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{- git-annex key/value backends
-
- Copyright 2010 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Backend (
list,
orderedList,
genKey,
lookupFile,
chooseBackend,
lookupBackendName,
maybeLookupBackendName
) where
import System.Posix.Files
import Common.Annex
import Config
import qualified Annex
import Annex.CheckAttr
import Types.Key
import Types.KeySource
import qualified Types.Backend as B
-- When adding a new backend, import it here and add it to the list.
import qualified Backend.SHA
import qualified Backend.WORM
import qualified Backend.URL
list :: [Backend]
list = Backend.SHA.backends ++ Backend.WORM.backends ++ Backend.URL.backends
{- List of backends in the order to try them when storing a new key. -}
orderedList :: Annex [Backend]
orderedList = do
l <- Annex.getState Annex.backends -- list is cached here
if not $ null l
then return l
else handle =<< Annex.getState Annex.forcebackend
where
handle Nothing = standard
handle (Just "") = standard
handle (Just name) = do
l' <- (lookupBackendName name :) <$> standard
Annex.changeState $ \s -> s { Annex.backends = l' }
return l'
standard = parseBackendList <$> getConfig (annexConfig "backends") ""
parseBackendList [] = list
parseBackendList s = map lookupBackendName $ words s
{- Generates a key for a file, trying each backend in turn until one
- accepts it.
-}
genKey :: KeySource -> Maybe Backend -> Annex (Maybe (Key, Backend))
genKey source trybackend = do
bs <- orderedList
let bs' = maybe bs (: bs) trybackend
genKey' bs' source
genKey' :: [Backend] -> KeySource -> Annex (Maybe (Key, Backend))
genKey' [] _ = return Nothing
genKey' (b:bs) source = do
r <- B.getKey b source
case r of
Nothing -> genKey' bs source
Just k -> return $ Just (makesane k, b)
where
-- keyNames should not contain newline characters.
makesane k = k { keyName = map fixbadchar (keyName k) }
fixbadchar c
| c == '\n' = '_'
| otherwise = c
{- Looks up the key and backend corresponding to an annexed file,
- by examining what the file symlinks to. -}
lookupFile :: FilePath -> Annex (Maybe (Key, Backend))
lookupFile file = do
tl <- liftIO $ tryIO $ readSymbolicLink file
case tl of
Left _ -> return Nothing
Right l -> makekey l
where
makekey l = maybe (return Nothing) (makeret l) (fileKey $ takeFileName l)
makeret l k = let bname = keyBackendName k in
case maybeLookupBackendName bname of
Just backend -> do
return $ Just (k, backend)
Nothing -> do
when (isLinkToAnnex l) $ warning $
"skipping " ++ file ++
" (unknown backend " ++
bname ++ ")"
return Nothing
{- Looks up the backend that should be used for a file.
- That can be configured on a per-file basis in the gitattributes file.
-}
chooseBackend :: FilePath -> Annex (Maybe Backend)
chooseBackend f = Annex.getState Annex.forcebackend >>= go
where
go Nothing = maybeLookupBackendName <$>
checkAttr "annex.backend" f
go (Just _) = Just . Prelude.head <$> orderedList
{- Looks up a backend by name. May fail if unknown. -}
lookupBackendName :: String -> Backend
lookupBackendName s = fromMaybe unknown $ maybeLookupBackendName s
where
unknown = error $ "unknown backend " ++ s
maybeLookupBackendName :: String -> Maybe Backend
maybeLookupBackendName s = headMaybe matches
where
matches = filter (\b -> s == B.name b) list
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