diff -r e31281e9da96 -r 1760b7d150cf src/System/IO/Streams/Concurrent/Unagi/Bounded.hs --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/System/IO/Streams/Concurrent/Unagi/Bounded.hs Tue Dec 09 13:37:21 2014 -0600 @@ -0,0 +1,72 @@ +{-# LANGUAGE BangPatterns #-} + +module System.IO.Streams.Concurrent.Unagi.Bounded + ( -- * Channel conversions + inputToChan + , chanToInput + , chanToOutput + , makeChanPipe + , dupStream + , DupHandle + ) where + + +------------------------------------------------------------------------------ +import Control.Applicative (pure, (<$>), (<*>)) +import Control.Concurrent.Chan.Unagi.Bounded (InChan, OutChan, + dupChan, newChan, + readChan, writeChan) +import Control.Monad ((>=>)) +import Prelude hiding (read) +import System.IO.Streams.Internal (InputStream, + OutputStream, + makeInputStream, + makeOutputStream, read) + + +newtype DupHandle a = DupHandle { unDupHandle :: InChan (Maybe a) } + +------------------------------------------------------------------------------ +-- | Writes the contents of an input stream to a channel until the input stream +-- yields end-of-stream. +inputToChan :: InputStream a -> InChan (Maybe a) -> IO () +inputToChan is ch = go + where + go = do + mb <- read is + writeChan ch mb + maybe (return $! ()) (const go) mb + + +------------------------------------------------------------------------------ +-- | Turns an 'OutChan' into an input stream. +-- +chanToInput :: OutChan (Maybe a) -> IO (InputStream a) +chanToInput ch = makeInputStream $! readChan ch + + +------------------------------------------------------------------------------ +-- | Turns an 'InChan' into an output stream. +-- +chanToOutput :: InChan (Maybe a) -> IO (OutputStream a) +chanToOutput = makeOutputStream . writeChan + + +-------------------------------------------------------------------------------- +-- | Create a new pair of streams using an underlying 'Chan'. Everything written +-- to the 'OutputStream' will appear as-is on the 'InputStream'. +-- +-- Since reading from the 'InputStream' and writing to the 'OutputStream' are +-- blocking calls, be sure to do so in different threads. +makeChanPipe :: Int -> IO (InputStream a, OutputStream a, DupHandle a) +makeChanPipe size = do + (inChan, outChan) <- newChan size + (,,) <$> chanToInput outChan <*> chanToOutput inChan <*> pure (DupHandle inChan) + + +------------------------------------------------------------------------------ +-- | Use a 'DupHandle' to replicate everything written on the +-- associated 'OutputStream' to the 'InputStream'. +-- +dupStream :: DupHandle a -> IO (InputStream a) +dupStream = dupChan . unDupHandle >=> chanToInput