2 {-# OPTIONS_GHC -fno-implicit-prelude #-}
3 -----------------------------------------------------------------------------
6 -- Copyright : (c) The University of Glasgow, 1994-2002
7 -- License : see libraries/base/LICENSE
9 -- Maintainer : cvs-ghc@haskell.org
10 -- Stability : internal
11 -- Portability : non-portable (GHC extensions)
13 -- Basic concurrency stuff.
15 -----------------------------------------------------------------------------
17 -- No: #hide, because bits of this module are exposed by the stm package.
18 -- However, we don't want this module to be the home location for the
19 -- bits it exports, we'd rather have Control.Concurrent and the other
20 -- higher level modules be the home. Hence:
26 -- Forking and suchlike
27 , myThreadId -- :: IO ThreadId
28 , killThread -- :: ThreadId -> IO ()
29 , throwTo -- :: ThreadId -> Exception -> IO ()
30 , par -- :: a -> b -> b
31 , pseq -- :: a -> b -> b
33 , labelThread -- :: ThreadId -> String -> IO ()
36 , threadDelay -- :: Int -> IO ()
37 , threadWaitRead -- :: Int -> IO ()
38 , threadWaitWrite -- :: Int -> IO ()
42 , newMVar -- :: a -> IO (MVar a)
43 , newEmptyMVar -- :: IO (MVar a)
44 , takeMVar -- :: MVar a -> IO a
45 , putMVar -- :: MVar a -> a -> IO ()
46 , tryTakeMVar -- :: MVar a -> IO (Maybe a)
47 , tryPutMVar -- :: MVar a -> a -> IO Bool
48 , isEmptyMVar -- :: MVar a -> IO Bool
49 , addMVarFinalizer -- :: MVar a -> IO () -> IO ()
53 , atomically -- :: STM a -> IO a
55 , orElse -- :: STM a -> STM a -> STM a
56 , catchSTM -- :: STM a -> (Exception -> STM a) -> STM a
58 , newTVar -- :: a -> STM (TVar a)
59 , readTVar -- :: TVar a -> STM a
60 , writeTVar -- :: a -> TVar a -> STM ()
61 , unsafeIOToSTM -- :: IO a -> STM a
63 #ifdef mingw32_HOST_OS
64 , asyncRead -- :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
65 , asyncWrite -- :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
66 , asyncDoProc -- :: FunPtr (Ptr a -> IO Int) -> Ptr a -> IO Int
68 , asyncReadBA -- :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int, Int)
69 , asyncWriteBA -- :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int, Int)
73 import System.Posix.Types
74 import System.Posix.Internals
82 import GHC.Num ( Num(..) )
83 import GHC.Real ( fromIntegral, quot )
84 import GHC.Base ( Int(..) )
85 import GHC.Exception ( Exception(..), AsyncException(..) )
86 import GHC.Pack ( packCString# )
87 import GHC.Ptr ( Ptr(..), plusPtr, FunPtr(..) )
91 infixr 0 `par`, `pseq`
94 %************************************************************************
96 \subsection{@ThreadId@, @par@, and @fork@}
98 %************************************************************************
101 data ThreadId = ThreadId ThreadId# deriving( Typeable )
102 -- ToDo: data ThreadId = ThreadId (Weak ThreadId#)
103 -- But since ThreadId# is unlifted, the Weak type must use open
106 A 'ThreadId' is an abstract type representing a handle to a thread.
107 'ThreadId' is an instance of 'Eq', 'Ord' and 'Show', where
108 the 'Ord' instance implements an arbitrary total ordering over
109 'ThreadId's. The 'Show' instance lets you convert an arbitrary-valued
110 'ThreadId' to string form; showing a 'ThreadId' value is occasionally
111 useful when debugging or diagnosing the behaviour of a concurrent
114 /Note/: in GHC, if you have a 'ThreadId', you essentially have
115 a pointer to the thread itself. This means the thread itself can\'t be
116 garbage collected until you drop the 'ThreadId'.
117 This misfeature will hopefully be corrected at a later date.
119 /Note/: Hugs does not provide any operations on other threads;
120 it defines 'ThreadId' as a synonym for ().
123 --forkIO has now been hoisted out into the Concurrent library.
125 {- | 'killThread' terminates the given thread (GHC only).
126 Any work already done by the thread isn\'t
127 lost: the computation is suspended until required by another thread.
128 The memory used by the thread will be garbage collected if it isn\'t
129 referenced from anywhere. The 'killThread' function is defined in
132 > killThread tid = throwTo tid (AsyncException ThreadKilled)
135 killThread :: ThreadId -> IO ()
136 killThread tid = throwTo tid (AsyncException ThreadKilled)
138 {- | 'throwTo' raises an arbitrary exception in the target thread (GHC only).
140 'throwTo' does not return until the exception has been raised in the
141 target thread. The calling thread can thus be certain that the target
142 thread has received the exception. This is a useful property to know
143 when dealing with race conditions: eg. if there are two threads that
144 can kill each other, it is guaranteed that only one of the threads
145 will get to kill the other. -}
146 throwTo :: ThreadId -> Exception -> IO ()
147 throwTo (ThreadId id) ex = IO $ \ s ->
148 case (killThread# id ex s) of s1 -> (# s1, () #)
150 -- | Returns the 'ThreadId' of the calling thread (GHC only).
151 myThreadId :: IO ThreadId
152 myThreadId = IO $ \s ->
153 case (myThreadId# s) of (# s1, id #) -> (# s1, ThreadId id #)
156 -- |The 'yield' action allows (forces, in a co-operative multitasking
157 -- implementation) a context-switch to any other currently runnable
158 -- threads (if any), and is occasionally useful when implementing
159 -- concurrency abstractions.
162 case (yield# s) of s1 -> (# s1, () #)
164 {- | 'labelThread' stores a string as identifier for this thread if
165 you built a RTS with debugging support. This identifier will be used in
166 the debugging output to make distinction of different threads easier
167 (otherwise you only have the thread state object\'s address in the heap).
169 Other applications like the graphical Concurrent Haskell Debugger
170 (<http://www.informatik.uni-kiel.de/~fhu/chd/>) may choose to overload
171 'labelThread' for their purposes as well.
174 labelThread :: ThreadId -> String -> IO ()
175 labelThread (ThreadId t) str = IO $ \ s ->
176 let ps = packCString# str
177 adr = byteArrayContents# ps in
178 case (labelThread# t adr s) of s1 -> (# s1, () #)
180 -- Nota Bene: 'pseq' used to be 'seq'
181 -- but 'seq' is now defined in PrelGHC
183 -- "pseq" is defined a bit weirdly (see below)
185 -- The reason for the strange "lazy" call is that
186 -- it fools the compiler into thinking that pseq and par are non-strict in
187 -- their second argument (even if it inlines pseq at the call site).
188 -- If it thinks pseq is strict in "y", then it often evaluates
189 -- "y" before "x", which is totally wrong.
193 pseq x y = x `seq` lazy y
197 par x y = case (par# x) of { _ -> lazy y }
201 %************************************************************************
203 \subsection[stm]{Transactional heap operations}
205 %************************************************************************
207 TVars are shared memory locations which support atomic memory
211 newtype STM a = STM (State# RealWorld -> (# State# RealWorld, a #)) deriving( Typeable )
213 unSTM :: STM a -> (State# RealWorld -> (# State# RealWorld, a #))
216 instance Functor STM where
217 fmap f x = x >>= (return . f)
219 instance Monad STM where
220 {-# INLINE return #-}
224 return x = returnSTM x
225 m >>= k = bindSTM m k
227 bindSTM :: STM a -> (a -> STM b) -> STM b
228 bindSTM (STM m) k = STM ( \s ->
230 (# new_s, a #) -> unSTM (k a) new_s
233 thenSTM :: STM a -> STM b -> STM b
234 thenSTM (STM m) k = STM ( \s ->
236 (# new_s, a #) -> unSTM k new_s
239 returnSTM :: a -> STM a
240 returnSTM x = STM (\s -> (# s, x #))
242 -- | Unsafely performs IO in the STM monad.
