C# 版 雪花ID

在分布式系统中，生成唯一的ID是非常重要的。雪花算法是一种生成全局唯一ID的算法，它可以在分布式系统中生成唯一的ID，避免重复。

下面是一个C#版本的雪花ID生成器的示例代码：

csharpusing System;

public class SnowflakeIdGenerator{
 private const long Twepoch =1288834974657L;
 private const int WorkerIdBits =5;
 private const int DatacenterIdBits =5;
 private const int SequenceBits =12;

 private const long MaxWorkerId = -1L ^ (-1L << WorkerIdBits);
 private const long MaxDatacenterId = -1L ^ (-1L << DatacenterIdBits);

 private const int WorkerIdShift = SequenceBits;
 private const int DatacenterIdShift = SequenceBits + WorkerIdBits;
 private const int TimestampLeftShift = SequenceBits + WorkerIdBits + DatacenterIdBits;
 private const long SequenceMask = -1L ^ (-1L << SequenceBits);

 private readonly object _lock = new object();

 private long _lastTimestamp = -1L;
 private long _sequence =0L;

 public long WorkerId { get; }
 public long DatacenterId { get; }

 public SnowflakeIdGenerator(long workerId, long datacenterId)
 {
 if (workerId > MaxWorkerId || workerId <0)
 {
 throw new ArgumentException($"Worker ID must be between0 and {MaxWorkerId}");
 }

 if (datacenterId > MaxDatacenterId || datacenterId <0)
 {
 throw new ArgumentException($"Datacenter ID must be between0 and {MaxDatacenterId}");
 }

 WorkerId = workerId;
 DatacenterId = datacenterId;
 }

 public long NextId()
 {
 lock (_lock)
 {
 long timestamp = GetCurrentTimestamp();

 if (timestamp < _lastTimestamp)
 {
 throw new Exception("Clock moved backwards. Refusing to generate ID");
 }

 if (timestamp == _lastTimestamp)
 {
 _sequence = (_sequence +1) & SequenceMask;
 if (_sequence ==0)
 {
 timestamp = WaitNextMillis(timestamp);
 }
 }
 else {
 _sequence =0;
 }

 _lastTimestamp = timestamp;

 return ((timestamp - Twepoch) << TimestampLeftShift)
 | (DatacenterId << DatacenterIdShift)
 | (WorkerId << WorkerIdShift)
 | _sequence;
 }
 }

 private long GetCurrentTimestamp()
 {
 return (long)(DateTime.UtcNow - new DateTime(1970,1,1)).TotalMilliseconds;
 }

 private long WaitNextMillis(long lastTimestamp)
 {
 long timestamp = GetCurrentTimestamp();
 while (timestamp <= lastTimestamp)
 {
 timestamp = GetCurrentTimestamp();
 }
 return timestamp;
 }
}

csharpvar generator = new SnowflakeIdGenerator(1,1);
var id = generator.NextId();
Console.WriteLine($"Generated ID: {id}");