读取 mysql binlog 开始和结束时间(3)

        $head = unpack($this->eventHeadPackStr, $head_str);
        if ($head['type_code'] != self::FORMAT_DESCRIPTION_EVENT) {
            return null;
        }
        $data_str= fread($file, self::FORMAT_DESCRIPTION_EVENT_DATA_SIZE);
        $data = unpack($this->formatDescriptionEventDataPackStr, $data_str);
 
        return array('head'=>$head, 'data'=>$data);
    }
 
    /**
     * @param resource $file
     *
     * Rotate event is the last event of a binglog.
     * After event header, there is a 64bit int indicate the first event
     * position of next binlog file and next binlog file name without \0 at end.
     * The position is always be 4 (hex: 0400000000000000).
     *
     */
    protected function readRotateEvent($file)
    {
        /**
         * Rotate event size is 19(head size) + 8(pos) + len(filename).
         * 100 bytes can contain a filename which length less than 73 bytes and
         * it is short than the length of format description event so filesize -
         * bufsize will never be negative.
         */
        $bufsize = 100;
        $size_pos = 8;
        fseek($file, -$bufsize, SEEK_END);
        $buf = fread($file, $bufsize);
        $min_begin = strlen(self::BINLOG_HEAD) + self::EVENT_HEAD_SIZE + $size_pos;
        $ok = false;
        for ($i = $bufsize - 1; $i > $min_begin; $i--) {
            if ($buf[$i] == "\0") {
                $ok = true;
                break;
            }
        }
        if (!$ok) {
            return null;