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<title>Data/Conduit/Util/Sink.hs</title>
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<pre><a name="line-1"></a><span class='hs-comment'>{-# LANGUAGE RankNTypes #-}</span>
<a name="line-2"></a><span class='hs-comment'>{-# LANGUAGE FlexibleContexts #-}</span>
<a name="line-3"></a><span class='hs-comment'>{-# LANGUAGE TypeFamilies #-}</span>
<a name="line-4"></a><span class='hs-comment'>{-# LANGUAGE CPP #-}</span>
<a name="line-5"></a><span class='hs-comment'>-- | Utilities for constructing 'Sink's. Please see "Data.Conduit.Types.Sink"</span>
<a name="line-6"></a><span class='hs-comment'>-- for more information on the base types.</span>
<a name="line-7"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Conduit</span><span class='hs-varop'>.</span><span class='hs-conid'>Util</span><span class='hs-varop'>.</span><span class='hs-conid'>Sink</span>
<a name="line-8"></a> <span class='hs-layout'>(</span> <span class='hs-varid'>sinkState</span>
<a name="line-9"></a> <span class='hs-layout'>,</span> <span class='hs-conid'>SinkStateResult</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span>
<a name="line-10"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>sinkIO</span>
<a name="line-11"></a> <span class='hs-layout'>,</span> <span class='hs-conid'>SinkIOResult</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span>
<a name="line-12"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>transSink</span>
<a name="line-13"></a> <span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-14"></a>
<a name="line-15"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span><span class='hs-varop'>.</span><span class='hs-conid'>Trans</span><span class='hs-varop'>.</span><span class='hs-conid'>Resource</span>
<a name="line-16"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span><span class='hs-varop'>.</span><span class='hs-conid'>Trans</span><span class='hs-varop'>.</span><span class='hs-conid'>Class</span> <span class='hs-layout'>(</span><span class='hs-varid'>lift</span><span class='hs-layout'>)</span>
<a name="line-17"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Conduit</span><span class='hs-varop'>.</span><span class='hs-conid'>Types</span><span class='hs-varop'>.</span><span class='hs-conid'>Sink</span>
<a name="line-18"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span> <span class='hs-layout'>(</span><span class='hs-varid'>liftM</span><span class='hs-layout'>)</span>
<a name="line-19"></a>
<a name="line-20"></a><a name="SinkStateResult"></a><span class='hs-comment'>-- | A helper type for @sinkState@, indicating the result of being pushed to.</span>
<a name="line-21"></a><a name="SinkStateResult"></a><span class='hs-comment'>-- It can either indicate that processing is done, or to continue with the</span>
<a name="line-22"></a><a name="SinkStateResult"></a><span class='hs-comment'>-- updated state.</span>
<a name="line-23"></a><a name="SinkStateResult"></a><span class='hs-comment'>--</span>
<a name="line-24"></a><a name="SinkStateResult"></a><span class='hs-comment'>-- Since 0.2.0</span>
<a name="line-25"></a><a name="SinkStateResult"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>SinkStateResult</span> <span class='hs-varid'>state</span> <span class='hs-varid'>input</span> <span class='hs-varid'>output</span> <span class='hs-keyglyph'>=</span>
<a name="line-26"></a> <span class='hs-conid'>StateDone</span> <span class='hs-layout'>(</span><span class='hs-conid'>Maybe</span> <span class='hs-varid'>input</span><span class='hs-layout'>)</span> <span class='hs-varid'>output</span>
<a name="line-27"></a> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>StateProcessing</span> <span class='hs-varid'>state</span>
<a name="line-28"></a>
<a name="line-29"></a><a name="sinkState"></a><span class='hs-comment'>-- | Construct a 'Sink' with some stateful functions. This function addresses</span>
<a name="line-30"></a><span class='hs-comment'>-- threading the state value for you.</span>
<a name="line-31"></a><span class='hs-comment'>--</span>
<a name="line-32"></a><span class='hs-comment'>-- Since 0.2.0</span>
<a name="line-33"></a><span class='hs-definition'>sinkState</span>
<a name="line-34"></a> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Resource</span> <span class='hs-varid'>m</span>
<a name="line-35"></a> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>state</span> <span class='hs-comment'>-- ^ initial state</span>
