Helpers.hs

module Network.AMQP.Helpers where

import Control.Exception


import Control.Concurrent.Chan
import Control.Concurrent.MVar
import qualified Data.ByteString.Char8 as BS
import qualified Data.ByteString.Lazy.Char8 as BL
import Control.Applicative


toStrict :: BL.ByteString -> BS.ByteString
toStrict x = BS.concat $ BL.toChunks x

toLazy :: BS.ByteString -> BL.ByteString
toLazy x = BL.fromChunks [x]


    
-- if the lock is open, calls to waitLock will immediately return. if it is closed, calls to waitLock will block. if the lock is killed, it will always be open and can't be closed anymore
data Lock = Lock (MVar Bool) (MVar ())

newLock = do
    a <- newMVar False
    b <- newMVar ()
    return $ Lock a b 
     
openLock :: Lock -> IO ()
openLock (Lock a b) = do
    tryPutMVar b ()
    return ()

closeLock :: Lock -> IO ()
closeLock (Lock a b) = do
    withMVar a $ \killed ->
        if killed 
            then return ()
            else tryTakeMVar b >> return ()
    return ()
            
  
waitLock (Lock a b) = readMVar b

killLock (Lock a b) = do
    modifyMVar_ a $ \x -> return True
    tryPutMVar b ()