1 // Copyright 2014 The Chromium OS 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 // DBusParamWriter::Append(writer, ...) provides functionality opposite 6 // to that of DBusParamReader. It writes each of the arguments to D-Bus message 7 // writer and return true if successful. 8 9 // DBusParamWriter::AppendDBusOutParams(writer, ...) is similar to Append() 10 // but is used to send out the D-Bus OUT (pointer type) parameters in a D-Bus 11 // method response message. This method skips any non-pointer parameters and 12 // only appends the data for arguments that are pointers. 13 14 #ifndef LIBBRILLO_BRILLO_DBUS_DBUS_PARAM_WRITER_H_ 15 #define LIBBRILLO_BRILLO_DBUS_DBUS_PARAM_WRITER_H_ 16 17 #include <brillo/dbus/data_serialization.h> 18 #include <dbus/message.h> 19 20 namespace brillo { 21 namespace dbus_utils { 22 23 class DBusParamWriter final { 24 public: 25 // Generic writer method that takes 1 or more arguments. It recursively calls 26 // itself (each time with one fewer arguments) until no more is left. 27 template<typename ParamType, typename... RestOfParams> 28 static void Append(dbus::MessageWriter* writer, 29 const ParamType& param, 30 const RestOfParams&... rest) { 31 // Append the current |param| to D-Bus, then call Append() with one 32 // fewer arguments, until none is left and stand-alone version of 33 // Append(dbus::MessageWriter*) is called to end the iteration. 34 DBusType<ParamType>::Write(writer, param); 35 Append(writer, rest...); 36 } 37 38 // The final overload of DBusParamWriter::Append() used when no more 39 // parameters are remaining to be written. 40 // Does nothing and finishes meta-recursion. 41 static void Append(dbus::MessageWriter* /*writer*/) {} 42 43 // Generic writer method that takes 1 or more arguments. It recursively calls 44 // itself (each time with one fewer arguments) until no more is left. 45 // Handles non-pointer parameter by just skipping over it. 46 template<typename ParamType, typename... RestOfParams> 47 static void AppendDBusOutParams(dbus::MessageWriter* writer, 48 const ParamType& /* param */, 49 const RestOfParams&... rest) { 50 // Skip the current |param| and call Append() with one fewer arguments, 51 // until none is left and stand-alone version of 52 // AppendDBusOutParams(dbus::MessageWriter*) is called to end the iteration. 53 AppendDBusOutParams(writer, rest...); 54 } 55 56 // Generic writer method that takes 1 or more arguments. It recursively calls 57 // itself (each time with one fewer arguments) until no more is left. 58 // Handles only a parameter of pointer type and writes the data pointed to 59 // to the output message buffer. 60 template<typename ParamType, typename... RestOfParams> 61 static void AppendDBusOutParams(dbus::MessageWriter* writer, 62 ParamType* param, 63 const RestOfParams&... rest) { 64 // Append the current |param| to D-Bus, then call Append() with one 65 // fewer arguments, until none is left and stand-alone version of 66 // Append(dbus::MessageWriter*) is called to end the iteration. 67 DBusType<ParamType>::Write(writer, *param); 68 AppendDBusOutParams(writer, rest...); 69 } 70 71 // The final overload of DBusParamWriter::AppendDBusOutParams() used when no 72 // more parameters are remaining to be written. 73 // Does nothing and finishes meta-recursion. 74 static void AppendDBusOutParams(dbus::MessageWriter* /*writer*/) {} 75 }; 76 77 } // namespace dbus_utils 78 } // namespace brillo 79 80 #endif // LIBBRILLO_BRILLO_DBUS_DBUS_PARAM_WRITER_H_ 81
