It's also possible to chunk the index array: to store the byte-index of every 16th rune, say, and do a bit of cheap iteration afterward. I've had good success w

It's also possible to chunk the index array: to store the byte-index of every 16th rune, say, and do a bit of cheap iteration afterward. I've had good success with this approach: it's fast, it's light on memory, and it preserves constant-time indexing by code point.