使用反射将字节读入结构

Question

I'm trying to write functions that will allow me to marshal/unmarshal simple structs into byte arrays. I've succeeded in writing Marshal, with help from the kind folks at #go-nuts, but I'm running into trouble writing Unmarshal.

// Unmarshal unpacks the binary data and stores it in the packet using
// reflection.
func Unmarshal(b []byte, t reflect.Type) (pkt interface{}, err error) {
    buf := bytes.NewBuffer(b)
    p := reflect.New(t)
    v := reflect.ValueOf(p)
    for i := 0; i < t.NumField(); i++ {
        f := v.Field(i)
        switch f.Kind() {
        case reflect.String:
            // length of string
            var l int16
            var e error
            e = binary.Read(buf, binary.BigEndian, &l)
            if e != nil {
                err = e
                return
            }

            // read length-of-string bytes from the buffer
            raw := make([]byte, l)
            _, e = buf.Read(raw)
            if e != nil {
                err = e
                return
            }

            // convert the bytes to a string
            f.SetString(bytes.NewBuffer(raw).String())
        default:
            e := binary.Read(buf, binary.BigEndian, f.Addr())
            if e != nil {
                err = e
                return
            }
        }
    }

    pkt = p
    return
}

The problem with the code above is that the call to f.Addr() near the end is apparently trying to get the address of an unaddressable value.

If there is an alternative solution, I would appreciate that as well. Either way, any help would be much appreciated.

Thanks!

Answer 1

I think you should use

v := p.Elem()   // Get the value that 'p' points to

instead of

v := reflect.ValueOf(p)