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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 (
BackendFile,
list,
orderedList,
genKey,
lookupFile,
chooseBackends,
lookupBackendName,
maybeLookupBackendName
) where
import Control.Monad.State (liftIO, when)
import Control.Applicative
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 = takeFileName <$> readSymbolicLink file
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 ++ ")"
type BackendFile = (Maybe (Backend Annex), FilePath)
{- 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 [BackendFile]
chooseBackends fs = do
g <- Annex.gitRepo
forced <- Annex.getState Annex.forcebackend
if isJust forced
then do
l <- orderedList
return $ map (\f -> (Just $ head l, f)) fs
else do
pairs <- liftIO $ Git.checkAttr g "annex.backend" fs
return $ map (\(f,b) -> (maybeLookupBackendName b, f)) 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
|
