subscriber.cpp

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#include "image_transport/subscriber.h"
#include "image_transport/subscriber_plugin.h"
#include <ros/names.h>
#include <pluginlib/class_loader.h>
#include <boost/scoped_ptr.hpp>

namespace image_transport {

struct Subscriber::Impl
{
  Impl()
    : unsubscribed_(false)
  {
  }

  ~Impl()
  {
    shutdown();
  }

  bool isValid() const
  {
    return !unsubscribed_;
  }

  void shutdown()
  {
    if (!unsubscribed_) {
      unsubscribed_ = true;
      if (subscriber_)
        subscriber_->shutdown();
    }
  }
  
  SubLoaderPtr loader_;
  boost::shared_ptr<SubscriberPlugin> subscriber_;
  bool unsubscribed_;
  //double constructed_;
};

Subscriber::Subscriber(ros::NodeHandle& nh, const std::string& base_topic, uint32_t queue_size,
                       const boost::function<void(const sensor_msgs::ImageConstPtr&)>& callback,
                       const ros::VoidPtr& tracked_object, const TransportHints& transport_hints,
                       const SubLoaderPtr& loader)
  : impl_(new Impl)
{
  // Load the plugin for the chosen transport.
  std::string lookup_name = SubscriberPlugin::getLookupName(transport_hints.getTransport());
  try {
    impl_->subscriber_ = loader->createInstance(lookup_name);
  }
  catch (pluginlib::PluginlibException& e) {
    throw TransportLoadException(transport_hints.getTransport(), e.what());
  }
  // Hang on to the class loader so our shared library doesn't disappear from under us.
  impl_->loader_ = loader;

  // Try to catch if user passed in a transport-specific topic as base_topic.
  std::string clean_topic = ros::names::clean(base_topic);
  size_t found = clean_topic.rfind('/');
  if (found != std::string::npos) {
    std::string transport = clean_topic.substr(found+1);
    std::string plugin_name = SubscriberPlugin::getLookupName(transport);
    std::vector<std::string> plugins = loader->getDeclaredClasses();
    if (std::find(plugins.begin(), plugins.end(), plugin_name) != plugins.end()) {
      std::string real_base_topic = clean_topic.substr(0, found);
      ROS_WARN("[image_transport] It looks like you are trying to subscribe directly to a "
               "transport-specific image topic '%s', in which case you will likely get a connection "
               "error. Try subscribing to the base topic '%s' instead with parameter ~image_transport "
               "set to '%s' (on the command line, _image_transport:=%s). "
               "See http://ros.org/wiki/image_transport for details.",
               clean_topic.c_str(), real_base_topic.c_str(), transport.c_str(), transport.c_str());
    }
  }

  // Tell plugin to subscribe.
  impl_->subscriber_->subscribe(nh, base_topic, queue_size, callback, tracked_object, transport_hints);
}

std::string Subscriber::getTopic() const
{
  if (impl_) return impl_->subscriber_->getTopic();
  return std::string();
}

uint32_t Subscriber::getNumPublishers() const
{
  if (impl_) return impl_->subscriber_->getNumPublishers();
  return 0;
}

std::string Subscriber::getTransport() const
{
  if (impl_) return impl_->subscriber_->getTransportName();
  return std::string();
}

void Subscriber::shutdown()
{
  if (impl_) impl_->shutdown();
}

Subscriber::operator void*() const
{
  return (impl_ && impl_->isValid()) ? (void*)1 : (void*)0;
}

} //namespace image_transport