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<pre><a name="line-1"></a><span class='hs-comment'>{-# OPTIONS_GHC -fno-warn-name-shadowing #-}</span>
<a name="line-2"></a><span class='hs-comment'>{-# LANGUAGE DeriveDataTypeable #-}</span>
<a name="line-3"></a>
<a name="line-4"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-5"></a><span class='hs-comment'>-- |</span>
<a name="line-6"></a><span class='hs-comment'>-- Module : Control.Concurrent.STM.TChan</span>
<a name="line-7"></a><span class='hs-comment'>-- Copyright : (c) The University of Glasgow 2004</span>
<a name="line-8"></a><span class='hs-comment'>-- License : BSD-style (see the file libraries/base/LICENSE)</span>
<a name="line-9"></a><span class='hs-comment'>-- </span>
<a name="line-10"></a><span class='hs-comment'>-- Maintainer : libraries@haskell.org</span>
<a name="line-11"></a><span class='hs-comment'>-- Stability : experimental</span>
<a name="line-12"></a><span class='hs-comment'>-- Portability : non-portable (requires STM)</span>
<a name="line-13"></a><span class='hs-comment'>--</span>
<a name="line-14"></a><span class='hs-comment'>-- TChan: Transactional channels</span>
<a name="line-15"></a><span class='hs-comment'>-- (GHC only)</span>
<a name="line-16"></a><span class='hs-comment'>--</span>
<a name="line-17"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-18"></a>
<a name="line-19"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Concurrent</span><span class='hs-varop'>.</span><span class='hs-conid'>STM</span><span class='hs-varop'>.</span><span class='hs-conid'>TChan</span> <span class='hs-layout'>(</span>
<a name="line-20"></a><span class='hs-cpp'>#ifdef __GLASGOW_HASKELL__</span>
<a name="line-21"></a> <span class='hs-comment'>-- * TChans</span>
<a name="line-22"></a> <span class='hs-conid'>TChan</span><span class='hs-layout'>,</span>
<a name="line-23"></a> <span class='hs-varid'>newTChan</span><span class='hs-layout'>,</span>
<a name="line-24"></a> <span class='hs-varid'>newTChanIO</span><span class='hs-layout'>,</span>
<a name="line-25"></a> <span class='hs-varid'>readTChan</span><span class='hs-layout'>,</span>
<a name="line-26"></a> <span class='hs-varid'>writeTChan</span><span class='hs-layout'>,</span>
<a name="line-27"></a> <span class='hs-varid'>dupTChan</span><span class='hs-layout'>,</span>
<a name="line-28"></a> <span class='hs-varid'>unGetTChan</span><span class='hs-layout'>,</span>
<a name="line-29"></a> <span class='hs-varid'>isEmptyTChan</span>
<a name="line-30"></a><span class='hs-cpp'>#endif</span>
<a name="line-31"></a> <span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-32"></a>
<a name="line-33"></a><span class='hs-cpp'>#ifdef __GLASGOW_HASKELL__</span>
<a name="line-34"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>GHC</span><span class='hs-varop'>.</span><span class='hs-conid'>Conc</span>
<a name="line-35"></a>
<a name="line-36"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Typeable</span> <span class='hs-layout'>(</span><span class='hs-conid'>Typeable</span><span class='hs-layout'>)</span>
<a name="line-37"></a>
<a name="line-38"></a><a name="TChan"></a><span class='hs-comment'>-- | 'TChan' is an abstract type representing an unbounded FIFO channel.</span>
<a name="line-39"></a><a name="TChan"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>TChan</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>TChan</span> <span class='hs-layout'>(</span><span class='hs-conid'>TVar</span> <span class='hs-layout'>(</span><span class='hs-conid'>TVarList</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>TVar</span> <span class='hs-layout'>(</span><span class='hs-conid'>TVarList</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyword'>deriving</span> <span class='hs-conid'>Typeable</span>
<a name="line-40"></a>
<a name="line-41"></a><a name="TVarList"></a><span class='hs-keyword'>type</span> <span class='hs-conid'>TVarList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>TVar</span> <span class='hs-layout'>(</span><span class='hs-conid'>TList</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-42"></a><a name="TList"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>TList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>TNil</span> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>TCons</span> <span class='hs-varid'>a</span> <span class='hs-layout'>(</span><span class='hs-conid'>TVarList</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-43"></a>
<a name="line-44"></a><a name="newTChan"></a><span class='hs-comment'>-- |Build and returns a new instance of 'TChan'</span>
