Actually I was wrong about where the error was here, encode_rle actually works like it should the shift isn't the problem there. It actually blew up later in a different place. The second one is just a bizarre way to write that but sure, it counts the first N repeats in the input slice.. There's plenty of bizarre stuff in here[1], but mostly the general shape of the idea is directionally correct. A couple notably questionable things, though, like the assumption that RLE is always the way to go if the run length is greater than 8, perplexing style choices, etc.

[1] https://play.rust-lang.org/?version=stable&mode=debug&editio...