uid.go
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// This package provides unique id in distribute system
// the algorithm is inspired by Twitter's famous snowflake
// its link is: https://github.com/twitter/snowflake/releases/tag/snowflake-2010
//
// +---------------+----------------+----------------+
// |timestamp(ms)42 | worker id(10) | sequence(12) |
// +---------------+----------------+----------------+
// Copyright (C) 2016 by zheng-ji.info
package goSnowFlake
import (
"errors"
"sync"
"time"
)
const (
CEpoch = 1474802888000
CWorkerIdBits = 10 // Num of WorkerId Bits
CSenquenceBits = 12 // Num of Sequence Bits
CWorkerIdShift = 12
CTimeStampShift = 22
CSequenceMask = 0xfff // equal as getSequenceMask()
CMaxWorker = 0x3ff // equal as getMaxWorkerId()
)
// IdWorker Struct
type IdWorker struct {
workerId int64
lastTimeStamp int64
sequence int64
maxWorkerId int64
lock *sync.Mutex
}
// NewIdWorker Func: Generate NewIdWorker with Given workerid
func NewIdWorker(workerid int64) (iw *IdWorker, err error) {
iw = new(IdWorker)
iw.maxWorkerId = getMaxWorkerId()
if workerid > iw.maxWorkerId || workerid < 0 {
return nil, errors.New("worker not fit")
}
iw.workerId = workerid
iw.lastTimeStamp = -1
iw.sequence = 0
iw.lock = new(sync.Mutex)
return iw, nil
}
func getMaxWorkerId() int64 {
return -1 ^ -1<<CWorkerIdBits
}
func getSequenceMask() int64 {
return -1 ^ -1<<CSenquenceBits
}
// return in ms
func (iw *IdWorker) timeGen() int64 {
return time.Now().UnixNano() / 1000 / 1000
}
func (iw *IdWorker) timeReGen(last int64) int64 {
ts := time.Now().UnixNano()
for {
if ts < last {
ts = iw.timeGen()
} else {
break
}
}
return ts
}
// NewId Func: Generate next id
func (iw *IdWorker) NextId() (ts int64, err error) {
iw.lock.Lock()
defer iw.lock.Unlock()
ts = iw.timeGen()
if ts == iw.lastTimeStamp {
iw.sequence = (iw.sequence + 1) & CSequenceMask
if iw.sequence == 0 {
ts = iw.timeReGen(ts)
}
} else {
iw.sequence = 0
}
if ts < iw.lastTimeStamp {
err = errors.New("Clock moved backwards, Refuse gen id")
return 0, err
}
iw.lastTimeStamp = ts
ts = (ts-CEpoch)<<CTimeStampShift | iw.workerId<<CWorkerIdShift | iw.sequence
return ts, nil
}
// ParseId Func: reverse uid to timestamp, workid, seq
func ParseId(id int64) (t time.Time, ts int64, workerId int64, seq int64) {
seq = id & CSequenceMask
workerId = (id >> CWorkerIdShift) & CMaxWorker
ts = (id >> CTimeStampShift) + CEpoch
t = time.Unix(ts/1000, (ts%1000)*1000000)
return
}