#include 
#include 
#include 
#include 
template
class threadsafe_queue
{
private:
    mutable std::mutex mut;      ❶ 
    std::queue data_queue;
    std::condition_variable data_cond;
public:
    threadsafe_queue()
    {}
    threadsafe_queue(threadsafe_queue const& other)
    {
        std::lock_guard lk(other.mut);
        data_queue=other.data_queue;
    }
    void push(T new_value)
    {
        std::lock_guard lk(mut);
        data_queue.push(new_value);
        data_cond.notify_one();
    }
    void wait_and_pop(T& value)
    {
        std::unique_lock lk(mut);
        data_cond.wait(lk,[this]{return !data_queue.empty();});
        value=data_queue.front();
        data_queue.pop();
    }
    std::shared_ptr wait_and_pop()
    {
        std::unique_lock lk(mut);
        data_cond.wait(lk,[this]{return !data_queue.empty();});
        std::shared_ptr res(std::make_shared(data_queue.front()));
        data_queue.pop();
        return res;
    }
    bool try_pop(T& value)
    {
        std::lock_guard lk(mut);
        if(data_queue.empty())
            return false;
        value=data_queue.front();
        data_queue.pop();
        return true;
    }
    std::shared_ptr try_pop()
    {
        std::lock_guard lk(mut);
        if(data_queue.empty())
            return std::shared_ptr();
        std::shared_ptr res(std::make_shared(data_queue.front()));
        data_queue.pop();
        return res;
    }
    bool empty() const
    {
        std::lock_guard lk(mut);
        return data_queue.empty();
    }
};