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|
{-# LANGUAGE ViewPatterns #-}
import Control.Monad
import Control.Concurrent
import Control.Concurrent.Async
import Data.Maybe
import System.Environment
import System.Exit
import System.Process
import System.IO
import System.FileLock
main :: IO ()
main = do
hSetBuffering stdout LineBuffering
args <- getArgs
case args of
["shared", read -> duration]
-> holdLock "shared" Shared duration
["exclusive", read -> duration]
-> holdLock "exclusive" Exclusive duration
["try"]
-> tryTakingLock
["tryshared", read -> duration]
-> tryHoldLock "shared" Shared duration
["tryexclusive", read -> duration]
-> tryHoldLock "exclusive" Exclusive duration
_ -> do
withFile "lock.log" WriteMode $ \h ->
void $ mapConcurrently id
[ callSelf h ["shared", "5"]
, callSelf h ["shared", "2"]
, sleep 1 >> callSelf h ["exclusive", "3"]
, sleep 3 >> callSelf h ["try"]
, sleep 4 >> callSelf h ["shared", "1"]
, sleep 6 >> callSelf h ["shared", "1"]
, sleep 10 >> callSelf h ["try"]
]
sleep 11
log <- readFile "lock.log"
expected <- readFile "tests/lock.log.expected"
when (log /= expected) $ do
putStrLn "log mismatch!"
putStrLn "log:"
putStrLn log
putStrLn "expected:"
putStrLn expected
exitFailure
callSelf :: Handle -> [String] -> IO ()
callSelf out args = do
self <- getExecutablePath
(_hin, _hout, _herr, ph) <- createProcess_ "callSelf"
(proc self args) { std_out = UseHandle out }
ExitSuccess <- waitForProcess ph
return ()
sleep :: Int -> IO ()
sleep = threadDelay . (*1000000)
holdLock :: String -> SharedExclusive -> Int -> IO ()
holdLock ty sex duration = do
withFileLock lockfile sex $ \_ -> do
putStrLn $ "took " ++ desc
sleep duration
putStrLn $ "releasing " ++ desc
where
desc = ty ++ " lock"
tryTakingLock :: IO ()
tryTakingLock = do
ml <- tryLockFile lockfile Exclusive
case ml of
Nothing -> putStrLn "lock not available"
Just l -> do
putStrLn "lock was available"
unlockFile l
tryHoldLock :: String -> SharedExclusive -> Int -> IO ()
tryHoldLock ty sex duration = do
res <- withTryFileLock lockfile sex $ \_ -> do
putStrLn $ "took " ++ desc
sleep duration
putStrLn $ "released " ++ desc
when (isNothing res) $ putStrLn "lock not available"
where
desc = ty ++ " lock"
lockfile :: String
lockfile = "lock"
|
