public function getHeaderLine()
    {
        if (null === $this->headerLine) {
            $line = '@@';
            $line .= ' -' . $this->getOriginStartLine() . ',' . $this->getOriginEndLine();
            $line .= ' +' . $this->getDestStartLine() . ',' . $this->getDestEndLine();
            $line .= ' @@';

            $this->headerLine = $line;
        }

        return $this->headerLine;
    }