I just released a new, fairly tailored crate for small ASCII string manipulation - tinystr.
The code has been written by @raphlinus, and I mostly packaged it and added some tests, benchmarks and docs.
The crate is useful when you have a 4/8 char max ASCII strings that you need to work with and change their case. The perfect use case is
unic-langid where we have a bunch of "en", "US", "Latn" etc. strings but you may find a different use case as well!
Performance is quite spectacular