If you decode a struct which contains a slice of bytes, the returned slice shares the same underlying array with the buffer passed to Decode().

The consequences are:

• If the buffer is later overwritten, the contents of the decoded slice change (see demonstration below).
• If a (potentially large) buffer is no longer in use, the memory underlying array can't be freed as long as there is a reference to the decoded slice of bytes.

I think these consequences aren't intended. It seems better for Decode() to return a copy of the slice of bytes.

package main

import "go.dedis.ch/protobuf"
import "fmt"

func main() {
	type foo struct{ Bar []byte }
	buf, _ := protobuf.Encode(&foo{[]byte{44, 45}})

	var decoded foo
	protobuf.Decode(buf, &decoded)
	fmt.Println(decoded) // {[44 45]}

	buf[len(buf)-1] = 99
	fmt.Println(decoded) // {[44 99]}
}