<a name="line-36"></a> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>state</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>input</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>ResourceT</span> <span class='hs-varid'>m</span> <span class='hs-layout'>(</span><span class='hs-conid'>SinkStateResult</span> <span class='hs-varid'>state</span> <span class='hs-varid'>input</span> <span class='hs-varid'>output</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-comment'>-- ^ push</span>
<a name="line-37"></a> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>state</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>ResourceT</span> <span class='hs-varid'>m</span> <span class='hs-varid'>output</span><span class='hs-layout'>)</span> <span class='hs-comment'>-- ^ Close. Note that the state is not returned, as it is not needed.</span>
<a name="line-38"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Sink</span> <span class='hs-varid'>input</span> <span class='hs-varid'>m</span> <span class='hs-varid'>output</span>
<a name="line-39"></a><span class='hs-definition'>sinkState</span> <span class='hs-varid'>state0</span> <span class='hs-varid'>push0</span> <span class='hs-varid'>close0</span> <span class='hs-keyglyph'>=</span>
<a name="line-40"></a> <span class='hs-conid'>SinkData</span> <span class='hs-layout'>(</span><span class='hs-varid'>push</span> <span class='hs-varid'>state0</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>close0</span> <span class='hs-varid'>state0</span><span class='hs-layout'>)</span>
<a name="line-41"></a> <span class='hs-keyword'>where</span>
<a name="line-42"></a> <span class='hs-varid'>push</span> <span class='hs-varid'>state</span> <span class='hs-varid'>input</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-43"></a> <span class='hs-varid'>res</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>state</span> <span class='hs-varop'>`seq`</span> <span class='hs-varid'>push0</span> <span class='hs-varid'>state</span> <span class='hs-varid'>input</span>
<a name="line-44"></a> <span class='hs-keyword'>case</span> <span class='hs-varid'>res</span> <span class='hs-keyword'>of</span>
<a name="line-45"></a> <span class='hs-conid'>StateProcessing</span> <span class='hs-varid'>state'</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>return</span> <span class='hs-varop'>$</span> <span class='hs-conid'>Processing</span> <span class='hs-layout'>(</span><span class='hs-varid'>push</span> <span class='hs-varid'>state'</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>close0</span> <span class='hs-varid'>state'</span><span class='hs-layout'>)</span>
<a name="line-46"></a> <span class='hs-conid'>StateDone</span> <span class='hs-varid'>mleftover</span> <span class='hs-varid'>output</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>return</span> <span class='hs-varop'>$</span> <span class='hs-conid'>Done</span> <span class='hs-varid'>mleftover</span> <span class='hs-varid'>output</span>
<a name="line-47"></a>
<a name="line-48"></a><a name="SinkIOResult"></a><span class='hs-comment'>-- | A helper type for @sinkIO@, indicating the result of being pushed to. It</span>
<a name="line-49"></a><a name="SinkIOResult"></a><span class='hs-comment'>-- can either indicate that processing is done, or to continue.</span>
<a name="line-50"></a><a name="SinkIOResult"></a><span class='hs-comment'>--</span>
<a name="line-51"></a><a name="SinkIOResult"></a><span class='hs-comment'>-- Since 0.2.0</span>
<a name="line-52"></a><a name="SinkIOResult"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>SinkIOResult</span> <span class='hs-varid'>input</span> <span class='hs-varid'>output</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>IODone</span> <span class='hs-layout'>(</span><span class='hs-conid'>Maybe</span> <span class='hs-varid'>input</span><span class='hs-layout'>)</span> <span class='hs-varid'>output</span> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>IOProcessing</span>
<a name="line-53"></a>
<a name="line-54"></a><a name="sinkIO"></a><span class='hs-comment'>-- | Construct a 'Sink'. Note that your push and close functions need not</span>
<a name="line-55"></a><span class='hs-comment'>-- explicitly perform any cleanup.</span>
<a name="line-56"></a><span class='hs-comment'>--</span>
<a name="line-57"></a><span class='hs-comment'>-- Since 0.2.0</span>
<a name="line-58"></a><span class='hs-definition'>sinkIO</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>ResourceIO</span> <span class='hs-varid'>m</span>
<a name="line-59"></a> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>state</span> <span class='hs-comment'>-- ^ resource and/or state allocation</span>
<a name="line-60"></a> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>state</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-conid'>()</span><span class='hs-layout'>)</span> <span class='hs-comment'>-- ^ resource and/or state cleanup</span>
