Directory special remotes now support chunking files written to them

Avoiding writing files larger than a specified size is useful on certian
things. For example, box.com has a file size limit of 100 mb. Could also
be useful on really crappy removable media.

Remote/Directory.hs

@@ -1,6 +1,6 @@
 {- A "remote" that is just a filesystem directory.
  -
- - Copyright 2011 Joey Hess <joey@kitenet.net>
+ - Copyright 2011-2012 Joey Hess <joey@kitenet.net>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
@@ -19,6 +19,8 @@ import Utility.FileMode
 import Remote.Helper.Special
 import Remote.Helper.Encryptable
 import Crypto
+import Utility.DataUnits
+import Data.Int
 
 remote :: RemoteType
 remote = RemoteType {
@@ -32,24 +34,39 @@ gen :: Git.Repo -> UUID -> Maybe RemoteConfig -> Annex Remote
 gen r u c = do
 	dir <- getConfig r "directory" (error "missing directory")
 	cst <- remoteCost r cheapRemoteCost
+	let chunksize = chunkSize c
 	return $ encryptableRemote c
-		(storeEncrypted dir)
-		(retrieveEncrypted dir)
+		(storeEncrypted dir chunksize)
+		(retrieveEncrypted dir chunksize)
 		Remote {
 			uuid = u,
 			cost = cst,
 			name = Git.repoDescribe r,
- 			storeKey = store dir,
-			retrieveKeyFile = retrieve dir,
-			retrieveKeyFileCheap = retrieveCheap dir,
-			removeKey = remove dir,
-			hasKey = checkPresent dir,
+ 			storeKey = store dir chunksize,
+			retrieveKeyFile = retrieve dir chunksize,
+			retrieveKeyFileCheap = retrieveCheap dir chunksize,
+			removeKey = remove dir chunksize,
+			hasKey = checkPresent dir chunksize,
 			hasKeyCheap = True,
 			whereisKey = Nothing,
 			config = Nothing,
 			repo = r,
 			remotetype = remote
 		}
+	where
+
+type ChunkSize = Maybe Int64
+
+chunkSize :: Maybe RemoteConfig -> ChunkSize
+chunkSize Nothing = Nothing
+chunkSize (Just m) =
+	case M.lookup "chunksize" m of
+		Nothing -> Nothing
+		Just v -> case readSize dataUnits v of
+			Nothing -> error "bad chunksize"
+			Just size
+				| size <= 0 -> error "bad chunksize"
+				| otherwise -> Just $ fromInteger size
 
 directorySetup :: UUID -> RemoteConfig -> Annex RemoteConfig
 directorySetup u c = do
@@ -69,69 +86,158 @@ directorySetup u c = do
 locations :: FilePath -> Key -> [FilePath]
 locations d k = map (d </>) (keyPaths k)
 
-withCheckedFile :: (FilePath -> IO Bool) -> FilePath -> Key -> (FilePath -> IO Bool) -> IO Bool
-withCheckedFile _ [] _ _ = return False
-withCheckedFile check d k a = go $ locations d k
+{- An infinite stream of chunks to use for a given file. -}
+chunkStream :: FilePath -> [FilePath]
+chunkStream f = map tochunk [1 :: Integer ..]
+	where
+		tochunk n = f ++ ".chunk" ++ show n
+
+{- A file that records the number of chunks used. -}
+chunkCount :: FilePath -> FilePath
+chunkCount f = f ++ ".chunkcount"
+
+withCheckedFiles :: (FilePath -> IO Bool) -> ChunkSize -> FilePath -> Key -> ([FilePath] -> IO Bool) -> IO Bool
+withCheckedFiles _ _ [] _ _ = return False
+withCheckedFiles check Nothing d k a = go $ locations d k
 	where
 		go [] = return False
 		go (f:fs) = do
 			use <- check f
 			if use
-				then a f
+				then a [f]
 				else go fs
-
-withStoredFile :: FilePath -> Key -> (FilePath -> IO Bool) -> IO Bool
-withStoredFile = withCheckedFile doesFileExist
-
-store :: FilePath -> Key -> Annex Bool
-store d k = do
-	src <- inRepo $ gitAnnexLocation k
-	liftIO $ catchBoolIO $ storeHelper d k $ copyFileExternal src
-
-storeEncrypted :: FilePath -> (Cipher, Key) -> Key -> Annex Bool
-storeEncrypted d (cipher, enck) k = do
-	src <- inRepo $ gitAnnexLocation k
-	liftIO $ catchBoolIO $ storeHelper d enck $ encrypt src
+withCheckedFiles check (Just _) d k a = go $ locations d k
 	where
-		encrypt src dest = do
-			withEncryptedContent cipher (L.readFile src) $ L.writeFile dest
-			return True
+		go [] = return False
+		go (f:fs) = do
+			let chunkcount = chunkCount f
+			use <- check chunkcount
+			if use
+				then do
+					count <- readcount chunkcount
+					let chunks = take count $ chunkStream f
+					ok <- all id <$> mapM check chunks
+					if ok
+						then a chunks
+						else return False
+				else go fs
+		readcount f = fromMaybe (error $ "cannot parse " ++ f)
+			. (readish :: String -> Maybe Int)
+			<$> readFile f
 
