Oh, you would reuse the same SHA256 object multiple times for multiple files? I thought we had in mind API which where we would create new SHA256 object each time. (Internally we could keep worker thread up, if you think, but I think this would just make it more complicated.)

Server side [digest](http://nodejs.org/api/crypto.html#crypto_hash_digest_encoding) cannot be used anymore after `final`. I think this is why I was not assuming that we can reuse SHA256 objects again.