protected function parseHeader($block)
    {
        if (!$block || strlen($block) != 512) {
            throw new ArchiveCorruptedException('Unexpected length of header');
        }

        // null byte blocks are ignored
        if(trim($block) === '') return false;

        for ($i = 0, $chks = 0; $i < 148; $i++) {
            $chks += ord($block[$i]);
        }

        for ($i = 156, $chks += 256; $i < 512; $i++) {
            $chks += ord($block[$i]);
        }

        $header = @unpack(
            "a100filename/a8perm/a8uid/a8gid/a12size/a12mtime/a8checksum/a1typeflag/a100link/a6magic/a2version/a32uname/a32gname/a8devmajor/a8devminor/a155prefix",
            $block
        );
        if (!$header) {
            throw new ArchiveCorruptedException('Failed to parse header');
        }

        $return['checksum'] = OctDec(trim($header['checksum']));
        if ($return['checksum'] != $chks) {
            throw new ArchiveCorruptedException('Header does not match it\'s checksum');
        }

        $return['filename'] = trim($header['filename']);
        $return['perm']     = OctDec(trim($header['perm']));
        $return['uid']      = OctDec(trim($header['uid']));
        $return['gid']      = OctDec(trim($header['gid']));
        $return['size']     = OctDec(trim($header['size']));
        $return['mtime']    = OctDec(trim($header['mtime']));
        $return['typeflag'] = $header['typeflag'];
        $return['link']     = trim($header['link']);
        $return['uname']    = trim($header['uname']);
        $return['gname']    = trim($header['gname']);

        // Handle ustar Posix compliant path prefixes
        if (trim($header['prefix'])) {
            $return['filename'] = trim($header['prefix']).'/'.$return['filename'];
        }

        // Handle Long-Link entries from GNU Tar
        if ($return['typeflag'] == 'L') {
            // following data block(s) is the filename
            $filename = trim($this->readbytes(ceil($return['size'] / 512) * 512));
            // next block is the real header
            $block  = $this->readbytes(512);
            $return = $this->parseHeader($block);
            // overwrite the filename
            $return['filename'] = $filename;
        }

        return $return;
    }