Control.Concurrent.STM.TQueue
A TQueue
is like a TChan
, with two important differences:
- it has faster throughput than both
TChan
andChan
(although the costs are amortised, so the cost of individual operations can vary a lot). - it does not provide equivalents of the
dupTChan
andcloneTChan
operations.
The implementation is based on the traditional purely-functional queue representation that uses two lists to obtain amortised O(1) enqueue and dequeue operations.
Since: stm-2.4
TQueue
TQueue
is an abstract type representing an unbounded FIFO channel.
Since: stm-2.4
newTQueueIO :: IO (TQueue a) Source #
IO
version of newTQueue
. This is useful for creating top-level
TQueue
s using unsafePerformIO
, because using
atomically
inside unsafePerformIO
isn't
possible.
tryReadTQueue :: TQueue a -> STM (Maybe a) Source #
A version of readTQueue
which does not retry. Instead it
returns Nothing
if no value is available.
flushTQueue :: TQueue a -> STM [a] Source #
Efficiently read the entire contents of a TQueue
into a list. This
function never retries.
Since: stm-2.4.5
peekTQueue :: TQueue a -> STM a Source #
Get the next value from the TQueue
without removing it,
retrying if the channel is empty.
tryPeekTQueue :: TQueue a -> STM (Maybe a) Source #
A version of peekTQueue
which does not retry. Instead it
returns Nothing
if no value is available.
unGetTQueue :: TQueue a -> a -> STM () Source #
Put a data item back onto a channel, where it will be the next item read.