Pipes.Concurrent

Asynchronous communication between pipes

Inputs and Outputs

newtype Input a

An exhaustible source of values

recv returns Nothing if the source is exhausted

Constructors

Input

Fields

recv :: STM (Maybe a)

Instances

Monad Input

Functor Input

Applicative Input

Alternative Input

Monoid (Input a)

newtype Output a

An exhaustible sink of values

send returns False if the sink is exhausted

Constructors

Output

Fields

send :: a -> STM Bool

Instances

Monoid (Output a)

Pipe utilities

fromInput :: MonadIO m => Input a -> Producer' a m ()

Convert an Input to a Producer

fromInput terminates when the Input is exhausted.

toOutput :: MonadIO m => Output a -> Consumer' a m ()

Convert an Output to a Consumer

toOutput terminates when the Output is exhausted.

Actors

spawn :: Buffer a -> IO (Output a, Input a)

Spawn a mailbox using the specified Buffer to store messages

Using send on the Output

• fails and returns False if the mailbox is sealed, otherwise it:
• retries if the mailbox is full, or:
• adds a message to the mailbox and returns True.

Using recv on the Input:

• retrieves a message from the mailbox wrapped in Just if the mailbox is not empty, otherwise it:
• retries if the mailbox is not sealed, or:
• fails and returns Nothing.

If either the Input or Output is garbage collected the mailbox will become sealed.

spawn' :: Buffer a -> IO (Output a, Input a, STM ())

Like spawn, but also returns an action to manually seal the mailbox early:

 (output, input, seal) <- spawn' buffer
 ...

Use the seal action to allow early cleanup of readers and writers to the mailbox without waiting for the next garbage collection cycle.

data Buffer a

Buffer specifies how to buffer messages stored within the mailbox

Constructors

Unbounded

Store an Unbounded number of messages in a FIFO queue

Bounded Int

Store a Bounded number of messages, specified by the Int argument

Single

Store a Single message (like Bounded 1, but more efficient)

Latest a

Only store the Latest message, beginning with an initial value

Latest is never empty nor full.

Newest Int

Like Bounded, but send never fails (the buffer is never full). Instead, old elements are discard to make room for new elements

New

Like Newest 1, but more efficient

Re-exports

Control.Concurrent re-exports forkIO, although I recommend using the async library instead.

Control.Concurrent.STM re-exports atomically and STM.

System.Mem re-exports performGC.

module Control.Concurrent

module Control.Concurrent.STM

module System.Mem