Control.Concurrent.STM.TBQueue

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.

TBQueue

data TBQueue a

TBQueue is an abstract type representing a bounded FIFO channel.

Instances

Typeable1 TBQueue

Eq (TBQueue a)

newTBQueue

Arguments

:: Int

maximum number of elements the queue can hold

-> STM (TBQueue a)

Build and returns a new instance of TBQueue

newTBQueueIO :: Int -> IO (TBQueue a)

IO version of newTBQueue. This is useful for creating top-level TBQueues using unsafePerformIO, because using atomically inside unsafePerformIO isn't possible.

readTBQueue :: TBQueue a -> STM a

Read the next value from the TBQueue.

tryReadTBQueue :: TBQueue a -> STM (Maybe a)

A version of readTBQueue which does not retry. Instead it returns Nothing if no value is available.

peekTBQueue :: TBQueue a -> STM a

Get the next value from the TBQueue without removing it, retrying if the channel is empty.

tryPeekTBQueue :: TBQueue a -> STM (Maybe a)

A version of peekTBQueue which does not retry. Instead it returns Nothing if no value is available.

writeTBQueue :: TBQueue a -> a -> STM ()

Write a value to a TBQueue; blocks if the queue is full.

unGetTBQueue :: 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.

isEmptyTBQueue :: TBQueue a -> STM Bool

Returns True if the supplied TBQueue is empty.