<a name="line-45"></a><span class='hs-definition'>newTChan</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>STM</span> <span class='hs-layout'>(</span><span class='hs-conid'>TChan</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-46"></a><span class='hs-definition'>newTChan</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-47"></a> <span class='hs-varid'>hole</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>newTVar</span> <span class='hs-conid'>TNil</span>
<a name="line-48"></a> <span class='hs-varid'>read</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>newTVar</span> <span class='hs-varid'>hole</span>
<a name="line-49"></a> <span class='hs-varid'>write</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>newTVar</span> <span class='hs-varid'>hole</span>
<a name="line-50"></a> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-conid'>TChan</span> <span class='hs-varid'>read</span> <span class='hs-varid'>write</span><span class='hs-layout'>)</span>
<a name="line-51"></a>
<a name="line-52"></a><a name="newTChanIO"></a><span class='hs-comment'>-- |@IO@ version of 'newTChan'. This is useful for creating top-level</span>
<a name="line-53"></a><span class='hs-comment'>-- 'TChan's using 'System.IO.Unsafe.unsafePerformIO', because using</span>
<a name="line-54"></a><span class='hs-comment'>-- 'atomically' inside 'System.IO.Unsafe.unsafePerformIO' isn't</span>
<a name="line-55"></a><span class='hs-comment'>-- possible.</span>
<a name="line-56"></a><span class='hs-definition'>newTChanIO</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>IO</span> <span class='hs-layout'>(</span><span class='hs-conid'>TChan</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-57"></a><span class='hs-definition'>newTChanIO</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-58"></a> <span class='hs-varid'>hole</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>newTVarIO</span> <span class='hs-conid'>TNil</span>
<a name="line-59"></a> <span class='hs-varid'>read</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>newTVarIO</span> <span class='hs-varid'>hole</span>
<a name="line-60"></a> <span class='hs-varid'>write</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>newTVarIO</span> <span class='hs-varid'>hole</span>
<a name="line-61"></a> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-conid'>TChan</span> <span class='hs-varid'>read</span> <span class='hs-varid'>write</span><span class='hs-layout'>)</span>
<a name="line-62"></a>
<a name="line-63"></a><a name="writeTChan"></a><span class='hs-comment'>-- |Write a value to a 'TChan'.</span>
<a name="line-64"></a><span class='hs-definition'>writeTChan</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>TChan</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>STM</span> <span class='hs-conid'>()</span>
<a name="line-65"></a><span class='hs-definition'>writeTChan</span> <span class='hs-layout'>(</span><span class='hs-conid'>TChan</span> <span class='hs-sel'>_read</span> <span class='hs-varid'>write</span><span class='hs-layout'>)</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-66"></a> <span class='hs-varid'>listend</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>readTVar</span> <span class='hs-varid'>write</span> <span class='hs-comment'>-- listend == TVar pointing to TNil</span>
<a name="line-67"></a> <span class='hs-varid'>new_listend</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>newTVar</span> <span class='hs-conid'>TNil</span>
<a name="line-68"></a> <span class='hs-varid'>writeTVar</span> <span class='hs-varid'>listend</span> <span class='hs-layout'>(</span><span class='hs-conid'>TCons</span> <span class='hs-varid'>a</span> <span class='hs-varid'>new_listend</span><span class='hs-layout'>)</span>
<a name="line-69"></a> <span class='hs-varid'>writeTVar</span> <span class='hs-varid'>write</span> <span class='hs-varid'>new_listend</span>
<a name="line-70"></a>
<a name="line-71"></a><a name="readTChan"></a><span class='hs-comment'>-- |Read the next value from the 'TChan'.</span>
<a name="line-72"></a><span class='hs-definition'>readTChan</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>TChan</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>STM</span> <span class='hs-varid'>a</span>
<a name="line-73"></a><span class='hs-definition'>readTChan</span> <span class='hs-layout'>(</span><span class='hs-conid'>TChan</span> <span class='hs-varid'>read</span> <span class='hs-sel'>_write</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-74"></a> <span class='hs-varid'>listhead</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>readTVar</span> <span class='hs-varid'>read</span>
<a name="line-75"></a> <span class='hs-varid'>head</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>readTVar</span> <span class='hs-varid'>listhead</span>
<a name="line-76"></a> <span class='hs-keyword'>case</span> <span class='hs-varid'>head</span> <span class='hs-keyword'>of</span>
<a name="line-77"></a> <span class='hs-conid'>TNil</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>retry</span>
