package snowflake
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import (
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"errors"
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"sync"
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"time"
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)
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const (
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CEpoch = 1474802888000
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CWorkerIdBits = 10 // Num of WorkerId Bits
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CSenquenceBits = 12 // Num of Sequence Bits
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CWorkerIdShift = 12
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CTimeStampShift = 22
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CSequenceMask = 0xfff // equal as getSequenceMask()
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CMaxWorker = 0x3ff // equal as getMaxWorkerId()
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)
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type IdWorker struct {
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workerId int64
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lastTimeStamp int64
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sequence int64
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maxWorkerId int64
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lock *sync.Mutex
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}
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func NewIdWorker(workerId int64) (iw *IdWorker, err error) {
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iw = new(IdWorker)
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iw.maxWorkerId = getMaxWorkerId()
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if workerId > iw.maxWorkerId || workerId < 0 {
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return nil, errors.New("worker not fit")
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}
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iw.workerId = workerId
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iw.lastTimeStamp = -1
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iw.sequence = 0
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iw.lock = new(sync.Mutex)
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return iw, nil
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}
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func getMaxWorkerId() int64 {
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return -1 ^ -1<<CWorkerIdBits
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}
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func getSequenceMask() int64 {
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return -1 ^ -1<<CSenquenceBits
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}
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// return in ms
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func (iw *IdWorker) timeGen() int64 {
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return time.Now().UnixNano() / 1000 / 1000
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}
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func (iw *IdWorker) timeReGen(last int64) int64 {
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ts := time.Now().UnixNano() / 1000 / 1000
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for {
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if ts <= last {
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ts = iw.timeGen()
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} else {
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break
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}
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}
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return ts
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}
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func (iw *IdWorker) NextId() (ts int64, err error) {
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iw.lock.Lock()
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defer iw.lock.Unlock()
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ts = iw.timeGen()
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if ts == iw.lastTimeStamp {
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iw.sequence = (iw.sequence + 1) & CSequenceMask
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if iw.sequence == 0 {
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ts = iw.timeReGen(ts)
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}
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} else {
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iw.sequence = 0
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}
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if ts < iw.lastTimeStamp {
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err = errors.New("Clock moved backwards, Refuse gen id")
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return 0, err
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}
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iw.lastTimeStamp = ts
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ts = (ts-CEpoch)<<CTimeStampShift | iw.workerId<<CWorkerIdShift | iw.sequence
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return ts, nil
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}
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func ParseId(id int64) (t time.Time, ts int64, workerId int64, seq int64) {
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seq = id & CSequenceMask
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workerId = (id >> CWorkerIdShift) & CMaxWorker
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ts = (id >> CTimeStampShift) + CEpoch
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t = time.Unix(ts/1000, (ts%1000)*1000000)
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return
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}
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var idGenerater, _ = NewIdWorker(0)
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func GenerateId() int64 {
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start:
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id, err := idGenerater.NextId()
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if err != nil {
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goto start
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}
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return id
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}
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