-storeHelper :: FilePath -> Key -> (FilePath -> IO Bool) -> IO Bool
-storeHelper d key a = do
-	let dest = Prelude.head $ locations d key
-	let tmpdest = dest ++ ".tmp"
-	let dir = parentDir dest
+withStoredFiles :: ChunkSize -> FilePath -> Key -> ([FilePath] -> IO Bool) -> IO Bool
+withStoredFiles = withCheckedFiles doesFileExist
+
+store :: FilePath -> ChunkSize -> Key -> Annex Bool
+store d chunksize k = do
+	src <- inRepo $ gitAnnexLocation k
+	liftIO $ catchBoolIO $ storeHelper d chunksize k $ \dests ->
+		case chunksize of
+			Nothing -> do
+				let dest = Prelude.head dests
+				ok <- copyFileExternal src dest
+				return $ if ok then [dest] else []
+			Just _ -> storeSplit chunksize dests =<< L.readFile src
+
+storeEncrypted :: FilePath -> ChunkSize -> (Cipher, Key) -> Key -> Annex Bool
+storeEncrypted d chunksize (cipher, enck) k = do
+	src <- inRepo $ gitAnnexLocation k
+	liftIO $ catchBoolIO $ storeHelper d chunksize enck $ encrypt src
+	where
+		encrypt src dests = withEncryptedContent cipher (L.readFile src) $ \s ->
+			case chunksize of
+				Nothing -> do
+					let dest = Prelude.head dests
+					L.writeFile dest s
+					return [dest]
+				Just _ -> storeSplit chunksize dests s
+
+{- Splits a ByteString into chunks and writes to dests.
+ - Note: Must always write at least one file, even for empty ByteString. -}
+storeSplit :: ChunkSize -> [FilePath] -> L.ByteString -> IO [FilePath]
+storeSplit Nothing _ _ = error "bad storeSplit call"
+storeSplit _ [] _ = error "bad storeSplit call"
+storeSplit (Just chunksize) alldests@(firstdest:_) s
+	| L.null s = do
+		-- must always write at least one file, even for empty
+		L.writeFile firstdest s
+		return [firstdest]
+	| otherwise = storeSplit' chunksize alldests s []
+storeSplit' :: Int64 -> [FilePath] -> L.ByteString -> [FilePath] -> IO [FilePath]
+storeSplit' _ [] _ _ = error "expected an infinite list"
+storeSplit' chunksize (d:dests) s c
+	| L.null s = return $ reverse c
+	| otherwise = do
+		let (chunk, rest) = L.splitAt chunksize s
+		L.writeFile d chunk
+		storeSplit' chunksize dests rest (d:c)
+
+{- Generates a list of destinations to write to in order to store a key.
+ - When chunksize is specified, this list will be a list of chunks.
+ - The action should store the file, and return a list of the destinations
+ - it stored it to, or [] on error.
+ - The stored files are only put into their final place once storage is
+ - complete.
+ -}
+storeHelper :: FilePath -> ChunkSize -> Key -> ([FilePath] -> IO [FilePath]) -> IO Bool
+storeHelper d chunksize key a = do
+	let dir = parentDir desttemplate
 	createDirectoryIfMissing True dir
 	allowWrite dir
-	ok <- a tmpdest
-	when ok $ do
-		renameFile tmpdest dest
+	stored <- a tmpdests
+	forM_ stored $ \f -> do
+		let dest = detmpprefix f
+		renameFile f dest
 		preventWrite dest
-		preventWrite dir
-	return ok
+	when (chunksize /= Nothing) $ do
+		let chunkcount = chunkCount desttemplate
+		_ <- tryIO $ allowWrite chunkcount
+		writeFile chunkcount (show $ length stored)
+		preventWrite chunkcount
+	preventWrite dir
+	return (not $ null stored)
+	where
+		desttemplate = Prelude.head $ locations d key
+		tmpdests = case chunksize of
+			Nothing -> [desttemplate ++ tmpprefix]
+			Just _ -> map (++ tmpprefix) (chunkStream desttemplate)
+		tmpprefix = ".tmp"
+		detmpprefix f = take (length f - tmpprefixlen) f
+		tmpprefixlen = length tmpprefix
 
