https://morestina.net/blog/1400/minimalistic-blocking-bounded-queue-for-c

main.hpp

// https://morestina.net/blog/1400/minimalistic-blocking-bounded-queue-for-c
template<typename T>
class queue {
  std::deque<T> content;
  size_t capacity;

  std::mutex mutex;
  std::condition_variable not_empty;
  std::condition_variable not_full;

  queue(const queue &) = delete;
  queue(queue &&) = delete;
  queue &operator = (const queue &) = delete;
  queue &operator = (queue &&) = delete;

 public:
  queue(size_t capacity): capacity(capacity) {}

  void push(T &&item) {
    {
      std::unique_lock<std::mutex> lk(mutex);
      not_full.wait(lk, [this]() { return content.size() < capacity; });
      content.push_back(std::move(item));
    }
    not_empty.notify_one();
  }

  bool try_push(T &&item) {
    {
      std::unique_lock<std::mutex> lk(mutex);
      if (content.size() == capacity)
        return false;
      content.push_back(std::move(item));
    }
    not_empty.notify_one();
    return true;
  }

  void pop(T &item) {
    {
      std::unique_lock<std::mutex> lk(mutex);
      not_empty.wait(lk, [this]() { return !content.empty(); });
      item = std::move(content.front());
      content.pop_front();
    }
    not_full.notify_one();
  }

  bool try_pop(T &item) {
    {
      std::unique_lock<std::mutex> lk(mutex);
      if (content.empty())
        return false;
      item = std::move(content.front());
      content.pop_front();
    }
    not_full.notify_one();
    return true;
  }
};