stealth_relay_nodelet.cpp

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// -*- mode: C++ -*-
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/*
 * stealth_relay_nodelet.cpp
 * Author: Furushchev <furushchev@jsk.imi.i.u-tokyo.ac.jp>
 */

#include <jsk_topic_tools/stealth_relay.h>


namespace jsk_topic_tools
{
  void StealthRelay::onInit()
  {
    bool use_multithread;
    ros::param::param<bool>("~use_multithread_callback", use_multithread, true);
    if (use_multithread) {
      NODELET_DEBUG("use multithread callback");
      nh_.reset (new ros::NodeHandle (getMTNodeHandle ()));
      pnh_.reset (new ros::NodeHandle (getMTPrivateNodeHandle ()));
    } else {
      NODELET_DEBUG("use singlethread callback");
      nh_.reset (new ros::NodeHandle (getNodeHandle ()));
      pnh_.reset (new ros::NodeHandle (getPrivateNodeHandle ()));
    }

    subscribed_ = false;
    advertised_ = false;

    pnh_->param<int>("queue_size", queue_size_, 1);
    pnh_->param<std::string>("monitoring_topic", monitoring_topic_,
                             pnh_->resolveName("input"));

    double monitor_rate;
    pnh_->param<double>("monitor_rate", monitor_rate, 1.0);
    poll_timer_ = pnh_->createTimer(ros::Duration(monitor_rate),
                                    &StealthRelay::timerCallback, this);

    NODELET_DEBUG("Started monitoring %s at %.2f Hz", monitoring_topic_.c_str(), monitor_rate);
    subscribe();
  }

  void StealthRelay::subscribe()
  {
    NODELET_DEBUG("subscribe");
    sub_ = pnh_->subscribe("input", queue_size_,
                           &StealthRelay::inputCallback, this);
    subscribed_ = true;
  }

  void StealthRelay::unsubscribe()
  {
    NODELET_DEBUG("unsubscribe");
    sub_.shutdown();
    subscribed_ = false;
  }

  bool StealthRelay::isSubscribed()
  {
    return subscribed_;
  }

  void StealthRelay::inputCallback(const AnyMsgConstPtr& msg)
  {
    boost::mutex::scoped_lock lock(mutex_);

    if (!advertised_)
    {
      pub_ = msg->advertise(*pnh_, "output", 1);
      advertised_ = true;
      unsubscribe();
      return;
    }

    pub_.publish(msg);
  }

  void StealthRelay::timerCallback(const ros::TimerEvent& event)
  {
    boost::mutex::scoped_lock lock(mutex_);

    if (pub_.getNumSubscribers() == 0 && subscribed_)
    {
      unsubscribe();
      return;
    }

    int subscribing_num = 0;
    if (!getNumOtherSubscribers(monitoring_topic_, subscribing_num))
    {
      if (subscribed_) unsubscribe();
    }
    else if (subscribed_ && subscribing_num == 0)
      unsubscribe();
    else if (!subscribed_ && subscribing_num > 0)
      subscribe();
  }

  bool StealthRelay::getNumOtherSubscribers(const std::string& name, int& num)
  {
    XmlRpc::XmlRpcValue req(ros::this_node::getName()), res, data;
    bool ok = ros::master::execute("getSystemState", req, res, data, false);

    XmlRpc::XmlRpcValue& sub_info = data[1];
    for (size_t i = 0; i < sub_info.size(); ++i)
    {
      std::string topic_name = sub_info[i][0];
      if (topic_name == name)
      {
        XmlRpc::XmlRpcValue& subscribers = sub_info[i][1];
        int cnt = 0;
        for (size_t j = 0; j < subscribers.size(); ++j)
        {
          std::string subscriber = subscribers[j];
          if (subscriber != ros::this_node::getName()) ++cnt;
        }
        num = cnt;
        return true;
      }
    }
    return false;
  }
}

#include <pluginlib/class_list_macros.h>
typedef jsk_topic_tools::StealthRelay StealthRelay;
PLUGINLIB_EXPORT_CLASS(StealthRelay, nodelet::Nodelet)