函数更改字节片参数

Question

I have the following code where I have a slice of bytes with the alphabet, I copy this alphabet array in a new variable (cryptkey) and I use a function to shuffle it. The result is that the alphabet and the cryptkey byte slice get shuffled. How can I prevent this from happening?

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
}

Result :

ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz. miclOfEInzJNvZe.YuVMCdTbXyqtaLwHGjUrABhog xQPWSpKRkDsF

Playground!

Answer 1

Make a copy. For example,

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
}

Output:

ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz.
ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz.