template<typename T>
class Counter {
private:
    std::atomic<T> counter_;
    twist::mutex mtx_;
    twist::conditional_variable cv_is_zero_;
public:
    explicit Counter(T init_value = 0) : counter_(init_value) {};

    void Increment() {
        auto locker = twist::LockUnique(mtx_);
        counter_.fetch_add(1);
        if (!counter_)
            cv_is_zero_.notify_all();
    }

    void Decrement() {
        auto locker = twist::LockUnique(mtx_);
        counter_.fetch_sub(1);
        if (!counter_)
            cv_is_zero_.notify_all();
    }

    void AwaitZero() {
        auto locker = twist::LockUnique(mtx_);
        while (counter_ != 0) {
            cv_is_zero_.wait(locker);
        }
    }
};