select-0.3: example/Example.hs

module Main where

import System.Posix.IO
import System.Posix.IO.Select
import Control.Concurrent
import Control.Concurrent.STM.OrElseIO
import Control.Concurrent.STM
import Control.Concurrent.STM.TMVar
import Control.Concurrent.STM.TChan

flags :: OpenFileFlags
flags = OpenFileFlags { append = False, exclusive = False, noctty = False, nonBlock = True, trunc = False }

-- Needs the threaded runtime!
main :: IO ()
main = 
    newEmptyTMVarIO >>= \t ->
    forkIO (interruptor t) >>
    putStrLn "The interruptor has been launched." >>
    newTChanIO >>= \c ->
    forkIO (interruptor2 c) >>
    putStrLn "The TChan interruptor has been launched." >>
    openFd "fifo" ReadOnly Nothing flags >>= \fd -> 
    openFd "fifo2" ReadOnly Nothing flags >>= \fd2 -> 
    openFd "fifo3" ReadOnly Nothing flags >>= \fd3 -> 
    openFd "fifo4" ReadOnly Nothing flags >>= \fd4 -> 
    putStrLn "The file was opened, so let the waiting game begin!" >>
    runOrElse (select [fd,fd2,fd3,fd4] [] [] (Time 9 0)) (readTChan c) >>= \ret ->
        case ret of
          Left 0 -> putStrLn "select() timed out on the files."
          Left x -> putStrLn "There's data in one of the files!"
          Right s -> putStrLn $ "Oh no, the interruptor is here: " ++ s   

interruptor :: TMVar String -> IO ()
interruptor t = threadDelay (10 * 1000000) >>
                atomically (putTMVar t "Bwahahaha, the interruptor was first!")

interruptor2 :: TChan String -> IO ()
interruptor2 c = threadDelay (10 * 1000000) >>
                 atomically (writeTChan c "Bwhaha, TChan interruptor was first!")