System.Timer.Updatable

An updatable timer is a timer for which it is possible to update the remaining time.

Methods are exposed in STM to give composability. IO wrappers for those are exported also.

Parallel and serial update politics are implemented.

In the example we start a timer with a time to wait of 10 seconds, hang 2 threads which will wait for it to finish and update it after 5 seconds to wait for other 6 seconds. It will complete and run its action and the hanged threads after 11 seconds because of its parallel nature. The serial timer would have ringed after 16 seconds.

 import Control.Concurrent
 import System.Timer.Updatable
 import Data.Maybe
 main = do
  t <- parallel (return 5) $ 10^7
  forkIO $ waitIO t >>= print . (+1) . fromJust 
  forkIO $ waitIO t >>= print . (+2) . fromJust
  threadDelay $ 5 * 10 ^ 6
  renewIO t $ 6 * 10 ^ 6
  waitIO t >>= print . fromJust 

Documentation

type Delay = Int

A delay in microseconds

Datatype

data Updatable a

Abstract timers that can be updated. Hanging via wait function can be done by any number of threads, which is sinchronization.

Instances

Killable (Updatable a)

wait :: Updatable a -> STM (Maybe a)

wait until the timer rings, or signal Nothing if timer is destroyed

renew :: Updatable a -> Delay -> STM ()

update the delay in the timer

IO wrappers

waitIO :: Updatable a -> IO (Maybe a)

Wait in IO

renewIO :: Updatable a -> Delay -> IO ()

Renew in IO

Builders

parallel

Arguments

:: IO a

the action to run when timer rings

-> Delay

time to wait

-> IO (Updatable a)

the updatable parallel timer

Create and start a parallel updatable timer. This timer renew actions will start parallel timers. Last timer that is over will compute the given action.

serial

Arguments

:: IO a

the action to run when timer rings

-> Delay

time to wait

-> IO (Updatable a)

the updatable parallel timer

Create and start a serial updatable timer. This timer renew action will schedule new timer after the running one. The timer will run the given action after the sum of all scheduled times is over.