public class IdWorker
{
//机器标识位数
private const int WORKER_ID_BITS = 4;
//机器标识位的最大值
private const long MAX_WORKER_ID = -1L ^ -1L << WORKER_ID_BITS;
//毫秒内自增位
private const int SEQUENCE_BITS = 10;
//自增位最大值
private const long SEQUENCE_Mask = -1L ^ -1L << SEQUENCE_BITS;
private const long twepoch = 1398049504651L;
//时间毫秒值向左偏移位
private const int timestampLeftShift = SEQUENCE_BITS + WORKER_ID_BITS;
//机器标识位向左偏移位
private const int WORKER_ID_SHIFT = SEQUENCE_BITS;
private static readonly DateTime START_TIME = new System.DateTime(1970, 1, 1, 0, 0, 0, 0);
private static readonly object LOCK = new object();
private long sequence = 0L;
private long lastTimestamp = -1L;
private long workerId;
public IdWorker(long workerId)
{
if (workerId > MAX_WORKER_ID || workerId < 0)
{
throw new ArgumentException(string.Format("worker id can't be greater than {0} or less than 0", MAX_WORKER_ID));
}
this.workerId = workerId;
}
///
/// 获取下一个id值
///
///
public long NextId()
{
lock (LOCK)
{
long timestamp = TimeGen();
//当前时间小于上一次时间,错误
if (timestamp < this.lastTimestamp)
{
throw new Exception(string.Format("Clock moved backwards. Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
}
//当前毫秒内
if (this.lastTimestamp == timestamp)
{
//+1 求余
this.sequence = (this.sequence + 1) & SEQUENCE_Mask;
//当前毫秒内计数满了,等待下一秒
if (this.sequence == 0)
{
timestamp = tilNextMillis(lastTimestamp);
}
}
else //不是当前毫秒内
{
this.sequence = 0; //重置当前毫秒计数
}
this.lastTimestamp = timestamp;
//当前毫秒值 | 机器标识值 | 当前毫秒内自增值
long nextId = ((timestamp - twepoch << timestampLeftShift))
| (this.workerId << WORKER_ID_SHIFT) | (this.sequence);
return nextId;
}
}
///
/// 等待下一个毫秒
///
///
///
private long tilNextMillis(long lastTimestamp)
{
long timestamp = TimeGen();
while (timestamp <= lastTimestamp)
{
timestamp = TimeGen();
}
return timestamp;
}
///
/// 获取当前时间的Unix时间戳
///
///
private long TimeGen()
{
return (DateTime.UtcNow.Ticks - START_TIME.Ticks) / 10000;
}
}
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