thirdParty/PCL 1.12.0/include/pcl-1.12/pcl/io/impl/synchronized_queue.hpp

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/* SynchronizedQueue Template, taken from
 * http://stackoverflow.com/questions/10139251/shared-queue-c
 */
#pragma once

#include <condition_variable>
#include <mutex>
#include <queue>

namespace pcl
{

  template<typename T>
  class SynchronizedQueue
  {
    public:

      SynchronizedQueue () :
        queue_(), request_to_end_(false), enqueue_data_(true) { }

      void
      enqueue (const T& data)
      {
        std::unique_lock<std::mutex> lock (mutex_);

        if (enqueue_data_)
        {
          queue_.push (data);
          cond_.notify_one ();
        }
      }

      bool
      dequeue (T& result)
      {
        std::unique_lock<std::mutex> lock (mutex_);

        while (queue_.empty () && (!request_to_end_))
        {
          cond_.wait (lock);
        }

        if (request_to_end_)
        {
          doEndActions ();
          return false;
        }

        result = queue_.front ();
        queue_.pop ();

        return true;
      }

      void
      stopQueue ()
      {
        std::unique_lock<std::mutex> lock (mutex_);
        request_to_end_ = true;
        cond_.notify_one ();
      }

      unsigned int
      size ()
      {
        std::unique_lock<std::mutex> lock (mutex_);
        return static_cast<unsigned int> (queue_.size ());
      }

      bool
      isEmpty () const
      {
        std::unique_lock<std::mutex> lock (mutex_);
        return (queue_.empty ());
      }

    private:
      void
      doEndActions ()
      {
        enqueue_data_ = false;

        while (!queue_.empty ())
        {
          queue_.pop ();
        }
      }

      std::queue<T> queue_;              // Use STL queue to store data
      mutable std::mutex mutex_;       // The mutex to synchronise on
      std::condition_variable cond_;   // The condition to wait for

      bool request_to_end_;
      bool enqueue_data_;
  };
}