-- Hoogle documentation, generated by Haddock -- See Hoogle, http://www.haskell.org/hoogle/ -- | Software Transactional Memory -- -- A modular composable concurrency abstraction. @package stm @version 2.4.4.1 -- | TBQueue is a bounded version of TQueue. The queue has -- a maximum capacity set when it is created. If the queue already -- contains the maximum number of elements, then writeTBQueue -- blocks until an element is removed from the queue. -- -- The implementation is based on the traditional purely-functional queue -- representation that uses two lists to obtain amortised O(1) -- enqueue and dequeue operations. module Control.Concurrent.STM.TBQueue -- | TBQueue is an abstract type representing a bounded FIFO -- channel. data TBQueue a -- | Build and returns a new instance of TBQueue newTBQueue :: Int -> STM (TBQueue a) -- | IO version of newTBQueue. This is useful for creating -- top-level TBQueues using unsafePerformIO, because using -- atomically inside unsafePerformIO isn't possible. newTBQueueIO :: Int -> IO (TBQueue a) -- | Read the next value from the TBQueue. readTBQueue :: TBQueue a -> STM a -- | A version of readTBQueue which does not retry. Instead it -- returns Nothing if no value is available. tryReadTBQueue :: TBQueue a -> STM (Maybe a) -- | Get the next value from the TBQueue without removing it, -- retrying if the channel is empty. peekTBQueue :: TBQueue a -> STM a -- | A version of peekTBQueue which does not retry. Instead it -- returns Nothing if no value is available. tryPeekTBQueue :: TBQueue a -> STM (Maybe a) -- | Write a value to a TBQueue; blocks if the queue is full. writeTBQueue :: TBQueue a -> a -> STM () -- | Put a data item back onto a channel, where it will be the next item -- read. Blocks if the queue is full. unGetTBQueue :: TBQueue a -> a -> STM () -- | Returns True if the supplied TBQueue is empty. isEmptyTBQueue :: TBQueue a -> STM Bool -- | Returns True if the supplied TBQueue is full. isFullTBQueue :: TBQueue a -> STM Bool instance GHC.Classes.Eq (Control.Concurrent.STM.TBQueue.TBQueue a) -- | A TQueue is like a TChan, with two important -- differences: -- --
-- serve :: TChan Message -> Client -> IO loop -- serve broadcastChan client = do -- myChan <- dupTChan broadcastChan -- forever $ do -- message <- readTChan myChan -- send client message ---- -- The problem with using newTChan to create the broadcast channel -- is that if it is only written to and never read, items will pile up in -- memory. By using newBroadcastTChan to create the broadcast -- channel, items can be garbage collected after clients have seen them. newBroadcastTChan :: STM (TChan a) -- | IO version of newBroadcastTChan. newBroadcastTChanIO :: IO (TChan a) -- | Duplicate a TChan: the duplicate channel begins empty, but data -- written to either channel from then on will be available from both. -- Hence this creates a kind of broadcast channel, where data written by -- anyone is seen by everyone else. dupTChan :: TChan a -> STM (TChan a) -- | Clone a TChan: similar to dupTChan, but the cloned channel -- starts with the same content available as the original channel. cloneTChan :: TChan a -> STM (TChan a) -- | Read the next value from the TChan. readTChan :: TChan a -> STM a -- | A version of readTChan which does not retry. Instead it returns -- Nothing if no value is available. tryReadTChan :: TChan a -> STM (Maybe a) -- | Get the next value from the TChan without removing it, -- retrying if the channel is empty. peekTChan :: TChan a -> STM a -- | A version of peekTChan which does not retry. Instead it returns -- Nothing if no value is available. tryPeekTChan :: TChan a -> STM (Maybe a) -- | Write a value to a TChan. writeTChan :: TChan a -> a -> STM () -- | Put a data item back onto a channel, where it will be the next item -- read. unGetTChan :: TChan a -> a -> STM () -- | Returns True if the supplied TChan is empty. isEmptyTChan :: TChan a -> STM Bool instance GHC.Classes.Eq (Control.Concurrent.STM.TChan.TChan a) -- | TMVar: Transactional MVars, for use in the STM monad (GHC only) module Control.Concurrent.STM.TMVar -- | A TMVar is a synchronising variable, used for communication -- between concurrent threads. It can be thought of as a box, which may -- be empty or full. data TMVar a -- | Create a TMVar which contains the supplied value. newTMVar :: a -> STM (TMVar a) -- | Create a TMVar which is initially empty. newEmptyTMVar :: STM (TMVar a) -- | IO version of newTMVar. This is useful for creating -- top-level TMVars using unsafePerformIO, because using -- atomically inside unsafePerformIO isn't possible. newTMVarIO :: a -> IO (TMVar a) -- | IO version of newEmptyTMVar. This is useful for -- creating top-level TMVars using unsafePerformIO, because -- using atomically inside unsafePerformIO isn't possible. newEmptyTMVarIO :: IO (TMVar a) -- | Return the contents of the TMVar. If the TMVar is -- currently empty, the transaction will retry. After a -- takeTMVar, the TMVar is left empty. takeTMVar :: TMVar a -> STM a -- | Put a value into a TMVar. If the TMVar is currently -- full, putTMVar will retry. putTMVar :: TMVar a -> a -> STM () -- | This is a combination of takeTMVar and putTMVar; ie. it -- takes the value from the TMVar, puts it back, and also returns -- it. readTMVar :: TMVar a -> STM a -- | A version of readTMVar which does not retry. Instead it returns -- Nothing if no value is available. tryReadTMVar :: TMVar a -> STM (Maybe a) -- | Swap the contents of a TMVar for a new value. swapTMVar :: TMVar a -> a -> STM a -- | A version of takeTMVar that does not retry. The -- tryTakeTMVar function returns Nothing if the -- TMVar was empty, or Just a if the TMVar -- was full with contents a. After tryTakeTMVar, the -- TMVar is left empty. tryTakeTMVar :: TMVar a -> STM (Maybe a) -- | A version of putTMVar that does not retry. The -- tryPutTMVar function attempts to put the value a into -- the TMVar, returning True if it was successful, or -- False otherwise. tryPutTMVar :: TMVar a -> a -> STM Bool -- | Check whether a given TMVar is empty. isEmptyTMVar :: TMVar a -> STM Bool -- | Make a Weak pointer to a TMVar, using the second -- argument as a finalizer to run when the TMVar is -- garbage-collected. mkWeakTMVar :: TMVar a -> IO () -> IO (Weak (TMVar a)) instance GHC.Classes.Eq (Control.Concurrent.STM.TMVar.TMVar a) -- | TVar: Transactional variables module Control.Concurrent.STM.TVar -- | Shared memory locations that support atomic memory transactions. data TVar a :: * -> * -- | Create a new TVar holding a value supplied newTVar :: a -> STM (TVar a) -- | IO version of newTVar. This is useful for creating -- top-level TVars using unsafePerformIO, because using -- atomically inside unsafePerformIO isn't possible. newTVarIO :: a -> IO (TVar a) -- | Return the current value stored in a TVar readTVar :: TVar a -> STM a -- | Return the current value stored in a TVar. This is equivalent to -- --
-- readTVarIO = atomically . readTVar ---- -- but works much faster, because it doesn't perform a complete -- transaction, it just reads the current value of the TVar. readTVarIO :: TVar a -> IO a -- | Write the supplied value into a TVar writeTVar :: TVar a -> a -> STM () -- | Mutate the contents of a TVar. N.B., this version is -- non-strict. modifyTVar :: TVar a -> (a -> a) -> STM () -- | Strict version of modifyTVar. modifyTVar' :: TVar a -> (a -> a) -> STM () -- | Swap the contents of a TVar for a new value. swapTVar :: TVar a -> a -> STM a -- | Set the value of returned TVar to True after a given number of -- microseconds. The caveats associated with threadDelay also apply. registerDelay :: Int -> IO (TVar Bool) -- | Make a Weak pointer to a TVar, using the second argument -- as a finalizer to run when TVar is garbage-collected mkWeakTVar :: TVar a -> IO () -> IO (Weak (TVar a)) -- | TArrays: transactional arrays, for use in the STM monad module Control.Concurrent.STM.TArray -- | TArray is a transactional array, supporting the usual MArray -- interface for mutable arrays. -- -- It is currently implemented as Array ix (TVar e), but it may -- be replaced by a more efficient implementation in the future (the -- interface will remain the same, however). data TArray i e instance GHC.Arr.Ix i => GHC.Classes.Eq (Control.Concurrent.STM.TArray.TArray i e) instance Data.Array.Base.MArray Control.Concurrent.STM.TArray.TArray e GHC.Conc.Sync.STM -- | Software Transactional Memory: a modular composable concurrency -- abstraction. See -- --
-- throw e `seq` x ===> throw e -- throwSTM e `seq` x ===> x ---- -- The first example will cause the exception e to be raised, -- whereas the second one won't. In fact, throwSTM will only cause -- an exception to be raised when it is used within the STM monad. -- The throwSTM variant should be used in preference to -- throw to raise an exception within the STM monad because -- it guarantees ordering with respect to other STM operations, -- whereas throw does not. throwSTM :: Exception e => e -> STM a -- | Exception handling within STM actions. catchSTM :: Exception e => STM a -> (e -> STM a) -> STM a instance Control.Monad.Fix.MonadFix GHC.Conc.Sync.STM -- | Software Transactional Memory: a modular composable concurrency -- abstraction. See -- --