 class SequencedTaskRunner;
-class SequencedWorkerPool;
 class Value;
 }
 
+namespace leveldb {
+class DB;
+}
 
 // A writable PrefStore implementation that is used for user preferences.
-class BASE_PREFS_EXPORT JsonPrefStore
-    : public PersistentPrefStore,
-      public base::ImportantFileWriter::DataSerializer {
+class BASE_PREFS_EXPORT LevelDBPrefStore : public PersistentPrefStore {
  public:
-  // Returns instance of SequencedTaskRunner which guarantees that file
-  // operations on the same file will be executed in sequenced order.
-  static scoped_refptr<base::SequencedTaskRunner> GetTaskRunnerForFile(
-      const base::FilePath& pref_filename,
-      base::SequencedWorkerPool* worker_pool);
-
   // |sequenced_task_runner| is must be a shutdown-blocking task runner, ideally
   // created by GetTaskRunnerForFile() method above.
-  JsonPrefStore(const base::FilePath& pref_filename,
-                base::SequencedTaskRunner* sequenced_task_runner,
-                scoped_ptr<PrefFilter> pref_filter);
+  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;
 
-  // This method is called after JSON file has been read. Method takes
-  // ownership of the |value| pointer. Note, this method is used with
-  // asynchronous file reading, so class exposes it only for the internal needs.
-  // (read: do not call it manually).
-  void OnFileRead(base::Value* value_owned, PrefReadError error, bool no_dir);
+ private:
+  struct ReadingResults;
+  class FileThreadSerializer;
 
- private:
-  virtual ~JsonPrefStore();
+  virtual ~LevelDBPrefStore();
 
-  // ImportantFileWriter::DataSerializer overrides:
-  virtual bool SerializeData(std::string* output) OVERRIDE;
+  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_;
 
-  scoped_ptr<base::DictionaryValue> prefs_;
+  PrefValueMap prefs_;
 
   bool read_only_;
 
-  // Helper for safely writing pref data.
-  base::ImportantFileWriter writer_;
-
-  scoped_ptr<PrefFilter> pref_filter_;
   ObserverList<PrefStore::Observer, true> observers_;
 
   scoped_ptr<ReadErrorDelegate> error_delegate_;
 
   bool initialized_;
   PrefReadError read_error_;
 
-  std::set<std::string> keys_need_empty_value_;
+  // 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_;
+  std::set<std::string> keys_to_delete_;

[Mattias Nissler (ping if slow), 2014/04/14 10:11:41]

Please document |keys_to_delete_|, |keys_to_set_| and |timer_|

[dgrogan, 2014/04/17 01:10:27]

Done.

+  std::map<std::string, std::string> keys_to_set_;
+  base::OneShotTimer<LevelDBPrefStore> timer_;
 
-  DISALLOW_COPY_AND_ASSIGN(JsonPrefStore);
+  base::WeakPtrFactory<LevelDBPrefStore> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(LevelDBPrefStore);
 };
 
 #endif  // BASE_PREFS_JSON_PREF_STORE_H_