243 unsafeIOToSTM :: IO a -> STM a
244 unsafeIOToSTM (IO m) = STM m
246 -- |Perform a series of STM actions atomically.
247 atomically :: STM a -> IO a
248 atomically (STM m) = IO (\s -> (atomically# m) s )
250 -- |Retry execution of the current memory transaction because it has seen
251 -- values in TVars which mean that it should not continue (e.g. the TVars
252 -- represent a shared buffer that is now empty). The implementation may
253 -- block the thread until one of the TVars that it has read from has been
256 retry = STM $ \s# -> retry# s#
258 -- |Compose two alternative STM actions. If the first action completes without
259 -- retrying then it forms the result of the orElse. Otherwise, if the first
260 -- action retries, then the second action is tried in its place. If both actions
261 -- retry then the orElse as a whole retries.
262 orElse :: STM a -> STM a -> STM a
263 orElse (STM m) e = STM $ \s -> catchRetry# m (unSTM e) s
265 -- |Exception handling within STM actions.
266 catchSTM :: STM a -> (Exception -> STM a) -> STM a
267 catchSTM (STM m) k = STM $ \s -> catchSTM# m (\ex -> unSTM (k ex)) s
269 data TVar a = TVar (TVar# RealWorld a) deriving( Typeable )
271 instance Eq (TVar a) where
272 (TVar tvar1#) == (TVar tvar2#) = sameTVar# tvar1# tvar2#
274 -- |Create a new TVar holding a value supplied
275 newTVar :: a -> STM (TVar a)
276 newTVar val = STM $ \s1# ->
277 case newTVar# val s1# of
278 (# s2#, tvar# #) -> (# s2#, TVar tvar# #)
280 -- |Return the current value stored in a TVar
281 readTVar :: TVar a -> STM a
282 readTVar (TVar tvar#) = STM $ \s# -> readTVar# tvar# s#
284 -- |Write the supplied value into a TVar
285 writeTVar :: TVar a -> a -> STM ()
286 writeTVar (TVar tvar#) val = STM $ \s1# ->
287 case writeTVar# tvar# val s1# of
292 %************************************************************************
294 \subsection[mvars]{M-Structures}
296 %************************************************************************
298 M-Vars are rendezvous points for concurrent threads. They begin
299 empty, and any attempt to read an empty M-Var blocks. When an M-Var
300 is written, a single blocked thread may be freed. Reading an M-Var
301 toggles its state from full back to empty. Therefore, any value
302 written to an M-Var may only be read once. Multiple reads and writes
303 are allowed, but there must be at least one read between any two
307 --Defined in IOBase to avoid cycle: data MVar a = MVar (SynchVar# RealWorld a)
309 -- |Create an 'MVar' which is initially empty.
310 newEmptyMVar :: IO (MVar a)
311 newEmptyMVar = IO $ \ s# ->
313 (# s2#, svar# #) -> (# s2#, MVar svar# #)
315 -- |Create an 'MVar' which contains the supplied value.
316 newMVar :: a -> IO (MVar a)
318 newEmptyMVar >>= \ mvar ->
319 putMVar mvar value >>
322 -- |Return the contents of the 'MVar'. If the 'MVar' is currently
323 -- empty, 'takeMVar' will wait until it is full. After a 'takeMVar',
324 -- the 'MVar' is left empty.
326 -- If several threads are competing to take the same 'MVar', one is chosen
327 -- to continue at random when the 'MVar' becomes full.
