broadcast-chan (empty) → 0.1.0

raw patch · 4 files changed

+178/−0 lines, 4 filesdep +basesetup-changed

Dependencies added: base

Files

• Control/Concurrent/BroadcastChan.hs +96/−0
• LICENSE +30/−0
• Setup.hs +2/−0
• broadcast-chan.cabal +50/−0

@@ -0,0 +1,96 @@+{-# LANGUAGE DataKinds #-}+{-# LANGUAGE AutoDeriveTypeable #-}+{-# LANGUAGE GADTs #-}+{-# LANGUAGE KindSignatures #-}+{-# LANGUAGE StandaloneDeriving #-}+{-# LANGUAGE Trustworthy #-}+-------------------------------------------------------------------------------+-- |+-- Module      :  Contro.Concurrent.BroadcastChan+-- Copyright   :  (C) 2014 Merijn Verstraaten+-- License     :  BSD-style (see the file LICENSE)+-- Maintainer  :  Merijn Verstraaten <merijn@inconsistent.nl>+-- Stability   :  experimental+-- Portability :  haha+--+-- A variation of "Control.Concurrent.Chan" from base, which allows to the easy+-- creation of broadcast channels without the space-leaks that may arise from+-- using 'Control.Concurrent.Chan.dupChan'.+--+-- The 'Control.Concurrent.Chan.Chan' type from "Control.Concurrent.Chan"+-- consists of both a read and write end. This presents a problem when one+-- wants to have a broadcast channel that, at times, has zero listeners. To+-- write to a 'Control.Concurrent.Chan.Chan' there must always be a read end+-- and this read end will hold ALL messages alive until read.+--+-- The simple solution applied in this module is to separate read and write+-- ends. As a result, any messages written to the write end can be immediately+-- garbage collected if there are no active read ends, avoding space leaks.+-------------------------------------------------------------------------------+module Control.Concurrent.BroadcastChan+    ( BroadcastChan+    , In+    , Out+    , newBroadcastChan+    , writeBChan+    , readBChan+    , newBChanListener+    ) where++import Control.Concurrent.MVar+import Control.Exception (mask_)++data Direction = In | Out++-- | Alias for the 'In' type from the 'Direction' kind, allows users to write+-- the 'BroadcastChan In a' type without enabling DataKinds.+type In = 'In+-- | Alias for the 'Out' type from the 'Direction' kind, allows users to write+-- the 'BroadcastChan Out a' type without enabling DataKinds.+type Out = 'Out++-- | The abstract type representing the read or write end of a 'BroadcastChan'.+data BroadcastChan :: Direction -> * -> * where+    WriteEnd :: {-# UNPACK #-} !(MVar (Stream a)) -> BroadcastChan In a+    ReadEnd  :: {-# UNPACK #-} !(MVar (Stream a)) -> BroadcastChan Out a++deriving instance Eq (BroadcastChan i a)++type Stream a = MVar (ChItem a)++data ChItem a = ChItem a {-# UNPACK #-} !(Stream a)++-- | Creates a new 'BroadcastChan' write end.+newBroadcastChan :: IO (BroadcastChan In a)+newBroadcastChan = do+   hole  <- newEmptyMVar+   writeVar <- newMVar hole+   return (WriteEnd writeVar)++-- | Write a value to write end of a 'BroadcastChan'. Any messages written+-- while there are no live read ends can be immediately garbage collected, thus+-- avoiding space leaks.+writeBChan :: BroadcastChan In a -> a -> IO ()+writeBChan (WriteEnd writeVar) val = do+  new_hole <- newEmptyMVar+  mask_ $ do+    old_hole <- takeMVar writeVar+    putMVar old_hole (ChItem val new_hole)+    putMVar writeVar new_hole++-- | Read the next value from the read end of a 'BroadcastChan'.+readBChan :: BroadcastChan Out a -> IO a+readBChan (ReadEnd readVar) = do+  modifyMVarMasked readVar $ \read_end -> do -- Note [modifyMVarMasked]+    (ChItem val new_read_end) <- readMVar read_end+        -- Use readMVar here, not takeMVar,+        -- else dupBroadcastChan doesn't work+    return (new_read_end, val)++-- | Create a new read end for a 'BroadcastChan'. Will receive all messages+-- written to the channel's write end after the read end's creation.+newBChanListener :: BroadcastChan In a -> IO (BroadcastChan Out a)+newBChanListener (WriteEnd writeVar) = do+   hole       <- readMVar writeVar+   newReadVar <- newMVar hole+   return (ReadEnd newReadVar)

@@ -0,0 +1,30 @@+Copyright (c) 2013, Merijn Verstraaten++All rights reserved.++Redistribution and use in source and binary forms, with or without+modification, are permitted provided that the following conditions are met:++    * Redistributions of source code must retain the above copyright+      notice, this list of conditions and the following disclaimer.++    * Redistributions in binary form must reproduce the above+      copyright notice, this list of conditions and the following+      disclaimer in the documentation and/or other materials provided+      with the distribution.++    * Neither the name of Merijn Verstraaten nor the names of other+      contributors may be used to endorse or promote products derived+      from this software without specific prior written permission.++THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

@@ -0,0 +1,2 @@+import Distribution.Simple+main = defaultMain

@@ -0,0 +1,50 @@+Name:                broadcast-chan+Version:             0.1.0++Homepage:            https://github.com/merijn/broadcast-chan+Bug-Reports:         https://github.com/merijn/broadcast-chan/issues++Author:              Merijn Verstraaten+Maintainer:          Merijn Verstraaten <merijn@inconsistent.nl>+Copyright:           Copyright © 2014 Merijn Verstraaten++License:             BSD3+License-File:        LICENSE++Category:            System+Cabal-Version:       >= 1.10+Build-Type:          Simple+Tested-With:         GHC == 7.8.3++Synopsis:            Broadcast channel type that avoids 0 reader space leaks.++Description:+    A variation of "Control.Concurrent.Chan" from base, which allows to the+    easy creation of broadcast channels without the space-leaks that may arise+    from using 'Control.Concurrent.Chan.dupChan'.++    The 'Control.Concurrent.Chan.Chan' type from "Control.Concurrent.Chan"+    consists of both a read and write end. This presents a problem when one+    wants to have a broadcast channel that, at times, has zero listeners. To+    write to a 'Control.Concurrent.Chan.Chan' there must always be a read end+    and this read end will hold ALL messages alive until read.++    The simple solution applied in this module is to separate read and write+    ends. As a result, any messages written to the write end can be immediately+    garbage collected if there are no active read ends, avoding space leaks.++Library+  Default-Language:     Haskell2010+  GHC-Options:          -Wall -fno-warn-unused-do-bind+  GHC-Prof-Options:     -auto-all -caf-all -rtsopts+  Exposed-Modules:      Control.Concurrent.BroadcastChan++  Build-Depends:        base >= 4 && < 5++Source-Repository head+  Type:     mercurial+  Location: https://bitbucket.org/merijnv/broadcast-chan++Source-Repository head+  Type:     mercurial+  Location: git+ssh://github.com:merijn/broadcast-chan