Method tryPopFront

src/threaded_queue.hh:140–153

Get the first element from the queue without blocking. Returns a null value if the queue is empty.

  // Get the first element from the queue without blocking. Returns a null
  // value if the queue is empty.
  std::optional<T> tryPopFront() {
    std::lock_guard<std::mutex> lock(mutex_);
    auto execute = [&](std::deque<T> *q) {
      auto val = std::move(q->front());
      q->pop_front();
      --total_count_;
      return val;
    };
    if (priority_.size())
      return execute(&priority_);
    if (queue_.size())
      return execute(&queue_);
    return std::nullopt;
  }

  template <typename Fn> void apply(Fn fn) {
    std::lock_guard<std::mutex> lock(mutex_);