Function sbuf_nl_terminate

freebsd/kern/subr_sbuf.c:740–766

* Append a trailing newline to a non-empty sbuf, if one is not already * present. Handles sbufs with drain functions correctly. */

 * present.  Handles sbufs with drain functions correctly.
 */
int
sbuf_nl_terminate(struct sbuf *s)
{

	assert_sbuf_integrity(s);
	assert_sbuf_state(s, 0);

	/*
	 * If the s_buf isn't empty, the last byte is simply s_buf[s_len - 1].
	 *
	 * If the s_buf is empty because a drain function drained it, we
	 * remember if the last byte was a \n with the SBUF_DRAINATEOL flag in
	 * sbuf_drain().
	 *
	 * In either case, we only append a \n if the previous character was
	 * something else.
	 */
	if (s->s_len == 0) {
		if (!SBUF_ISDRAINATEOL(s))
			sbuf_put_byte(s, '\n');
	} else if (s->s_buf[s->s_len - 1] != '\n')
		sbuf_put_byte(s, '\n');

	if (s->s_error != 0)
		return (-1);
	return (0);
}

/*
 * Trim whitespace characters from end of an sbuf.