better byteRetriever

Make the byteRetriever be passed the callback that consumes the bytestring.

This way, there's no worries about the lazy bytestring not all being read
when the resource that's creating it is closed.

Which in turn lets bup, ddar, and S3 each switch from using an unncessary
fileRetriver to a byteRetriever. So, more efficient on chunks and encrypted
files.

The only remaining fileRetrievers are hook and external, which really do
retrieve to files.

Remote/Bup.hs

@@ -8,6 +8,7 @@
 module Remote.Bup (remote) where
 
 import qualified Data.Map as M
+import qualified Data.ByteString.Lazy as L
 import Data.ByteString.Lazy.UTF8 (fromString)
 
 import Common.Annex
@@ -127,12 +128,12 @@ store r buprepo = byteStorer $ \k b p -> do
 		return True
 
 retrieve :: BupRepo -> Retriever
-retrieve buprepo = fileRetriever $ \d k _p ->
-	liftIO $ withFile d WriteMode $ \h -> do
-		let params = bupParams "join" buprepo [Param $ bupRef k]
-		let p = proc "bup" (toCommand params)
-		(_, _, _, pid) <- createProcess $ p { std_out = UseHandle h }
-		forceSuccessProcess p pid
+retrieve buprepo = byteRetriever $ \k sink -> do
+	let params = bupParams "join" buprepo [Param $ bupRef k]
+	let p = proc "bup" (toCommand params)
+	(_, Just h, _, pid) <- liftIO $ createProcess $ p { std_out = CreatePipe }
+	liftIO (hClose h >> forceSuccessProcess p pid)
+		`after` (sink =<< liftIO (L.hGetContents h))
 
 retrieveCheap :: BupRepo -> Key -> FilePath -> Annex Bool
 retrieveCheap _ _ _ = return False

Remote/Ddar.hs

@@ -10,8 +10,8 @@ module Remote.Ddar (remote) where
 
 import Control.Exception
 import qualified Data.Map as M
+import qualified Data.ByteString.Lazy as L
 import System.IO.Error
-import System.Process
 
 import Data.String.Utils
 import Common.Annex
@@ -127,12 +127,12 @@ ddarExtractRemoteCall ddarrepo k =
 	ddarRemoteCall ddarrepo 'x' [Param "--force-stdout", Param $ key2file k]
 
 retrieve :: DdarRepo -> Retriever
-retrieve ddarrepo = fileRetriever $ \d k _p -> do
+retrieve ddarrepo = byteRetriever $ \k sink -> do
 	(cmd, params) <- ddarExtractRemoteCall ddarrepo k
-	liftIO $ withFile d WriteMode $ \h -> do
-		let p = (proc cmd $ toCommand params){ std_out = UseHandle h }
-		(_, _, _, pid) <- Common.Annex.createProcess p
-		forceSuccessProcess p pid
+	let p = (proc cmd $ toCommand params) { std_out = CreatePipe }
+	(_, Just h, _, pid) <- liftIO $ createProcess p
+	liftIO (hClose h >> forceSuccessProcess p pid)
+		`after` (sink =<< liftIO (L.hGetContents h))
 
 retrieveCheap :: Key -> FilePath -> Annex Bool
 retrieveCheap _ _ = return False

Remote/Directory.hs

@@ -136,8 +136,8 @@ store d chunkconfig k b p = liftIO $ do
 
 retrieve :: FilePath -> ChunkConfig -> Preparer Retriever
 retrieve d (LegacyChunks _) = Legacy.retrieve locations d
-retrieve d _ = simplyPrepare $ byteRetriever $ \k ->
-	liftIO $ L.readFile =<< getLocation d k
+retrieve d _ = simplyPrepare $ byteRetriever $ \k sink ->
+	sink =<< liftIO (L.readFile =<< getLocation d k)
 
 retrieveCheap :: FilePath -> ChunkConfig -> Key -> FilePath -> Annex Bool
 -- no cheap retrieval possible for chunks

Remote/Directory/LegacyChunked.hs

@@ -94,14 +94,14 @@ retrieve locations d basek a = do
 	tmpdir <- fromRepo $ gitAnnexTmpMiscDir
 	createAnnexDirectory tmpdir
 	let tmp = tmpdir </> keyFile basek ++ ".directorylegacy.tmp"
-	a $ Just $ byteRetriever $ \k -> liftIO $ do
-		void $ withStoredFiles d locations k $ \fs -> do
+	a $ Just $ byteRetriever $ \k sink -> do
+		liftIO $ void $ withStoredFiles d locations k $ \fs -> do
 			forM_ fs $
 				S.appendFile tmp <=< S.readFile
 			return True
-		b <- L.readFile tmp
-		nukeFile tmp
-		return b
+		b <- liftIO $ L.readFile tmp
+		liftIO $ nukeFile tmp
+		sink b
 
 checkPresent :: FilePath -> (FilePath -> Key -> [FilePath]) -> Key -> Annex (Either String Bool)
 checkPresent d locations k = liftIO $ catchMsgIO $