<a name="line-61"></a> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>state</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>input</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-layout'>(</span><span class='hs-conid'>SinkIOResult</span> <span class='hs-varid'>input</span> <span class='hs-varid'>output</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-comment'>-- ^ push</span>
<a name="line-62"></a> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>state</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-varid'>output</span><span class='hs-layout'>)</span> <span class='hs-comment'>-- ^ close</span>
<a name="line-63"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Sink</span> <span class='hs-varid'>input</span> <span class='hs-varid'>m</span> <span class='hs-varid'>output</span>
<a name="line-64"></a><span class='hs-definition'>sinkIO</span> <span class='hs-varid'>alloc</span> <span class='hs-varid'>cleanup</span> <span class='hs-varid'>push0</span> <span class='hs-varid'>close0</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>SinkData</span>
<a name="line-65"></a> <span class='hs-layout'>{</span> <span class='hs-varid'>sinkPush</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>input</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>do</span>
<a name="line-66"></a> <span class='hs-layout'>(</span><span class='hs-varid'>key</span><span class='hs-layout'>,</span> <span class='hs-varid'>state</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>withIO</span> <span class='hs-varid'>alloc</span> <span class='hs-varid'>cleanup</span>
<a name="line-67"></a> <span class='hs-varid'>push</span> <span class='hs-varid'>key</span> <span class='hs-varid'>state</span> <span class='hs-varid'>input</span>
<a name="line-68"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>sinkClose</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-69"></a> <span class='hs-layout'>(</span><span class='hs-varid'>key</span><span class='hs-layout'>,</span> <span class='hs-varid'>state</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>withIO</span> <span class='hs-varid'>alloc</span> <span class='hs-varid'>cleanup</span>
<a name="line-70"></a> <span class='hs-varid'>close</span> <span class='hs-varid'>key</span> <span class='hs-varid'>state</span>
<a name="line-71"></a> <span class='hs-layout'>}</span>
<a name="line-72"></a> <span class='hs-keyword'>where</span>
<a name="line-73"></a> <span class='hs-varid'>push</span> <span class='hs-varid'>key</span> <span class='hs-varid'>state</span> <span class='hs-varid'>input</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-74"></a> <span class='hs-varid'>res</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>lift</span> <span class='hs-varop'>$</span> <span class='hs-varid'>push0</span> <span class='hs-varid'>state</span> <span class='hs-varid'>input</span>
<a name="line-75"></a> <span class='hs-keyword'>case</span> <span class='hs-varid'>res</span> <span class='hs-keyword'>of</span>
<a name="line-76"></a> <span class='hs-conid'>IODone</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>do</span>
<a name="line-77"></a> <span class='hs-varid'>release</span> <span class='hs-varid'>key</span>
<a name="line-78"></a> <span class='hs-varid'>return</span> <span class='hs-varop'>$</span> <span class='hs-conid'>Done</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span>
<a name="line-79"></a> <span class='hs-conid'>IOProcessing</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>return</span> <span class='hs-varop'>$</span> <span class='hs-conid'>Processing</span>
<a name="line-80"></a> <span class='hs-layout'>(</span><span class='hs-varid'>push</span> <span class='hs-varid'>key</span> <span class='hs-varid'>state</span><span class='hs-layout'>)</span>
<a name="line-81"></a> <span class='hs-layout'>(</span><span class='hs-varid'>close</span> <span class='hs-varid'>key</span> <span class='hs-varid'>state</span><span class='hs-layout'>)</span>
<a name="line-82"></a> <span class='hs-varid'>close</span> <span class='hs-varid'>key</span> <span class='hs-varid'>state</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-83"></a> <span class='hs-varid'>res</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>lift</span> <span class='hs-varop'>$</span> <span class='hs-varid'>close0</span> <span class='hs-varid'>state</span>
<a name="line-84"></a> <span class='hs-varid'>release</span> <span class='hs-varid'>key</span>
<a name="line-85"></a> <span class='hs-varid'>return</span> <span class='hs-varid'>res</span>
<a name="line-86"></a>
