C# 根据twitter的snowflake算法生成唯一ID

C# 版算法：

 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;

 namespace Demo
 {

         /// <summary>
         /// 根据twitter的snowflake算法生成唯一ID
         /// snowflake算法 64 位
         /// 0---0000000000 0000000000 0000000000 0000000000 0 --- 00000 ---00000 ---000000000000
         /// 第一位为未使用（实际上也可作为long的符号位），接下来的41位为毫秒级时间，然后5位datacenter标识位，5位机器ID（并不算标识符，实际是为线程标识），然后12位该毫秒内的当前毫秒内的计数，加起来刚好64位，为一个Long型。
         /// 其中datacenter标识位起始是机器位，机器ID其实是线程标识，可以同一一个10位来表示不同机器
         /// </summary>
         public class IdWorker
         {
             //机器ID
             private 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 = ; //机器码字节数。4个字节用来保存机器码
             public static long maxWorkerId = -1L ^ -1L << workerIdBits; //最大机器ID
             private static int sequenceBits = ; //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;

             public long nextId()
             {
                 lock (this)
                 {
                     long timestamp = timeGen();
                     if (this.lastTimestamp == timestamp)
                     { //同一微妙中生成ID
                         IdWorker.sequence = (IdWorker.sequence + ) & 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 == )
                         {
                             //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ID
                         IdWorker.sequence = ; //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(, , , , , , DateTimeKind.Utc)).TotalMilliseconds;
             }
         }
     }

Java 版算法：

 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.stereotype.Component;

 public class IdWorker {

     protected static final Logger LOG = LoggerFactory.getLogger(IdWorker.class);

     private long workerId;
     private long datacenterId;
     private long sequence = 0L;

     private long twepoch = 1288834974657L;

     private long workerIdBits = 5L;
     private long datacenterIdBits = 5L;
     private long maxWorkerId = -1L ^ (-1L << workerIdBits);
     private long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
     private long sequenceBits = 12L;

     private long workerIdShift = sequenceBits;
     private long datacenterIdShift = sequenceBits + workerIdBits;
     private long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
     private long sequenceMask = -1L ^ (-1L << sequenceBits);

     private long lastTimestamp = -1L;

     public IdWorker(long workerId, long datacenterId) {
         // sanity check for workerId
         if (workerId > maxWorkerId || workerId < 0) {
             throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
         }
         if (datacenterId > maxDatacenterId || datacenterId < 0) {
             throw new IllegalArgumentException(String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
         }
         this.workerId = workerId;
         this.datacenterId = datacenterId;
         LOG.info(String.format("worker starting. timestamp left shift %d, datacenter id bits %d, worker id bits %d, sequence bits %d, workerid %d", timestampLeftShift, datacenterIdBits, workerIdBits, sequenceBits, workerId));
     }

     public synchronized long nextId() {
         long timestamp = timeGen();

         if (timestamp < lastTimestamp) {
             LOG.error(String.format("clock is moving backwards.  Rejecting requests until %d.", lastTimestamp));
             throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
         }

         if (lastTimestamp == timestamp) {
             sequence = (sequence + 1) & sequenceMask;
             if (sequence == 0) {
                 timestamp = tilNextMillis(lastTimestamp);
             }
         } else {
             sequence = 0L;
         }

         lastTimestamp = timestamp;

         return ((timestamp - twepoch) << timestampLeftShift) | (datacenterId << datacenterIdShift) | (workerId << workerIdShift) | sequence;
     }

     protected long tilNextMillis(long lastTimestamp) {
         long timestamp = timeGen();
         while (timestamp <= lastTimestamp) {
             timestamp = timeGen();
         }
         return timestamp;
     }

     protected long timeGen() {
         return System.currentTimeMillis();
     }

 }

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