Go进阶39:math/rand VS crypto/rand
1. 前言
之前发现了golang标准库中又两个rand软件包,开始非常想知道他们之间的差异.
math/rand软件包可以用于简单的游戏,但不能用于真正的随机性.
math/rand: 伪随机数生成器crypto/rand: 加密安全的随机数生成器
Rob Pike的代码
package main
import (
"fmt"
"math/rand"
"time"
)
func main() {
c := fanIn(boring("Joe"), boring("Ann"))
for i := 0; i < 10; i++ {
fmt.Println(<-c)
}
fmt.Println("You're both boring; I'm leaving.")
}
func boring(msg string) <-chan string {
c := make(chan string)
go func() {
for i := 0; ; i++ {
c <- fmt.Sprintf("%s %d", msg, i)
time.Sleep(time.Duration(rand.Intn(1e3)) * time.Millisecond)
}
}()
return c
}
// FAN IN
func fanIn(input1, input2 <-chan string) <-chan string {
c := make(chan string)
go func() {
for {
c <- <-input1
}
}()
go func() {
for {
c <- <-input2
}
}()
return c
}
2. Math/rand 伪随机数生成器
实现伪随机数生成器.
随机数由源生成.顶级函数（例如Float64和Int）使用默认的共享源,该源在每次运行程序时都会产生确定的值序列. 如果每次运行需要不同的行为, 请使用种子函数初始化默认的源. 默认的Source可安全地供多个goroutine并发使用,但不是由NewSource创建的Source.
package main
import (
"fmt"
"math/rand"
"time"
)
func init(){
rand.Seed(time.Now().UTC().UnixNano())
}
func main() {
// launches 2 generators and the fanIn collector function
c := fanIn(genrt(), genrt())
for i := 0; i < 10000; i++ {
fmt.Println(<-c)
}
}
func fanIn(a <-chan int, b <-chan int) <-chan string {
c := make(chan string)
// launch collector from a to channel
go func() {
var count int
for {
count += <-a
c <- fmt.Sprintf("Tally of A is: %d", count)
}
}()
// launch collector from b to channel
go func() {
var count int
for {
count += <-b
c <- fmt.Sprintf("Tally of B is: %d", count)
}
}()
return c
}
func genrt() <-chan int {
c := make(chan int)
// launch generator of Dice rolls
go func() {
for i := 0; ; i++ {
c <- rand.Intn(6) + 1
time.Sleep(time.Duration(500 * time.Millisecond))
}
}()
return c
}
打印输出
...
Tally of B is: 17656
Tally of A is: 17438
Tally of A is: 17440
Tally of B is: 17659
Tally of B is: 17660
Tally of A is: 17445
3. Crypto/rand 加密安全的随机数生成器
实现了加密安全的随机数生成器.
package main
import (
"crypto/rand"
"fmt"
"math/big"
"time"
)
func main() {
// launches 2 generatores and the fanIn collector function
c := fanIn(genrt(), genrt())
for i := 0; i < 10000; i++ {
fmt.Println(<-c)
}
}
func fanIn(a <-chan int, b <-chan int) <-chan string {
c := make(chan string)
// launch collector from a to channel
go func() {
var count int
for {
count += <-a
c <- fmt.Sprintf("Tally of A is: %d", count)
}
}()
// launch collector from b to channel
go func() {
var count int
for {
count += <-b
c <- fmt.Sprintf("Tally of B is: %d", count)
}
}()
return c
}
func genrt() <-chan int {
c := make(chan int)
// launch generator of Dice rolls
go func() {
for i := 0; ; i++ {
dice, err := rand.Int(rand.Reader, big.NewInt(6))
if err != nil {
fmt.Println(err)
}
c <- int(dice.Int64()) + 1
time.Sleep(time.Duration(1 * time.Millisecond))
}
}()
return c
}
打印输出
...
Tally of B is: 17496
Tally of A is: 17570
Tally of A is: 17574
Tally of B is: 17500
Tally of B is: 17505
Tally of A is: 17576