142 lines
4 KiB
Haskell
142 lines
4 KiB
Haskell
{- git-annex SHA backends
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-
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- Copyright 2011,2012 Joey Hess <joey@kitenet.net>
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-
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- Licensed under the GNU GPL version 3 or higher.
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-}
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module Backend.SHA (backends) where
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import Common.Annex
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import qualified Annex
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import Types.Backend
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import Types.Key
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import Types.KeySource
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import qualified Build.SysConfig as SysConfig
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import Data.Digest.Pure.SHA
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import qualified Data.ByteString.Lazy as L
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import System.Process
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type SHASize = Int
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{- Order is slightly significant; want SHA256 first, and more general
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- sizes earlier. -}
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sizes :: [Int]
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sizes = [256, 1, 512, 224, 384]
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{- The SHA256E backend is the default. -}
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backends :: [Backend]
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backends = catMaybes $ map genBackendE sizes ++ map genBackend sizes
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genBackend :: SHASize -> Maybe Backend
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genBackend size = Just $ Backend
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{ name = shaName size
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, getKey = keyValue size
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, fsckKey = Just $ checkKeyChecksum size
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}
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genBackendE :: SHASize -> Maybe Backend
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genBackendE size = do
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b <- genBackend size
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return $ b
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{ name = shaNameE size
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, getKey = keyValueE size
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}
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shaName :: SHASize -> String
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shaName size = "SHA" ++ show size
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shaNameE :: SHASize -> String
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shaNameE size = shaName size ++ "E"
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shaN :: SHASize -> FilePath -> Integer -> Annex String
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shaN shasize file filesize = do
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showAction "checksum"
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case shaCommand shasize filesize of
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Left sha -> liftIO $ sha <$> L.readFile file
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Right command -> liftIO $ parse command . lines <$>
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readsha command (toCommand [File file])
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where
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parse command [] = bad command
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parse command (l:_)
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| null sha = bad command
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| otherwise = sha
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where
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sha = fst $ separate (== ' ') l
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bad command = error $ command ++ " parse error"
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{- sha commands output the filename, so need to set fileEncoding -}
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readsha command args =
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withHandle StdoutHandle createProcessSuccess p $ \h -> do
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fileEncoding h
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output <- hGetContentsStrict h
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hClose h
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return output
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where
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p = (proc command args) { std_out = CreatePipe }
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shaCommand :: SHASize -> Integer -> Either (L.ByteString -> String) String
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shaCommand shasize filesize
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| shasize == 1 = use SysConfig.sha1 sha1
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| shasize == 256 = use SysConfig.sha256 sha256
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| shasize == 224 = use SysConfig.sha224 sha224
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| shasize == 384 = use SysConfig.sha384 sha384
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| shasize == 512 = use SysConfig.sha512 sha512
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| otherwise = error $ "bad sha size " ++ show shasize
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where
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use Nothing sha = Left $ showDigest . sha
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use (Just c) sha
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{- use builtin, but slower sha for small files
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- benchmarking indicates it's faster up to
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- and slightly beyond 50 kb files -}
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| filesize < 51200 = use Nothing sha
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| otherwise = Right c
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{- A key is a checksum of its contents. -}
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keyValue :: SHASize -> KeySource -> Annex (Maybe Key)
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keyValue shasize source = do
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let file = contentLocation source
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stat <- liftIO $ getFileStatus file
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let filesize = fromIntegral $ fileSize stat
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s <- shaN shasize file filesize
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return $ Just $ stubKey
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{ keyName = s
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, keyBackendName = shaName shasize
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, keySize = Just filesize
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}
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{- Extension preserving keys. -}
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keyValueE :: SHASize -> KeySource -> Annex (Maybe Key)
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keyValueE size source = keyValue size source >>= maybe (return Nothing) addE
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where
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addE k = return $ Just $ k
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{ keyName = keyName k ++ selectExtension (keyFilename source)
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, keyBackendName = shaNameE size
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}
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selectExtension :: FilePath -> String
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selectExtension f
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| null es = ""
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| otherwise = join "." ("":es)
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where
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es = filter (not . null) $ reverse $
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take 2 $ takeWhile shortenough $
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reverse $ split "." $ takeExtensions f
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shortenough e
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| '\n' `elem` e = False -- newline in extension?!
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| otherwise = length e <= 4 -- long enough for "jpeg"
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{- A key's checksum is checked during fsck. -}
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checkKeyChecksum :: SHASize -> Key -> FilePath -> Annex Bool
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checkKeyChecksum size key file = do
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fast <- Annex.getState Annex.fast
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mstat <- liftIO $ catchMaybeIO $ getFileStatus file
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case (mstat, fast) of
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(Just stat, False) -> do
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let filesize = fromIntegral $ fileSize stat
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check <$> shaN size file filesize
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_ -> return True
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where
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check s
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| s == dropExtensions (keyName key) = True
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| otherwise = False
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