git-annex/Types/Backend.hs

41 lines
1.2 KiB
Haskell

{- git-annex key/value backend data type
-
- 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 Types.Backend where
import Types.Key
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,
-- Is a newer repesentation possible for a key?
upgradableKey :: Key -> a Bool
}
instance Show (Backend a) where
show backend = "Backend { name =\"" ++ name backend ++ "\" }"
instance Eq (Backend a) where
a == b = name a == name b