-retrieve :: FilePath -> Key -> FilePath -> Annex Bool
-retrieve d k f = liftIO $ withStoredFile d k $ \file -> copyFileExternal file f
+retrieve :: FilePath -> ChunkSize -> Key -> FilePath -> Annex Bool
+retrieve d chunksize k f = liftIO $ withStoredFiles chunksize d k go
+	where
+		go [file] = copyFileExternal file f
+		go files = catchBoolIO $ do
+			L.writeFile f =<< (L.concat <$> mapM L.readFile files)
+			return True
 
-retrieveCheap :: FilePath -> Key -> FilePath -> Annex Bool
-retrieveCheap d k f = liftIO $ withStoredFile d k $ \file ->
-	catchBoolIO $ createSymbolicLink file f >> return True
-
-retrieveEncrypted :: FilePath -> (Cipher, Key) -> FilePath -> Annex Bool
-retrieveEncrypted d (cipher, enck) f =
-	liftIO $ withStoredFile d enck $ \file -> catchBoolIO $ do
-		withDecryptedContent cipher (L.readFile file) $ L.writeFile f
+retrieveEncrypted :: FilePath -> ChunkSize -> (Cipher, Key) -> FilePath -> Annex Bool
+retrieveEncrypted d chunksize (cipher, enck) f =
+	liftIO $ withStoredFiles chunksize d enck $ \files -> catchBoolIO $ do
+		withDecryptedContent cipher (L.concat <$> mapM L.readFile files) $
+			L.writeFile f
 		return True
 
-remove :: FilePath -> Key -> Annex Bool
-remove d k = liftIO $ withStoredFile d k $ \file -> catchBoolIO $ do
-	let dir = parentDir file
-	allowWrite dir
-	removeFile file
-	removeDirectory dir
-	return True
+retrieveCheap :: FilePath -> ChunkSize -> Key -> FilePath -> Annex Bool
+retrieveCheap _ (Just _) _ _ = return False -- no cheap retrieval for chunks
+retrieveCheap d _ k f = liftIO $ withStoredFiles Nothing d k go
+	where
+		go [file] = catchBoolIO $ createSymbolicLink file f >> return True
+		go _files = return False
 
-checkPresent :: FilePath -> Key -> Annex (Either String Bool)
-checkPresent d k = liftIO $ catchMsgIO $ withStoredFile d k $
-	const $ return True -- withStoredFile checked that it exists
+remove :: FilePath -> ChunkSize -> Key -> Annex Bool
+remove d chunksize k = liftIO $ withStoredFiles chunksize d k go
+	where
+		go files = all id <$> mapM removefile files
+		removefile file = catchBoolIO $ do
+			let dir = parentDir file
+			allowWrite dir
+			removeFile file
+			_ <- tryIO $ removeDirectory dir
+			return True
+
+checkPresent :: FilePath -> ChunkSize -> Key -> Annex (Either String Bool)
+checkPresent d chunksize k = liftIO $ catchMsgIO $ withStoredFiles chunksize d k $
+	const $ return True -- withStoredFiles checked that it exists

debian/changelog

@@ -2,6 +2,8 @@ git-annex (3.20120230) UNRELEASED; urgency=low
 
   * "here" can be used to refer to the current repository,
     which can read better than the old "." (which still works too).
+  * Directory special remotes now support chunking files written to them,
+    avoiding writing files larger than a specified size.
 
  -- Joey Hess <joeyh@debian.org>  Thu, 01 Mar 2012 22:34:27 -0400
 

doc/special_remotes/directory.mdwn

@@ -5,6 +5,25 @@ you want to use it to sneakernet files between systems (possibly with
 [[encrypted|encryption]] contents). Just set up both systems to use
 the drive's mountpoint as a directory remote.
 
+## configuration
+
+These parameters can be passed to `git annex initremote` to configure the
+remote:
+
+* `encryption` - Required. Either "none" to disable encryption of content
+  stored in the directory,
+  or a value that can be looked up (using gpg -k) to find a gpg encryption
+  key that will be given access to the remote. Note that additional gpg
+  keys can be given access to a remote by rerunning initremote with
+  the new key id. See [[encryption]].
+* `chunksize` - Avoid storing files larger than the specified size in the
+  directory. For use on directories on mount points that have file size
+  limitations. The default is to never chunk files.
+  Note that changing the chunk size of an existing remote is 
+  not recommended.
+  The value can use specified using any commonly used units.
+  Example: `chunksize=100 megabytes`
+
 Setup example:
 
 	# git annex initremote usbdrive type=directory directory=/media/usbdrive/ encryption=none