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