128 lines
3.6 KiB
Haskell
128 lines
3.6 KiB
Haskell
{- git-annex key/value backends
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-
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- Copyright 2010 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 (
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list,
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orderedList,
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genKey,
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lookupFile,
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chooseBackends,
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lookupBackendName,
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maybeLookupBackendName
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) where
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import Control.Monad.State (liftIO, when)
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import System.IO.Error (try)
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import System.FilePath
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import System.Posix.Files
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import Data.Maybe
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import Locations
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import qualified Git
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import qualified Annex
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import Types
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import Types.Key
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import qualified Types.Backend as B
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import Messages
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-- When adding a new backend, import it here and add it to the list.
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import qualified Backend.WORM
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import qualified Backend.SHA
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import qualified Backend.URL
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list :: [Backend Annex]
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list = Backend.WORM.backends ++ Backend.SHA.backends ++ Backend.URL.backends
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{- List of backends in the order to try them when storing a new key. -}
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orderedList :: Annex [Backend Annex]
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orderedList = do
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l <- Annex.getState Annex.backends -- list is cached here
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if not $ null l
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then return l
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else do
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s <- getstandard
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d <- Annex.getState Annex.forcebackend
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handle d s
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where
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parseBackendList [] = list
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parseBackendList s = map lookupBackendName $ words s
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handle Nothing s = return s
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handle (Just "") s = return s
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handle (Just name) s = do
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let l' = lookupBackendName name : s
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Annex.changeState $ \state -> state { Annex.backends = l' }
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return l'
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getstandard = do
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g <- Annex.gitRepo
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return $ parseBackendList $
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Git.configGet g "annex.backends" ""
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{- Generates a key for a file, trying each backend in turn until one
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- accepts it. -}
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genKey :: FilePath -> Maybe (Backend Annex) -> Annex (Maybe (Key, Backend Annex))
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genKey file trybackend = do
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bs <- orderedList
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let bs' = maybe bs (: bs) trybackend
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genKey' bs' file
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genKey' :: [Backend Annex] -> FilePath -> Annex (Maybe (Key, Backend Annex))
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genKey' [] _ = return Nothing
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genKey' (b:bs) file = do
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r <- (B.getKey b) file
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case r of
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Nothing -> genKey' bs file
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Just k -> return $ Just (k, b)
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{- Looks up the key and backend corresponding to an annexed file,
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- by examining what the file symlinks to. -}
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lookupFile :: FilePath -> Annex (Maybe (Key, Backend Annex))
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lookupFile file = do
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tl <- liftIO $ try getsymlink
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case tl of
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Left _ -> return Nothing
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Right l -> makekey l
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where
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getsymlink = do
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l <- readSymbolicLink file
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return $ takeFileName l
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makekey l = maybe (return Nothing) (makeret l) (fileKey l)
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makeret l k =
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case maybeLookupBackendName bname of
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Just backend -> return $ Just (k, backend)
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Nothing -> do
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when (isLinkToAnnex l) $
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warning skip
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return Nothing
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where
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bname = keyBackendName k
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skip = "skipping " ++ file ++
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" (unknown backend " ++ bname ++ ")"
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{- Looks up the backends that should be used for each file in a list.
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- That can be configured on a per-file basis in the gitattributes file.
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-}
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chooseBackends :: [FilePath] -> Annex [(FilePath, Maybe (Backend Annex))]
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chooseBackends fs = do
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g <- Annex.gitRepo
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forced <- Annex.getState Annex.forcebackend
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if forced /= Nothing
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then do
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l <- orderedList
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return $ map (\f -> (f, Just $ head l)) fs
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else do
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pairs <- liftIO $ Git.checkAttr g "annex.backend" fs
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return $ map (\(f,b) -> (f, maybeLookupBackendName b)) pairs
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{- Looks up a backend by name. May fail if unknown. -}
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lookupBackendName :: String -> Backend Annex
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lookupBackendName s = fromMaybe unknown $ maybeLookupBackendName s
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where
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unknown = error $ "unknown backend " ++ s
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maybeLookupBackendName :: String -> Maybe (Backend Annex)
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maybeLookupBackendName s
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| length matches == 1 = Just $ head matches
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| otherwise = Nothing
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where matches = filter (\b -> s == B.name b) list
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