分布式ID自增算法 Snowflake

Snowflake.cs

using System;
namespace XCode.Common
{

    #region 算法1
    ///// <summary>
    ///// 动态生产有规律的ID
    ///// </summary>
    //public class Snowflake
    //{
    //    private static long machineId;//机器ID
    //    private static long datacenterId = 0L;//数据ID
    //    private static long sequence = 0L;//计数从零开始

    //    private static long twepoch = 687888001020L; //唯一时间随机量

    //    private static long machineIdBits = 5L; //机器码字节数
    //    private static long datacenterIdBits = 5L;//数据字节数
    //    public static long maxMachineId = -1L ^ -1L << (int)machineIdBits; //最大机器ID
    //    private static long maxDatacenterId = -1L ^ (-1L << (int)datacenterIdBits);//最大数据ID

    //    private static long sequenceBits = 12L; //计数器字节数，12个字节用来保存计数码        
    //    private static long machineIdShift = sequenceBits; //机器码数据左移位数，就是后面计数器占用的位数
    //    private static long datacenterIdShift = sequenceBits + machineIdBits;
    //    private static long timestampLeftShift = sequenceBits + machineIdBits + datacenterIdBits; //时间戳左移动位数就是机器码+计数器总字节数+数据字节数
    //    public static long sequenceMask = -1L ^ -1L << (int)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 static long lastTimestamp = -1L;//最后时间戳

    //    private static object syncRoot = new object();//加锁对象
    //    static Snowflake snowflake;

    //    public static Snowflake Instance()
    //    {
    //        if (snowflake == null)
    //            snowflake = new Snowflake();
    //        return snowflake;
    //    }

    //    public Snowflake()
    //    {
    //        Snowflakes(0L, -1);
    //    }

    //    public Snowflake(long machineId)
    //    {
    //        Snowflakes(machineId, -1);
    //    }

    //    public Snowflake(long machineId, long datacenterId)
    //    {
    //        Snowflakes(machineId, datacenterId);
    //    }

    //    private void Snowflakes(long machineId, long datacenterId)
    //    {
    //        if (machineId >= 0)
    //        {
    //            if (machineId > maxMachineId)
    //            {
    //                throw new XCode.PowerException("机器码{0}非法".CC().F("ID"));
    //            }
    //            Snowflake.machineId = machineId;
    //        }
    //        if (datacenterId >= 0)
    //        {
    //            if (datacenterId > maxDatacenterId)
    //            {
    //                throw new XCode.PowerException("数据中心{0}非法".CC().F("ID"));
    //            }
    //            Snowflake.datacenterId = datacenterId;
    //        }
    //    }

    //    /// <summary>
    //    /// 生成当前时间戳
    //    /// </summary>
    //    /// <returns>毫秒</returns>
    //    private static long GetTimestamp()
    //    {
    //        return (long)(DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc)).TotalMilliseconds;
    //    }

    //    /// <summary>
    //    /// 获取下一微秒时间戳
    //    /// </summary>
    //    /// <param name="lastTimestamp"></param>
    //    /// <returns></returns>
    //    private static long GetNextTimestamp(long lastTimestamp)
    //    {
    //        long timestamp = GetTimestamp();
    //        if (timestamp <= lastTimestamp)
    //        {
    //            timestamp = GetTimestamp();
    //        }
    //        return timestamp;
    //    }

    //    /// <summary>
    //    /// 获取长整形的ID
    //    /// </summary>
    //    /// <returns></returns>
    //    public long GetId()
    //    {
    //        lock (syncRoot)
    //        {
    //            long timestamp = GetTimestamp();
    //            if (Snowflake.lastTimestamp == timestamp)
    //            { //同一微妙中生成ID
    //                sequence = (sequence + 1) & sequenceMask; //用&运算计算该微秒内产生的计数是否已经到达上限
    //                if (sequence == 0)
    //                {
    //                    //一微妙内产生的ID计数已达上限，等待下一微妙
    //                    timestamp = GetNextTimestamp(Snowflake.lastTimestamp);
    //                }
    //            }
    //            else
    //            {
    //                //不同微秒生成ID
    //                sequence = 0L;
    //            }
    //            if (timestamp < lastTimestamp)
    //            {
    //                throw new XCode.PowerException("时间戳比上一次生成{0}时时间戳还小，故异常".CC().F("ID"));
    //            }
    //            Snowflake.lastTimestamp = timestamp; //把当前时间戳保存为最后生成ID的时间戳
    //            long Id = ((timestamp - twepoch) << (int)timestampLeftShift)
    //                | (datacenterId << (int)datacenterIdShift)
    //                | (machineId << (int)machineIdShift)
    //                | sequence;
    //            return Id;
    //        }
    //    }
    //}
    #endregion

