[Someone]

A text editor edits a (potentially very long) string, but apart from, possibly, the likes of Notepad, none of them store that string as a single byte array.

So, look at text editor data structures for other representations. Examples:

- https://en.wikipedia.org/wiki/Gap_buffer

- https://en.wikipedia.org/wiki/Rope_(computer_science)

- https://en.wikipedia.org/wiki/Piece_table