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|
{- git-annex key/value backend data types
-
- Most things should not need this, using Types instead
-
- Copyright 2010 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module BackendTypes where
import Data.String.Utils
import Test.QuickCheck
type KeyName = String
type BackendName = String
newtype Key = Key (BackendName, KeyName) deriving (Eq, Ord)
data Backend a = Backend {
-- name of this backend
name :: String,
-- converts a filename to a key
getKey :: FilePath -> a (Maybe Key),
-- stores a file's contents to a key
storeFileKey :: FilePath -> Key -> a Bool,
-- retrieves a key's contents to a file
retrieveKeyFile :: Key -> FilePath -> a Bool,
-- removes a key, optionally checking that enough copies are stored
-- elsewhere
removeKey :: Key -> Maybe Int -> a Bool,
-- checks if a backend is storing the content of a key
hasKey :: Key -> a Bool,
-- called during fsck to check a key
-- (second parameter may be the filename associated with it)
-- (third parameter may be the number of copies that there should
-- be of the key)
fsckKey :: Key -> Maybe FilePath -> Maybe Int -> a Bool
}
instance Show (Backend a) where
show backend = "Backend { name =\"" ++ name backend ++ "\" }"
instance Eq (Backend a) where
a == b = name a == name b
-- accessors for the parts of a key
keyName :: Key -> KeyName
keyName (Key (_,k)) = k
backendName :: Key -> BackendName
backendName (Key (b,_)) = b
-- constructs a key in a backend
genKey :: Backend a -> KeyName -> Key
genKey b f = Key (name b,f)
-- show a key to convert it to a string; the string includes the
-- name of the backend to avoid collisions between key strings
instance Show Key where
show (Key (b, k)) = b ++ ":" ++ k
instance Read Key where
readsPrec _ s = [(Key (b,k), "")]
where
l = split ":" s
b = if null l then "" else head l
k = join ":" $ drop 1 l
-- for quickcheck
instance Arbitrary Key where
arbitrary = do
backendname <- arbitrary
keyname <- arbitrary
return $ Key (backendname, keyname)
prop_idempotent_key_read_show :: Key -> Bool
prop_idempotent_key_read_show k
-- backend names will never contain colons
| ':' `elem` (backendName k) = True
| otherwise = k == (read $ show k)
|
