private function _createExtendedBag()
    {
        if ($this->extended) {
            $hashEncoding = $this->getHashEncoding();
            $this->tagManifest = new BagItManifest(
                "{$this->bagDirectory}/tagmanifest-$hashEncoding.txt",
                $this->bagDirectory . '/',
                $this->tagFileEncoding
            );

            $fetchFile = $this->bagDirectory . '/fetch.txt';
            $this->fetch = new BagItFetch($fetchFile, $this->tagFileEncoding);

            $this->bagInfoFile = $this->bagDirectory . '/bag-info.txt';
            touch($this->bagInfoFile);
            if (is_null($this->bagInfoData)) {
                $this->bagInfoData = array();
            }
        }
    }