go - 函数改变字节 slice 参数

Question

我有以下代码，其中我有一段带有字母表的字节，我将这个字母表数组复制到一个新变量 (cryptkey) 中，然后使用一个函数对其进行洗牌。结果是字母表和 cryptkey 字节 slice 被打乱。我怎样才能防止这种情况发生？

package main

import (
    "fmt"
    "math/rand"
)

func main() {
    alphabet := []byte("ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz.")
    cryptkey := alphabet
    fmt.Println(string(alphabet))
    cryptkey = shuffle(cryptkey)
    fmt.Println(string(alphabet))
}

func shuffle(b []byte) []byte {
    l := len(b)
    out := b
    for key := range out {
        dest := rand.Intn(l)
        out[key], out[dest] = out[dest], out[key]
    }
    return out
}

结果:

ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz. miclOfEInzJNvZe.YuVMCdTbXyqtaLwHGjUrABhog xQPWSpKRkDsF

Playground !

Answer 1

复制一份。例如，

package main

import (
    "fmt"
    "math/rand"
)

func main() {
    alphabet := []byte("ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz.")
    cryptkey := alphabet
    fmt.Println(string(alphabet))
    cryptkey = shuffle(cryptkey)
    fmt.Println(string(alphabet))
}

func shuffle(b []byte) []byte {
    l := len(b)
    out := append([]byte(nil), b...)
    for key := range out {
        dest := rand.Intn(l)
        out[key], out[dest] = out[dest], out[key]
    }
    return out
}

输出:

ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz.
ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz.