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diff --git a/src/Erebos/Storage/Disk.hs b/src/Erebos/Storage/Disk.hs
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+module Erebos.Storage.Disk (
+ openStorage,
+) where
+
+import Codec.Compression.Zlib
+
+import Control.Arrow
+import Control.Concurrent
+import Control.Exception
+import Control.Monad
+
+import Data.ByteArray qualified as BA
+import Data.ByteString (ByteString)
+import Data.ByteString qualified as B
+import Data.ByteString.Char8 qualified as BC
+import Data.ByteString.Lazy qualified as BL
+import Data.ByteString.Lazy.Char8 qualified as BLC
+import Data.Function
+import Data.List
+import Data.Maybe
+import Data.UUID qualified as U
+
+import System.Directory
+import System.FSNotify
+import System.FilePath
+import System.IO
+import System.IO.Error
+
+import Erebos.Object
+import Erebos.Storage.Backend
+import Erebos.Storage.Head
+import Erebos.Storage.Internal
+import Erebos.Storage.Platform
+
+
+data DiskStorage = StorageDir
+ { dirPath :: FilePath
+ , dirWatchers :: MVar ( Maybe WatchManager, [ HeadTypeID ], WatchList )
+ }
+
+instance Eq DiskStorage where
+ (==) = (==) `on` dirPath
+
+instance Show DiskStorage where
+ show StorageDir { dirPath = path } = "dir:" ++ path
+
+instance StorageBackend DiskStorage where
+ backendLoadBytes StorageDir {..} dgst =
+ handleJust (guard . isDoesNotExistError) (const $ return Nothing) $
+ Just . decompress . BL.fromChunks . (:[]) <$> (B.readFile $ refPath dirPath dgst)
+ backendStoreBytes StorageDir {..} dgst = writeFileOnce (refPath dirPath dgst) . compress
+
+
+ backendLoadHeads StorageDir {..} tid = do
+ let hpath = headTypePath dirPath tid
+
+ files <- filterM (doesFileExist . (hpath </>)) =<<
+ handleJust (\e -> guard (isDoesNotExistError e)) (const $ return [])
+ (getDirectoryContents hpath)
+ fmap catMaybes $ forM files $ \hname -> do
+ case U.fromString hname of
+ Just hid -> do
+ content <- B.readFile (hpath </> hname)
+ return $ do
+ (h : _) <- Just (BC.lines content)
+ dgst <- readRefDigest h
+ Just $ ( HeadID hid, dgst )
+ Nothing -> return Nothing
+
+ backendLoadHead StorageDir {..} tid hid = do
+ handleJust (guard . isDoesNotExistError) (const $ return Nothing) $ do
+ (h:_) <- BC.lines <$> B.readFile (headPath dirPath tid hid)
+ return $ readRefDigest h
+
+ backendStoreHead StorageDir {..} tid hid dgst = do
+ Right () <- writeFileChecked (headPath dirPath tid hid) Nothing $
+ showRefDigest dgst `B.append` BC.singleton '\n'
+ return ()
+
+ backendReplaceHead StorageDir {..} tid hid expected new = do
+ let filename = headPath dirPath tid hid
+ showDgstL r = showRefDigest r `B.append` BC.singleton '\n'
+
+ writeFileChecked filename (Just $ showDgstL expected) (showDgstL new) >>= \case
+ Left Nothing -> return $ Left Nothing
+ Left (Just bs) -> do Just cur <- return $ readRefDigest $ BC.takeWhile (/='\n') bs
+ return $ Left $ Just cur
+ Right () -> return $ Right new
+
+ backendWatchHead st@StorageDir {..} tid hid cb = do
+ modifyMVar dirWatchers $ \( mbmanager, ilist, wl ) -> do
+ manager <- maybe startManager return mbmanager
+ ilist' <- case tid `elem` ilist of
+ True -> return ilist
+ False -> do
+ void $ watchDir manager (headTypePath dirPath tid) (const True) $ \case
+ Added { eventPath = fpath } | Just ihid <- HeadID <$> U.fromString (takeFileName fpath) -> do
+ backendLoadHead st tid ihid >>= \case
+ Just dgst -> do
+ (_, _, iwl) <- readMVar dirWatchers
+ mapM_ ($ dgst) . map wlFun . filter ((== (tid, ihid)) . wlHead) . wlList $ iwl
+ Nothing -> return ()
+ _ -> return ()
+ return $ tid : ilist
+ return $ first ( Just manager, ilist', ) $ watchListAdd tid hid cb wl
+
+ backendUnwatchHead StorageDir {..} wid = do
+ modifyMVar_ dirWatchers $ \( mbmanager, ilist, wl ) -> do
+ return ( mbmanager, ilist, watchListDel wid wl )
+
+
+ backendListKeys StorageDir {..} = do
+ catMaybes . map (readRefDigest . BC.pack) <$>
+ listDirectory (keyDirPath dirPath)
+
