Program Listing for File time_sequencer.h

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#ifndef MESSAGE_FILTERS__TIME_SEQUENCER_H_
#define MESSAGE_FILTERS__TIME_SEQUENCER_H_

#include <rclcpp/rclcpp.hpp>

#include "message_filters/connection.h"
#include "message_filters/message_traits.h"
#include "message_filters/simple_filter.h"

namespace message_filters
{

template<class M>
class TimeSequencer : public SimpleFilter<M>
{
public:
  typedef std::shared_ptr<M const> MConstPtr;
  typedef MessageEvent<M const> EventType;

  template<class F>
  TimeSequencer(F& f, rclcpp::Duration delay, rclcpp::Duration update_rate, uint32_t queue_size, rclcpp::Node::SharedPtr node)
  : delay_(delay)
  , update_rate_(update_rate)
  , queue_size_(queue_size)
  , node_(node)
  {
    init();
    connectInput(f);
  }

  TimeSequencer(rclcpp::Duration delay, rclcpp::Duration update_rate, uint32_t queue_size, rclcpp::Node::SharedPtr node)
  : delay_(delay)
  , update_rate_(update_rate)
  , queue_size_(queue_size)
  , node_(node)
  {
    init();
  }

  template<class F>
  void connectInput(F& f)
  {
    incoming_connection_.disconnect();
    incoming_connection_ = f.registerCallback(typename SimpleFilter<M>::EventCallback(std::bind(&TimeSequencer::cb, this, std::placeholders::_1)));
  }

  ~TimeSequencer()
  {
    update_timer_->cancel();
    incoming_connection_.disconnect();
  }

  void add(const EventType& evt)
  {
    namespace mt = message_filters::message_traits;

    std::lock_guard<std::mutex> lock(messages_mutex_);
    if (mt::TimeStamp<M>::value(*evt.getMessage()) < last_time_)
    {
      return;
    }

    messages_.insert(evt);

    if (queue_size_ != 0 && messages_.size() > queue_size_)
    {
      messages_.erase(*messages_.begin());
    }
  }

  void add(const MConstPtr& msg)
  {
    EventType evt(msg);
    add(evt);
  }

private:
  class MessageSort
  {
  public:
    bool operator()(const EventType& lhs, const EventType& rhs) const
    {
      namespace mt = message_filters::message_traits;
      return mt::TimeStamp<M>::value(*lhs.getMessage()) < mt::TimeStamp<M>::value(*rhs.getMessage());
    }
  };
  typedef std::multiset<EventType, MessageSort> S_Message;
  typedef std::vector<EventType> V_Message;

  void cb(const EventType& evt)
  {
    add(evt);
  }

  void dispatch()
  {
    namespace mt = message_filters::message_traits;

    V_Message to_call;

    {
      std::lock_guard<std::mutex> lock(messages_mutex_);

      while (!messages_.empty())
      {
        const EventType& e = *messages_.begin();
        rclcpp::Time stamp = mt::TimeStamp<M>::value(*e.getMessage());
        if ((stamp + delay_) <= rclcpp::Clock().now())
        {
          last_time_ = stamp;
          to_call.push_back(e);
          messages_.erase(messages_.begin());
        }
        else
        {
          break;
        }
      }
    }

    {
      typename V_Message::iterator it = to_call.begin();
      typename V_Message::iterator end = to_call.end();
      for (; it != end; ++it)
      {
        this->signalMessage(*it);
      }
    }
  }

  void init()
  {
    update_timer_ = node_->create_wall_timer(std::chrono::nanoseconds(update_rate_.nanoseconds()), [this]() {
      dispatch();
      });
  }

  rclcpp::Duration delay_;
  rclcpp::Duration update_rate_;
  uint32_t queue_size_;
  rclcpp::Node::SharedPtr node_;
  rclcpp::TimerBase::SharedPtr update_timer_;
  Connection incoming_connection_;


  S_Message messages_;
  std::mutex messages_mutex_;
  rclcpp::Time last_time_;
};

}  // namespace message_filters

#endif  // MESSAGE_FILTERS__TIME_SEQUENCER_H_