Snowflake.cs 5.1 KB

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  1. using System;
  2. namespace Admin.Core.Common.Helpers
  3. {
  4. public class Snowflake
  5. {
  6. //基准时间
  7. private static long StartStmp = 1288834974657L;
  8. //private const long START_STMP = 1480166465631L;
  9. /*每一部分占用的位数*/
  10. //机器标识位数
  11. private const int MachineIdBits = 5;
  12. //数据标志位数
  13. private const int DatacenterIdBits = 5;
  14. //序列号识位数
  15. private const int SequenceBits = 12;
  16. /* 每一部分的最大值*/
  17. //机器ID最大值
  18. private const long MaxMachineNum = -1L ^ (-1L << MachineIdBits);
  19. //数据标志ID最大值
  20. private const long MaxDatacenterNum = -1L ^ (-1L << DatacenterIdBits);
  21. //序列号ID最大值
  22. private const long MaxSequenceNum = -1L ^ (-1L << SequenceBits);
  23. /*每一部分向左的位移*/
  24. //机器ID偏左移12位
  25. private const int MachineShift = SequenceBits;
  26. //数据ID偏左移17位
  27. private const int DatacenterIdShift = SequenceBits + MachineIdBits;
  28. //时间毫秒左移22位
  29. public const int TimestampLeftShift = SequenceBits + MachineIdBits + DatacenterIdBits;
  30. private long _sequence = 0L;//序列号
  31. private long _lastTimestamp = -1L;//上一次时间戳
  32. public long MachineId { get; protected set; }//机器标识
  33. public long DatacenterId { get; protected set; }//数据中心
  34. //public long Sequence = 0L;//序列号
  35. //{
  36. // get { return _sequence; }
  37. // internal set { _sequence = value; }
  38. //}
  39. private readonly DateTime Jan1st1970 = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
  40. private readonly object _lock = new Object();
  41. public Snowflake(long machineId, long datacenterId)
  42. {
  43. // 如果超出范围就抛出异常
  44. if (machineId > MaxMachineNum || machineId < 0)
  45. {
  46. throw new ArgumentException(string.Format("machineId 必须大于0,MaxMachineNum: {0}", MaxMachineNum));
  47. }
  48. if (datacenterId > MaxDatacenterNum || datacenterId < 0)
  49. {
  50. throw new ArgumentException(string.Format("datacenterId必须大于0,且不能大于MaxDatacenterNum: {0}", MaxDatacenterNum));
  51. }
  52. //先检验再赋值
  53. MachineId = machineId;
  54. DatacenterId = datacenterId;
  55. //_sequence = sequence;
  56. }
  57. //public static Init(long machineId, long datacenterId)
  58. //{
  59. //}
  60. public long NextId()
  61. {
  62. lock (_lock)
  63. {
  64. var timestamp = TimeGen();
  65. if (timestamp < _lastTimestamp)
  66. {
  67. throw new Exception(string.Format("时间戳必须大于上一次生成ID的时间戳. 拒绝为{0}毫秒生成id", _lastTimestamp - timestamp));
  68. }
  69. //如果上次生成时间和当前时间相同,在同一毫秒内
  70. if (_lastTimestamp == timestamp)
  71. {
  72. //sequence自增,和sequenceMask相与一下,去掉高位
  73. _sequence = (_sequence + 1) & MaxSequenceNum;
  74. //判断是否溢出,也就是每毫秒内超过1024,当为1024时,与sequenceMask相与,sequence就等于0
  75. if (_sequence == 0L)
  76. {
  77. //等待到下一毫秒
  78. timestamp = TilNextMillis(_lastTimestamp);
  79. }
  80. }
  81. else
  82. {
  83. //如果和上次生成时间不同,重置sequence,就是下一毫秒开始,sequence计数重新从0开始累加,
  84. //为了保证尾数随机性更大一些,最后一位可以设置一个随机数
  85. _sequence = 0L;//new Random().Next(10);
  86. }
  87. _lastTimestamp = timestamp;
  88. return ((timestamp - StartStmp) << TimestampLeftShift) | (DatacenterId << DatacenterIdShift) | (MachineId << MachineShift) | _sequence;
  89. }
  90. }
  91. // 防止产生的时间比之前的时间还要小(由于NTP回拨等问题),保持增量的趋势.
  92. protected virtual long TilNextMillis(long lastTimestamp)
  93. {
  94. var timestamp = TimeGen();
  95. while (timestamp <= lastTimestamp)
  96. {
  97. timestamp = TimeGen();
  98. }
  99. return timestamp;
  100. }
  101. // 获取当前的时间戳
  102. protected virtual long TimeGen()
  103. {
  104. //return TimeExtensions.CurrentTimeMillis();
  105. return (long)(DateTime.UtcNow - Jan1st1970).TotalMilliseconds;
  106. }
  107. }
  108. public class IdWorkerHelper
  109. {
  110. private static Snowflake _idWorker = null;
  111. private IdWorkerHelper()
  112. {
  113. }
  114. static IdWorkerHelper()
  115. {
  116. _idWorker = new Snowflake(1, 1);
  117. }
  118. public static long GenId64()
  119. {
  120. return _idWorker.NextId();
  121. }
  122. }
  123. }