ThreadsafeQueue.h

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#ifndef THREADSAFEQUEUE_H
#define THREADSAFEQUEUE_H
 
////////////////////////////////////////////////////////////////////////////////
///
/// \class ThreadsafeQueue
///
/// Template for all queues used to send data from one thread/loop to the next.
///
////////////////////////////////////////////////////////////////////////////////
 
#include <cassert>
#include <iostream>
 
#ifndef __CINT__
#include <atomic>
#include <memory>
#include <chrono>
#include <condition_variable>
#include <mutex>
#include <queue>
#include <utility>
#endif
 
class TDetector;
 
template <typename T>
class ThreadsafeQueue {
public:
   explicit ThreadsafeQueue(std::string name = "default", size_t maxSize = 100000);
   ThreadsafeQueue(const ThreadsafeQueue&)                = default;
   ThreadsafeQueue(ThreadsafeQueue&&) noexcept            = default;
   ThreadsafeQueue& operator=(const ThreadsafeQueue&)     = default;
   ThreadsafeQueue& operator=(ThreadsafeQueue&&) noexcept = default;
   ~ThreadsafeQueue()                                     = default;
#ifndef __CINT__
   int    Push(T obj);
   size_t Pop(T& output, int millisecond_wait = 1000);
 
   size_t ItemsPushed() const;
   size_t ItemsPopped() const;
   size_t Size() const;
 
   std::string Name() { return fName; }
 
   // int ObjectSize(T&) const;
 
   bool IsFinished() const;
   void SetFinished(bool finished = true);
 
private:
   std::string             fName;
   mutable std::mutex      mutex;
   std::queue<T>           queue;
   std::condition_variable can_push;
   std::condition_variable can_pop;
 
   std::atomic_int num_writers{0};
 
   size_t max_queue_size{100000};
 
   size_t items_in_queue{0};
   size_t items_pushed{0};
   size_t items_popped{0};
 
   std::atomic_bool is_finished;
#endif
};
 
#ifndef __CINT__
template <typename T>
ThreadsafeQueue<T>::ThreadsafeQueue(std::string name, size_t maxSize)
   : fName(std::move(name)), max_queue_size(maxSize), is_finished(false)
{
}
 
template <typename T>
int ThreadsafeQueue<T>::Push(T obj)
{
   std::unique_lock<std::mutex> lock(mutex);
   if(queue.size() > max_queue_size) {
      can_push.wait(lock);
   }
 
   items_pushed++;
   items_in_queue++;
 
   queue.push(obj);
   can_pop.notify_one();
   return 1;
}
 
template <typename T>
size_t ThreadsafeQueue<T>::Pop(T& output, int millisecond_wait)
{
   std::unique_lock<std::mutex> lock(mutex);
   if(!queue.size() && millisecond_wait) {
      can_pop.wait_for(lock, std::chrono::milliseconds(millisecond_wait));
   }
 
   if(!queue.size()) {
      return -1;
   }
 
   output = queue.front();
   queue.pop();
 
   items_popped++;
   items_in_queue--;
 
   can_push.notify_one();
   return queue.size();
   // return ObjectSize(output);
}
 
template <typename T>
size_t ThreadsafeQueue<T>::Size() const
{
   std::unique_lock<std::mutex> lock(mutex);
   return items_in_queue;
}
 
template <typename T>
size_t ThreadsafeQueue<T>::ItemsPushed() const
{
   std::unique_lock<std::mutex> lock(mutex);
   return items_pushed;
}
 
template <typename T>
size_t ThreadsafeQueue<T>::ItemsPopped() const
{
   std::unique_lock<std::mutex> lock(mutex);
   return items_popped;
}
 
template <typename T>
bool ThreadsafeQueue<T>::IsFinished() const
{
   return is_finished;
}
 
template <typename T>
void ThreadsafeQueue<T>::SetFinished(bool finished)
{
   // std::cout<<std::endl<<fName<<": finished = "<<finished<<std::endl;
   is_finished = finished;
}
#endif /* __CINT__ */
 
#endif /* _THREADSAFEQUEUE_H_ */