-{-# OPTIONS -fglasgow-exts #-}
-------------------------------------------------------------------------------
-- |
-- Module : System.Timeout
--
-------------------------------------------------------------------------------
+#include "Typeable.h"
+
module System.Timeout ( timeout ) where
-import Prelude (IO, Ord((<)), Eq((==)), Int, (.), otherwise, fmap)
+#if __NHC__
+timeout :: Int -> IO a -> IO (Maybe a)
+timeout n f = fmap Just f
+#else
+
+import Prelude (Show(show), IO, Ord((<)), Eq((==)), Int,
+ (.), otherwise, fmap)
import Data.Maybe (Maybe(..))
import Control.Monad (Monad(..), guard)
import Control.Concurrent (forkIO, threadDelay, myThreadId, killThread)
-import Control.Exception (handleJust, throwDynTo, dynExceptions, bracket)
+import Control.Exception (Exception, handleJust, throwTo, bracket)
import Data.Dynamic (Typeable, fromDynamic)
+import Data.Typeable
import Data.Unique (Unique, newUnique)
-- An internal type that is thrown as a dynamic exception to
-- interrupt the running IO computation when the timeout has
-- expired.
-data Timeout = Timeout Unique deriving (Eq, Typeable)
+data Timeout = Timeout Unique deriving Eq
+INSTANCE_TYPEABLE0(Timeout,timeoutTc,"Timeout")
+
+instance Show Timeout where
+ show _ = "<<timeout>>"
+
+instance Exception Timeout
-- |Wrap an 'IO' computation to time out and return @Nothing@ in case no result
-- is available within @n@ microseconds (@1\/10^6@ seconds). In case a result
-- blocks, no timeout event can be delivered until the FFI call returns, which
-- pretty much negates the purpose of the combinator. In practice, however,
-- this limitation is less severe than it may sound. Standard I\/O functions
--- like 'System.IO.hGetBuf', 'System.IO.hPutBuf', 'Network.Socket.accept', or
+-- like 'System.IO.hGetBuf', 'System.IO.hPutBuf', Network.Socket.accept, or
-- 'System.IO.hWaitForInput' appear to be blocking, but they really don't
-- because the runtime system uses scheduling mechanisms like @select(2)@ to
-- perform asynchronous I\/O, so it is possible to interrupt standard socket
| otherwise = do
pid <- myThreadId
ex <- fmap Timeout newUnique
- handleJust (\e -> dynExceptions e >>= fromDynamic >>= guard . (ex ==))
+ handleJust (\e -> if e == ex then Just () else Nothing)
(\_ -> return Nothing)
- (bracket (forkIO (threadDelay n >> throwDynTo pid ex))
+ (bracket (forkIO (threadDelay n >> throwTo pid ex))
(killThread)
(\_ -> fmap Just f))
+#endif