/// <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 IdWorker(long workerId)

        {

            if (workerId > maxWorkerId || workerId < )

                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;

        }

    }