Application Plugin for GSLAM

The GSLAM application is similar to the Nodelet in ROS.

This allows zero copy passing of data between nodelets instead of messaging passing with buffer, which is recommended in ROS2. However, writing a GSLAM application is even more easier.

Tiny Demo Using Arguments with Tab Completation

Some application is stand alone and so that does not need Messenger to contact with other applications. This makes the application just like traditional c++ excutables. Here is a tiny demo:

#include <GSLAM/core/GSLAM.h>

using namespace GSLAM;

int run(Svar config){

    config.arg<std::string>("plugin","","The svar module plugin wanna to show.");
    config.arg<std::string>("key","","The name in the module wanna to show");

    if(config.get("help",false)) {return config.help();}

    std::string pluginPath=config.get<std::string>("plugin","");
    std::string key=config.get("key","");

    Svar inst=Registry::load(pluginPath);
    GSLAM::Svar var=key.empty()?(inst):inst.get(key,Svar(),true);

    if(var.isFunction())
        std::cout<<var.as<SvarFunction>()<<std::endl;
    else if(var.isClass())
        std::cout<<var.as<SvarClass>()<<std::endl;
    else std::cout<<var;
    return 0;
}

GSLAM_REGISTER_APPLICATION(doc,run);

When we typing 'gslam doc', we acqually use this tiny code. Writing a GSLAM application is just like to write a traditional 'main' function, which accept arguments and returns an int. By using Svar, we recommend developers to list all used parameters and provide a help firstly. GSLAM will provides the tab completation and help infomation below:

~> gslam doc -help
Usage:
exe [--help] [-conf configure_file] [-arg_name arg_value]...

Using Svar supported argument parsing. The following table listed several argume
nt introductions.

Argument        Type(default->setted)           Introduction
--------------------------------------------------------------------------------
-plugin         str("")                         The svar module plugin wanna to
                                                show.
-key            str("")                         The name in the module wanna to
                                                show
-conf           str("Default.cfg")              The default configure file going
                                                 to parse.
-help           bool(false->true)               Show the help information.

Application with Messenger Topics

Since most application should communicate with other applications, Messenger is used to publish and subscribe messages. It is highly recommended to assign the Messenger topic usages with "__usage__", for the following code:

#include "MapHash.h"

using namespace GSLAM;

int run(Svar config){
    std::string in =config.arg<std::string>("in","","the map to load");
    std::string out=config.arg<std::string>("out","","the map file to save");
    std::string map=config.arg<std::string>("map","map","the map topic to publish or subscribe");

    Publisher   pub=messenger.advertise<MapPtr>(map);

    Subscriber  sub=messenger.subscribe(map,[out](MapPtr mp){
            if(out.size()) mp->save(out);
    });

    Subscriber  subOpen=messenger.subscribe("qviz/open",1,[&](std::string file){
        if(file.find(".gmap")==std::string::npos) return;
        MapPtr mapHash(new MapHash());
        mapHash->load(file);
        pub.publish(Svar::create(mapHash));
    });

    if(config.get("help",false)){
        config["__usage__"]=messenger.introduction();
        return config.help();
    }

    if(in.size()){
        MapPtr mapHash(new MapHash());
        mapHash->load(in);
        pub.publish(mapHash);
    }

    return Messenger::exec();
}

GSLAM_REGISTER_APPLICATION(gmap,run);

Here is the usage help:

~> gslam gmap -help
Publisher and Subscriber lists:
Type            Topic                           Payload
--------------------------------------------------------------------------------
Subscriber*1    qviz/open                       str
Publisher*1     messenger/newsub                GSLAM::Publisher
Subscriber*1    messenger/stop                  bool
Publisher*1     messenger/newpub                GSLAM::Subscriber
Publisher*1     map                             std::shared_ptr<GSLAM::Map>
Subscriber*1    map                             std::shared_ptr<GSLAM::Map>

Using Svar supported argument parsing. The following table listed several argume
nt introductions.

Argument        Type(default->setted)           Introduction
--------------------------------------------------------------------------------
-in             str("")                         the map to load
-out            str("")                         the map file to save
-map            str("map")                      the map topic to publish or subs
                                                cribe
-conf           str("Default.cfg")              The default configure file going
                                                 to parse.
-help           bool(false->true)               Show the help information.

The usage of an application contains two parts: parameters and in/output. Svar handles all parameters and Messenger handles all data communication.

Applications