+/** null buffer */
+extern struct lu_buf LU_BUF_NULL;
+
+void lu_buf_free(struct lu_buf *buf);
+void lu_buf_alloc(struct lu_buf *buf, int size);
+void lu_buf_realloc(struct lu_buf *buf, int size);
+
+int lu_buf_check_and_grow(struct lu_buf *buf, int len);
+struct lu_buf *lu_buf_check_and_alloc(struct lu_buf *buf, int len);
+