000002c0  95 fd 37 14 8c 34 f3 07  10 f8 dd e3 66 28 1c b2  |..7..4......f(..|
000002d0  a0 14 03 03 00 01 01 16  03 03 00 40 00 00 00 00  |...........@....|
000002e0  00 00 00 00 00 00 00 00  00 00 00 00 6c b8 ab 0b  |............l...|
000002f0  c1 2d 2f 4e d2 25 14 96  24 c6 18 97 82 93 1c 1b  |.-/N.%..$.......|
00000300  b4 ca 77 8b 17 7c cf 08  ca 06 e2 ef f3 97 6a 31  |..w..|........j1|

 *   <dt>From the IPv6 reserved documentation prefix ({@code 2001:db8::/32}), {@code "2001:db8::1"}.
 *   <dd>{@code 20 01 0d b8 00 00 00 00 00 00 00 00 00 00 00 01}
 *   <dt>An IPv6 "IPv4 compatible" (or "compat") address, {@code "::192.168.0.1"}.
 *   <dd>{@code 00 00 00 00 00 00 00 00 00 00 00 00 c0 a8 00 01}
 *   <dt>An IPv6 "IPv4 mapped" address, {@code "::ffff:192.168.0.1"}.
 *   <dd>{@code 00 00 00 00 00 00 00 00 00 00 ff ff c0 a8 00 01}

 *   <dt>From the IPv6 reserved documentation prefix ({@code 2001:db8::/32}), {@code "2001:db8::1"}.
 *   <dd>{@code 20 01 0d b8 00 00 00 00 00 00 00 00 00 00 00 01}
 *   <dt>An IPv6 "IPv4 compatible" (or "compat") address, {@code "::192.168.0.1"}.
 *   <dd>{@code 00 00 00 00 00 00 00 00 00 00 00 00 c0 a8 00 01}
 *   <dt>An IPv6 "IPv4 mapped" address, {@code "::ffff:192.168.0.1"}.
 *   <dd>{@code 00 00 00 00 00 00 00 00 00 00 ff ff c0 a8 00 01}

	}
	return ret
}

// StringExpanded is like [Addr.String] but IPv6 addresses are expanded with leading
// zeroes and no "::" compression. For example, "2001:db8::1" becomes
// "2001:0db8:0000:0000:0000:0000:0000:0001".
func (ip Addr) StringExpanded() string {
	switch ip.z {
	case z0, z4:
		return ip.String()
	}

	const size = len("ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff")
	ret := make([]byte, 0, size)