On 17 February 2011 20:34, Bas van Dijk <v.dijk....@gmail.com> wrote:
> Speaking of Uniques: what is the best way to create them?
> I see 3 options:
There may be a 4th option but it requires changing the
System.Event.Manager.registerTimeout function from:
registerTimeout :: EventManager
-> Int
-> TimeoutCallback
-> IO TimeoutKey
to:
registerTimeout :: EventManager
-> Int
-> (TimeoutKey -> TimeoutCallback)
-> IO TimeoutKey
Then we can use the TimeoutKey as our Unique (Note that a TimeoutKey
is actually a newtype for a Unique):
newtype Timeout = Timeout TimeoutKey deriving Eq
instance Exception Timeout
timeout :: Int -> IO a -> IO (Maybe a)
timeout usecs f
| usecs < 0 = fmap Just f
| usecs == 0 = return Nothing
| otherwise = do
myTid <- myThreadId
Just mgr <- readIORef eventManager
mask $ \restore -> do
reg <- registerTimeout mgr usecs $ \reg -> throwTo myTid $ Timeout reg
let unregTimeout = M.unregisterTimeout mgr reg
(restore (fmap Just f) >>= \mb -> unregTimeout >> return mb)
`catch` \e ->
case fromException e of
Just (Timeout reg') | reg' == reg -> return Nothing
_ -> unregTimeout >> throwIO e
Bas
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