# Write the header for an application-specific extension of `len` data bytes
	#
	# After writing the header, clients should write the data bytes.
	#
	# Require: `len >= 0 and <= 0xFF`
	fun write_msgpack_ext8(typ, len: Int)
	do
		assert len >= 0 and len <= 0xFF
		write_byte 0xC7
		write_byte len
		write_byte typ
	end