# Index of the character `index` in `_items`
	fun char_to_byte_index(index: Int): Int do
		var dpos = index - _position
		var b = _bytepos
		var its = _items

		if dpos == 1 then
			if its[b] & 0x80 == 0x00 then
				b += 1
			else
				b += its.length_of_char_at(b)
			end
			_bytepos = b
			_position = index
			return b
		end
		if dpos == -1 then
			b = its.find_beginning_of_char_at(b - 1)
			_bytepos = b
			_position = index
			return b
		end
		if dpos == 0 then return b

		var ln = _length
		var pos = _position
		# Find best insertion point
		var delta_begin = index
		var delta_end = (ln - 1) - index
		var delta_cache = (pos - index).abs
		var min = delta_begin

		if delta_cache < min then min = delta_cache
		if delta_end < min then min = delta_end

		var ns_i: Int
		var my_i: Int

		if min == delta_cache then
			ns_i = _bytepos
			my_i = pos
		else if min == delta_begin then
			ns_i = first_byte
			my_i = 0
		else
			ns_i = its.find_beginning_of_char_at(last_byte)
			my_i = _length - 1
		end

		ns_i = its.char_to_byte_index_cached(index, my_i, ns_i)

		_position = index
		_bytepos = ns_i

		return ns_i
	end