struct Data { Data(int i) :id(i) {} int id; };

class list
{
public:
    struct Node { std::shared_ptr<Data> d_; std::shared_ptr<Node> next; };

private:
    CRITICAL_SECTION update_lock;
    concurrency::concurrent_queue<std::shared_ptr<Data>> to_add;
    concurrency::concurrent_queue<int> to_remove;
    std::shared_ptr<Node> head;
    std::atomic_uint32_t  count;

    void push_back(std::shared_ptr<Data> d) {
        std::shared_ptr<Node> n = std::make_shared<Node>();
        n->d_ = std::move(d);
        n->next = head;
        while (!std::atomic_compare_exchange_weak(&head, &head, n)) {}
        count++;
    }

    void remove(int id) {
        std::shared_ptr<Node> t_0 = nullptr;
        std::shared_ptr<Node> t_1 = head;
        while (1)
        {
            if (!t_1) break;

            if (t_1->d_->id == id)
            {
                if (!t_0) { while (1) { if (std::atomic_compare_exchange_weak(&head, &head, head->next))break; } }
                else { while (1) { if (std::atomic_compare_exchange_weak(&t_0->next, &t_0->next, t_1->next))break; } }

                t_1 = nullptr;
                count--;
                break;
            }
            t_0 = t_1;
            t_1 = t_1->next;
        }
    }




public:
    list() : head(nullptr) { InitializeCriticalSection(&update_lock); }
    ~list() {

        //clear the list
        while (head)
        {
            head = head->next;
        }

        DeleteCriticalSection(&update_lock);
    }

    uint32_t get_count() { return count.load(std::memory_order_relaxed); }

    void add_remove(std::shared_ptr<Data> d, bool add) {
        if (add) to_add.push(std::move(d)); else to_remove.push(d->id);

        unsigned char t_c = 0;

        /*IMPORTANT-TO-GET: no. of instructions it takes for the function to exit the while_loop and leave the critical_section*/
        unsigned char n = 10;

        while (1) {
            if (++t_c > n) return;
            if (TryEnterCriticalSection(&update_lock)) break;
        }


        std::shared_ptr<Data> temp = nullptr;
        while (1)
        {
            if (!to_add.try_pop(temp)) break;
            push_back(temp);
        }


        int temp_id;
        while (1)
        {
            if (!to_remove.try_pop(temp_id)) break;
            remove(temp_id);
        }

        LeaveCriticalSection(&update_lock);
    }


};