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.
// Note that 0.0.0.0 is not the zero Addr.
func (ip Addr) As4() (a4 [4]byte) {
	if ip.z == z4 || ip.Is4In6() {
		byteorder.BePutUint32(a4[:], uint32(ip.addr.lo))
		return a4
	}
	if ip.z == z0 {
		panic("As4 called on IP zero value")
	}

		},
		{
			ip:        mustIP("::1"),
			wantPanic: true,
		},
	}
	as4 := func(ip Addr) (v [4]byte, gotPanic bool) {
		defer func() {
			if recover() != nil {
				gotPanic = true
				return
			}
		}()
		v = ip.As4()
		return
	}
	for i, tt := range tests {
		got, gotPanic := as4(tt.ip)
		if gotPanic != tt.wantPanic {

	addr := ap.Addr()
	if !addr.Is4() {
		return syscall.SockaddrInet4{}, &AddrError{Err: "non-IPv4 address", Addr: addr.String()}
	}
	sa := syscall.SockaddrInet4{
		Addr: addr.As4(),
		Port: int(ap.Port()),
	}
	return sa, nil
}

func addrPortToSockaddrInet6(ap netip.AddrPort) (syscall.SockaddrInet6, error) {
	// ipToSockaddrInet6 has special handling here for zero length slices.

		{"(*AddrPort).UnmarshalText", Method, 18},
		{"(*Prefix).UnmarshalBinary", Method, 18},
		{"(*Prefix).UnmarshalText", Method, 18},
		{"(Addr).AppendTo", Method, 18},
		{"(Addr).As16", Method, 18},
		{"(Addr).As4", Method, 18},
		{"(Addr).AsSlice", Method, 18},
		{"(Addr).BitLen", Method, 18},
		{"(Addr).Compare", Method, 18},
		{"(Addr).Is4", Method, 18},
		{"(Addr).Is4In6", Method, 18},
		{"(Addr).Is6", Method, 18},