test

        ClusterBackend(const char *domain, size_t version, const char *filepath = nullptr);

        virtual ~ClusterBackend();

        void write(const unsigned char *dest, size_t destsize);

        void read(unsigned char *src, size_t srcsize);

        void write(const unsigned char *dest, size_t destsize) override;

        void read(unsigned char *src, size_t srcsize) override;

        void prefetch() override;

        void lock();

        void unlock();

        void lock() override;

        void unlock() override;

        void setPos(size_t pos);

        size_t getPos();

        void setPos(size_t pos) override;

        size_t getPos() override;

        size_t end();

        size_t end() override;

        size_t getRevesion();

        void newRevesion();

        size_t getRevesion() override;

        void newRevesion() override;

        void vacuum();

        void purge();

        void vacuum() override;

        void purge() override;

        void flushSync() override;

        bool clusterDataExists() const override { return _ClusterDataExists.load(); }