    {-# LANGUAGE CPP, ForeignFunctionInterface #-}
    module Distribution.Compat.CreatePipe (createPipe) where

    import System.IO (Handle, hSetEncoding, localeEncoding)

    -- The mingw32_HOST_OS CPP macro is GHC-specific
    #if mingw32_HOST_OS
    import Control.Exception (onException)
    import Foreign.C.Error (throwErrnoIfMinus1_)
    import Foreign.C.Types (CInt(..), CUInt(..))
    import Foreign.Ptr (Ptr)
    import Foreign.Marshal.Array (allocaArray)
    import Foreign.Storable (peek, peekElemOff)
    import GHC.IO.FD (mkFD)
    import GHC.IO.Device (IODeviceType(Stream))
    import GHC.IO.Handle.FD (mkHandleFromFD)
    import System.IO (IOMode(ReadMode, WriteMode))
    #elif ghcjs_HOST_OS
    #else
    import System.Posix.IO (fdToHandle)
    import qualified System.Posix.IO as Posix
    #endif

    createPipe :: IO (Handle, Handle)
    -- The mingw32_HOST_OS CPP macro is GHC-specific
    #if mingw32_HOST_OS
    createPipe = do
        (readfd, writefd) <- allocaArray 2 $ \ pfds -> do
            throwErrnoIfMinus1_ "_pipe" $ c__pipe pfds 2 ({- _O_BINARY -} 32768)
            readfd <- peek pfds
            writefd <- peekElemOff pfds 1
            return (readfd, writefd)
        (do readh <- fdToHandle readfd ReadMode
            writeh <- fdToHandle writefd WriteMode
            hSetEncoding readh localeEncoding
            hSetEncoding writeh localeEncoding
            return (readh, writeh)) `onException` (close readfd >> close writefd)
      where
        fdToHandle :: CInt -> IOMode -> IO Handle
        fdToHandle fd mode = do
            (fd', deviceType) <- mkFD fd mode (Just (Stream, 0, 0)) False False
            mkHandleFromFD fd' deviceType "" mode False Nothing

        close :: CInt -> IO ()
        close = throwErrnoIfMinus1_ "_close" . c__close

    foreign import ccall "io.h _pipe" c__pipe ::
        Ptr CInt -> CUInt -> CInt -> IO CInt

    foreign import ccall "io.h _close" c__close ::
        CInt -> IO CInt
    #elif ghcjs_HOST_OS
    createPipe = error "createPipe"
    #else
    createPipe = do
        (readfd, writefd) <- Posix.createPipe
        readh <- fdToHandle readfd
        writeh <- fdToHandle writefd
        hSetEncoding readh localeEncoding
        hSetEncoding writeh localeEncoding
        return (readh, writeh)
    #endif