/**
* Takes a slice of messages according to limit and offset given
* in option at initialisation time. Calls the callback to provide
* information how much messages there is.
*/
protected function doPaging()
{
$total = count($this->collection);
$offsets = $this->collection->slice($this->options['offset'], $this->options['limit']);
$left = count($this->collection);
$this->offsets = array('backwardsOffset' => $offsets[0], 'forwardsOffset' => $offsets[1], 'start' => $offsets[2], 'count' => $left, 'total' => $total);
}
