最近看了twitter的分布式自增ID算法Snowflak，自己根据开源的代码写了一个C#的版本，以记录学习。 twitter的开源项目地址为： 用Scala实现

class IdWorker    {        //机器标识位数        private const int WORKER_ID_BITS = 4;        //机器标识位的最大值        private const long MAX_WORKER_ID = -1L ^ -1L << WORKER_ID_BITS;        //毫秒内自增位        private const int SEQUENCE_BITS = 10;        //自增位最大值        private const long SEQUENCE_Mask = -1L ^ -1L << SEQUENCE_BITS;        private const long twepoch = 1398049504651L;        //时间毫秒值向左偏移位        private const int timestampLeftShift = SEQUENCE_BITS + WORKER_ID_BITS;        //机器标识位向左偏移位        private const int WORKER_ID_SHIFT = SEQUENCE_BITS;        private static readonly DateTime START_TIME = new System.DateTime(1970, 1, 1, 0, 0, 0, 0);        private static readonly object LOCK = new object();        private long sequence = 0L;        private long lastTimestamp = -1L;        private long workerId;        public IdWorker(long workerId)        {            if (workerId > MAX_WORKER_ID || workerId < 0)            {                throw new ArgumentException(string.Format("worker id can't be greater than {0} or less than 0", MAX_WORKER_ID));            }            this.workerId = workerId;        }        /// 
        /// 获取下一个id值        /// 
        /// 
             public long NextId()        {            lock (LOCK)            {                long timestamp = TimeGen();                //当前时间小于上一次时间，错误                if (timestamp < this.lastTimestamp)                {                    throw new Exception(string.Format("Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));                }                //当前毫秒内                if (this.lastTimestamp == timestamp)                {                    //+1 求余                    this.sequence = (this.sequence + 1) & SEQUENCE_Mask;                    //当前毫秒内计数满了，等待下一秒                    if (this.sequence == 0)                    {                        timestamp = tilNextMillis(lastTimestamp);                    }                }                else      //不是当前毫秒内                {                    this.sequence = 0;   //重置当前毫秒计数                }                this.lastTimestamp = timestamp;                //当前毫秒值 | 机器标识值 | 当前毫秒内自增值                long nextId = ((timestamp - twepoch << timestampLeftShift))                | (this.workerId << WORKER_ID_SHIFT) | (this.sequence);                return nextId;            }        }        /// 
        /// 等待下一个毫秒        /// 
        ///         /// 
             private long tilNextMillis(long lastTimestamp)        {            long timestamp = TimeGen();            while (timestamp <= lastTimestamp)            {                timestamp = TimeGen();            }            return timestamp;        }        /// 
        /// 获取当前时间的Unix时间戳        /// 
        /// 
             private long TimeGen()        {            return (DateTime.UtcNow.Ticks - START_TIME.Ticks) / 10000;        }    }

调用方式如下

static void Main(string[] args){    IdWorker worker = new IdWorker(12L);    for (int i = 0; i < 100000; i++)    {        Console.WriteLine(worker.NextId());    }}