func (o BlockInfo) EncodeXDRInto(xw *xdr.Writer) (int, error) {
	xw.WriteUint32(uint32(o.Size))
	if l := len(o.Hash); l > 64 {
		return xw.Tot(), xdr.ElementSizeExceeded("Hash", l, 64)
	}
	xw.WriteBytes(o.Hash)
	return xw.Tot(), xw.Error()
}

func (o Query) EncodeXDRInto(xw *xdr.Writer) (int, error) {
	xw.WriteUint32(o.Magic)
	if l := len(o.DeviceID); l > 32 {
		return xw.Tot(), xdr.ElementSizeExceeded("DeviceID", l, 32)
	}
	xw.WriteBytes(o.DeviceID)
	return xw.Tot(), xw.Error()
}

func (o Query) encodeXDR(xw *xdr.Writer) (int, error) {
	xw.WriteUint32(o.Magic)
	if len(o.DeviceID) > 32 {
		return xw.Tot(), xdr.ErrElementSizeExceeded
	}
	xw.WriteBytes(o.DeviceID)
	return xw.Tot(), xw.Error()
}

func (o BlockInfo) encodeXDR(xw *xdr.Writer) (int, error) {
	xw.WriteUint32(o.Size)
	if len(o.Hash) > 64 {
		return xw.Tot(), xdr.ErrElementSizeExceeded
	}
	xw.WriteBytes(o.Hash)
	return xw.Tot(), xw.Error()
}

func (o Relay) EncodeXDRInto(xw *xdr.Writer) (int, error) {
	if l := len(o.Address); l > 256 {
		return xw.Tot(), xdr.ElementSizeExceeded("Address", l, 256)
	}
	xw.WriteString(o.Address)
	xw.WriteUint32(uint32(o.Latency))
	return xw.Tot(), xw.Error()
}

func (o Relay) EncodeXDRInto(xw *xdr.Writer) (int, error) {
	if l := len(o.URL); l > 2083 {
		return xw.Tot(), xdr.ElementSizeExceeded("URL", l, 2083)
	}
	xw.WriteString(o.URL)
	xw.WriteUint32(uint32(o.Latency))
	return xw.Tot(), xw.Error()
}

func (o ConnectRequest) EncodeXDRInto(xw *xdr.Writer) (int, error) {
	if l := len(o.ID); l > 32 {
		return xw.Tot(), xdr.ElementSizeExceeded("ID", l, 32)
	}
	xw.WriteBytes(o.ID)
	return xw.Tot(), xw.Error()
}

func (o fileVersion) EncodeXDRInto(xw *xdr.Writer) (int, error) {
	_, err := o.version.EncodeXDRInto(xw)
	if err != nil {
		return xw.Tot(), err
	}
	xw.WriteBytes(o.device)
	return xw.Tot(), xw.Error()
}

func (o addressList) encodeXDR(xw *xdr.Writer) (int, error) {
	xw.WriteUint32(uint32(len(o.addresses)))
	for i := range o.addresses {
		o.addresses[i].encodeXDR(xw)
	}
	return xw.Tot(), xw.Error()
}

func timeoutWriteHeader(w *xdr.Writer, hdr header) {
	// This tries to write a message header to w, but times out after a while.
	// This is useful because in testing, with a PipeWriter, it will block
	// forever if the other side isn't reading any more. On the other hand we
	// can't just "go" it into the background, because if the other side is
	// still there we should wait for the write to complete. Yay.

	var buf [8]byte // header and message length
	binary.BigEndian.PutUint32(buf[:], encodeHeader(hdr))
	binary.BigEndian.PutUint32(buf[4:], 0) // zero message length, explicitly

	done := make(chan struct{})
	go func() {
		w.WriteRaw(buf[:])
		l.Infoln("write completed")
		close(done)
	}()
	select {
	case <-done:
	case <-time.After(250 * time.Millisecond):
	}
}

func (o Option) encodeXDR(xw *xdr.Writer) (int, error) {
	if l := len(o.Key); l > 64 {
		return xw.Tot(), xdr.ElementSizeExceeded("Key", l, 64)
	}
	xw.WriteString(o.Key)
	if l := len(o.Value); l > 1024 {
		return xw.Tot(), xdr.ElementSizeExceeded("Value", l, 1024)
	}
	xw.WriteString(o.Value)
	return xw.Tot(), xw.Error()
}

func (h header) encodeXDR(xw *xdr.Writer) (int, error) {
	u := encodeHeader(h)
	return xw.WriteUint32(u)
}