90 lines
2.6 KiB
Go
90 lines
2.6 KiB
Go
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/*
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* 薄雾算法
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*
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* 1 2 48 56 64
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* +------+-----------------------------------------------------+----------+----------+
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* retain | increas | salt | sequence |
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* +------+-----------------------------------------------------+----------+----------+
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* 0 | 0000000000 0000000000 0000000000 0000000000 0000000 | 00000000 | 00000000 |
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* +------+-----------------------------------------------------+------------+--------+
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*
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* 0. 最高位，占 1 位，保持为 0，使得值永远为正数；
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* 1. 自增数，占 47 位，自增数在高位能保证结果值呈递增态势，遂低位可以为所欲为；
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* 2. 随机因子一，占 8 位，上限数值 255，使结果值不可预测；
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* 3. 随机因子二，占 8 位，上限数值 255，使结果值不可预测；
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*
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* 编号上限为百万亿级，上限值计算为 140737488355327 即 int64(1 << 47 - 1)，假设每天取值 10 亿，能使用 385+ 年
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*/
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package main
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import (
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"crypto/rand"
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"fmt"
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"math/big"
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"strconv"
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"sync"
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"time"
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)
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const startYear = 2019
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const saltBit = uint(8) // 随机因子二进制位数
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const saltShift = uint(8) // 随机因子移位数
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const increasShift = saltBit + saltShift // 自增数移位数
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func NewIncreaserFromTime(t time.Time) int64 {
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year := t.Year() - startYear
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day := t.YearDay()
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secs := 60*60*t.Hour() + 60*t.Minute() + t.Second()
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s := fmt.Sprintf("%d%d%05d", year, day, secs)
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v, _ := strconv.ParseInt(s, 10, 64)
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return v
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}
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type Mist struct {
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sync.Mutex // 互斥锁
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increas int64 // 自增数
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saltA int64 // 随机因子一
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saltB int64 // 随机因子二
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}
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/* 初始化 Mist 结构体*/
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func NewMist(c int64) *Mist {
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mist := Mist{increas: c}
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return &mist
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}
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/* 生成唯一编号 */
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func (c *Mist) Generate() int64 {
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c.Lock()
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defer c.Unlock()
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c.increas++
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// 获取随机因子数值 ｜ 使用真随机函数提高性能
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randA, _ := c.newRand()
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c.saltA = randA.Int64()
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randB, _ := c.newRand()
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c.saltB = randB.Int64()
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// 通过位运算实现自动占位
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mist := int64((c.increas << increasShift) | (c.saltA << saltShift) | c.saltB)
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return mist
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}
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func (c Mist) newRand() (*big.Int, error) {
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return rand.Int(rand.Reader, big.NewInt(255))
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}
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func main() {
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// 使用方法
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// mist := NewMist(NewIncreaserFromTime(time.Now()))
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mist := NewMist(31175572)
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m := make(map[int64]int)
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for i := 0; i < 10; i++ {
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v := mist.Generate()
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if _, ok := m[v]; ok {
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fmt.Println(v, i)
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}
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m[v] = i
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fmt.Println(v)
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}
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}
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