golang 實現twitter雪花算法

/*
 * twitter雪花算法golang實現,生成唯一趨勢自增id
 * 保留位:63位
 * 毫秒時間戳:[62-20]43位,時間范圍[1970-01-01 00:00:00.000,2248-09-26 15:10:22.207]
 * 機器id:[19-12]8位,十進制范圍[0,255]
 * 序列號:[11-0]12位,十進制范圍[0,4095]
 * bobo
 */

package test

import (
    "runtime"
    "sync"
    "time"
)

type SnowFlake struct {
    machineID int64      //機器 id占8位,十進制范圍是[0,255]
    sn        int64      //序列號占12位,十進制范圍是[0,4095]
    lastTime  int64      //上次的時間戳(毫秒級)
    _lock     sync.Mutex //鎖
}

var Snow = &SnowFlake{
    lastTime: time.Now().UnixNano() / 1000000,
}

func (c *SnowFlake) lock() {
    c._lock.Lock()
}

func (c *SnowFlake) unLock() {
    c._lock.Unlock()
}

//獲取當前毫秒
func (c *SnowFlake) getCurMilliSecond() int64 {
    return time.Now().UnixNano() / 1000000
}

//設置機器id,默認為0,范圍[0,255]
func (c *SnowFlake) SetMachineId(mId int64) {
    //保留8位
    mId = mId & 0xFF
    //左移12位,序列號是12位的
    mId <<= 12
    c.machineID = mId
}

//獲取機器id
func (c *SnowFlake) GetMachineId() int64 {
    mId := c.machineID
    mId >>= 12
    return mId | 0xFF
}

//解析雪花(id)
// 返回值
// milliSecond:毫秒數
// mId:機器id
// sn:序列號
func (c *SnowFlake) ParseId(id int64) (milliSecond, mId, sn int64) {
    sn = id & 0xFFF
    id >>= 12
    mId = id & 0xFF
    id >>= 8
    milliSecond = id & 0x7FFFFFFFFFF

    return
}

//毫秒轉換成time
func (c *SnowFlake) MilliSecondToTime(milliSecond int64) (t time.Time) {
    return time.Unix(milliSecond/1000, milliSecond%1000*1000000)
}

//毫秒轉換成"20060102T150405.999Z"
func (c *SnowFlake) MillisecondToTimeTz(ts int64) string {
    tm := Snow.MilliSecondToTime(ts)
    return tm.UTC().Format("20060102T150405.999Z")
}

//毫秒轉換成"2006-01-02 15:04:05.999"
func (c *SnowFlake) MillisecondToTimeDb(ts int64) string {
    tm := Snow.MilliSecondToTime(ts)
    return tm.UTC().Format("2006-01-02 15:04:05.999")
}

//獲取雪花
//返回值
//id:自增id
//ts:生成該id的毫秒時間戳
func (c *SnowFlake) GetSnowflakeId() (id, ts int64) {
    curTime := c.getCurMilliSecond()
    var sn int64 = 0

    c.lock()
    // 同一毫秒
    if curTime == c.lastTime {
        c.sn++
        // 序列號占 12 位,十進制范圍是 [0,4095]
        if c.sn > 4095 {
            for {
                // 讓出當前線程
                runtime.Gosched()
                curTime = c.getCurMilliSecond()
                if curTime != c.lastTime {
                    break
                }
            }
            c.sn = 0
        }
    } else {
        c.sn = 0
    }
    sn = c.sn
    c.lastTime = curTime
    c.unLock()

    //當前時間小於上次的時間，系統時間改過了嗎?
    /*
        if curTimeStamp < c.lastTimeStamp {
                return 0, curTimeStamp
        }
    */
    //機器id占用8位空間,序列號占用12位空間,所以左移20位
    rightBinValue := curTime & 0x7FFFFFFFFFF
    rightBinValue <<= 20
    id = rightBinValue | c.machineID | sn

    return id, curTime
}

測試

func testFun() {
    var count int = 1000000
    mapId := make(map[int64]int64, count)
    fmt.Println("start,count:", count)
    for i := 0; i < count; i++ {
        id, ts := test.Snow.GetSnowflakeId()
        mapId[id] = ts
    }
    fmt.Println("done,count:", count, ",mapCount:", len(mapId))
}