/**
* returns actual vtable offset
*
* @param $vtable_offset
* @return int offset > 0 means exist value. 0 means not exist
*/
protected function __offset($vtable_offset)
{
$vtable = $this->bb_pos - $this->bb->getInt($this->bb_pos);
return $vtable_offset < $this->bb->getShort($vtable) ? $this->bb->getShort($vtable + $vtable_offset) : 0;
}
