雪花算法-唯一ID生成器
demo:
1 public class Snowflake 2 { 3 private static long machineId;//机器ID 4 private static long datacenterId = 0L;//数据ID 5 private static long sequence = 0L;//计数从零开始 6 7 private static readonly long twepoch = 806083200000L; //唯一时间随机量 8 9 private static readonly long machineIdBits = 5L; //机器码字节数 10 private static readonly long datacenterIdBits = 5L;//数据字节数 11 public static long maxMachineId = -1L ^ (-1L << (int)machineIdBits); //最大机器ID 12 private static readonly long maxDatacenterId = -1L ^ (-1L << (int)datacenterIdBits);//最大数据ID 13 14 private static readonly long sequenceBits = 12L; //计数器字节数，12个字节用来保存计数码 15 private static readonly long machineIdShift = sequenceBits; //机器码数据左移位数，就是后面计数器占用的位数 16 private static readonly long datacenterIdShift = sequenceBits + machineIdBits; 17 private static readonly 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 18 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 19 private static long lastTimestamp = -1L;//最后时间戳 20 21 private static object syncRoot = new object();//加锁对象 22 static Snowflake snowflake; 23 24 public static Snowflake Instance() 25 { 26 if (snowflake == null) 27 snowflake = new Snowflake(); 28 return snowflake; 29 } 30 31 public Snowflake() 32 { 33 Snowflakes(0L, 0L); 34 } 35 36 public Snowflake(long machineId) 37 { 38 Snowflakes(machineId, -1); 39 } 40 41 public Snowflake(long machineId, long datacenterId) 42 { 43 Snowflakes(machineId, datacenterId); 44 } 45 46 private void Snowflakes(long machineId, long datacenterId) 47 { 48 if (machineId >= 0) 49 { 50 if (machineId > maxMachineId) 51 { 52 throw new Exception("机器码ID非法"); 53 } 54 Snowflake.machineId = machineId; 55 } 56 if (datacenterId >= 0) 57 { 58 if (datacenterId > maxDatacenterId) 59 { 60 throw new Exception("数据中心ID非法"); 61 } 62 Snowflake.datacenterId = datacenterId; 63 } 64 } 65 66 /// <summary> 67 /// 生成当前时间戳 68 /// </summary> 69 /// <returns>毫秒</returns> 70 private static long GetTimestamp() 71 { 72 return (long)(DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc)).TotalMilliseconds; 73 } 74 75 /// <summary> 76 /// 获取下一微秒时间戳 77 /// </summary> 78 /// <param name="lastTimestamp"></param> 79 /// <returns></returns> 80 private static long GetNextTimestamp(long lastTimestamp) 81 { 82 long timestamp = GetTimestamp(); 83 if (timestamp <= lastTimestamp) 84 { 85 timestamp = GetTimestamp(); 86 } 87 return timestamp; 88 } 89 90 /// <summary> 91 /// 获取长整形的ID 92 /// </summary> 93 /// <returns></returns> 94 public long GetId() 95 { 96 lock (syncRoot) 97 { 98 long timestamp = GetTimestamp(); 99 if (lastTimestamp == timestamp) 100 { //同一微妙中生成ID 101 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 102 if (sequence == 0) 103 { 104 //一微妙内产生的ID计数已达上限，等待下一微妙 105 timestamp = GetNextTimestamp(lastTimestamp); 106 } 107 } 108 else 109 { 110 //不同微秒生成ID 111 sequence = 0L; 112 } 113 if (timestamp < lastTimestamp) 114 { 115 throw new Exception("时间戳比上一次生成ID时时间戳还小，故异常"); 116 } 117 lastTimestamp = timestamp; //把当前时间戳保存为最后生成ID的时间戳 118 long Id = ((timestamp - twepoch) << (int)timestampLeftShift) 119 | (datacenterId << (int)datacenterIdShift) 120 | (machineId << (int)machineIdShift) 121 | sequence; 122 return Id; 123 } 124 } 125 }