Remote/Glacier.hs

@@ -20,7 +20,6 @@ import Config.Cost
 import Remote.Helper.Special
 import Remote.Helper.ChunkedEncryptable
 import qualified Remote.Helper.AWS as AWS
-import Crypto
 import Creds
 import Utility.Metered
 import qualified Annex
@@ -120,11 +119,10 @@ store r k b p = go =<< glacierEnv c u
 				return True
 
 prepareRetrieve :: Remote -> Preparer Retriever
-prepareRetrieve r = simplyPrepare $ fileRetriever $ \d k p ->
-	retrieve r k (readBytes (meteredWriteFile p d))
+prepareRetrieve = simplyPrepare . byteRetriever . retrieve
 
-retrieve :: Remote -> Key -> (Handle -> IO ()) -> Annex ()
-retrieve r k reader = go =<< glacierEnv c u
+retrieve :: Remote -> Key -> (L.ByteString -> Annex Bool) -> Annex Bool
+retrieve r k sink = go =<< glacierEnv c u
   where
 	c = config r
 	u = uuid r
@@ -138,17 +136,21 @@ retrieve r k reader = go =<< glacierEnv c u
 	go Nothing = error "cannot retrieve from glacier"
 	go (Just e) = do
 		let cmd = (proc "glacier" (toCommand params)) { env = Just e }
-		ok <- liftIO $ catchBoolIO $
-			withHandle StdoutHandle createProcessSuccess cmd $ \h ->
-				ifM (hIsEOF h)
-					( return False
-					, do
-						reader h
-						return True
-					)
+		(_, Just h, _, pid) <- liftIO $ createProcess cmd
+		-- Glacier cannot store empty files, so if the output is
+		-- empty, the content is not available yet.
+		ok <- ifM (liftIO $ hIsEOF h)
+			( return False
+			, sink =<< liftIO (L.hGetContents h)
+			)
+		liftIO $ hClose h
+		liftIO $ forceSuccessProcess cmd pid
 		unless ok $ do
 			showLongNote "Recommend you wait up to 4 hours, and then run this command again."
-			error "not yet available"
+		return ok
+
+retrieveCheap :: Remote -> Key -> FilePath -> Annex Bool
+retrieveCheap _ _ _ = return False
 
 remove :: Remote -> Key -> Annex Bool
 remove r k = glacierAction r
@@ -159,9 +161,6 @@ remove r k = glacierAction r
 	, Param $ archive r k
 	]
 
-retrieveCheap :: Remote -> Key -> FilePath -> Annex Bool
-retrieveCheap _ _ _ = return False
-
 checkPresent :: Remote -> Key -> Annex (Either String Bool)
 checkPresent r k = do
 	showAction $ "checking " ++ name r

Remote/Helper/ChunkedEncryptable.hs

@@ -77,9 +77,11 @@ fileRetriever a k m callback = do
 	a f k m
 	callback (FileContent f)
 
--- A Retriever that generates a L.ByteString containing the Key's content.
-byteRetriever :: (Key -> Annex L.ByteString) -> Retriever
-byteRetriever a k _m callback = callback =<< (ByteContent <$> a k)
+-- A Retriever that generates a lazy ByteString containing the Key's
+-- content, and passes it to a callback action which will fully consume it
+-- before returning.
+byteRetriever :: (Key -> (L.ByteString -> Annex Bool) -> Annex Bool) -> Retriever
+byteRetriever a k _m callback = a k (callback . ByteContent)
 
 {- The base Remote that is provided to chunkedEncryptableRemote
  - needs to have storeKey and retreiveKeyFile methods, but they are

Remote/S3.hs

@@ -147,9 +147,9 @@ store (conn, bucket) r k p file = do
 
 prepareRetrieve :: Remote -> Preparer Retriever
 prepareRetrieve r = resourcePrepare (const $ s3Action r False) $ \(conn, bucket) ->
-	byteRetriever $ \k ->
+	byteRetriever $ \k sink ->
 		liftIO (getObject conn $ bucketKey r bucket k)
-			>>= either s3Error (return . obj_data)
+			>>= either s3Error (sink . obj_data)
 
 retrieveCheap :: Remote -> Key -> FilePath -> Annex Bool
 retrieveCheap _ _ _ = return False

Types/StoreRetrieve.hs

@@ -30,6 +30,6 @@ isByteContent (FileContent _) = False
 type Storer = Key -> ContentSource -> MeterUpdate -> Annex Bool
 
 -- Action that retrieves a Key's content from a remote, passing it to a
--- callback.
+-- callback, which will fully consume the content before returning.
 -- Throws exception if key is not present, or remote is not accessible.
 type Retriever = Key -> MeterUpdate -> (ContentSource -> Annex Bool) -> Annex Bool