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 = 1;
            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
            public static long maxWorkerId = -1L ^ -1L << workerIdBits; //最大机器ID
            private 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;

            public long nextId()
            {
                lock (this)
                {
                    long timestamp = timeGen();
                    if (this.lastTimestamp == timestamp)
                    { //同一微妙中生成ID
                        IdWorker.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ID
                        IdWorker.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;
            }
        }
    }

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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