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