C# 雪花算法生成Id工具类

写在前面

传说自然界中并不存在两片完全一样的雪花的，每一片雪花都拥有自己漂亮独特的形状、独一无二；雪花算法也表示生成的ID如雪花般独一无二，该算法源自Twitter。

雪花算法主要用于解决分布式系统的唯一Id生成问题，在生产环境中可以部署一个单独的服务来运行雪花算法，然后通过请求该服务获取全局Id。

相对于UUID来说，其长度短，生成快，做数据库主键时方便建立索引，所以整体效率要高很多。

代码实现

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;public class IdWorker
{//机器IDprivate static long workerId;private static long twepoch = 687888001020L; //唯一时间，这是一个避免重复的随机量，自行设定不要大于当前时间戳private static long sequence = 0L;private static int workerIdBits = 4; //机器码字节数。4个字节用来保存机器码(定义为Long类型会出现，最大偏移64位，所以左移64位没有意义)public static long maxWorkerId = -1L ^ -1L << workerIdBits; //最大机器IDprivate static int sequenceBits = 10; //计数器字节数，10个字节用来保存计数码private static int workerIdShift = sequenceBits; //机器码数据左移位数，就是后面计数器占用的位数private static int timestampLeftShift = sequenceBits + workerIdBits; //时间戳左移动位数就是机器码和计数器总字节数public static long sequenceMask = -1L ^ -1L << sequenceBits; //一微秒内可以产生计数，如果达到该值则等到下一微妙在进行生成private long lastTimestamp = -1L;/// <summary>/// 机器码/// </summary>/// <param name="workerId"></param>public IdWorker(long workerId){if (workerId > maxWorkerId || workerId < 0)throw new Exception(string.Format("worker Id can't be greater than {0} or less than 0 ", workerId));IdWorker.workerId = workerId;}public long nextId(){lock (this){long timestamp = timeGen();if (this.lastTimestamp == timestamp){ //同一微妙中生成IDIdWorker.sequence = (IdWorker.sequence + 1) & IdWorker.sequenceMask; //用&运算计算该微秒内产生的计数是否已经到达上限if (IdWorker.sequence == 0){//一微妙内产生的ID计数已达上限，等待下一微妙timestamp = tillNextMillis(this.lastTimestamp);}}else{ //不同微秒生成IDIdWorker.sequence = 0; //计数清0}if (timestamp < lastTimestamp){ //如果当前时间戳比上一次生成ID时时间戳还小，抛出异常，因为不能保证现在生成的ID之前没有生成过throw new Exception(string.Format("Clock moved backwards.  Refusing to generate id for {0} milliseconds",this.lastTimestamp - timestamp));}this.lastTimestamp = timestamp; //把当前时间戳保存为最后生成ID的时间戳long nextId = (timestamp - twepoch << timestampLeftShift) | IdWorker.workerId << IdWorker.workerIdShift | IdWorker.sequence;return nextId;}}/// <summary>/// 获取下一微秒时间戳/// </summary>/// <param name="lastTimestamp"></param>/// <returns></returns>private long tillNextMillis(long lastTimestamp){long timestamp = timeGen();while (timestamp <= lastTimestamp){timestamp = timeGen();}return timestamp;}/// <summary>/// 生成当前时间戳/// </summary>/// <returns></returns>private long timeGen(){return (long)(DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc)).TotalMilliseconds;}
}/// <summary>
/// 生成雪花ID
/// </summary>
public static class SnowFlake
{private static long _workerId = 9;private static IdWorker _idWorker = null;public static string NewId(){if (_idWorker == null)_idWorker = new IdWorker(_workerId);return _idWorker.nextId().ToString();}
}

调用示例