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