Twitter全局唯一ID生成算法

测试：private static void TestIdWorker()
{
HashSet<long> set = new HashSet<long>();
IdWorker idWorker1 = new IdWorker(0, 0);
IdWorker idWorker2 = new IdWorker(1, 0);
//762884413578018816
//762884520121729024
Stopwatch sw = new Stopwatch();
sw.Start();
for (int i = 0; i < 1; i++)
{
long id = idWorker1.nextId();
set.Add(id);
//if (!set.Add(id))
//{
//Console.WriteLine("duplicate:" + id);
//}
}
sw.Stop();
foreach (var item in set)
{
Console.WriteLine("结果:" + item);
}
Console.WriteLine("时间:" + sw.ElapsedTicks);
return;
}

算法：

/// <summary>
/// From: https://github.com/twitter/snowflake /// An object that generates IDs.
/// This is broken into a separate class in case
/// we ever want to support multiple worker threads
/// per process
/// </summary>
public class IdWorker
{
private long workerId;
private long datacenterId;
private long sequence = 0L;

private static long twepoch = 1288834974657L;

private static long workerIdBits = 5L;
private static long datacenterIdBits = 5L;
private static long maxWorkerId = -1L ^ (-1L << (int)workerIdBits);
private static long maxDatacenterId = -1L ^ (-1L << (int)datacenterIdBits);
private static long sequenceBits = 12L;

private long workerIdShift = sequenceBits;
private long datacenterIdShift = sequenceBits + workerIdBits;
private long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
private long sequenceMask = -1L ^ (-1L << (int)sequenceBits);

private long lastTimestamp = -1L;
private static object syncRoot = new object();

public IdWorker(long workerId, long datacenterId)
{

// sanity check for workerId
if (workerId > maxWorkerId || workerId < 0)
{
throw new ArgumentException(string.Format("worker Id can't be greater than %d or less than 0", maxWorkerId));
}
if (datacenterId > maxDatacenterId || datacenterId < 0)
{
throw new ArgumentException(string.Format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
}
this.workerId = workerId;
this.datacenterId = datacenterId;
}

public long nextId()
{
lock (syncRoot)
{
long timestamp = timeGen();

if (timestamp < lastTimestamp)
{
throw new ApplicationException(string.Format("Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
}

if (lastTimestamp == timestamp)
{
sequence = (sequence + 1) & sequenceMask;
if (sequence == 0)
{
timestamp = tilNextMillis(lastTimestamp);
}
}
else
{
sequence = 0L;
}

lastTimestamp = timestamp;

return ((timestamp - twepoch) << (int)timestampLeftShift) | (datacenterId << (int)datacenterIdShift) | (workerId << (int)workerIdShift) | sequence;
}
}

protected long tilNextMillis(long lastTimestamp)
{
long timestamp = timeGen();
while (timestamp <= lastTimestamp)
{
timestamp = timeGen();
}
return timestamp;
}

protected long timeGen()
{
return (long)(DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc)).TotalMilliseconds;
}
}