雪花算法原理以及JS精度丢失问题

long twepoch = 1666108800000L;
long time = System.currentTimeMillis() - twepoch;

public class SystemClock {
    private final long period;
    private final AtomicLong now;
    private SystemClock(long period) {
        this.period = period;
        this.now = new AtomicLong(System.currentTimeMillis());
        scheduleClockUpdating();
    }
    private void scheduleClockUpdating() {
        ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor(runnable -> {
            Thread thread = new Thread(runnable, "System Clock");
            thread.setDaemon(true);
            return thread;
        });
        scheduler.scheduleAtFixedRate(() -> now.set(System.currentTimeMillis()), period, period, TimeUnit.MILLISECONDS);
    }
    private long currentTimeMillis() {
        return now.get();
    }
}

long id = 0L;
try {
  NetworkInterface network = NetworkInterface.getByInetAddress(getLocalAddress());
  if (null == network) {
    id = 1L;
  } else {
    byte[] mac = network.getHardwareAddress();
    if (null != mac) {
      id = ((0x000000FF & (long) mac[mac.length - 2]) | (0x0000FF00 & (((long) mac[mac.length - 1]) << 8))) >> 6;
      id = id & 1023;
    }
  }
} catch (Exception e) {
  log.warn(" getWorkId: " + e.getMessage());
}
return id;

private long getSequence(){
  long timestamp = timeGen();
  // 闰秒
  if (timestamp < lastTimestamp) {
    long offset = lastTimestamp - timestamp;
    if (offset <= 5) {
      try {
        // 休眠双倍差值后重新获取，再次校验
        wait(offset << 1);
        timestamp = timeGen();
        if (timestamp < lastTimestamp) {
          throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", offset));
        }
      } catch (Exception e) {
        throw new RuntimeException(e);
      }
    } else {
      throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", offset));
    }
  }
  if (lastTimestamp == timestamp) {
    // 相同毫秒内，序列号自增
    sequence = (sequence + 1) & sequenceMask;
    if (sequence == 0) {
      // 同一毫秒的序列数已经达到最大
      timestamp = tilNextMillis(lastTimestamp);
    }
  } else {
    // 不同毫秒内，序列号置为 0|1 随机数
    sequence = ThreadLocalRandom.current().nextLong(0, 2);
  }
  return sequence;
}
protected long tilNextMillis(long lastTimestamp) {
  long timestamp = timeGen();
  while (timestamp <= lastTimestamp) {
    timestamp = timeGen();
  }
  return timestamp;
}
protected long timeGen() {
  return System.currentTimeMillis();
}

public class MySequence {
    private static final Logger log = LoggerFactory.getLogger(MySequence.class);
    /**
     * 时间起始标记点，作为基准，一般取系统的最近时间（一旦确定不能变动）
     */
    private final long twepoch = 1666108800000L;
    /**
     * 10位的机器id
     */
    private final long workerIdBits = 10L;
    /**
     * 12位的序列号 每毫秒内产生的id数: 2的12次方个
     */
    private final long sequenceBits = 12L;
    /**
     * 1023
     */
    protected final long maxWorkerId = ~(-1L << workerIdBits);
    /**
     * 机器id左移动位
     */
    private final long workerIdShift = sequenceBits;
    /**
     * 时间戳左移动位
     */
    private final long timestampLeftShift = sequenceBits + workerIdBits;
    /**
     * 4095
     */
    private final long sequenceMask = ~(-1L << sequenceBits);
    /**
     * 所属机器id
     */
    private final long workerId;
    /**
     * 并发控制序列
     */
    private long sequence = 0L;
    /**
     * 上次生产 ID 时间戳
     */
    private long lastTimestamp = -1L;
    public MySequence() {
        this.workerId = getWorkerId();
    }
    /**
     * 有参构造器
     *
     * @param workerId     工作机器 ID
     */
    public MySequence(long workerId) {
        if (workerId > maxWorkerId || workerId < 0) {
            throw new IllegalArgumentException(String.format("Worker Id can't be greater than %d or less than 0", maxWorkerId));
        }
        this.workerId = workerId;
    }
    /**
     * 基于网卡MAC地址计算余数作为机器id
     */
    protected long getWorkerId() {
        long id = 0L;
        try {
            NetworkInterface network = NetworkInterface.getByInetAddress(InetAddress.getLocalHost());
            if (null == network) {
                id = 1L;
            } else {
                byte[] mac = network.getHardwareAddress();
                if (null != mac) {
                    id = ((0x000000FF & (long) mac[mac.length - 2]) | (0x0000FF00 & (((long) mac[mac.length - 1]) << 8))) >> 6;
                    id = id % (maxWorkerId + 1);
                }
            }
        } catch (Exception e) {
            log.warn("getWorkerId: " + e.getMessage());
        }
        return id;
    }
    /**
     * 获取下一个 ID
     *
     */
    public synchronized long nextId() {
        long timestamp = timeGen();
        // 闰秒
        if (timestamp < lastTimestamp) {
            long offset = lastTimestamp - timestamp;
            if (offset <= 5) {
                try {
                    // 休眠双倍差值后重新获取，再次校验
                    wait(offset << 1);
                    timestamp = timeGen();
                    if (timestamp < lastTimestamp) {
                        throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", offset));
                    }
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }
            } else {
                throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", offset));
            }
        }
        if (lastTimestamp == timestamp) {
            // 相同毫秒内，序列号自增
            sequence = (sequence + 1) & sequenceMask;
            if (sequence == 0) {
                // 同一毫秒的序列数已经达到最大
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
            // 不同毫秒内，序列号置为 1 - 3 随机数
            sequence = ThreadLocalRandom.current().nextLong(1, 3);
        }
        lastTimestamp = timestamp;
        // 时间戳部分 | 机器标识部分 | 序列号部分
        return ((timestamp - twepoch) << timestampLeftShift)
                | (workerId << workerIdShift)
                | sequence;
    }
    protected long tilNextMillis(long lastTimestamp) {
        long timestamp = timeGen();
        while (timestamp <= lastTimestamp) {
            timestamp = timeGen();
        }
        return timestamp;
    }
    protected long timeGen() {
        return System.currentTimeMillis();
    }
}