328 takeMVar :: MVar a -> IO a
329 takeMVar (MVar mvar#) = IO $ \ s# -> takeMVar# mvar# s#
331 -- |Put a value into an 'MVar'. If the 'MVar' is currently full,
332 -- 'putMVar' will wait until it becomes empty.
334 -- If several threads are competing to fill the same 'MVar', one is
335 -- chosen to continue at random when the 'MVar' becomes empty.
336 putMVar :: MVar a -> a -> IO ()
337 putMVar (MVar mvar#) x = IO $ \ s# ->
338 case putMVar# mvar# x s# of
341 -- |A non-blocking version of 'takeMVar'. The 'tryTakeMVar' function
342 -- returns immediately, with 'Nothing' if the 'MVar' was empty, or
343 -- @'Just' a@ if the 'MVar' was full with contents @a@. After 'tryTakeMVar',
344 -- the 'MVar' is left empty.
345 tryTakeMVar :: MVar a -> IO (Maybe a)
346 tryTakeMVar (MVar m) = IO $ \ s ->
347 case tryTakeMVar# m s of
348 (# s, 0#, _ #) -> (# s, Nothing #) -- MVar is empty
349 (# s, _, a #) -> (# s, Just a #) -- MVar is full
351 -- |A non-blocking version of 'putMVar'. The 'tryPutMVar' function
352 -- attempts to put the value @a@ into the 'MVar', returning 'True' if
353 -- it was successful, or 'False' otherwise.
354 tryPutMVar :: MVar a -> a -> IO Bool
355 tryPutMVar (MVar mvar#) x = IO $ \ s# ->
356 case tryPutMVar# mvar# x s# of
357 (# s, 0# #) -> (# s, False #)
358 (# s, _ #) -> (# s, True #)
360 -- |Check whether a given 'MVar' is empty.
362 -- Notice that the boolean value returned is just a snapshot of
363 -- the state of the MVar. By the time you get to react on its result,
364 -- the MVar may have been filled (or emptied) - so be extremely
365 -- careful when using this operation. Use 'tryTakeMVar' instead if possible.
366 isEmptyMVar :: MVar a -> IO Bool
367 isEmptyMVar (MVar mv#) = IO $ \ s# ->
368 case isEmptyMVar# mv# s# of
369 (# s2#, flg #) -> (# s2#, not (flg ==# 0#) #)
371 -- |Add a finalizer to an 'MVar' (GHC only). See "Foreign.ForeignPtr" and
372 -- "System.Mem.Weak" for more about finalizers.
373 addMVarFinalizer :: MVar a -> IO () -> IO ()
374 addMVarFinalizer (MVar m) finalizer =
375 IO $ \s -> case mkWeak# m () finalizer s of { (# s1, w #) -> (# s1, () #) }
379 %************************************************************************
381 \subsection{Thread waiting}
383 %************************************************************************
386 #ifdef mingw32_HOST_OS
388 -- Note: threadDelay, threadWaitRead and threadWaitWrite aren't really functional
389 -- on Win32, but left in there because lib code (still) uses them (the manner
390 -- in which they're used doesn't cause problems on a Win32 platform though.)
392 asyncRead :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
393 asyncRead (I# fd) (I# isSock) (I# len) (Ptr buf) =
394 IO $ \s -> case asyncRead# fd isSock len buf s of
395 (# s, len#, err# #) -> (# s, (I# len#, I# err#) #)
397 asyncWrite :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
398 asyncWrite (I# fd) (I# isSock) (I# len) (Ptr buf) =
399 IO $ \s -> case asyncWrite# fd isSock len buf s of
400 (# s, len#, err# #) -> (# s, (I# len#, I# err#) #)
402 asyncDoProc :: FunPtr (Ptr a -> IO Int) -> Ptr a -> IO Int
403 asyncDoProc (FunPtr proc) (Ptr param) =
404 -- the 'length' value is ignored; simplifies implementation of
405 -- the async*# primops to have them all return the same result.
