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|
----------------------------------------------------------------------
-- |
-- Module : GF.System.UseSignal
-- Maintainer : Bjorn Bringert
-- Stability : (stability)
-- Portability : (portability)
--
-- > CVS $Date: 2005/11/11 11:12:50 $
-- > CVS $Author: bringert $
-- > CVS $Revision: 1.1 $
--
-- Allows SIGINT (Ctrl-C) to interrupt computations.
-----------------------------------------------------------------------------
module GF.System.UseSignal where
import Control.Concurrent (myThreadId, killThread)
import Control.Exception (Exception,catch)
import Prelude hiding (catch)
import System.IO
import System.Posix.Signals
{-# NOINLINE runInterruptibly #-}
-- | Run an IO action, and allow it to be interrupted
-- by a SIGINT to the current process. Returns
-- an exception if the process did not complete
-- normally.
-- NOTES:
-- * This will replace any existing SIGINT
-- handler during the action. After the computation
-- has completed the existing handler will be restored.
-- * If the IO action is lazy (e.g. using readFile,
-- unsafeInterleaveIO etc.) the lazy computation will
-- not be interruptible, as it will be performed
-- after the signal handler has been removed.
runInterruptibly :: IO a -> IO (Either Exception a)
runInterruptibly a =
do t <- myThreadId
oldH <- installHandler sigINT (Catch (killThread t)) Nothing
x <- p `catch` h
installHandler sigINT oldH Nothing
return x
where p = a >>= \x -> return $! Right $! x
h e = return $ Left e
-- | Like 'runInterruptibly', but always returns (), whether
-- the computation fails or not.
runInterruptibly_ :: IO () -> IO ()
runInterruptibly_ = fmap (either (const ()) id) . runInterruptibly
-- | Run an action with SIGINT blocked.
blockInterrupt :: IO a -> IO a
blockInterrupt a =
do oldH <- installHandler sigINT Ignore Nothing
x <- a
installHandler sigINT oldH Nothing
return x
|