+ backendLoadKey StorageDir {..} dgst = do
+ tryIOError (BC.readFile (keyFilePath dirPath dgst)) >>= \case
+ Right kdata -> return $ Just $ BA.convert kdata
+ Left _ -> return Nothing
+
+ backendStoreKey StorageDir {..} dgst key = do
+ writeFileOnce (keyFilePath dirPath dgst) (BL.fromStrict $ BA.convert key)
+
+ backendRemoveKey StorageDir {..} dgst = do
+ void $ tryIOError (removeFile $ keyFilePath dirPath dgst)
+
+
+storageVersion :: String
+storageVersion = "0.1"
+
+openStorage :: FilePath -> IO Storage
+openStorage path = modifyIOError annotate $ do
+ let versionFileName = "erebos-storage"
+ let versionPath = path </> versionFileName
+ let writeVersionFile = writeFileOnce versionPath $ BLC.pack $ storageVersion <> "\n"
+
+ maybeVersion <- handleJust (guard . isDoesNotExistError) (const $ return Nothing) $
+ Just <$> readFile versionPath
+ version <- case maybeVersion of
+ Just versionContent -> do
+ return $ takeWhile (/= '\n') versionContent
+
+ Nothing -> do
+ files <- handleJust (guard . isDoesNotExistError) (const $ return []) $
+ listDirectory path
+ when (not $ or
+ [ null files
+ , versionFileName `elem` files
+ , (versionFileName ++ ".lock") `elem` files
+ , "objects" `elem` files && "heads" `elem` files
+ ]) $ do
+ fail "directory is neither empty, nor an existing erebos storage"
+
+ createDirectoryIfMissing True $ path
+ writeVersionFile
+ takeWhile (/= '\n') <$> readFile versionPath
+
+ when (version /= storageVersion) $ do
+ fail $ "unsupported storage version " <> version
+
+ createDirectoryIfMissing True $ path </> "objects"
+ createDirectoryIfMissing True $ path </> "heads"
+ watchers <- newMVar ( Nothing, [], WatchList startWatchID [] )
+ newStorage $ StorageDir path watchers
+ where
+ annotate e = annotateIOError e "failed to open storage" Nothing (Just path)
+
+
+refPath :: FilePath -> RefDigest -> FilePath
+refPath spath rdgst = intercalate "/" [ spath, "objects", BC.unpack alg, pref, rest ]
+ where (alg, dgst) = showRefDigestParts rdgst
+ (pref, rest) = splitAt 2 $ BC.unpack dgst
+
+headTypePath :: FilePath -> HeadTypeID -> FilePath
+headTypePath spath (HeadTypeID tid) = spath </> "heads" </> U.toString tid
+
+headPath :: FilePath -> HeadTypeID -> HeadID -> FilePath
+headPath spath tid (HeadID hid) = headTypePath spath tid </> U.toString hid
+
+keyDirPath :: FilePath -> FilePath
+keyDirPath sdir = sdir </> "keys"
+
+keyFilePath :: FilePath -> RefDigest -> FilePath
+keyFilePath sdir dgst = keyDirPath sdir </> (BC.unpack $ showRefDigest dgst)
+
+
+openLockFile :: FilePath -> IO Handle
+openLockFile path = do
+ createDirectoryIfMissing True (takeDirectory path)
+ retry 10 $ createFileExclusive path
+ where
+ retry :: Int -> IO a -> IO a
+ retry 0 act = act
+ retry n act = catchJust (\e -> if isAlreadyExistsError e then Just () else Nothing)
+ act (\_ -> threadDelay (100 * 1000) >> retry (n - 1) act)
+
+writeFileOnce :: FilePath -> BL.ByteString -> IO ()
+writeFileOnce file content = bracket (openLockFile locked)
+ hClose $ \h -> do
+ doesFileExist file >>= \case
+ True -> removeFile locked
+ False -> do BL.hPut h content
+ hClose h
+ renameFile locked file
+ where locked = file ++ ".lock"
+
+writeFileChecked :: FilePath -> Maybe ByteString -> ByteString -> IO (Either (Maybe ByteString) ())
+writeFileChecked file prev content = bracket (openLockFile locked)
+ hClose $ \h -> do
+ (prev,) <$> doesFileExist file >>= \case
+ (Nothing, True) -> do
+ current <- B.readFile file
+ removeFile locked
+ return $ Left $ Just current
+ (Nothing, False) -> do B.hPut h content
+ hClose h
+ renameFile locked file
+ return $ Right ()
+ (Just expected, True) -> do
+ current <- B.readFile file
+ if current == expected then do B.hPut h content
+ hClose h
+ renameFile locked file
+ return $ return ()
+ else do removeFile locked
+ return $ Left $ Just current
+ (Just _, False) -> do
+ removeFile locked
+ return $ Left Nothing
+ where locked = file ++ ".lock"
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