57 lines
1.6 KiB
Haskell
57 lines
1.6 KiB
Haskell
{- thread scheduling
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-
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- Copyright 2012 Joey Hess <joey@kitenet.net>
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- Copyright 2011 Bas van Dijk & Roel van Dijk
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-
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- Licensed under the GNU GPL version 3 or higher.
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-}
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module Utility.ThreadScheduler where
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import Common
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import Control.Concurrent
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import System.Posix.Terminal
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import System.Posix.Signals
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newtype Seconds = Seconds { fromSeconds :: Int }
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deriving (Eq, Ord, Show)
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{- Runs an action repeatedly forever, sleeping at least the specified number
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- of seconds in between. -}
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runEvery :: Seconds -> IO a -> IO a
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runEvery n a = forever $ do
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threadDelaySeconds n
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a
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threadDelaySeconds :: Seconds -> IO ()
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threadDelaySeconds (Seconds n) = unboundDelay (fromIntegral n * oneSecond)
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where
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oneSecond = 1000000 -- microseconds
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{- Like threadDelay, but not bounded by an Int.
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-
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- There is no guarantee that the thread will be rescheduled promptly when the
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- delay has expired, but the thread will never continue to run earlier than
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- specified.
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-
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- Taken from the unbounded-delay package to avoid a dependency for 4 lines
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- of code.
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-}
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unboundDelay :: Integer -> IO ()
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unboundDelay time = do
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let maxWait = min time $ toInteger (maxBound :: Int)
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threadDelay $ fromInteger maxWait
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when (maxWait /= time) $ unboundDelay (time - maxWait)
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{- Pauses the main thread, letting children run until program termination. -}
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waitForTermination :: IO ()
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waitForTermination = do
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lock <- newEmptyMVar
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check softwareTermination lock
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whenM (queryTerminal stdInput) $
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check keyboardSignal lock
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takeMVar lock
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where
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check sig lock = void $
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installHandler sig (CatchOnce $ putMVar lock ()) Nothing
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