ThreadSafeFramesQueue.hpp

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#pragma once
#include <limits>
#include <queue>
#include <mutex>
#include <thread>
#include <opencv2/core/utility.hpp>

template <typename T>
class ThreadSafeFramesQueue : public std::queue<T> {
public:
  ThreadSafeFramesQueue()
  : maxDepth(5) {
    tm.reset();
    tm.start();
  }
  
  explicit ThreadSafeFramesQueue(size_t const& _maxDepth)
  : maxDepth(_maxDepth) {
    tm.reset();
    tm.start();
  }

  void Push(const T& entry) noexcept {
    std::lock_guard<std::mutex> lock(mtx);
    while (this->size() >= maxDepth) {
      T elem;
      static_cast<void>(Pop(elem));
    }
    this->push(entry);
  }

  bool Pop(T& out) noexcept {
    std::lock_guard<std::mutex> lock(mtx);
    if (this->empty()) {
      return false;
    }
    out = this->front();
    this->pop();
    tm.stop();
    tm.start();
    return true;
  }

  double GetFPS() noexcept {
    std::lock_guard<std::mutex> lock(mtx);
    return tm.getFPS();
  }

  void Clear() noexcept {
    std::lock_guard<std::mutex> lock(mtx);
    while (!this->empty()) {
      this->pop();
    }
  }

private:
  cv::TickMeter tm;  
  std::mutex mtx;  
  size_t const maxDepth;  
};