dbus: add ObjectPath type

dbus/object_path.h

+// Copyright (c) 2012 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 DBUS_OBJECT_PATH_H_
+#define DBUS_OBJECT_PATH_H_
+#pragma once
+
+#include <string>
+
+namespace dbus {
+
+// ObjectPath is a type used to distinguish D-Bus object paths from simple
+// strings, especially since normal practice is that these should be only
+// initialized from static constants or obtained from remote objects and no
+// assumptions about their value made.
+class ObjectPath {
+ public:
+  // Permit initialization without a value for passing to
+  // dbus::MessageReader::PopObjectPath to fill in and from std::string
+  // objects.
+  //
+  // The compiler synthesised copy constructor and assignment operator are
+  // sufficient for our needs, as is implicit initialization of a std::string
+  // from a string constant.
+  ObjectPath() {}
+  explicit ObjectPath(const std::string& value) : value_(value) {}
+
+  // Retrieves value as a std::string.
+  const std::string& value() const { return value_; }
+
+  // Permit sufficient comparison to allow an ObjectPath to be used as a
+  // key in a std::map.
+  bool operator<(const ObjectPath&) const;
+
+  // Permit testing for equality, required for mocks to work and useful for
+  // observers.
+  bool operator==(const ObjectPath&) const;
+  bool operator!=(const ObjectPath&) const;
+ private:
+  std::string value_;
+};
+
+}  // namespace dbus
+
+#endif  // DBUS_OBJECT_PATH_H_