git-annex/Backend.hs
Joey Hess 62e152f210
incremental checksum on download from ssh or p2p
Checksum as content is received from a remote git-annex repository, rather
than doing it in a second pass.

Not tested at all yet, but I imagine it will work!

Not implemented for any special remotes, and also not implemented for
copies from local remotes. It may be that, for local remotes, it will
suffice to use rsync, rely on its checksumming, and simply return Verified.
(It would still make a checksumming pass when cp is used for COW, I guess.)
2021-02-09 17:03:27 -04:00

142 lines
4.7 KiB
Haskell

{- git-annex key/value backends
-
- Copyright 2010-2021 Joey Hess <id@joeyh.name>
-
- Licensed under the GNU AGPL version 3 or higher.
-}
module Backend (
builtinList,
defaultBackend,
genKey,
getBackend,
chooseBackend,
lookupBackendVariety,
lookupBuiltinBackendVariety,
maybeLookupBackendVariety,
isStableKey,
isCryptographicallySecure,
isVerifiable,
startVerifyKeyContentIncrementally,
) where
import Annex.Common
import qualified Annex
import Annex.CheckAttr
import Annex.Verify
import Types.Key
import Types.KeySource
import qualified Types.Backend as B
import Utility.Metered
-- When adding a new backend, import it here and add it to the builtinList.
import qualified Backend.Hash
import qualified Backend.WORM
import qualified Backend.URL
import qualified Backend.External
import qualified Data.Map as M
import qualified Data.ByteString.Char8 as S8
{- Build-in backends. Does not include externals. -}
builtinList :: [Backend]
builtinList = Backend.Hash.backends ++ Backend.WORM.backends ++ Backend.URL.backends
{- Backend to use by default when generating a new key. -}
defaultBackend :: Annex Backend
defaultBackend = maybe cache return =<< Annex.getState Annex.backend
where
cache = do
n <- maybe (annexBackend <$> Annex.getGitConfig) (return . Just)
=<< Annex.getState Annex.forcebackend
b <- case n of
Just name | valid name -> lookupname name
_ -> pure (Prelude.head builtinList)
Annex.changeState $ \s -> s { Annex.backend = Just b }
return b
valid name = not (null name)
lookupname = lookupBackendVariety . parseKeyVariety . encodeBS
{- Generates a key for a file. -}
genKey :: KeySource -> MeterUpdate -> Maybe Backend -> Annex (Key, Backend)
genKey source meterupdate preferredbackend = do
b <- maybe defaultBackend return preferredbackend
case B.genKey b of
Just a -> do
k <- a source meterupdate
return (makesane k, b)
Nothing -> giveup $ "Cannot generate a key for backend " ++
decodeBS (formatKeyVariety (B.backendVariety b))
where
-- keyNames should not contain newline characters.
makesane k = alterKey k $ \d -> d
{ keyName = S8.map fixbadchar (fromKey keyName k)
}
fixbadchar c
| c == '\n' = '_'
| otherwise = c
getBackend :: FilePath -> Key -> Annex (Maybe Backend)
getBackend file k = maybeLookupBackendVariety (fromKey keyVariety k) >>= \case
Just backend -> return $ Just backend
Nothing -> do
warning $ "skipping " ++ file ++ " (" ++ unknownBackendVarietyMessage (fromKey keyVariety k) ++ ")"
return Nothing
unknownBackendVarietyMessage :: KeyVariety -> String
unknownBackendVarietyMessage v =
"unknown backend " ++ decodeBS (formatKeyVariety v)
{- Looks up the backend that should be used for a file.
- That can be configured on a per-file basis in the gitattributes file,
- or forced with --backend. -}
chooseBackend :: RawFilePath -> Annex (Maybe Backend)
chooseBackend f = Annex.getState Annex.forcebackend >>= go
where
go Nothing = maybeLookupBackendVariety . parseKeyVariety . encodeBS
=<< checkAttr "annex.backend" f
go (Just _) = Just <$> defaultBackend
{- Looks up a backend by variety. May fail if unsupported or disabled. -}
lookupBackendVariety :: KeyVariety -> Annex Backend
lookupBackendVariety v = fromMaybe (giveup (unknownBackendVarietyMessage v))
<$> maybeLookupBackendVariety v
lookupBuiltinBackendVariety :: KeyVariety -> Backend
lookupBuiltinBackendVariety v = fromMaybe (giveup (unknownBackendVarietyMessage v)) $
maybeLookupBuiltinBackendVariety v
maybeLookupBackendVariety :: KeyVariety -> Annex (Maybe Backend)
maybeLookupBackendVariety (ExternalKey s hasext) =
Just <$> Backend.External.makeBackend s hasext
maybeLookupBackendVariety v =
pure $ M.lookup v varietyMap
maybeLookupBuiltinBackendVariety :: KeyVariety -> Maybe Backend
maybeLookupBuiltinBackendVariety v = M.lookup v varietyMap
varietyMap :: M.Map KeyVariety Backend
varietyMap = M.fromList $ zip (map B.backendVariety builtinList) builtinList
isStableKey :: Key -> Annex Bool
isStableKey k = maybe False (`B.isStableKey` k)
<$> maybeLookupBackendVariety (fromKey keyVariety k)
isCryptographicallySecure :: Key -> Annex Bool
isCryptographicallySecure k = maybe False (`B.isCryptographicallySecure` k)
<$> maybeLookupBackendVariety (fromKey keyVariety k)
isVerifiable :: Key -> Annex Bool
isVerifiable k = maybe False (isJust . B.verifyKeyContent)
<$> maybeLookupBackendVariety (fromKey keyVariety k)
startVerifyKeyContentIncrementally :: VerifyConfig -> Key -> Annex (Maybe B.IncrementalVerifier)
startVerifyKeyContentIncrementally verifyconfig k =
ifM (shouldVerify verifyconfig)
( maybeLookupBackendVariety (fromKey keyVariety k) >>= \case
Just b -> case B.verifyKeyContentIncrementally b of
Just v -> Just <$> v k
Nothing -> return Nothing
Nothing -> return Nothing
, return Nothing
)