<a name="line-78"></a> <span class='hs-conid'>TCons</span> <span class='hs-varid'>a</span> <span class='hs-varid'>tail</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>do</span>
<a name="line-79"></a> <span class='hs-varid'>writeTVar</span> <span class='hs-varid'>read</span> <span class='hs-varid'>tail</span>
<a name="line-80"></a> <span class='hs-varid'>return</span> <span class='hs-varid'>a</span>
<a name="line-81"></a>
<a name="line-82"></a><a name="dupTChan"></a><span class='hs-comment'>-- |Duplicate a 'TChan': the duplicate channel begins empty, but data written to</span>
<a name="line-83"></a><span class='hs-comment'>-- either channel from then on will be available from both. Hence this creates</span>
<a name="line-84"></a><span class='hs-comment'>-- a kind of broadcast channel, where data written by anyone is seen by</span>
<a name="line-85"></a><span class='hs-comment'>-- everyone else.</span>
<a name="line-86"></a><span class='hs-definition'>dupTChan</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>TChan</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>STM</span> <span class='hs-layout'>(</span><span class='hs-conid'>TChan</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-87"></a><span class='hs-definition'>dupTChan</span> <span class='hs-layout'>(</span><span class='hs-conid'>TChan</span> <span class='hs-sel'>_read</span> <span class='hs-varid'>write</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-88"></a> <span class='hs-varid'>hole</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>readTVar</span> <span class='hs-varid'>write</span>
<a name="line-89"></a> <span class='hs-varid'>new_read</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>newTVar</span> <span class='hs-varid'>hole</span>
<a name="line-90"></a> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-conid'>TChan</span> <span class='hs-varid'>new_read</span> <span class='hs-varid'>write</span><span class='hs-layout'>)</span>
<a name="line-91"></a>
<a name="line-92"></a><a name="unGetTChan"></a><span class='hs-comment'>-- |Put a data item back onto a channel, where it will be the next item read.</span>
<a name="line-93"></a><span class='hs-definition'>unGetTChan</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>TChan</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>STM</span> <span class='hs-conid'>()</span>
<a name="line-94"></a><span class='hs-definition'>unGetTChan</span> <span class='hs-layout'>(</span><span class='hs-conid'>TChan</span> <span class='hs-varid'>read</span> <span class='hs-sel'>_write</span><span class='hs-layout'>)</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-95"></a> <span class='hs-varid'>listhead</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>readTVar</span> <span class='hs-varid'>read</span>
<a name="line-96"></a> <span class='hs-varid'>newhead</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>newTVar</span> <span class='hs-layout'>(</span><span class='hs-conid'>TCons</span> <span class='hs-varid'>a</span> <span class='hs-varid'>listhead</span><span class='hs-layout'>)</span>
<a name="line-97"></a> <span class='hs-varid'>writeTVar</span> <span class='hs-varid'>read</span> <span class='hs-varid'>newhead</span>
<a name="line-98"></a>
<a name="line-99"></a><a name="isEmptyTChan"></a><span class='hs-comment'>-- |Returns 'True' if the supplied 'TChan' is empty.</span>
<a name="line-100"></a><span class='hs-definition'>isEmptyTChan</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>TChan</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>STM</span> <span class='hs-conid'>Bool</span>
<a name="line-101"></a><span class='hs-definition'>isEmptyTChan</span> <span class='hs-layout'>(</span><span class='hs-conid'>TChan</span> <span class='hs-varid'>read</span> <span class='hs-sel'>_write</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-102"></a> <span class='hs-varid'>listhead</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>readTVar</span> <span class='hs-varid'>read</span>
<a name="line-103"></a> <span class='hs-varid'>head</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>readTVar</span> <span class='hs-varid'>listhead</span>
<a name="line-104"></a> <span class='hs-keyword'>case</span> <span class='hs-varid'>head</span> <span class='hs-keyword'>of</span>
<a name="line-105"></a> <span class='hs-conid'>TNil</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>return</span> <span class='hs-conid'>True</span>
<a name="line-106"></a> <span class='hs-conid'>TCons</span> <span class='hs-keyword'>_</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>return</span> <span class='hs-conid'>False</span>
<a name="line-107"></a><span class='hs-cpp'>#endif</span>
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