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{-# LANGUAGE CPP, ForeignFunctionInterface #-}
-- | File functions using System.Event instead of GHC's I/O manager.
module EventFile
(
read
) where
import Data.ByteString (ByteString)
import Data.ByteString.Internal (createAndTrim)
import Data.Word (Word8)
import qualified Data.ByteString as B
import Foreign.Ptr (Ptr, castPtr)
import Foreign.C.Error (eINTR, getErrno, throwErrno)
#if __GLASGOW_HASKELL__ < 612
import GHC.IOBase (IOErrorType(..))
#else
import GHC.IO.Exception (IOErrorType(..))
#endif
#if defined(USE_GHC_IO_MANAGER)
import GHC.Conc (threadWaitRead)
#else
import System.Event.Thread (threadWaitRead)
#endif
import System.IO.Error (ioeSetErrorString, mkIOError)
import System.Posix.Internals (c_read)
import System.Posix.Types (Fd)
import Prelude hiding (read)
import EventUtil
read :: Fd -> Int -> IO ByteString
read fd nbytes
| nbytes <= 0 = ioError (mkInvalidReadArgError "read")
| otherwise = createAndTrim nbytes $ readInner fd nbytes
readInner :: Fd -> Int -> Ptr Word8 -> IO Int
readInner fd nbytes ptr = do
len <- throwErrnoIfMinus1Retry_repeatOnBlock "read"
(threadWaitRead (fromIntegral fd)) $
c_read (fromIntegral fd) (castPtr ptr) (fromIntegral nbytes)
case fromIntegral len of
(-1) -> do errno <- getErrno
if errno == eINTR
then readInner fd nbytes ptr
else throwErrno "read"
n -> return n
mkInvalidReadArgError :: String -> IOError
mkInvalidReadArgError loc = ioeSetErrorString (mkIOError
InvalidArgument
loc Nothing Nothing)
"non-positive length"
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