private function zeroPad(array $number, $right)
    {
        $log = (int) log($this->target->getRadix(), $this->source->getRadix());

        if ($log > 1 && count($number) % $log) {
            $pad = count($number) + ($log - count($number) % $log);
            $number = array_pad($number, $right ? $pad : -$pad, $this->source->getDigit(0));
        }

        return $number;
    }