xso_sstream_append
if (!xso_sstream_append(args->xso, args->buf, args->len, &actual_written))
if (!xso_sstream_append(xso, buf, len, &actual_written)) {
if (!xso_sstream_append(xso, actual_buf, actual_len, &actual_written)) {
if (!xso_sstream_append(xso, buf, len, written)) {