# Gets the byte index of char at position `n` in UTF-8 String
	#
	# `char_from` and `byte_from` are cached values to seek from.
	#
	# NOTE: char_from and byte_from are not guaranteed to be valid cache values
	# It it up to the client to ensure the validity of the information
	fun char_to_byte_index_cached(n, char_from, byte_from: Int): Int do
		var ns_i = byte_from
		var my_i = char_from

		var dist = n - my_i

		while dist > 0 do
			while dist >= 4 do
				var i = fetch_4_chars(ns_i)
				if i & 0x80808080u32 != 0u32 then break
				ns_i += 4
				my_i += 4
				dist -= 4
			end
			if dist == 0 then break
			ns_i += length_of_char_at(ns_i)
			my_i += 1
			dist -= 1
		end

		while dist < 0 do
			while dist <= -4 do
				var i = fetch_4_chars(ns_i - 4)
				if i & 0x80808080u32 != 0u32 then break
				ns_i -= 4
				my_i -= 4
				dist += 4
			end
			if dist == 0 then break
			ns_i = find_beginning_of_char_at(ns_i - 1)
			my_i -= 1
			dist += 1
		end

		return ns_i
	end