406 IO $ \s -> case asyncDoProc# proc param s of
407 (# s, len#, err# #) -> (# s, I# err# #)
409 -- to aid the use of these primops by the IO Handle implementation,
410 -- provide the following convenience funs:
412 -- this better be a pinned byte array!
413 asyncReadBA :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int,Int)
414 asyncReadBA fd isSock len off bufB =
415 asyncRead fd isSock len ((Ptr (byteArrayContents# (unsafeCoerce# bufB))) `plusPtr` off)
417 asyncWriteBA :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int,Int)
418 asyncWriteBA fd isSock len off bufB =
419 asyncWrite fd isSock len ((Ptr (byteArrayContents# (unsafeCoerce# bufB))) `plusPtr` off)
423 -- -----------------------------------------------------------------------------
426 -- | Block the current thread until data is available to read on the
427 -- given file descriptor (GHC only).
428 threadWaitRead :: Fd -> IO ()
430 #ifndef mingw32_HOST_OS
431 | threaded = waitForReadEvent fd
433 | otherwise = IO $ \s ->
434 case fromIntegral fd of { I# fd# ->
435 case waitRead# fd# s of { s -> (# s, () #)
438 -- | Block the current thread until data can be written to the
439 -- given file descriptor (GHC only).
440 threadWaitWrite :: Fd -> IO ()
442 #ifndef mingw32_HOST_OS
443 | threaded = waitForWriteEvent fd
445 | otherwise = IO $ \s ->
446 case fromIntegral fd of { I# fd# ->
447 case waitWrite# fd# s of { s -> (# s, () #)
450 -- | Suspends the current thread for a given number of microseconds
453 -- Note that the resolution used by the Haskell runtime system's
454 -- internal timer is 1\/50 second, and 'threadDelay' will round its
455 -- argument up to the nearest multiple of this resolution.
457 -- There is no guarantee that the thread will be rescheduled promptly
458 -- when the delay has expired, but the thread will never continue to
459 -- run /earlier/ than specified.
461 threadDelay :: Int -> IO ()
463 #ifndef mingw32_HOST_OS
464 | threaded = waitForDelayEvent time
466 | threaded = c_Sleep (fromIntegral (time `quot` 1000))
468 | otherwise = IO $ \s ->
469 case fromIntegral time of { I# time# ->
470 case delay# time# s of { s -> (# s, () #)
473 -- On Windows, we just make a safe call to 'Sleep' to implement threadDelay.
474 #ifdef mingw32_HOST_OS
475 foreign import ccall safe "Sleep" c_Sleep :: CInt -> IO ()
478 foreign import ccall unsafe "rtsSupportsBoundThreads" threaded :: Bool
480 -- ----------------------------------------------------------------------------
481 -- Threaded RTS implementation of threadWaitRead, threadWaitWrite, threadDelay
483 -- In the threaded RTS, we employ a single IO Manager thread to wait
484 -- for all outstanding IO requests (threadWaitRead,threadWaitWrite)
485 -- and delays (threadDelay).
487 -- We can do this because in the threaded RTS the IO Manager can make
488 -- a non-blocking call to select(), so we don't have to do select() in
489 -- the scheduler as we have to in the non-threaded RTS. We get performance
490 -- benefits from doing it this way, because we only have to restart the select()
491 -- when a new request arrives, rather than doing one select() each time
492 -- around the scheduler loop. Furthermore, the scheduler can be simplified
493 -- by not having to check for completed IO requests.
495 -- Issues, possible problems:
497 -- - we might want bound threads to just do the blocking
498 -- operation rather than communicating with the IO manager
499 -- thread. This would prevent simgle-threaded programs which do
500 -- IO from requiring multiple OS threads. However, it would also
501 -- prevent bound threads waiting on IO from being killed or sent
504 -- - Apprently exec() doesn't work on Linux in a multithreaded program.
505 -- I couldn't repeat this.
507 -- - How do we handle signal delivery in the multithreaded RTS?
