Is it equivalent use "copy" or "append" slice type in golang

Question

    a := []byte{1, 2, 3}
    // Method: 1
    b := make([]byte, len(a))
    copy(b, a)
    // Method: 2
    c := append([]byte(nil), a...)

Q: Is the method 2 more concise and efficient than method 1?

Q: Whether mode 2 and mode 1 are equivalent, both are deep copy?

thank you for your help

Answer 1

Method 1 is more precise - as it allocates exactly the slice size it needs & fills it.

Method 2's append will allocate a slice of capacity (depending probably on your architecture) in units of 8. So those 3 initial items will be copied to a backing array of size 8:

https://go.dev/play/p/C2nPQFflsM2