98 lines
4.6 KiB
C#
98 lines
4.6 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Text;
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using System.Threading;
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namespace Nirvana.Common
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{
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/// <summary>
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/// 根据twitter的snowflake算法生成唯一ID
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/// snowflake算法 64 位
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/// 0---0000000000 0000000000 0000000000 0000000000 0 --- 00000 ---00000 ---000000000000
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/// 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。
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/// 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
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/// </summary>
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public class IdWorker
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{
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//机器ID
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private static long workerId;
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private static long twepoch = 1514736000L; //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
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private static long sequence = 0L;
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private static int workerIdBits = 4; //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)
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public static long maxWorkerId = -1L ^ -1L << workerIdBits; //最大机器ID
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private static int sequenceBits = 10; //计数器字节数，10个字节用来保存计数码
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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
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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
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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
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private long lastTimestamp = -1L;
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private static readonly Object _Locker = new Object();
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/// <summary>
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/// 机器码
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/// </summary>
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/// <param name="workerId"></param>
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public IdWorker(long workerId)
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{
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if (workerId > maxWorkerId || workerId < 0)
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throw new Exception(string.Format("worker Id can't be greater than {0} or less than 0 ", workerId));
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IdWorker.workerId = workerId;
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}
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public long nextid()
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{
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//var worder = new Snowflake.Net.IdWorker(workerId, 1);
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//return worder.NextId();
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lock (_Locker)
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{
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long timestamp = timeGen();
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if (timestamp < lastTimestamp)
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{//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
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throw new Exception(string.Format("Clock moved backwards. Refusing to generate id for {0} milliseconds",
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this.lastTimestamp - timestamp));
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}
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if (this.lastTimestamp == timestamp)
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{//同一微妙中生成ID
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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
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if (IdWorker.sequence == 0)
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{
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//一微妙内产生的ID计数已达上限，等待下一微妙
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timestamp = tillNextMillis(this.lastTimestamp);
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}
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}
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else
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{//不同微秒生成ID
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IdWorker.sequence = 0;//计数清0
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}
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this.lastTimestamp = timestamp; //把当前时间戳保存为最后生成ID的时间戳
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long nextId = (timestamp - twepoch << timestampLeftShift) | IdWorker.workerId << IdWorker.workerIdShift | IdWorker.sequence;
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Thread.Sleep(10);
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return nextId;
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}
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}
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/// <summary>
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/// 获取下一微秒时间戳
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/// </summary>
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/// <param name="lastTimestamp"></param>
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/// <returns></returns>
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private long tillNextMillis(long lastTimestamp)
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{
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long timestamp = timeGen();
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while (timestamp <= lastTimestamp)
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{
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timestamp = timeGen();
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}
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return timestamp;
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}
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/// <summary>
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/// 生成当前时间戳
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/// </summary>
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/// <returns></returns>
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private long timeGen()
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{
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return (long)(DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc)).TotalMilliseconds;
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}
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}
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}
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