WebDAV: Avoid buffering whole file in memory when uploading.

The httpStorer will later also be used by S3.

This commit was sponsored by Torbjørn Thorsen.

Remote/Helper/Http.hs

@@ -0,0 +1,39 @@
+{- helpers for remotes using http
+ -
+ - Copyright 2014 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Remote.Helper.Http where
+
+import Common.Annex
+import Types.StoreRetrieve
+import Utility.Metered
+import Remote.Helper.Special
+import Network.HTTP.Client (RequestBody(..))
+
+import qualified Data.ByteString.Lazy as L
+import qualified Data.ByteString as S
+import Control.Concurrent
+
+-- A storer that expects to be provided with a http RequestBody containing
+-- the content to store.
+--
+-- Implemented as a fileStorer, so that the content can be streamed
+-- from the file in constant space.
+httpStorer :: (Key -> RequestBody -> Annex Bool) -> Storer
+httpStorer a = fileStorer $ \k f m -> do
+	size <- liftIO $ (fromIntegral . fileSize <$> getFileStatus f :: IO Integer)
+	let streamer sink = withMeteredFile f m $ \b -> do
+		mvar <- newMVar $ L.toChunks b
+		let getnextchunk = modifyMVar mvar $ pure . pop
+		sink getnextchunk
+	let body = RequestBodyStream (fromInteger size) streamer
+	a k body
+  where
+	pop [] = ([], S.empty)
+	pop (c:cs) = (cs, c)
+
+--httpRetriever :: (Key -> Annex Response) -> Retriever
+--httpRetriever a = byteRetriever $ \k sink