template<typename T> class double_buffer {
    T buffers[2];
    volatile std::size_t index;
public:
    double_buffer()
        : index(1) {}
    T& GetFirst() {
        return buffers[index];
    }
    T& GetSecond() {
        return buffers[!index];
    }
    void flip() {
        InterlockedXor(&index, 1);
    }
};