Async Pool

async.hpp

template<typename Fun, typename... Args>
class Pool {
  std::vector<std::thread> _workers;
  Queue<std::tuple<Args...>> _jobs;
  std::mutex _mutex;
  std::condition_variable _cv;
  std::atomic<bool> _finished = false;

public:

  template<typename F>
  Pool(F&& fun, std::size_t threads = 4) {
    auto worker = [&, fun](){
      auto ul = std::unique_lock{_mutex};
      while (true) {
        if (_jobs.empty())
          _cv.wait(ul, [&](){ return !_jobs.empty() || _finished; });
        if (_finished) break;
        std::apply(fun, _jobs.pop());
      }
    };

    for (std::size_t i = 0; i < threads; ++i)
      _workers.emplace_back(worker);
  }

  ~Pool() {
    _finished = true;
    _cv.notify_all();
    for (auto& worker: _workers)
      worker.join();
  }

  void run(Args... args) {
    _jobs.push(std::forward<Args>(args)...);
    _cv.notify_one();
  }
};