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/callback_forward.h"
  13 #include "base/compiler_specific.h"
  14 #include "base/files/file_path.h"
  15 #include "base/files/important_file_writer.h"
  16 #include "base/memory/scoped_ptr.h"
  17 #include "base/memory/weak_ptr.h"
  18 #include "base/message_loop/message_loop_proxy.h"
  19 #include "base/observer_list.h"
  20 #include "base/prefs/base_prefs_export.h"
  21 #include "base/prefs/persistent_pref_store.h"
  22
  23 class PrefFilter;
  24
  25 namespace base {
  26 class DictionaryValue;
  27 class FilePath;
  28 class SequencedTaskRunner;
  29 class SequencedWorkerPool;
  30 class Value;
  31 }
  32
  33
  34 // A writable PrefStore implementation that is used for user preferences.
  35 class BASE_PREFS_EXPORT JsonPrefStore
  36     : public PersistentPrefStore,
  37       public base::ImportantFileWriter::DataSerializer,
  38       public base::SupportsWeakPtr<JsonPrefStore> {
  39  public:
  40   // Returns instance of SequencedTaskRunner which guarantees that file
  41   // operations on the same file will be executed in sequenced order.
  42   static scoped_refptr<base::SequencedTaskRunner> GetTaskRunnerForFile(
  43       const base::FilePath& pref_filename,
  44       base::SequencedWorkerPool* worker_pool);
  45
  46   // Same as the constructor below with no alternate filename.
  47   JsonPrefStore(const base::FilePath& pref_filename,
  48                 base::SequencedTaskRunner* sequenced_task_runner,
  49                 scoped_ptr<PrefFilter> pref_filter);
  50
  51   // |sequenced_task_runner| must be a shutdown-blocking task runner, ideally
  52   // created by the GetTaskRunnerForFile() method above.
  53   // |pref_filename| is the path to the file to read prefs from.
  54   // |pref_alternate_filename| is the path to an alternate file which the
  55   // desired prefs may have previously been written to. If |pref_filename|
  56   // doesn't exist and |pref_alternate_filename| does, |pref_alternate_filename|
  57   // will be moved to |pref_filename| before the read occurs.
  58   JsonPrefStore(const base::FilePath& pref_filename,
  59                 const base::FilePath& pref_alternate_filename,
  60                 base::SequencedTaskRunner* sequenced_task_runner,
  61                 scoped_ptr<PrefFilter> pref_filter);
  62
  63   // PrefStore overrides:
  64   virtual bool GetValue(const std::string& key,
  65                         const base::Value** result) const OVERRIDE;
  66   virtual void AddObserver(PrefStore::Observer* observer) OVERRIDE;
  67   virtual void RemoveObserver(PrefStore::Observer* observer) OVERRIDE;
  68   virtual bool HasObservers() const OVERRIDE;
  69   virtual bool IsInitializationComplete() const OVERRIDE;
  70
  71   // PersistentPrefStore overrides:
  72   virtual bool GetMutableValue(const std::string& key,
  73                                base::Value** result) OVERRIDE;
  74   virtual void SetValue(const std::string& key, base::Value* value) OVERRIDE;
  75   virtual void SetValueSilently(const std::string& key,
  76                                 base::Value* value) OVERRIDE;
  77   virtual void RemoveValue(const std::string& key) OVERRIDE;
  78   virtual bool ReadOnly() const OVERRIDE;
  79   virtual PrefReadError GetReadError() const OVERRIDE;
  80   // Note this method may be asynchronous if this instance has a |pref_filter_|
  81   // in which case it will return PREF_READ_ERROR_ASYNCHRONOUS_TASK_INCOMPLETE.
  82   // See details in pref_filter.h.
  83   virtual PrefReadError ReadPrefs() OVERRIDE;
  84   virtual void ReadPrefsAsync(ReadErrorDelegate* error_delegate) OVERRIDE;
  85   virtual void CommitPendingWrite() OVERRIDE;
  86   virtual void ReportValueChanged(const std::string& key) OVERRIDE;
  87
  88   // Just like RemoveValue(), but doesn't notify observers. Used when doing some
  89   // cleanup that shouldn't otherwise alert observers.
  90   void RemoveValueSilently(const std::string& key);
  91
  92   // Registers |on_next_successful_write| to be called once, on the next
  93   // successful write event of |writer_|.
  94   void RegisterOnNextSuccessfulWriteCallback(
  95       const base::Closure& on_next_successful_write);
  96
  97   // This method is called after the JSON file has been read.  It then hands
  98   // |value| (or an empty dictionary in some read error cases) to the
  99   // |pref_filter| if one is set. It also gives a callback pointing at
 100   // FinalizeFileRead() to that |pref_filter_| which is then responsible for
 101   // invoking it when done. If there is no |pref_filter_|, FinalizeFileRead()
 102   // is invoked directly.
 103   // Note, this method is used with asynchronous file reading, so this class
 104   // exposes it only for the internal needs (read: do not call it manually).
 105   // TODO(gab): Move this method to the private section and hand a callback to
 106   // it to FileThreadDeserializer rather than exposing this public method and
 107   // giving a JsonPrefStore* to FileThreadDeserializer.
 108   void OnFileRead(scoped_ptr<base::Value> value,
 109                   PrefReadError error,
 110                   bool no_dir);
 111
 112  private:
 113   virtual ~JsonPrefStore();
 114
 115   // ImportantFileWriter::DataSerializer overrides:
 116   virtual bool SerializeData(std::string* output) OVERRIDE;
 117
 118   // This method is called after the JSON file has been read and the result has
 119   // potentially been intercepted and modified by |pref_filter_|.
 120   // |initialization_successful| is pre-determined by OnFileRead() and should
 121   // be used when reporting OnInitializationCompleted().
 122   // |schedule_write| indicates whether a write should be immediately scheduled
 123   // (typically because the |pref_filter_| has already altered the |prefs|) --
 124   // this will be ignored if this store is read-only.
 125   void FinalizeFileRead(bool initialization_successful,
 126                         scoped_ptr<base::DictionaryValue> prefs,
 127                         bool schedule_write);
 128
 129   const base::FilePath path_;
 130   const base::FilePath alternate_path_;
 131   const scoped_refptr<base::SequencedTaskRunner> sequenced_task_runner_;
 132
 133   scoped_ptr<base::DictionaryValue> prefs_;
 134
 135   bool read_only_;
 136
 137   // Helper for safely writing pref data.
 138   base::ImportantFileWriter writer_;
 139
 140   scoped_ptr<PrefFilter> pref_filter_;
 141   ObserverList<PrefStore::Observer, true> observers_;
 142
 143   scoped_ptr<ReadErrorDelegate> error_delegate_;
 144
 145   bool initialized_;
 146   bool filtering_in_progress_;
 147   PrefReadError read_error_;
 148
 149   std::set<std::string> keys_need_empty_value_;
 150
 151   DISALLOW_COPY_AND_ASSIGN(JsonPrefStore);
 152 };
 153
 154 #endif  // BASE_PREFS_JSON_PREF_STORE_H_