interval_intersection.cpp

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//#include <stdio.h>
//#include <iostream>
#include <vector>
#include <deque>
//#include <fstream>

#include <boost/thread/mutex.hpp>
#include <boost/bind.hpp>
#include "ros/console.h"
#include "interval_intersection/interval_intersection.hpp"

using namespace std;
using namespace interval_intersection;

IntervalIntersector::IntervalIntersector(boost::function<void (const calibration_msgs::Interval&)> output_callback):
  max_queue_size(200),
  output_callback_(output_callback)
{
}

IntervalIntersector::~IntervalIntersector()
{
  // If callbacks continue during or after destruction, bad things can happen,
  // so ensure proper shutdown of the callback streams before destruction.
}

boost::function<void (const calibration_msgs::IntervalConstPtr&)> IntervalIntersector::getNewInputStream() {
  // Changes the configuration of the set of queues,
  // so we lock all mutexes.
  boost::mutex::scoped_lock processing_lock(processing_mutex);
  size_t n = queues.size();  // Protected by above lock
  for (size_t i=0; i<n; i++) {
    mutexes[i]->lock();
  }
  queues.resize(n+1);
  mutexes.resize(n+1);
  mutexes[n].reset(new boost::mutex());
  for (size_t i=0; i<n; i++) {
    mutexes[i]->unlock();
  }
  return boost::bind(&IntervalIntersector::inputCallback, this, _1, n);
}

void IntervalIntersector::inputCallback(const calibration_msgs::IntervalConstPtr& interval_ptr, size_t i) {
  ROS_DEBUG("Got message on stream [%u]", i);
  boost::mutex::scoped_lock lock(*mutexes[i]);
  if (queues[i].size() < max_queue_size) {
    queues[i].push_back(interval_ptr);
  }
  lock.unlock();

  process_queues();
}

void IntervalIntersector::process_queues() {
  //cout << "processing" << endl;
  while (1) {
    // 1) Determine which interval to publish next
    ros::Time start = ros::TIME_MIN;
    ros::Time end = ros::TIME_MAX;
    int queue_to_pop = -1;
    boost::mutex::scoped_lock processing_lock(processing_mutex);
    for (size_t i=0; i<queues.size(); i++) {
      // It looks like we could get away without locking the mutexes to
      // determine the min and max since even though the queues may change
      // because new elements are added, the first element if it exists
      // does not change because we hold the processing mutex.
      // However there is a possibility that the location of queue[i][0]
      // changes after its address has been computed but before its value
      // has been read. In other words the statement
      // "start = queues[i][0]->start" is not atomic.
      // In fact even queues[i].empty() is only guaranteed to make sense
      // in between other method calls, not during.
      // Whether or not deque is in fact thread-safe here is implementation
      // dependent.
      boost::mutex::scoped_lock lock(*mutexes[i]);
      if (queues[i].empty()) {
        // We can't determine the next interval: nothing to do
        //cout << "nothing to do" << endl;
        return;
      }
      if (queues[i][0]->start > start) {
        start = queues[i][0]->start;
      }
      if (queues[i][0]->end < end) {
        end = queues[i][0]->end;
        queue_to_pop = i;
      }
      // mutexes[i] released
    }
    if (queue_to_pop < 0) {
      ROS_ERROR("IntervalIntersection logic error");
      exit(-1);
    }
    // 2) Publish the interval
    //cout << "about to publish" << endl;
    if (start < end) {
      // Output the interval
      calibration_msgs::Interval interval;
      interval.start = start;
      interval.end = end;
      output_callback_(interval);
    }
    else
    {
      ROS_DEBUG("Publishing null interval");
      calibration_msgs::Interval interval;
      interval.start = start;
      interval.end = start;
      output_callback_(interval);
    }
    // 3) Pop the input interval with earliest end time
    boost::mutex::scoped_lock lock(*mutexes[queue_to_pop]);
    queues[queue_to_pop].pop_front();
    // mutexes[queue_to_pop] unlocks
    // processing_mutex unlocks
  }
}

---

interval_intersection
Author(s): Romain Thibaux
autogenerated on Fri Jan 11 09:11:39 2013