---------- Forwarded message ---------- From: Anatoly Yakovenko Date: Jul 14, 2007 11:09 AM Subject: Re: Your SHA1 To: Dominic Steinitz

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1. Very good.

Thanks, it was a fun experiment.

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2. It has type hash::BS.ByteString -> IO [Word] but hash is a pure function. Can this be changed?

you can call it safely with unsafePerformIO, I do a lot of hacks to get the performance, like casting a C ptr from a bytestring to a word array, but each call to hash should have no side effects.

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3. I haven't tried but I assume it only runs with ghc and not hugs? I guess if point 1 could be addressed then we could put it in the crypto library (assuming you are happy with this) with some sort of conditional flag to use your code if the library is being built for ghc but to use the slow version for other compilers / interpreters.

i would be surprised if this ran on hugs, i havent tried. Also, i haven't verified that my implementation is correct, as far as the sha1 algorithm is concerned. the complexity is the same, so if there any bugs in the math they can be easily fixed without making it slower.

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On a more discursive note, I still don't think we have found the holy grail here: idiomatic functional programming (probably not using StorableArray and unsafeRead and unsafeWrite) and lightning fast speed.

yea, i agree, i am doing a lot of ugly hacks to get things going faster. Actually i think the "cleaner" approach would be to use Harpy extension and do the math with x86 assembly :). This way its at least straight forward, cause right now, i was just randomly changing strictness and unboxing things so ghc generates the fastest code, but a different haskell compiler would have completely different results.

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Dominic.

PS I noticed you have:

splitByN::Int -> BS.ByteString -> [BS.ByteString] splitByN nn ll = st : (if (BS.null en) then [] else (splitByN nn en)) where (st,en) = BS.splitAt nn ll

It's a function I often use:

splitByN n = unfoldr k where k [] = Nothing k p = Just (splitAt n p)

Maybe it should be a standard part of List and ByteString?

yea i agree, i've seen a couple other implementations as well. seems like its something that should be in Prelude and ByteString. Anatoly