{-# LANGUAGE Trustworthy #-} {-# LANGUAGE GeneralizedNewtypeDeriving , NoImplicitPrelude , BangPatterns #-} module GHC.Event.Poll ( new , available ) where #include "EventConfig.h" #if !defined(HAVE_POLL_H) import GHC.Base import qualified GHC.Event.Internal as E new :: IO E.Backend new = errorWithoutStackTrace "Poll back end not implemented for this platform" available :: Bool available = False {-# INLINE available #-} #else #include import Control.Concurrent.MVar (MVar, newMVar, swapMVar) import Data.Bits (Bits, FiniteBits, (.|.), (.&.)) import Foreign.C.Types (CInt(..), CShort(..)) import Foreign.Ptr (Ptr) import Foreign.Storable (Storable(..)) import GHC.Base import GHC.Conc.Sync (withMVar) import GHC.Enum (maxBound) import GHC.Num (Num(..)) import GHC.Real (fromIntegral, div) import GHC.Show (Show) import System.Posix.Types (Fd(..), CNfds(..)) import qualified GHC.Event.Array as A import qualified GHC.Event.Internal as E available :: Bool available = True {-# INLINE available #-} data Poll = Poll { pollChanges :: {-# UNPACK #-} !(MVar (A.Array PollFd)) , pollFd :: {-# UNPACK #-} !(A.Array PollFd) } new :: IO E.Backend new = E.backend poll modifyFd modifyFdOnce (\_ -> return ()) `liftM` liftM2 Poll (newMVar =<< A.empty) A.empty modifyFd :: Poll -> Fd -> E.Event -> E.Event -> IO Bool modifyFd p fd oevt nevt = withMVar (pollChanges p) $ \ary -> do A.snoc ary $ PollFd fd (fromEvent nevt) (fromEvent oevt) return True modifyFdOnce :: Poll -> Fd -> E.Event -> IO Bool modifyFdOnce = errorWithoutStackTrace "modifyFdOnce not supported in Poll backend" reworkFd :: Poll -> PollFd -> IO () reworkFd p (PollFd fd npevt opevt) = do let ary = pollFd p if opevt == 0 then A.snoc ary $ PollFd fd npevt 0 else do found <- A.findIndex ((== fd) . pfdFd) ary case found of Nothing -> errorWithoutStackTrace "reworkFd: event not found" Just (i,_) | npevt /= 0 -> A.unsafeWrite ary i $ PollFd fd npevt 0 | otherwise -> A.removeAt ary i poll :: Poll -> Maybe E.Timeout -> (Fd -> E.Event -> IO ()) -> IO Int poll p mtout f = do let a = pollFd p mods <- swapMVar (pollChanges p) =<< A.empty A.forM_ mods (reworkFd p) n <- A.useAsPtr a $ \ptr len -> E.throwErrnoIfMinus1NoRetry "c_poll" $ case mtout of Just tout -> c_pollLoop ptr (fromIntegral len) (fromTimeout tout) Nothing -> c_poll_unsafe ptr (fromIntegral len) 0 when (n /= 0) $ do A.loop a 0 $ \i e -> do let r = pfdRevents e if r /= 0 then do f (pfdFd e) (toEvent r) let i' = i + 1 return (i', i' == n) else return (i, True) return (fromIntegral n) where -- The poll timeout is specified as an Int, but c_poll takes a CInt. These -- can't be safely coerced as on many systems (e.g. x86_64) CInt has a -- maxBound of (2^32 - 1), even though Int may have a significantly higher -- bound. -- -- This function deals with timeouts greater than maxBound :: CInt, by -- looping until c_poll returns a non-zero value (0 indicates timeout -- expired) OR the full timeout has passed. c_pollLoop :: Ptr PollFd -> CNfds -> Int -> IO CInt c_pollLoop ptr len tout | isShortTimeout = c_poll ptr len (fromIntegral tout) | otherwise = do result <- c_poll ptr len (fromIntegral maxPollTimeout) if result == 0 then c_pollLoop ptr len (fromIntegral (tout - maxPollTimeout)) else return result where -- maxPollTimeout is smaller than 0 IFF Int is smaller than CInt. -- This means any possible Int input to poll can be safely directly -- converted to CInt. isShortTimeout = tout <= maxPollTimeout || maxPollTimeout < 0 -- We need to account for 3 cases: -- 1. Int and CInt are of equal size. -- 2. Int is larger than CInt -- 3. Int is smaller than CInt -- -- In case 1, the value of maxPollTimeout will be the maxBound of Int. -- -- In case 2, the value of maxPollTimeout will be the maxBound of CInt, -- which is the largest value accepted by c_poll. This will result in -- c_pollLoop recursing if the provided timeout is larger. -- -- In case 3, "fromIntegral (maxBound :: CInt) :: Int" will result in a -- negative Int. This will cause isShortTimeout to be true and result in -- the timeout being directly converted to a CInt. maxPollTimeout :: Int maxPollTimeout = fromIntegral (maxBound :: CInt) fromTimeout :: E.Timeout -> Int fromTimeout E.Forever = -1 fromTimeout (E.Timeout s) = fromIntegral $ s `divRoundUp` 1000000 where divRoundUp num denom = (num + denom - 1) `div` denom data PollFd = PollFd { pfdFd :: {-# UNPACK #-} !Fd , pfdEvents :: {-# UNPACK #-} !Event , pfdRevents :: {-# UNPACK #-} !Event } deriving Show -- ^ @since 4.4.0.0 newtype Event = Event CShort deriving ( Eq -- ^ @since 4.4.0.0 , Show -- ^ @since 4.4.0.0 , Num -- ^ @since 4.4.0.0 , Storable -- ^ @since 4.4.0.0 , Bits -- ^ @since 4.4.0.0 , FiniteBits -- ^ @since 4.7.0.0 ) #{enum Event, Event , pollIn = POLLIN , pollOut = POLLOUT , pollErr = POLLERR , pollHup = POLLHUP } fromEvent :: E.Event -> Event fromEvent e = remap E.evtRead pollIn .|. remap E.evtWrite pollOut where remap evt to | e `E.eventIs` evt = to | otherwise = 0 toEvent :: Event -> E.Event toEvent e = remap (pollIn .|. pollErr .|. pollHup) E.evtRead `mappend` remap (pollOut .|. pollErr .|. pollHup) E.evtWrite where remap evt to | e .&. evt /= 0 = to | otherwise = mempty -- | @since 4.3.1.0 instance Storable PollFd where sizeOf _ = #size struct pollfd alignment _ = alignment (undefined :: CInt) peek ptr = do fd <- #{peek struct pollfd, fd} ptr events <- #{peek struct pollfd, events} ptr revents <- #{peek struct pollfd, revents} ptr let !pollFd' = PollFd fd events revents return pollFd' poke ptr p = do #{poke struct pollfd, fd} ptr (pfdFd p) #{poke struct pollfd, events} ptr (pfdEvents p) #{poke struct pollfd, revents} ptr (pfdRevents p) foreign import ccall safe "poll.h poll" c_poll :: Ptr PollFd -> CNfds -> CInt -> IO CInt foreign import ccall unsafe "poll.h poll" c_poll_unsafe :: Ptr PollFd -> CNfds -> CInt -> IO CInt #endif /* defined(HAVE_POLL_H) */