text: // Copyright 2014 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #ifndef BASE_PREFS_WRITEABLE_PREF_STORE_H_
  #define BASE_PREFS_WRITEABLE_PREF_STORE_H_
  
  #include <string>
  
  #include "base/basictypes.h"
  #include "base/memory/scoped_ptr.h"
  #include "base/prefs/pref_store.h"
  
  namespace base {
  class Value;
  }
  
  // A pref store that can be written to as well as read from.
  class BASE_PREFS_EXPORT WriteablePrefStore : public PrefStore {
   public:
    // PrefWriteFlags can be used to change the way a pref will be written to
    // storage.
    enum PrefWriteFlags : uint32 {
      // No flags are specified.
      DEFAULT_PREF_WRITE_FLAGS = 0,
  
      // This marks the pref as "lossy". There is no strict time guarantee on when
      // a lossy pref will be persisted to permanent storage when it is modified.
      LOSSY_PREF_WRITE_FLAG = 1 << 1
    };
  
    WriteablePrefStore() {}
  
    // Sets a |value| for |key| in the store. |value| must be non-NULL. |flags| is
    // a bitmask of PrefWriteFlags.
    virtual void SetValue(const std::string& key,
                          scoped_ptr<base::Value> value,
                          uint32 flags) = 0;
  
    // Removes the value for |key|.
    virtual void RemoveValue(const std::string& key, uint32 flags) = 0;
  
    // Equivalent to PrefStore::GetValue but returns a mutable value.
    virtual bool GetMutableValue(const std::string& key,
                                 base::Value** result) = 0;
  
    // Triggers a value changed notification. This function needs to be called
    // if one retrieves a list or dictionary with GetMutableValue and change its
    // value. SetValue takes care of notifications itself. Note that
    // ReportValueChanged will trigger notifications even if nothing has changed.
    // |flags| is a bitmask of PrefWriteFlags.
    virtual void ReportValueChanged(const std::string& key, uint32 flags) = 0;
  
    // Same as SetValue, but doesn't generate notifications. This is used by
    // PrefService::GetMutableUserPref() in order to put empty entries
    // into the user pref store. Using SetValue is not an option since existing
    // tests rely on the number of notifications generated. |flags| is a bitmask
    // of PrefWriteFlags.
    virtual void SetValueSilently(const std::string& key,
                                  scoped_ptr<base::Value> value,
                                  uint32 flags) = 0;
  
   protected:
    ~WriteablePrefStore() override {}
  
   private:
    DISALLOW_COPY_AND_ASSIGN(WriteablePrefStore);
  };
  
  #endif  // BASE_PREFS_WRITEABLE_PREF_STORE_H_
  