-- Hoogle documentation, generated by Haddock
-- See Hoogle, http://www.haskell.org/hoogle/


-- | Updatable one-shot timer polled with STM
--   
--   This library lets you create a one-shot timer, poll it using STM, and
--   update it to ring at a different time than initially specified.
--   
--   It uses GHC event manager timeouts when available (GHC 7.2+,
--   <tt>-threaded</tt>, non-Windows OS), yielding performance similar to
--   <tt>threadDelay</tt> and <tt>registerDelay</tt>. Otherwise, it falls
--   back to forked threads and <tt>threadDelay</tt>.
@package stm-delay
@version 0.1


-- | One-shot timer whose duration can be updated
--   
--   Suppose you are managing a network connection, and want to time it out
--   if no messages are received in over five minutes. You can do something
--   like this:
--   
--   <pre>
--   import Control.Concurrent.Async (race_) -- from the async package
--   import Control.Concurrent.STM
--   import Control.Concurrent.STM.Delay
--   import Control.Exception
--   import Control.Monad
--   
--   manageConnection :: Connection -&gt; IO Message -&gt; (Message -&gt; IO a) -&gt; IO ()
--   manageConnection conn toSend onRecv =
--       bracket (newDelay five_minutes) cancelDelay $ \delay -&gt;
--       foldr1 race_
--           [ do atomically $ waitDelay delay
--                fail "Connection timed out"
--           , forever $ toSend &gt;&gt;= send conn
--           , forever $ do
--               msg &lt;- recv conn
--               updateDelay delay five_minutes
--               onRecv msg
--           ]
--     where
--       five_minutes = 5 * 60 * 1000000
--   </pre>
module Control.Concurrent.STM.Delay

-- | A <a>Delay</a> is an updatable timer that rings only once.
data Delay

-- | Create a new <a>Delay</a> that will ring in the given number of
--   microseconds.
newDelay :: Int -> IO Delay

-- | Set an existing <a>Delay</a> to ring in the given number of
--   microseconds (from the time <a>updateDelay</a> is called), rather than
--   when it was going to ring. If the <a>Delay</a> has already rung, do
--   nothing.
updateDelay :: Delay -> Int -> IO ()

-- | Set a <a>Delay</a> so it will never ring, even if <a>updateDelay</a>
--   is used later. If the <a>Delay</a> has already rung, do nothing.
cancelDelay :: Delay -> IO ()

-- | Block until the <a>Delay</a> rings. If the <a>Delay</a> has already
--   rung, return immediately.
waitDelay :: Delay -> STM ()

-- | Non-blocking version of <a>waitDelay</a>. Return <a>True</a> if the
--   <a>Delay</a> has rung.
tryWaitDelay :: Delay -> STM Bool
instance Eq Delay