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      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_
    155