    #region 算法2
    /// <summary>
    /// http://www.cnblogs.com/kasimlz/p/7511131.html
    /// </summary>
    public class Snowflake
    {
        /// <summary>
        /// 机器码
        /// </summary>
        private static long _workerId;

        /// <summary>
        /// 初始基准时间戳，小于当前时间点即可
        /// 分布式项目请保持此时间戳一致
        /// </summary>
        private static long _twepoch = 0L;

        /// <summary>
        /// 毫秒计数器
        /// </summary>
        private static long sequence = 0L;

        /// <summary>
        /// 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)
        /// </summary>
        private static int workerIdBits = 4;

        /// <summary>
        /// 最大机器ID所占的位数
        /// </summary>
        private static long maxWorkerId = -1L ^ -1L << workerIdBits;

        /// <summary>
        /// 计数器字节数，10个字节用来保存计数码
        /// </summary>
        private static int sequenceBits = 12;

        /// <summary>
        /// 机器码数据左移位数，就是后面计数器占用的位数
        /// </summary>
        private static int workerIdShift = sequenceBits;

        /// <summary>
        /// 时间戳左移动位数就是机器码和计数器总字节数
        /// </summary>
        private static int timestampLeftShift = sequenceBits + workerIdBits;

        /// <summary>
        /// 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
        /// </summary>
        private static long sequenceMask = -1L ^ -1L << sequenceBits;

        /// <summary>
        /// 最后一次的时间戳
        /// </summary>
        private static long lastTimestamp = -1L;

        /// <summary>
        /// 线程锁对象
        /// </summary>
        private static object locker = new object();

        static Snowflake()
        {
            _workerId = new Random(DateTime.Now.Millisecond).Next(1, (int)maxWorkerId);
            _twepoch = timeGen(2010, 1, 1, 0, 0, 0);
        }

        /// <summary>
        /// 机器编号
        /// </summary>
        public static long WorkerID
        {
            get { return _workerId; }
            set
            {
                if (value > 0 && value < maxWorkerId)
                    _workerId = value;
                else
                    throw new XCode.PowerException("{0}0{1}{2}".CC().F("Workeridmustbegreaterthan","orlessthan",maxWorkerId));
            }
        }

        /// <summary>
        /// 获取新的ID
        /// </summary>
        /// <returns></returns>
        public static long NewID()
        {
            lock (locker)
            {
                long timestamp = timeGen();
                if (lastTimestamp == timestamp)
                { //同一微妙中生成ID
                    sequence = (sequence + 1) & sequenceMask; //用&运算计算该微秒内产生的计数是否已经到达上限
                    if (sequence == 0)
                    {
                        //一微妙内产生的ID计数已达上限，等待下一微妙
                        timestamp = tillNextMillis(lastTimestamp);
                    }
                }
                else
                { //不同微秒生成ID
                    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 XCode.PowerException(string.Format("Clock moved backwards.  Refusing to generate id for {0} milliseconds", lastTimestamp - timestamp));
                }
                lastTimestamp = timestamp; //把当前时间戳保存为最后生成ID的时间戳
                return (timestamp - _twepoch << timestampLeftShift) | _workerId << workerIdShift | sequence;
            }
        }

        /// <summary>
        /// 获取下一微秒时间戳
        /// </summary>
        /// <param name="lastTimestamp"></param>
        /// <returns></returns>
        private static long tillNextMillis(long lastTimestamp)
        {
            long timestamp = timeGen();
            while (timestamp <= lastTimestamp)
            {
                timestamp = timeGen();
            }
            return timestamp;
        }

        /// <summary>
        /// 当前时间戳
        /// </summary>
        /// <returns></returns>
        private static long timeGen()
        {
            return (long)(DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc)).TotalMilliseconds;
        }

        /// <summary>
        /// 指定时间戳
        /// </summary>
        /// <param name="Year"></param>
        /// <param name="Month"></param>
        /// <param name="Day"></param>
        /// <param name="Hour"></param>
        /// <param name="Minute"></param>
        /// <param name="Second"></param>
        /// <returns></returns>
        private static long timeGen(int Year, int Month, int Day, int Hour, int Minute, int Second)
        {
            var UtcTime = new DateTime(Year, Month, Day, Hour, Minute, Second, DateTimeKind.Utc);
            return (long)(UtcTime - new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc)).TotalMilliseconds;
        }
    }
#endregion
}