pipes-concurrency-2.0.6: Concurrency for the pipes ecosystem

Safe HaskellSafe
LanguageHaskell98

Pipes.Concurrent

Contents

Description

Asynchronous communication between pipes

Synopsis

Inputs and Outputs

newtype Input a Source

An exhaustible source of values

recv returns Nothing if the source is exhausted

Constructors

Input 

Fields

recv :: STM (Maybe a)
 

newtype Output a Source

An exhaustible sink of values

send returns False if the sink is exhausted

Constructors

Output 

Fields

send :: a -> STM Bool
 

Instances

Divisible Output Source 
Decidable Output Source 
Contravariant Output Source

This instance is useful for creating new tagged address, similar to elm's Signal.forwardTo. In fact elm's forwardTo is just 'flip contramap'

Monoid (Output a) Source 

Pipe utilities

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

Convert an Input to a Producer

fromInput terminates when the Input is exhausted.

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

Convert an Output to a Consumer

toOutput terminates when the Output is exhausted.

Actors

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

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 ()) Source

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.

withSpawn :: Buffer a -> ((Output a, Input a) -> IO r) -> IO r Source

withSpawn passes its enclosed action an Output and Input like you'd get from spawn, but automatically seals them after the action completes. This can be used when you need the sealing behavior available from 'spawn\'', but want to work at a bit higher level:

withSpawn buffer $ \(output, input) -> ...

withSpawn is exception-safe, since it uses bracket internally.

data Buffer a Source

Buffer specifies how to buffer messages stored within the mailbox

Constructors

Unbounded

Deprecated: Use unbounded instead

Bounded Int

Deprecated: Use bounded instead

Single

Deprecated: Use bounded 1 instead

Latest a

Deprecated: Use latest instead

Newest Int

Deprecated: Use newest instead

New

Deprecated: Use newest 1 instead

unbounded :: Buffer a Source

Store an unbounded number of messages in a FIFO queue

bounded :: Int -> Buffer a Source

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

latest :: a -> Buffer a Source

Only store the Latest message, beginning with an initial value

Latest is never empty nor full.

newest :: Int -> Buffer a Source

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

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 System.Mem