base/prefs/pref_filter.h

   1 // Copyright 2013 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_PREF_FILTER_H_
   6 #define BASE_PREFS_PREF_FILTER_H_
   7
   8 #include <string>
   9
  10 #include "base/callback_forward.h"
  11 #include "base/memory/scoped_ptr.h"
  12 #include "base/prefs/base_prefs_export.h"
  13
  14 namespace base {
  15 class DictionaryValue;
  16 class Value;
  17 }  // namespace base
  18
  19 // Filters preferences as they are loaded from disk or updated at runtime.
  20 // Currently supported only by JsonPrefStore.
  21 class BASE_PREFS_EXPORT PrefFilter {
  22  public:
  23   // A callback to be invoked when |prefs| have been read (and possibly
  24   // pre-modified) and are now ready to be handed back to this callback's
  25   // builder. |schedule_write| indicates whether a write should be immediately
  26   // scheduled (typically because the |prefs| were pre-modified).
  27   typedef base::Callback<void(scoped_ptr<base::DictionaryValue> prefs,
  28                               bool schedule_write)> PostFilterOnLoadCallback;
  29
  30   virtual ~PrefFilter() {}
  31
  32   // This method is given ownership of the |pref_store_contents| read from disk
  33   // before the underlying PersistentPrefStore gets to use them. It must hand
  34   // them back via |post_filter_on_load_callback|, but may modify them first.
  35   // Note: This method is asynchronous, which may make calls like
  36   // PersistentPrefStore::ReadPrefs() asynchronous. The owner of filtered
  37   // PersistentPrefStores should handle this to make the reads look synchronous
  38   // to external users (see SegregatedPrefStore::ReadPrefs() for an example).
  39   virtual void FilterOnLoad(
  40       const PostFilterOnLoadCallback& post_filter_on_load_callback,
  41       scoped_ptr<base::DictionaryValue> pref_store_contents) = 0;
  42
  43   // Receives notification when a pref store value is changed, before Observers
  44   // are notified.
  45   virtual void FilterUpdate(const std::string& path) = 0;
  46
  47   // Receives notification when the pref store is about to serialize data
  48   // contained in |pref_store_contents| to a string. Modifications to
  49   // |pref_store_contents| will be persisted to disk and also affect the
  50   // in-memory state.
  51   virtual void FilterSerializeData(
  52       base::DictionaryValue* pref_store_contents) = 0;
  53 };
  54
  55 #endif  // BASE_PREFS_PREF_FILTER_H_