509 -- - forkProcess will kill the IO manager thread. Let's just
510 -- hope we don't need to do any blocking IO between fork & exec.
512 #ifndef mingw32_HOST_OS
515 = Read {-# UNPACK #-} !Fd {-# UNPACK #-} !(MVar ())
516 | Write {-# UNPACK #-} !Fd {-# UNPACK #-} !(MVar ())
519 = Delay {-# UNPACK #-} !Int {-# UNPACK #-} !(MVar ())
521 pendingEvents :: IORef [IOReq]
522 pendingDelays :: IORef [DelayReq]
523 -- could use a strict list or array here
524 {-# NOINLINE pendingEvents #-}
525 {-# NOINLINE pendingDelays #-}
526 (pendingEvents,pendingDelays) = unsafePerformIO $ do
531 -- the first time we schedule an IO request, the service thread
532 -- will be created (cool, huh?)
534 startIOServiceThread :: IO ()
535 startIOServiceThread = do
536 allocaArray 2 $ \fds -> do
537 throwErrnoIfMinus1 "startIOServiceThread" (c_pipe fds)
538 rd_end <- peekElemOff fds 0
539 wr_end <- peekElemOff fds 1
540 writeIORef stick (fromIntegral wr_end)
542 allocaBytes sizeofFdSet $ \readfds -> do
543 allocaBytes sizeofFdSet $ \writefds -> do
544 allocaBytes sizeofTimeVal $ \timeval -> do
545 service_loop (fromIntegral rd_end) readfds writefds timeval [] []
548 -- XXX: move real forkIO here from Control.Concurrent?
549 quickForkIO action = IO $ \s ->
550 case (fork# action s) of (# s1, id #) -> (# s1, ThreadId id #)
553 :: Fd -- listen to this for wakeup calls
560 service_loop wakeup readfds writefds ptimeval old_reqs old_delays = do
562 -- pick up new IO requests
563 new_reqs <- atomicModifyIORef pendingEvents (\a -> ([],a))
564 let reqs = new_reqs ++ old_reqs
566 -- pick up new delay requests
567 new_delays <- atomicModifyIORef pendingDelays (\a -> ([],a))
568 let delays = foldr insertDelay old_delays new_delays
570 -- build the FDSets for select()
574 maxfd <- buildFdSets 0 readfds writefds reqs
576 -- perform the select()
577 let do_select delays = do
578 -- check the current time and wake up any thread in
579 -- threadDelay whose timeout has expired. Also find the
580 -- timeout value for the select() call.
582 (delays', timeout) <- getDelay now ptimeval delays
584 res <- c_select ((max wakeup maxfd)+1) readfds writefds
590 then do_select delays'
591 else return (res,delays')
595 (res,delays') <- do_select delays
596 -- ToDo: check result
598 b <- takeMVar prodding
599 if b then alloca $ \p -> do c_read (fromIntegral wakeup) p 1; return ()
601 putMVar prodding False
603 reqs' <- completeRequests reqs readfds writefds []
604 service_loop wakeup readfds writefds ptimeval reqs' delays'
607 {-# NOINLINE stick #-}
608 stick = unsafePerformIO (newIORef 0)
610 prodding :: MVar Bool
611 {-# NOINLINE prodding #-}
612 prodding = unsafePerformIO (newMVar False)
614 prodServiceThread :: IO ()
615 prodServiceThread = do
616 b <- takeMVar prodding
618 then do fd <- readIORef stick
619 with 42 $ \pbuf -> do c_write (fromIntegral fd) pbuf 1; return ()
621 putMVar prodding True
623 -- -----------------------------------------------------------------------------
626 buildFdSets maxfd readfds writefds [] = return maxfd
627 buildFdSets maxfd readfds writefds (Read fd m : reqs) = do
629 buildFdSets (max maxfd fd) readfds writefds reqs
630 buildFdSets maxfd readfds writefds (Write fd m : reqs) = do
632 buildFdSets (max maxfd fd) readfds writefds reqs
634 completeRequests [] _ _ reqs' = return reqs'
635 completeRequests (Read fd m : reqs) readfds writefds reqs' = do
636 b <- fdIsSet fd readfds
638 then do putMVar m (); completeRequests reqs readfds writefds reqs'
639 else completeRequests reqs readfds writefds (Read fd m : reqs')
640 completeRequests (Write fd m : reqs) readfds writefds reqs' = do
641 b <- fdIsSet fd writefds
643 then do putMVar m (); completeRequests reqs readfds writefds reqs'
644 else completeRequests reqs readfds writefds (Write fd m : reqs')
646 waitForReadEvent :: Fd -> IO ()
647 waitForReadEvent fd = do
649 atomicModifyIORef pendingEvents (\xs -> (Read fd m : xs, ()))
653 waitForWriteEvent :: Fd -> IO ()
654 waitForWriteEvent fd = do
656 atomicModifyIORef pendingEvents (\xs -> (Write fd m : xs, ()))
660 -- XXX: move into GHC.IOBase from Data.IORef?
