git-annex/Utility/Hash.hs

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Use cryptohash rather than SHA for hashing. This is a massive win on OSX, which doesn't have a sha256sum normally. Only use external hash commands when the file is > 1 mb, since cryptohash is quite close to them in speed. SHA is still used to calculate HMACs. I don't quite understand cryptohash's API for those. Used the following benchmark to arrive at the 1 mb number. 1 mb file: benchmarking sha256/internal mean: 13.86696 ms, lb 13.83010 ms, ub 13.93453 ms, ci 0.950 std dev: 249.3235 us, lb 162.0448 us, ub 458.1744 us, ci 0.950 found 5 outliers among 100 samples (5.0%) 4 (4.0%) high mild 1 (1.0%) high severe variance introduced by outliers: 10.415% variance is moderately inflated by outliers benchmarking sha256/external mean: 14.20670 ms, lb 14.17237 ms, ub 14.27004 ms, ci 0.950 std dev: 230.5448 us, lb 150.7310 us, ub 427.6068 us, ci 0.950 found 3 outliers among 100 samples (3.0%) 2 (2.0%) high mild 1 (1.0%) high severe 2 mb file: benchmarking sha256/internal mean: 26.44270 ms, lb 26.23701 ms, ub 26.63414 ms, ci 0.950 std dev: 1.012303 ms, lb 925.8921 us, ub 1.122267 ms, ci 0.950 variance introduced by outliers: 35.540% variance is moderately inflated by outliers benchmarking sha256/external mean: 26.84521 ms, lb 26.77644 ms, ub 26.91433 ms, ci 0.950 std dev: 347.7867 us, lb 210.6283 us, ub 571.3351 us, ci 0.950 found 6 outliers among 100 samples (6.0%) import Crypto.Hash import Data.ByteString.Lazy as L import Criterion.Main import Common testfile :: FilePath testfile = "/run/shm/data" -- on ram disk main = defaultMain [ bgroup "sha256" [ bench "internal" $ whnfIO internal , bench "external" $ whnfIO external ] ] sha256 :: L.ByteString -> Digest SHA256 sha256 = hashlazy internal :: IO String internal = show . sha256 <$> L.readFile testfile external :: IO String external = do s <- readProcess "sha256sum" [testfile] return $ fst $ separate (== ' ') s
2013-09-22 23:45:08 +00:00
{- Convenience wrapper around cryptohash.
-
- The resulting Digests can be shown to get a canonical hash encoding. -}
module Utility.Hash where
import Crypto.Hash
import qualified Data.ByteString.Lazy as L
sha1 :: L.ByteString -> Digest SHA1
sha1 = hashlazy
sha224 :: L.ByteString -> Digest SHA224
sha224 = hashlazy
sha256 :: L.ByteString -> Digest SHA256
sha256 = hashlazy
sha384 :: L.ByteString -> Digest SHA384
sha384 = hashlazy
sha512 :: L.ByteString -> Digest SHA512
sha512 = hashlazy
-- sha3 is not yet fully standardized
--sha3 :: L.ByteString -> Digest SHA3
--sha3 = hashlazy