# Write an application-specific extension for `typ` and `bytes` in the shortest possible MessagePack _ext_ format
	#
	# Require: `bytes.length <= 0xFFFF_FFFF`
	#
	# ~~~
	# var writer = new BytesWriter
	# writer.write_msgpack_ext(0x0A, b"\x0B\x0C\x0D")
	# assert writer.bytes == b"\xC7\x03\x0A\x0B\x0C\x0D"
	# ~~~
	fun write_msgpack_ext(typ: Int, bytes: Bytes)
	do
		var len = bytes.length
		if len == 1 then
			write_msgpack_fixext1 typ
			write_byte bytes.first
		else if len == 2 then
			write_msgpack_fixext2 typ
			write_bytes bytes
		else if len == 4 then
			write_msgpack_fixext4 typ
			write_bytes bytes
		else if len == 8 then
			write_msgpack_fixext8 typ
			write_bytes bytes
		else if len == 16 then
			write_msgpack_fixext16 typ
			write_bytes bytes
		else if len <= 0xFF then
			write_msgpack_ext8(typ, len)
			write_bytes bytes
		else if len <= 0xFFFF then
			write_msgpack_ext16(typ, len)
			write_bytes bytes
		else if len <= 0xFFFF_FFFF then
			write_msgpack_ext32(typ, len)
			write_bytes bytes
		else
			abort
		end
	end