public extern static void dsn_file_task_enqueue(dsn_task_t cb_task, dsn_error_t err, size_t size);
public extern static void dsn_rpc_enqueue_response(dsn_task_t rpc_call, dsn_error_t err, dsn_message_t response);
public extern static IntPtr dsn_error_to_string(dsn_error_t err);
public static extern void dsn_rpc_reply(dsn_message_t response, dsn_error_t err);