publisher.cpp

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#include "image_transport/publisher.h"
#include "image_transport/publisher_plugin.h"
#include <pluginlib/class_loader.h>
#include <boost/ptr_container/ptr_vector.hpp>
#include <boost/foreach.hpp>
#include <boost/algorithm/string/erase.hpp>

// Workaround for #5357, #5380: failure to compile in some cases because for some
// compilers Boost.Foreach's const rvalue detection fails, and it tries to make a
// copy of abstract class PublisherPlugin.
// See https://svn.boost.org/trac/boost/ticket/3996 for details.
namespace boost { namespace foreach {
  template <>
  struct is_noncopyable<ptr_vector<image_transport::PublisherPlugin> > : mpl::true_ {};
}}

namespace image_transport {

struct Publisher::Impl
{
  Impl()
    : unadvertised_(false)
  {
  }

  ~Impl()
  {
    shutdown();
  }

  uint32_t getNumSubscribers() const
  {
    uint32_t count = 0;
    BOOST_FOREACH(const PublisherPlugin& pub, publishers_)
      count += pub.getNumSubscribers();
    return count;
  }

  std::string getTopic() const
  {
    return base_topic_;
  }

  bool isValid() const
  {
    return !unadvertised_;
  }
  
  void shutdown()
  {
    if (!unadvertised_) {
      unadvertised_ = true;
      BOOST_FOREACH(PublisherPlugin& pub, publishers_)
        pub.shutdown();
      publishers_.clear();
    }
  }

  void subscriberCB(const SingleSubscriberPublisher& plugin_pub,
                    const SubscriberStatusCallback& user_cb)
  {
    SingleSubscriberPublisher ssp(plugin_pub.getSubscriberName(), getTopic(),
                                  boost::bind(&Publisher::Impl::getNumSubscribers, this),
                                  plugin_pub.publish_fn_);
    user_cb(ssp);
  }
  
  std::string base_topic_;
  PubLoaderPtr loader_;
  boost::ptr_vector<PublisherPlugin> publishers_;
  bool unadvertised_;
  //double constructed_;
};


Publisher::Publisher(ros::NodeHandle& nh, const std::string& base_topic, uint32_t queue_size,
                     const SubscriberStatusCallback& connect_cb,
                     const SubscriberStatusCallback& disconnect_cb,
                     const ros::VoidPtr& tracked_object, bool latch,
                     const PubLoaderPtr& loader)
  : impl_(new Impl)
{
  // Resolve the name explicitly because otherwise the compressed topics don't remap
  // properly (#3652).
  impl_->base_topic_ = nh.resolveName(base_topic);
  impl_->loader_ = loader;
  
  BOOST_FOREACH(const std::string& lookup_name, loader->getDeclaredClasses()) {
    try {
      PublisherPlugin* pub = loader->createClassInstance(lookup_name);
      impl_->publishers_.push_back(pub);
      pub->advertise(nh, impl_->base_topic_, queue_size, rebindCB(connect_cb),
                     rebindCB(disconnect_cb), tracked_object, latch);
    }
    catch (const std::runtime_error& e) {
      ROS_DEBUG("Failed to load plugin %s, error string: %s",
                lookup_name.c_str(), e.what());
    }
  }

  if (impl_->publishers_.empty())
    throw Exception("No plugins found! Does `rospack plugins --attrib=plugin "
                    "image_transport` find any packages?");
}

uint32_t Publisher::getNumSubscribers() const
{
  if (impl_ && impl_->isValid()) return impl_->getNumSubscribers();
  return 0;
}

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

void Publisher::publish(const sensor_msgs::Image& message) const
{
  if (!impl_ || !impl_->isValid()) {
    ROS_ASSERT_MSG(false, "Call to publish() on an invalid image_transport::Publisher");
    return;
  }
  
  BOOST_FOREACH(const PublisherPlugin& pub, impl_->publishers_) {
    if (pub.getNumSubscribers() > 0)
      pub.publish(message);
  }
}

void Publisher::publish(const sensor_msgs::ImageConstPtr& message) const
{
  if (!impl_ || !impl_->isValid()) {
    ROS_ASSERT_MSG(false, "Call to publish() on an invalid image_transport::Publisher");
    return;
  }
  
  BOOST_FOREACH(const PublisherPlugin& pub, impl_->publishers_) {
    if (pub.getNumSubscribers() > 0)
      pub.publish(message);
  }
}

void Publisher::shutdown()
{
  if (impl_) {
    impl_->shutdown();
    impl_.reset();
  }
}

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

void Publisher::weakSubscriberCb(const ImplWPtr& impl_wptr,
                                 const SingleSubscriberPublisher& plugin_pub,
                                 const SubscriberStatusCallback& user_cb)
{
  if (ImplPtr impl = impl_wptr.lock())
    impl->subscriberCB(plugin_pub, user_cb);
}

SubscriberStatusCallback Publisher::rebindCB(const SubscriberStatusCallback& user_cb)
{
  // Note: the subscriber callback must be bound to the internal Impl object, not
  // 'this'. Due to copying behavior the Impl object may outlive the original Publisher
  // instance. But it should not outlive the last Publisher, so we use a weak_ptr.
  if (user_cb)
  {
    ImplWPtr impl_wptr(impl_);
    return boost::bind(&Publisher::weakSubscriberCb, impl_wptr, _1, user_cb);
  }
  else
    return SubscriberStatusCallback();
}

} //namespace image_transport