redef var byte_length = 0

	# Returns the number of UTF-8 code units (bytes) in `self`
	redef fun byte_length: Int do
		var offset = 0
		var l = 0
		var c = '\0'

		for i in chars do
			c = uchar_string.char_at_offset(offset, code_units)
			var b = c.to_i
			if b > 0xFFFF then offset += 2 else offset +=1

			if b <= 0x7F then
				l += 1
			else if b <= 0x7FF then
				l += 2
			else if b <= 0xD7FF or b > 0x10FFFF then
				l += 0
			else if b <= 0xFFFF then
				l += 3
			else
				l += 4
			end
		end
		return l
	end

	redef var byte_length is noinit

	redef fun byte_length do
		sys.byte_length_call.inc "Concat"
		return super
	end

	redef fun byte_length do
		sys.byte_length_call.inc "FlatString"
		return super
	end

	redef fun byte_length do
		sys.byte_length_call.inc "FlatBuffer"
		return super
	end