subscriber.h

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#ifndef ROSRT_SUBSCRIBER_H
#define ROSRT_SUBSCRIBER_H

#include <lockfree/object_pool.h>
#include "detail/pool_gc.h"

#include <ros/atomic.h>
#include <ros/ros.h>

namespace ros
{
class CallbackQueueInterface;
} // namespace ros

namespace rosrt
{

namespace detail
{
  ros::CallbackQueueInterface* getSubscriberCallbackQueue();
} // namespace detail

template<typename M>
class Subscriber
{
public:
  Subscriber()
  : pool_(0)
  {
  }

  Subscriber(uint32_t message_pool_size)
  : pool_(0)
  {
    initialize(message_pool_size);
  }

  Subscriber(uint32_t message_pool_size, ros::NodeHandle& nh, const std::string& topic, const ros::TransportHints& transport_hints = ros::TransportHints())
  : pool_(0)
  {
    initialize(message_pool_size);
    subscribe(nh, topic, transport_hints);
  }

  ~Subscriber()
  {
    M const* latest = latest_.exchange(0);
    if (latest)
    {
      pool_->free(latest);
    }

    detail::addPoolToGC((void*)pool_, detail::deletePool<M>, detail::poolIsDeletable<M>);
  }

  void initialize(uint32_t message_pool_size)
  {
    ROS_ASSERT(message_pool_size > 1);
    ROS_ASSERT(!pool_);
    pool_ = new lockfree::ObjectPool<M>();
    pool_->initialize(message_pool_size, M());
    latest_.store(0);
  }

  bool initialize(uint32_t message_pool_size, ros::NodeHandle& nh, const std::string& topic, const ros::TransportHints& transport_hints = ros::TransportHints())
  {
    initialize(message_pool_size);
    return subscribe(nh, topic, transport_hints);
  }

  bool subscribe(ros::NodeHandle& nh, const std::string& topic, const ros::TransportHints& transport_hints = ros::TransportHints())
  {
    ros::SubscribeOptions ops;
#ifdef ROS_NEW_SERIALIZATION_API
    ops.template init<M>(topic, 1, boost::bind(&Subscriber::callback, this, _1), boost::bind(&lockfree::ObjectPool<M>::allocateShared, pool_));
#else
    ops.template init<M>(topic, 1, boost::bind(&Subscriber::callback, this, _1));
#endif
    ops.callback_queue = detail::getSubscriberCallbackQueue();
    sub_ = nh.subscribe(ops);
    return (bool)sub_;
  }

  boost::shared_ptr<M const> poll()
  {
    M const* latest = latest_.exchange(0);
    if (!latest)
    {
      return boost::shared_ptr<M const>();
    }

    boost::shared_ptr<M const> ptr = pool_->makeShared(latest);
    if (!ptr)
    {
      pool_->free(latest);
      return boost::shared_ptr<M const>();
    }

    return ptr;
  }

private:
  void callback(const boost::shared_ptr<M const>& msg)
  {
    M const* latest = 0;
    // If our pool doesn't own this message (due to multiple subscribers on the same topic)
    // make a copy
    if (!pool_->owns(msg.get()))
    {
      M* copy = pool_->allocate();

      if (!copy)
      {
        return;
      }

      *copy = *msg;
      latest = copy;
    }
    else
    {
      latest = pool_->removeShared(msg);
    }

    M const* old = latest_.exchange(latest);
    if (old)
    {
      pool_->free(old);
    }
  }

  ros::atomic<M const*> latest_;

  lockfree::ObjectPool<M>* pool_;
  ros::Subscriber sub_;
};

} // namespace rosrt

#endif // ROSRT_SUBSCRIBER_H