snowflake算法

/** snowflake的结构如下(每部分用-分开): 0 - 0000000000 0000000000 0000000000 0000000000 0 - 00000 - 00000 - 000000000000 第一位为未使用，接下来的41位为毫秒级时间(41位的长度可以使用69年)，然后是5位datacenterId和5位workerId(10位的长度最多支持部署1024个节点） ，最后12位是毫秒内的计数（12位的计数顺序号支持每个节点每毫秒产生4096个ID序号） **/ public class IdWorker { //基准时间 public const long Twepoch = 1580896000000L; // 2016,12,5 //机器标识位数 const int WorkerIdBits = 5; //数据标志位数 const int DatacenterIdBits = 5; //序列号识位数 const int SequenceBits = 12; //机器ID最大值 const long MaxWorkerId = -1L ^ (-1L << WorkerIdBits); //数据标志ID最大值 const long MaxDatacenterId = -1L ^ (-1L << DatacenterIdBits); //序列号ID最大值 private const long SequenceMask = -1L ^ (-1L << SequenceBits); //机器ID偏左移12位 private const int WorkerIdShift = SequenceBits; //数据ID偏左移17位 private const int DatacenterIdShift = SequenceBits + WorkerIdBits; //时间毫秒左移22位 public const int TimestampLeftShift = SequenceBits + WorkerIdBits + DatacenterIdBits; private long _sequence = 0L; private long _lastTimestamp = -1L; public long WorkerId { get; protected set; } public long DatacenterId { get; protected set; } public long Sequence { get { return _sequence; } set { _sequence = value; } } public IdWorker(long workerId, long datacenterId, long sequence = 0L) { // 如果超出范围就抛出异常 if (workerId > MaxWorkerId || workerId < 0) { throw new ArgumentException(string.Format("worker Id 必须大于0，且不能大于MaxWorkerId： {0}", MaxWorkerId)); } if (datacenterId > MaxDatacenterId || datacenterId < 0) { throw new ArgumentException(string.Format("region Id 必须大于0，且不能大于MaxWorkerId： {0}", MaxDatacenterId)); } //先检验再赋值 WorkerId = workerId; DatacenterId = datacenterId; _sequence = sequence; } readonly object _lock = new Object(); public virtual long NextId() { lock (_lock) { var timestamp = TimeGen(); if (timestamp < _lastTimestamp) { throw new Exception(string.Format("时间戳必须大于上一次生成ID的时间戳. 拒绝为{0}毫秒生成id", _lastTimestamp - timestamp)); } //如果上次生成时间和当前时间相同,在同一毫秒内 if (_lastTimestamp == timestamp) { //sequence自增，和sequenceMask相与一下，去掉高位 _sequence = (_sequence + 1) & SequenceMask; //判断是否溢出,也就是每毫秒内超过1024，当为1024时，与sequenceMask相与，sequence就等于0 if (_sequence == 0) { //等待到下一毫秒 timestamp = TilNextMillis(_lastTimestamp); } } else { //如果和上次生成时间不同,重置sequence，就是下一毫秒开始，sequence计数重新从0开始累加, //为了保证尾数随机性更大一些,最后一位可以设置一个随机数 _sequence = 0;//new Random().Next(10); } _lastTimestamp = timestamp; return ((timestamp - Twepoch) << TimestampLeftShift) | (DatacenterId << DatacenterIdShift) | (WorkerId << WorkerIdShift) | _sequence; } } // 防止产生的时间比之前的时间还要小（由于NTP回拨等问题）,保持增量的趋势. protected virtual long TilNextMillis(long lastTimestamp) { var timestamp = TimeGen(); while (timestamp <= lastTimestamp) { timestamp = TimeGen(); } return timestamp; } // 获取当前的时间戳 protected virtual long TimeGen() { return TimeExtensions.CurrentTimeMillis(); } }