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

import System.IO (Handle)

#if !(defined(_MSC_VER) || defined(__MINGW32__) || defined(_WIN32))
import System.Posix.IO (fdToHandle)
import qualified System.Posix.IO as Posix
#else
# include <io.h>        /* for _close and _pipe */
# include <fcntl.h>     /* for _O_BINARY */
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))
#endif

createPipe :: IO (Handle, Handle)
#if !(defined(_MSC_VER) || defined(__MINGW32__) || defined(_WIN32))
createPipe = do
    (readfd, writefd) <- Posix.createPipe
    readh <- fdToHandle readfd
    writeh <- fdToHandle writefd
    return (readh, writeh)
#else
createPipe = do
    (readfd, writefd) <- allocaArray 2 $ \ pfds -> do
        throwErrnoIfMinus1_ "_pipe" $ c__pipe pfds 2 (#const _O_BINARY)
        readfd <- peek pfds
        writefd <- peekElemOff pfds 1
        return (readfd, writefd)
    (do readh <- fdToHandle readfd ReadMode
        writeh <- fdToHandle writefd WriteMode
        return (readh, writeh)) `onException` (close readfd >> close writefd)

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
#endif