一文详解使用snowflake算法生成唯一id

package main
import (
    "fmt"
    "time"
)
const (
    workerBits uint8 = 10
    seqBits    uint8 = 12
    maxWorkerNum int64 = -1 ^ (-1 << workerBits)
    maxSeqNum    int64 = -1 ^ (-1 << seqBits)
    timeShift   uint8 = workerBits + seqBits
    workerShift uint8 = seqBits
)
type snowflake struct {
    lastTimestamp int64
    workerId      int64
    sequence      int64
}
func newSnowflake(workerId int64) *snowflake {
    if workerId < 0 || workerId > maxWorkerNum {
        panic("workerId out of range")
    }
    return &snowflake{
        lastTimestamp: 0,
        workerId:      workerId,
        sequence:      0,
    }
}
func (sf *snowflake) NextId() int64 {
    timestamp := time.Now().UnixNano() / 1000000
    if timestamp < sf.lastTimestamp {
        panic("clock is moving backwards")
    }
    if timestamp == sf.lastTimestamp {
        sf.sequence = (sf.sequence + 1) & maxSeqNum
        if sf.sequence == 0 {
            for timestamp <= sf.lastTimestamp {
                timestamp = time.Now().UnixNano() / 1000000
            }
        }
    } else {
        sf.sequence = 0
    }
    sf.lastTimestamp = timestamp
    return (timestamp << timeShift) | (sf.workerId << workerShift) | sf.sequence
}
func main() {
    sf := newSnowflake(1)
    fmt.Println(sf.NextId())
}