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+// Copyright 2014 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// DBusParamWriter::Append(writer, ...) provides functionality opposite
+// to that of DBusParamReader. It writes each of the arguments to D-Bus message
+// writer and return true if successful.
+
+// DBusParamWriter::AppendDBusOutParams(writer, ...) is similar to Append()
+// but is used to send out the D-Bus OUT (pointer type) parameters in a D-Bus
+// method response message. This method skips any non-pointer parameters and
+// only appends the data for arguments that are pointers.
+
+#ifndef LIBCHROMEOS_BRILLO_DBUS_DBUS_PARAM_WRITER_H_
+#define LIBCHROMEOS_BRILLO_DBUS_DBUS_PARAM_WRITER_H_
+
+#include <brillo/dbus/data_serialization.h>
+#include <dbus/message.h>
+
+namespace brillo {
+namespace dbus_utils {
+
+class DBusParamWriter final {
+ public:
+  // Generic writer method that takes 1 or more arguments. It recursively calls
+  // itself (each time with one fewer arguments) until no more is left.
+  template<typename ParamType, typename... RestOfParams>
+  static void Append(dbus::MessageWriter* writer,
+                     const ParamType& param,
+                     const RestOfParams&... rest) {
+    // Append the current |param| to D-Bus, then call Append() with one
+    // fewer arguments, until none is left and stand-alone version of
+    // Append(dbus::MessageWriter*) is called to end the iteration.
+    DBusType<ParamType>::Write(writer, param);
+    Append(writer, rest...);
+  }
+
+  // The final overload of DBusParamWriter::Append() used when no more
+  // parameters are remaining to be written.
+  // Does nothing and finishes meta-recursion.
+  static void Append(dbus::MessageWriter* /*writer*/) {}
+
+  // Generic writer method that takes 1 or more arguments. It recursively calls
+  // itself (each time with one fewer arguments) until no more is left.
+  // Handles non-pointer parameter by just skipping over it.
+  template<typename ParamType, typename... RestOfParams>
+  static void AppendDBusOutParams(dbus::MessageWriter* writer,
+                                  const ParamType& param,
+                                  const RestOfParams&... rest) {
+    // Skip the current |param| and call Append() with one fewer arguments,
+    // until none is left and stand-alone version of
+    // AppendDBusOutParams(dbus::MessageWriter*) is called to end the iteration.
+    AppendDBusOutParams(writer, rest...);
+  }
+
+  // Generic writer method that takes 1 or more arguments. It recursively calls
+  // itself (each time with one fewer arguments) until no more is left.
+  // Handles only a parameter of pointer type and writes the data pointed to
+  // to the output message buffer.
+  template<typename ParamType, typename... RestOfParams>
+  static void AppendDBusOutParams(dbus::MessageWriter* writer,
+                                  ParamType* param,
+                                  const RestOfParams&... rest) {
+    // Append the current |param| to D-Bus, then call Append() with one
+    // fewer arguments, until none is left and stand-alone version of
+    // Append(dbus::MessageWriter*) is called to end the iteration.
+    DBusType<ParamType>::Write(writer, *param);
+    AppendDBusOutParams(writer, rest...);
+  }
+
+  // The final overload of DBusParamWriter::AppendDBusOutParams() used when no
+  // more parameters are remaining to be written.
+  // Does nothing and finishes meta-recursion.
+  static void AppendDBusOutParams(dbus::MessageWriter* /*writer*/) {}
+};
+
+}  // namespace dbus_utils
+}  // namespace brillo
+
+#endif  // LIBCHROMEOS_BRILLO_DBUS_DBUS_PARAM_WRITER_H_