Conduit.hs

{-# LANGUAGE FlexibleContexts      #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE RankNTypes            #-}
{-|
Module      : Control.Concurrent.NQE.Conduit
Copyright   : Haskoin Developers
License     : MIT
Maintainer  : jprupp@protonmail.ch
Stability   : experimental
Portability : POSIX

Mix NQE processes with conduits for easy concurrent IO.
-}
module Control.Concurrent.NQE.Conduit where

import           Conduit
import           Control.Concurrent.NQE.Process
import           Data.Typeable

-- | Consumes messages from a 'Conduit' and sends them to a channel.
--
-- Every value received from upstream is sent to the mailbox using 'send'. If
-- the mailbox is bounded and full, the conduit blocks until there is space,
-- providing back-pressure to upstream. The conduit finishes when upstream does.
--
-- @
-- runConduit $ sourceHandle h .| conduitMailbox mailbox
-- @
--
-- This is the bridge between streaming code and processes: a conduit that reads
-- a socket or a file can feed a process directly, and a bounded mailbox turns the
-- process's pace into back-pressure on the stream.
conduitMailbox ::
       (MonadIO m, OutChan mbox, Typeable msg)
    => mbox msg
    -> ConduitT msg o m ()
conduitMailbox mbox = awaitForever (`send` mbox)