luaZ_resetbuffer
if (!seminfo) luaZ_resetbuffer(ls->buff); /* avoid wasting space */
luaZ_resetbuffer(ls->buff); /* prepare error message */
luaZ_resetbuffer(ls->buff);
luaZ_resetbuffer(ls->buff); /* `skip_sep' may dirty the buffer */
luaZ_resetbuffer(ls->buff); /* previous call may dirty the buff. */