661 atomicModifyIORef :: IORef a -> (a -> (a,b)) -> IO b
662 atomicModifyIORef (IORef (STRef r#)) f = IO $ \s -> atomicModifyMutVar# r# f s
664 -- -----------------------------------------------------------------------------
667 waitForDelayEvent :: Int -> IO ()
668 waitForDelayEvent usecs = do
671 let target = now + usecs `quot` tick_usecs
672 atomicModifyIORef pendingDelays (\xs -> (Delay target m : xs, ()))
676 -- Walk the queue of pending delays, waking up any that have passed
677 -- and return the smallest delay to wait for. The queue of pending
678 -- delays is kept ordered.
679 getDelay :: Ticks -> Ptr CTimeVal -> [DelayReq] -> IO ([DelayReq], Ptr CTimeVal)
680 getDelay now ptimeval [] = return ([],nullPtr)
681 getDelay now ptimeval all@(Delay time m : rest)
684 getDelay now ptimeval rest
686 setTimevalTicks ptimeval (time - now)
687 return (all,ptimeval)
689 insertDelay :: DelayReq -> [DelayReq] -> [DelayReq]
690 insertDelay d@(Delay time m) [] = [d]
691 insertDelay d1@(Delay time m) ds@(d2@(Delay time' m') : rest)
692 | time <= time' = d1 : ds
693 | otherwise = d2 : insertDelay d1 rest
696 tick_freq = 50 :: Ticks -- accuracy of threadDelay (ticks per sec)
697 tick_usecs = 1000000 `quot` tick_freq :: Int
699 newtype CTimeVal = CTimeVal ()
701 foreign import ccall unsafe "sizeofTimeVal"
704 foreign import ccall unsafe "getTicksOfDay"
705 getTicksOfDay :: IO Ticks
707 foreign import ccall unsafe "setTimevalTicks"
708 setTimevalTicks :: Ptr CTimeVal -> Ticks -> IO ()
710 -- ----------------------------------------------------------------------------
711 -- select() interface
713 -- ToDo: move to System.Posix.Internals?
715 newtype CFdSet = CFdSet ()
717 foreign import ccall safe "select"
718 c_select :: Fd -> Ptr CFdSet -> Ptr CFdSet -> Ptr CFdSet -> Ptr CTimeVal
721 foreign import ccall unsafe "hsFD_CLR"
722 fdClr :: Fd -> Ptr CFdSet -> IO ()
724 foreign import ccall unsafe "hsFD_ISSET"
725 fdIsSet :: Fd -> Ptr CFdSet -> IO CInt
727 foreign import ccall unsafe "hsFD_SET"
728 fdSet :: Fd -> Ptr CFdSet -> IO ()
730 foreign import ccall unsafe "hsFD_ZERO"
731 fdZero :: Ptr CFdSet -> IO ()
733 foreign import ccall unsafe "sizeof_fd_set"