Added del operation
Getty Ritter
8 years ago
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ephemeralGet :: IORef Table -> ByteString -> IO (Maybe ByteString)
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ephemeralGet table key = M.lookup key `fmap` readIORef table
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ephemeralDel :: IORef Table -> ByteString -> IO ()
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ephemeralDel table key = modifyIORef table (M.delete key)
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-- | An 'EphemeralDb' is just an in-memory map, with no way of saving it.
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-- It is intended to be used for testing Tansu code.
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newtype EphemeralDb = EDB { fromEDB :: Table }
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{ dbRunTransaction = ephemeralRunTransaction lock
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, dbSet = ephemeralSet table
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, dbGet = ephemeralGet table
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, dbDel = ephemeralDel table
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}
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import Data.ByteString.Base64
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import qualified Data.ByteString.Char8 as BS
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import Database.Tansu.Internal (TansuDb(..))
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import System.Directory (createDirectoryIfMissing, doesFileExist)
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import System.Directory ( createDirectoryIfMissing
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, doesFileExist
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, removeFile
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)
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import System.FileLock (SharedExclusive(Exclusive), withFileLock)
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import System.FilePath.Posix ((</>))
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if exists
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then Just `fmap` BS.readFile keyPath
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else return Nothing
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filePathDel :: FilePath -> ByteString -> IO ()
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filePathDel path key = do
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let keyPath = path </> BS.unpack (encode key)
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removeFile keyPath
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filePathLock :: FilePath -> IO a -> IO a
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filePathLock path comp = do
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createDirectoryIfMissing True path
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comp $ TansuDb { dbSet = filePathSet path
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, dbGet = filePathGet path
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, dbDel = filePathDel path
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, dbRunTransaction = filePathLock path
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}
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data TansuDb = TansuDb
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{ dbSet :: ByteString -> ByteString -> IO ()
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, dbGet :: ByteString -> IO (Maybe ByteString)
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, dbDel :: ByteString -> IO ()
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, dbRunTransaction :: forall a. IO a -> IO a
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}
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, getMb
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, set
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, (=:)
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, del
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-- * Running a 'Tansu' operation
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, run
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) where
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Right val' -> return (Just val')
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Left err -> Tansu (raise (DecodeError err))
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del :: (Serialize k) => k -> Tansu ()
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del key = do
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db <- Tansu ask
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Tansu $ inBase $ dbDel db (encode key)
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-- | Given a storage backend and a 'Tansu' computation, execute the
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-- sequence of 'get' and 'set' commands and produce either the value
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-- or the error encountered while running the computation.
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way to interact with a `TansuDb` is by running a `Tansu` command, which
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represents a (possibly empty) sequence of stores and loads applied
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successively to the key-value mapping. Values can be set using the `set`
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command (or its operator synonym `=:`) and retrieved using the `get`
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command.
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command (or its operator synonym `=:`), retrieved using the `get`
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command, and deleted using the `del` command.
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~~~.haskell
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-- set a key to a value
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-- get a value, returning Nothing if it does not exist
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getMb :: (Serialize k, Serialize v) => k -> Tansu (Maybe v)
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-- remove a key and its associated value
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del :: (Serialize k) => k -> Tansu ()
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-- run a Tansu computation
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run :: TansuDb -> Tansu a -> IO (Either TansuError a)
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