I posted this to stack overflow
<https://stackoverflow.com/questions/49246763/adapting-store-decoding-for-streaming-library>
in case anyone might be able to help answer it there. The problem that I am
trying to solve is how to adapt the following decoding API from Store
<https://www.stackage.org/haddock/lts-10.9/store-0.4.3.2/Data-Store-Streaming.html>
to `Streaming` library:
decodeMessageBS :: (MonadIO
<https://www.stackage.org/haddock/lts-10.9/foundation-0.0.17/Foundation-Monad.html#t:MonadIO>
m, Store
<https://www.stackage.org/haddock/lts-10.9/store-0.4.3.2/Data-Store-Internal.html#t:Store>
a) => ByteBuffer
<https://www.stackage.org/haddock/lts-10.9/store-0.4.3.2/System-IO-ByteBuffer.html#t:ByteBuffer>
-> m (Maybe
<https://www.stackage.org/haddock/lts-10.9/basement-0.0.4/Basement-Compat-Base.html#t:Maybe>
ByteString
<https://www.stackage.org/haddock/lts-10.9/bytestring-0.10.8.2/Data-ByteString.html#t:ByteString>
) -> m (Maybe
<https://www.stackage.org/haddock/lts-10.9/basement-0.0.4/Basement-Compat-Base.html#t:Maybe>
(Message
<https://www.stackage.org/haddock/lts-10.9/store-0.4.3.2/Data-Store-Streaming.html#t:Message>
a))
I took a shot at it with the code below but am not able to figure it out
yet - there are some undefined statements in the code below btw as
placeholders - perhaps, there also exists a simpler and efficient way to
adapt `decodeMessageBS` to `Streaming`:
{-# LANGUAGE OverloadedStrings,ScopedTypeVariables #-}import
Data.ByteString (ByteString)import System.IO.ByteBuffer
(ByteBuffer)import qualified System.IO.ByteBuffer as BBimport
Data.Store.Streamingimport Data.Store (Store)import Streaming.Prelude as
Simport Data.IORef
streamDecodeH :: forall a r. (Store a) => ByteBuffer -> Stream (Of ByteString)
IO r -> Stream (Of (Message a)) IO r
streamDecodeH bb inp = do
ref <- newIORef inp
go (popper ref)
undefined
where
go src = do
r <- (decodeMessageBS :: ByteBuffer -> IO (Maybe ByteString) -> IO (Maybe
(Message a))) bb src
case r of
Nothing -> undefined
Just msg -> (S.yield :: Message a -> Stream (Of (Message a)) IO ()) msg
>> go src
popper :: IORef (Stream (Of ByteString) IO r) -> IO (Maybe ByteString)
popper ref = do
chunks <- readIORef ref
r <- S.uncons chunks
case r of
Nothing -> return Nothing
Just (a,rest) -> writeIORef ref rest >> return (Just a)
Will appreciate help with it, either here or at StackOverflow.
--
You received this message because you are subscribed to the Google Groups
"Haskell Pipes" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
