New macros for dbus-cpp

by mandel on June 18th, 2014

dbus-cpp is the libary that we are currently using to perform dbus calls from cpp within ubuntu touch. For those that are used to dbus-cpp know that the dbus interface can be defined via structures that are later checked at compile time. The following is an example of those definitions:

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struct Geoclue
{
    struct Master
    {
        struct Create
        {
            inline static std::string name()
            {
                return "Create";
            } typedef Master Interface;
            inline static const std::chrono::milliseconds default_timeout() { return std::chrono::seconds{1}; }
        };
    };
 
    struct MasterClient
    {
        struct SetRequirements
        {
            inline static std::string name()
            {
                return "SetRequirements";
            } typedef MasterClient Interface;
            inline static const std::chrono::milliseconds default_timeout() { return std::chrono::seconds{1}; }
        };
        struct GetAddressProvider
        {
            inline static std::string name()
            {
                return "GetAddressProvider";
            } typedef MasterClient Interface;
            inline static const std::chrono::milliseconds default_timeout() { return std::chrono::seconds{1}; }
        };
        struct GetPositionProvider
        {
            inline static std::string name()
            {
                return "GetPositionProvider";
            } typedef MasterClient Interface;
            inline static const std::chrono::milliseconds default_timeout() { return std::chrono::seconds{1}; }
        };
    };
 
    struct Address
    {
        struct GetAddress
        {
            inline static std::string name()
            {
                return "GetAddress";
            } typedef Address Interface;
            inline static const std::chrono::milliseconds default_timeout() { return std::chrono::seconds{1}; }
        };
    };
 
    struct Position
    {
        struct GetPosition
        {
            inline static std::string name()
            {
                return "GetPosition";
            } typedef Position Interface;
            inline static const std::chrono::milliseconds default_timeout() { return std::chrono::seconds{1}; }
        };
        struct Signals
        {
            struct PositionChanged
            {
                inline static std::string name()
                {
                    return "PositionChanged";
                };
                typedef Position Interface;
                typedef std::tuple<int32_t, int32_t, double, double, double, dbus::types::Struct<std::tuple<int32_t, double, double>>> ArgumentType;
            };
        };
    };
};
}

This is quite a lot of work and quite repetitive. We did notice that and used in some of our projects a set of macros to make us type less. We now will provide the following macros for other developers to use as part of dbus-cpp

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/*
 * Copyright © 2014 Canonical Ltd.
 *
 * This program is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License version 3,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of+
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 *
 * Authored by: Thomas Voß <thomas.voss@canonical.com>
 */
 
#ifndef CORE_DBUS_MACROS_H_
#define CORE_DBUS_MACROS_H_
 
#include <core/dbus/types/object_path.h>
 
#include <chrono>
#include <string>
 
#define DBUS_CPP_METHOD_WITH_TIMEOUT_DEF(Name, Itf, Timeout) \
 struct Name \
 { \
 typedef Itf Interface; \
 inline static const std::string& name() \
 { \
 static const std::string s{#Name}; \
 return s; \
 } \
 inline static const std::chrono::milliseconds default_timeout() { return std::chrono::milliseconds{Timeout}; } \
 };\

#define DBUS_CPP_METHOD_DEF(Name, Itf) DBUS_CPP_METHOD_WITH_TIMEOUT_DEF(Name, Itf, 2000)
 
#define DBUS_CPP_SIGNAL_DEF(Name, Itf, ArgType) \
 struct Name \
 { \
 inline static std::string name() \
 { \
 return #Name; \
 }; \
 typedef Itf Interface; \
 typedef ArgType ArgumentType; \
 };\

#define DBUS_CPP_READABLE_PROPERTY_DEF(Name, Itf, Type) \
 struct Name \
 { \
 inline static std::string name() \
 { \
 return #Name; \
 }; \
 typedef Itf Interface; \
 typedef Type ValueType; \
 static const bool readable = true; \
 static const bool writable = false; \
 }; \

#define DBUS_CPP_WRITABLE_PROPERTY_DEF(Name, Itf, Type) \
 struct Name \
 { \
 inline static std::string name() \
 { \
 return #Name; \
 }; \
 typedef Itf Interface; \
 typedef Type ValueType; \
 static const bool readable = true; \
 static const bool writable = true; \
 }; \

#endif // CORE_DBUS_MACROS_H_

Using those macros the above example is as follows

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struct Geoclue
{
    struct Master
    {
        DBUS_CPP_METHOD_DEF(Create, Master);
    };
 
    struct MasterClient
    {
        DBUS_CPP_METHOD_DEF(SetRequirements, MasterClient);
        DBUS_CPP_METHOD_DEF(GetAddressProvider, MasterClient);
        DBUS_CPP_METHOD_DEF(GetPositionProvider, MasterClient);
    };
 
    struct Address
    {
        DBUS_CPP_METHOD_DEF(GetAddress, Address);
    };
 
    struct Position
    {
        DBUS_CPP_METHOD_DEF(GetPosition, Position);
        struct Signals
        {
            DBUS_CPP_SIGNAL_DEF(PositionChanged, Position);
        };
    };
};
}

As you can see the amount of code that needs to be written is a lot less and a new developer can easily understand what is going on. Happy coding ;)

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