I'll answer here also the question about ```destroy``` inside ```finalize```.
I am not sure what happens with digest.js when finalize is called. I assumed it would just reset. That way we could reuse the same instance and the same Worker thread for multiple files. I think our next task is about that :) But then we have to call destroy explicitly. If we destroy it automatically it will spawn new thread for each file. Not sure which is better. If you like we'll automatically destroy and test only once. Differences and overhead are minor anyway.