protected function parsePalmDoc()
    {
        if (!$this->palmDbHeader) {
            return;
        }
        $file = $this->file;
        /** @var PalmRecord $firstPalmDbRecord */
        $firstPalmDbRecord = $this->palmDbHeader->getIterator()->offsetGet(0);
        $offset = $firstPalmDbRecord->getOffset();
        $this->palmDocHeaderStart = $offset;
        $file->fseek($offset);
        $this->palmDocHeader = new PalmDocHeader(
            $this->readData($file, 2),
            $this->readData($file, 4, $offset + 4),
            $this->readData($file, 2),
            $this->readData($file, 2),
            $this->readData($file, 2)
        );
    }