Pad a function with random bytes

Question

I'm writing a function to append 5-10 bytes (count is random) at the beginning of a byte array, and 5-10 random bytes at the end:

func padWithRandomBytes(b []byte) []byte { startBytes := make([]byte, 10-rand.Intn(5)) endBytes := make([]byte, 10-rand.Intn(5)) newSlice := make([]byte, len(startBytes)+len(b)+len(endBytes)) copy(newSlice[:len(startBytes)], startBytes) copy(newSlice[len(startBytes):len(startBytes)+len(b)], b) copy(newSlice[len(startBytes)+len(b):], endBytes) return newSlice } 

This feels pretty inefficient. Is there a more intuitive way to write this in Go?

Answer 1

For example,

package main import ( "fmt" "math/rand" "time" ) func padWithRandomBytes(b []byte) []byte { s := 5 + rand.Intn(5+1) e := 5 + rand.Intn(5+1) r := make([]byte, s+len(b)+e) copy(r[s:], b) return r } func main() { rand.Seed(time.Now().UnixNano()) b := []byte{1, 2, 3} fmt.Println(len(b), b) r := padWithRandomBytes(b) fmt.Println(len(r), r) } 

Output (random):

3 [1 2 3] 20 [0 0 0 0 0 0 0 0 1 2 3 0 0 0 0 0 0 0 0 0] 3 [1 2 3] 15 [0 0 0 0 0 0 1 2 3 0 0 0 0 0 0]