// IPv6 addresses with zones are returned without their zone (use the
// [Addr.Zone] method to get it).
// The ip zero value returns all zeroes.
func (ip Addr) As16() (a16 [16]byte) {
	byteorder.BePutUint64(a16[:8], ip.addr.hi)
	byteorder.BePutUint64(a16[8:], ip.addr.lo)
	return a16
}

// As4 returns an IPv4 or IPv4-in-IPv6 address in its 4-byte representation.
// If ip is the zero [Addr] or an IPv6 address, As4 panics.