fix correct finalizing of last block

Database/MongoDB/GridFS.hs

@@ -24,11 +24,11 @@ module Database.MongoDB.GridFS
   where
 
 import Control.Applicative((<$>))
-import Control.Concurrent(forkIO)
+
 import Control.Monad(when)
 import Control.Monad.IO.Class
 import Control.Monad.Trans(MonadTrans, lift)
-import Control.Monad.Trans.Resource(MonadResource(..))
+
 import Data.Conduit
 import Data.Digest.Pure.MD5
 import Data.Int
@@ -40,13 +40,17 @@ import Prelude
 import qualified Data.Bson as B
 import qualified Data.ByteString as S
 import qualified Data.ByteString.Lazy as L
-import qualified Data.Conduit.Binary as BI
-import qualified Data.Conduit.List as CL
+
 
 defaultChunkSize :: Int64
 -- ^ The default chunk size is 256 kB
 defaultChunkSize = 256 * 1024
 
+-- magic constant for the
+md5BlockSizeInBytes :: Int
+md5BlockSizeInBytes = 64
+
+
 data Bucket = Bucket {files :: Text, chunks :: Text}
 -- ^ Files are stored in "buckets". You open a bucket with openDefaultBucket or openBucket
 
@@ -130,7 +134,7 @@ data FileWriter = FileWriter
 -- Finalize file, calculating md5 digest, saving the last chunk, and creating the file in the bucket
 finalizeFile :: (Monad m, MonadIO m) => Text -> FileWriter -> Action m File
 finalizeFile filename (FileWriter chunkSize bucket files_id i size acc md5context md5acc) = do
-  let md5digest = md5Finalize md5context (L.toStrict md5acc)
+  let md5digest = finalizeMD5 md5context (L.toStrict md5acc)
   when (L.length acc > 0) $ putChunk bucket files_id i acc
   timestamp <- liftIO $ getCurrentTime
   let doc = [ "_id" =: files_id
@@ -140,12 +144,24 @@ finalizeFile filename (FileWriter chunkSize bucket files_id i size acc md5contex
             , "chunkSize" =: chunkSize
             , "filename" =: filename
             ]
+  _ <- liftIO $ putStrLn $ "md5 : " ++ (show md5digest)
   insert_ (files bucket) doc
   return $ File bucket doc
 
+-- finalize the remainder and return the MD5Digest.
+finalizeMD5 :: MD5Context -> S.ByteString -> MD5Digest
+finalizeMD5 ctx rest =
+  md5Finalize ctx2 (S.drop lu rest) -- can only handle max md5BlockSizeInBytes length
+  where
+    l = S.length rest
+    r = l `mod` md5BlockSizeInBytes
+    lu = l - r
+    ctx2 = md5Update ctx (S.take lu rest)
+
 -- Write as many chunks as can be written from the file writer
 writeChunks :: (Monad m, MonadIO m) => FileWriter -> L.ByteString -> Action m FileWriter
-writeChunks (FileWriter chunkSize bucket files_id i size acc md5context md5acc) chunk = do
+writeChunks (FileWriter chunkSize bucket files_id i size acc md5context md5acc) chunk =
+  do
     -- Update md5 context
     let md5BlockLength = fromIntegral $ untag (blockLength :: Tagged MD5Digest Int)
     let md5acc_temp = (md5acc `L.append` chunk)