content: {-# LINE 1 "libraries/base/GHC/Event/Poll.hsc" #-}
  {-# LANGUAGE Trustworthy #-}
  {-# LANGUAGE GeneralizedNewtypeDeriving
             , NoImplicitPrelude
             , BangPatterns
    #-}
  
  module GHC.Event.Poll
      (
        new
      , available
      ) where
  
  
  
  
  {-# LINE 26 "libraries/base/GHC/Event/Poll.hsc" #-}
  
  
  import Control.Concurrent.MVar (MVar, newMVar, swapMVar)
  import Data.Bits (Bits, FiniteBits, (.|.), (.&.))
  import Data.Word
  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(..))
  
  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 -> (Word64) -> Int -> IO CInt
  {-# LINE 114 "libraries/base/GHC/Event/Poll.hsc" #-}
      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)
  
  newtype Event = Event CShort
      deriving (Eq, Show, Num, Storable, Bits, FiniteBits)
  
  -- We have to duplicate the whole enum like this in order for the
  -- hsc2hs cross-compilation mode to work
  
  {-# LINE 170 "libraries/base/GHC/Event/Poll.hsc" #-}
  pollIn     :: Event
  pollIn     = Event 1
  pollOut    :: Event
  pollOut    = Event 4
  pollErr    :: Event
  pollErr    = Event 8
  pollHup    :: Event
  pollHup    = Event 16
  
  {-# LINE 176 "libraries/base/GHC/Event/Poll.hsc" #-}
  
  {-# LINE 177 "libraries/base/GHC/Event/Poll.hsc" #-}
  
  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 _    = (8)
  {-# LINE 195 "libraries/base/GHC/Event/Poll.hsc" #-}
      alignment _ = alignment (undefined :: CInt)
  
      peek ptr = do
        fd <- (\hsc_ptr -> peekByteOff hsc_ptr 0) ptr
  {-# LINE 199 "libraries/base/GHC/Event/Poll.hsc" #-}
        events <- (\hsc_ptr -> peekByteOff hsc_ptr 4) ptr
  {-# LINE 200 "libraries/base/GHC/Event/Poll.hsc" #-}
        revents <- (\hsc_ptr -> peekByteOff hsc_ptr 6) ptr
  {-# LINE 201 "libraries/base/GHC/Event/Poll.hsc" #-}
        let !pollFd' = PollFd fd events revents
        return pollFd'
  
      poke ptr p = do
        (\hsc_ptr -> pokeByteOff hsc_ptr 0) ptr (pfdFd p)
  {-# LINE 206 "libraries/base/GHC/Event/Poll.hsc" #-}
        (\hsc_ptr -> pokeByteOff hsc_ptr 4) ptr (pfdEvents p)
  {-# LINE 207 "libraries/base/GHC/Event/Poll.hsc" #-}
        (\hsc_ptr -> pokeByteOff hsc_ptr 6) ptr (pfdRevents p)
  {-# LINE 208 "libraries/base/GHC/Event/Poll.hsc" #-}
  
  foreign import ccall safe "poll.h poll"
      c_poll :: Ptr PollFd -> (Word64) -> CInt -> IO CInt
  {-# LINE 211 "libraries/base/GHC/Event/Poll.hsc" #-}
  
  foreign import ccall unsafe "poll.h poll"
      c_poll_unsafe :: Ptr PollFd -> (Word64) -> CInt -> IO CInt
  {-# LINE 214 "libraries/base/GHC/Event/Poll.hsc" #-}
  
  {-# LINE 215 "libraries/base/GHC/Event/Poll.hsc" #-}
  