go雪花算法

package main

import (
    "errors"
    "fmt"
    "sync"
    "time"
)

const (
    workerBits  uint8 = 10
    numberBits  uint8 = 12
    workerMax   int64 = -1 ^ (-1 << workerBits)
    numberMax   int64 = -1 ^ (-1 << numberBits)
    timeShift   uint8 = workerBits + numberBits
    workerShift uint8 = numberBits
    startTime   int64 = 1525705533000 // 如果在程序跑了一段时间修改了epoch这个值 可能会导致生成相同的ID
)

type Worker struct {
    mu        sync.Mutex
    timestamp int64
    workerId  int64
    number    int64
}

func NewWorker(workerId int64) (*Worker, error) {
    if workerId < 0 || workerId > workerMax {
        return nil, errors.New("Worker ID excess of quantity")
    }
    // 生成一个新节点
    return &Worker{
        timestamp: 0,
        workerId:  workerId,
        number:    0,
    }, nil
}

func (w *Worker) GetId() int64 {
    w.mu.Lock()
    defer w.mu.Unlock()
    now := time.Now().UnixNano() / 1e6
    if w.timestamp == now {
        w.number++
        if w.number > numberMax {
            for now <= w.timestamp {
                now = time.Now().UnixNano() / 1e6
            }
        }
    } else {
        w.number = 0
        w.timestamp = now
    }
    ID := int64((now-startTime)<<timeShift | (w.workerId << workerShift) | (w.number))
    return ID
}
func main() {
    // 生成节点实例
    node, err := NewWorker(1)
    if err != nil {
        panic(err)
    }
    for {
        fmt.Println(node.GetId())
    }
}