Filling table cells with <item>s

<root>
<item>item01</item>
<item>item02</item>
...
<item>item14</item>
<item>item15</item>
</root>

tables are necessary to exhaust all of the <item>s with the
last table possibly having some empty cells. For example
if n=15, nrows=3 and ncols=2, ntable=3 and the three tables
would be arranged one after the other as follows:

  +------+------+
  |item01|item02|
  +------+------+
  |item03|item04|
  +------+------+
  |item05|item06|
  +------+------+

  +------+------+
  |item07|item08|
  +------+------+
  |item09|item10|
  +------+------+
  |item11|item12|
  +------+------+

  +------+------+
  |item13|item14|
  +------+------+
  |item15|      |
  +------+------+
  |      |      |
  +------+------+

Also, I would like the option to fill the tables up by
rows (as shown above) or by columns:

  +------+------+
  |item01|item04|
  +------+------+
  |item02|item05|
  +------+------+
  |item03|item06|
  +------+------+

How would you go about implementing this in XSLT given
parameters nrows, ncols, by={"cols","rows"}? I am having
some trouble determining what my "outer" loop is since there
is the possibility of some empty cells (I can't just process
each <item>). Thx in advance.