100 lines
3 KiB
Haskell
100 lines
3 KiB
Haskell
{- git-annex key/value storage backends
|
|
-
|
|
- git-annex uses a key/value abstraction layer to allow files contents to be
|
|
- stored in different ways. In theory, any key/value storage system could be
|
|
- used to store the file contents, and git-annex would then retrieve them
|
|
- as needed and put them in `.git/annex/`.
|
|
-
|
|
- When a file is annexed, a key is generated from its content and/or metadata.
|
|
- This key can later be used to retrieve the file's content (its value). This
|
|
- key generation must be stable for a given file content, name, and size.
|
|
-
|
|
- Multiple pluggable backends are supported, and more than one can be used
|
|
- to store different files' contents in a given repository.
|
|
- -}
|
|
|
|
module Backend (
|
|
storeFileKey,
|
|
retrieveKeyFile,
|
|
removeKey,
|
|
hasKey,
|
|
lookupFile
|
|
) where
|
|
|
|
import Control.Monad.State
|
|
import Control.Exception
|
|
import System.Directory
|
|
import System.FilePath
|
|
import Data.String.Utils
|
|
import System.Posix.Files
|
|
import BackendList
|
|
import Locations
|
|
import qualified GitRepo as Git
|
|
import qualified Annex
|
|
import Utility
|
|
import Types
|
|
import qualified BackendTypes as B
|
|
import BackendList
|
|
|
|
{- List of backends in the order to try them when storing a new key. -}
|
|
backendList :: Annex [Backend]
|
|
backendList = do
|
|
l <- Annex.backends
|
|
if (0 < length l)
|
|
then return l
|
|
else do
|
|
g <- Annex.gitRepo
|
|
let l = parseBackendList $ Git.configGet g "annex.backends" ""
|
|
Annex.backendsChange l
|
|
return l
|
|
|
|
{- Attempts to store a file in one of the backends. -}
|
|
storeFileKey :: FilePath -> Annex (Maybe (Key, Backend))
|
|
storeFileKey file = do
|
|
g <- Annex.gitRepo
|
|
let relfile = Git.relative g file
|
|
b <- backendList
|
|
storeFileKey' b file relfile
|
|
storeFileKey' [] _ _ = return Nothing
|
|
storeFileKey' (b:bs) file relfile = do
|
|
try <- (B.getKey b) relfile
|
|
case (try) of
|
|
Nothing -> nextbackend
|
|
Just key -> do
|
|
stored <- (B.storeFileKey b) file key
|
|
if (not stored)
|
|
then nextbackend
|
|
else do
|
|
return $ Just (key, b)
|
|
where
|
|
nextbackend = storeFileKey' bs file relfile
|
|
|
|
{- Attempts to retrieve an key from one of the backends, saving it to
|
|
- a specified location. -}
|
|
retrieveKeyFile :: Backend -> Key -> FilePath -> Annex Bool
|
|
retrieveKeyFile backend key dest = (B.retrieveKeyFile backend) key dest
|
|
|
|
{- Removes a key from a backend. -}
|
|
removeKey :: Backend -> Key -> Annex Bool
|
|
removeKey backend key = (B.removeKey backend) key
|
|
|
|
{- Checks if a backend has its key. -}
|
|
hasKey :: Key -> Annex Bool
|
|
hasKey key = (B.hasKey (lookupBackendName $ backendName key)) key
|
|
|
|
{- Looks up the key and backend corresponding to an annexed file,
|
|
- by examining what the file symlinks to. -}
|
|
lookupFile :: FilePath -> IO (Maybe (Key, Backend))
|
|
lookupFile file = do
|
|
result <- try (lookup)::IO (Either SomeException (Maybe (Key, Backend)))
|
|
case (result) of
|
|
Left err -> return Nothing
|
|
Right succ -> return succ
|
|
where
|
|
lookup = do
|
|
l <- readSymbolicLink file
|
|
return $ Just $ pair $ takeFileName l
|
|
pair file = (k, b)
|
|
where
|
|
k = fileKey file
|
|
b = lookupBackendName $ backendName k
|