I had defined another instance of Transport, namely writing to a file. It
is no longer much important since you can generate a message stream and
output it either via OpenSoundControl or write it to a bytestring.
Nevertheless the File transport allows to write to a file whereever code
is written for immediate communication with the SuperCollider server. It
just replies to every 'recv' with a "/done" message. If we need more
specific answers, we could collect the incoming messages in an IORef and
ship according answers in the same order. It is however unfortunate that
everything runs in IO monad since instead of writing to disk it would be
better to write to bytestring and stay away from IO.
We could also emit an error if an asynchronous message without 'Bundle'
shall be written to disk. Even better would be to encourage time stamps
for asynchronous messages and enforce waiting for synchronous messages by
type system. I'm still thinking about how this could be done.
module Sound.OpenSoundControl.Transport.File (File, open) where
import Sound.OpenSoundControl.Transport (Transport(..))
import Sound.OpenSoundControl.Byte (encode_u32)
import Sound.OpenSoundControl.OSC (encodeOSC, OSC(Message))
import Control.Monad (liftM)
import qualified Data.ByteString.Lazy as B
import System.IO (Handle, openBinaryFile, hClose, IOMode(WriteMode))
-- | The File transport handle data type.
data File = File Handle
deriving (Eq, Show)
instance Transport File where
send (File fd) msg =
let b = encodeOSC msg
n = fromIntegral (B.length b)
-- B.reverse - What byte order is generally needed?
-- B.hPut fd (B.append (B.reverse (encode_u32 n)) b)
in B.hPut fd (B.append (encode_u32 n) b)
recv _ = return (Message "/done" [])
close (File fd) = hClose fd
-- | Open a command file
open :: FilePath -> IO File
open fileName =
liftM File $ openBinaryFile fileName WriteMode
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