/**
* Returns an available identifier for the given subtree
*
* @param string $dn
* @param boolean $hash
* @return integer|string
*/
protected function _getIdentifier($dn = null, $hash = false)
{
if ($dn && substr($dn, -1) != ',') {
$dn .= ',';
}
$next = $this->_ressource->countChildren($dn . $this->_currentDn) + 1;
return $hash ? base_convert($next, 10, 32) : $next;
}