base/prefs/writeable_pref_store.h

   1 // Copyright 2014 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_WRITEABLE_PREF_STORE_H_
   6 #define BASE_PREFS_WRITEABLE_PREF_STORE_H_
   7
   8 #include <string>
   9
  10 #include "base/basictypes.h"
  11 #include "base/memory/scoped_ptr.h"
  12 #include "base/prefs/pref_store.h"
  13
  14 namespace base {
  15 class Value;
  16 }
  17
  18 // A pref store that can be written to as well as read from.
  19 class BASE_PREFS_EXPORT WriteablePrefStore : public PrefStore {
  20  public:
  21   // PrefWriteFlags can be used to change the way a pref will be written to
  22   // storage.
  23   enum PrefWriteFlags : uint32 {
  24     // No flags are specified.
  25     DEFAULT_PREF_WRITE_FLAGS = 0,
  26
  27     // This marks the pref as "lossy". There is no strict time guarantee on when
  28     // a lossy pref will be persisted to permanent storage when it is modified.
  29     LOSSY_PREF_WRITE_FLAG = 1 << 1
  30   };
  31
  32   WriteablePrefStore() {}
  33
  34   // Sets a |value| for |key| in the store. |value| must be non-NULL. |flags| is
  35   // a bitmask of PrefWriteFlags.
  36   virtual void SetValue(const std::string& key,
  37                         scoped_ptr<base::Value> value,
  38                         uint32 flags) = 0;
  39
  40   // Removes the value for |key|.
  41   virtual void RemoveValue(const std::string& key, uint32 flags) = 0;
  42
  43   // Equivalent to PrefStore::GetValue but returns a mutable value.
  44   virtual bool GetMutableValue(const std::string& key,
  45                                base::Value** result) = 0;
  46
  47   // Triggers a value changed notification. This function needs to be called
  48   // if one retrieves a list or dictionary with GetMutableValue and change its
  49   // value. SetValue takes care of notifications itself. Note that
  50   // ReportValueChanged will trigger notifications even if nothing has changed.
  51   // |flags| is a bitmask of PrefWriteFlags.
  52   virtual void ReportValueChanged(const std::string& key, uint32 flags) = 0;
  53
  54   // Same as SetValue, but doesn't generate notifications. This is used by
  55   // PrefService::GetMutableUserPref() in order to put empty entries
  56   // into the user pref store. Using SetValue is not an option since existing
  57   // tests rely on the number of notifications generated. |flags| is a bitmask
  58   // of PrefWriteFlags.
  59   virtual void SetValueSilently(const std::string& key,
  60                                 scoped_ptr<base::Value> value,
  61                                 uint32 flags) = 0;
  62
  63  protected:
  64   ~WriteablePrefStore() override {}
  65
  66  private:
  67   DISALLOW_COPY_AND_ASSIGN(WriteablePrefStore);
  68 };
  69
  70 #endif  // BASE_PREFS_WRITEABLE_PREF_STORE_H_