183 lines
3.6 KiB
Go
183 lines
3.6 KiB
Go
/**
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* package utils
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* 作用：雪花ID生成器，生成全局唯一的ID
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* 说明：使用Twitter的雪花算法，生成64位整数ID
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*/
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package utils
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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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// 时间戳占用位数（41位，可以使用69年）
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timestampBits = 41
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// 数据中心ID占用位数（5位，最多32个数据中心）
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datacenterIDBits = 5
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// 机器ID占用位数（5位，每个数据中心最多32台机器）
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machineIDBits = 5
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// 序列号占用位数（12位，每毫秒最多4096个ID）
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sequenceBits = 12
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// 最大值
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maxDatacenterID = -1 ^ (-1 << datacenterIDBits)
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maxMachineID = -1 ^ (-1 << machineIDBits)
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maxSequence = -1 ^ (-1 << sequenceBits)
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// 位移
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machineIDShift = sequenceBits
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datacenterIDShift = sequenceBits + machineIDBits
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timestampShift = sequenceBits + machineIDBits + datacenterIDBits
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// 起始时间戳（2024-01-01 00:00:00）
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epoch int64 = 1704067200000
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)
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// Snowflake 雪花ID生成器
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type Snowflake struct {
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mutex sync.Mutex
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datacenterID int64
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machineID int64
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sequence int64
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lastStamp int64
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}
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var (
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// 全局雪花ID生成器实例
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globalSnowflake *Snowflake
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once sync.Once
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)
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/**
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* InitSnowflake
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* 功能：初始化全局雪花ID生成器
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* @param datacenterID 数据中心ID（0-31）
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* @param machineID 机器ID（0-31）
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*/
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func InitSnowflake(datacenterID, machineID int64) error {
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if datacenterID < 0 || datacenterID > maxDatacenterID {
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return errors.New("datacenter ID must be between 0 and 31")
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}
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if machineID < 0 || machineID > maxMachineID {
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return errors.New("machine ID must be between 0 and 31")
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}
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once.Do(func() {
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globalSnowflake = &Snowflake{
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datacenterID: datacenterID,
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machineID: machineID,
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sequence: 0,
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lastStamp: -1,
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}
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})
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return nil
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}
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/**
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* NextID
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* 功能：生成下一个ID
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* @returns 64位整数ID
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*/
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func NextID() (int64, error) {
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if globalSnowflake == nil {
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// 默认使用datacenterID=1, machineID=1
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if err := InitSnowflake(1, 1); err != nil {
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return 0, err
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}
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}
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return globalSnowflake.nextID()
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}
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/**
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* nextID
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* 功能：生成下一个ID（内部方法）
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*/
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func (s *Snowflake) nextID() (int64, error) {
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s.mutex.Lock()
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defer s.mutex.Unlock()
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now := time.Now().UnixMilli()
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// 如果当前时间小于上次时间，说明时钟回拨
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if now < s.lastStamp {
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return 0, errors.New("clock moved backwards")
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}
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// 如果是同一毫秒内
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if now == s.lastStamp {
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s.sequence = (s.sequence + 1) & maxSequence
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// 序列号溢出，等待下一毫秒
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if s.sequence == 0 {
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now = s.waitNextMillis(s.lastStamp)
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}
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} else {
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// 新的毫秒，序列号重置
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s.sequence = 0
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}
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s.lastStamp = now
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// 生成ID
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id := ((now - epoch) << timestampShift) |
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(s.datacenterID << datacenterIDShift) |
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(s.machineID << machineIDShift) |
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s.sequence
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return id, nil
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}
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/**
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* waitNextMillis
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* 功能：等待下一毫秒
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*/
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func (s *Snowflake) waitNextMillis(lastStamp int64) int64 {
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now := time.Now().UnixMilli()
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for now <= lastStamp {
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now = time.Now().UnixMilli()
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}
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return now
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}
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/**
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* NextIDString
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* 功能：生成下一个ID（字符串格式）
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*/
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func NextIDString() (string, error) {
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id, err := NextID()
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if err != nil {
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return "", err
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}
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return int64ToString(id), nil
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}
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/**
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* int64ToString
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* 功能：将int64转换为字符串
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*/
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func int64ToString(id int64) string {
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if id == 0 {
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return "0"
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}
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negative := id < 0
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if negative {
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id = -id
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}
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var result []byte
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for id > 0 {
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result = append([]byte{byte('0' + id%10)}, result...)
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id /= 10
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}
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if negative {
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result = append([]byte{'-'}, result...)
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}
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return string(result)
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}
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