<a name="line-87"></a><a name="transSink"></a><span class='hs-comment'>-- | Transform the monad a 'Sink' lives in.</span>
<a name="line-88"></a><span class='hs-comment'>--</span>
<a name="line-89"></a><span class='hs-comment'>-- See @transSource@ for more information.</span>
<a name="line-90"></a><span class='hs-comment'>--</span>
<a name="line-91"></a><span class='hs-comment'>-- Since 0.2.0</span>
<a name="line-92"></a><span class='hs-definition'>transSink</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Base</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>~</span> <span class='hs-conid'>Base</span> <span class='hs-varid'>n</span><span class='hs-layout'>,</span> <span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span>
<a name="line-93"></a> <span class='hs-keyglyph'>=></span> <span class='hs-layout'>(</span><span class='hs-keyword'>forall</span> <span class='hs-varid'>a</span><span class='hs-varop'>.</span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>n</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-94"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Sink</span> <span class='hs-varid'>input</span> <span class='hs-varid'>m</span> <span class='hs-varid'>output</span>
<a name="line-95"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Sink</span> <span class='hs-varid'>input</span> <span class='hs-varid'>n</span> <span class='hs-varid'>output</span>
<a name="line-96"></a><span class='hs-definition'>transSink</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>SinkNoData</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>SinkNoData</span> <span class='hs-varid'>x</span>
<a name="line-97"></a><span class='hs-definition'>transSink</span> <span class='hs-varid'>f</span> <span class='hs-layout'>(</span><span class='hs-conid'>SinkLift</span> <span class='hs-varid'>msink</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>SinkLift</span> <span class='hs-layout'>(</span><span class='hs-varid'>transResourceT</span> <span class='hs-varid'>f</span> <span class='hs-layout'>(</span><span class='hs-varid'>liftM</span> <span class='hs-layout'>(</span><span class='hs-varid'>transSink</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-varid'>msink</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-98"></a><span class='hs-definition'>transSink</span> <span class='hs-varid'>f</span> <span class='hs-layout'>(</span><span class='hs-conid'>SinkData</span> <span class='hs-varid'>push</span> <span class='hs-varid'>close</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>SinkData</span>
<a name="line-99"></a> <span class='hs-layout'>(</span><span class='hs-varid'>transResourceT</span> <span class='hs-varid'>f</span> <span class='hs-varop'>.</span> <span class='hs-varid'>fmap</span> <span class='hs-layout'>(</span><span class='hs-varid'>transSinkPush</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-varop'>.</span> <span class='hs-varid'>push</span><span class='hs-layout'>)</span>
<a name="line-100"></a> <span class='hs-layout'>(</span><span class='hs-varid'>transResourceT</span> <span class='hs-varid'>f</span> <span class='hs-varid'>close</span><span class='hs-layout'>)</span>
<a name="line-101"></a>
<a name="line-102"></a><a name="transSinkPush"></a><span class='hs-definition'>transSinkPush</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Base</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>~</span> <span class='hs-conid'>Base</span> <span class='hs-varid'>n</span><span class='hs-layout'>,</span> <span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span>
<a name="line-103"></a> <span class='hs-keyglyph'>=></span> <span class='hs-layout'>(</span><span class='hs-keyword'>forall</span> <span class='hs-varid'>a</span><span class='hs-varop'>.</span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>n</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-104"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>SinkResult</span> <span class='hs-varid'>input</span> <span class='hs-varid'>m</span> <span class='hs-varid'>output</span>
<a name="line-105"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>SinkResult</span> <span class='hs-varid'>input</span> <span class='hs-varid'>n</span> <span class='hs-varid'>output</span>
<a name="line-106"></a><span class='hs-definition'>transSinkPush</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>Done</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Done</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span>
<a name="line-107"></a><span class='hs-definition'>transSinkPush</span> <span class='hs-varid'>f</span> <span class='hs-layout'>(</span><span class='hs-conid'>Processing</span> <span class='hs-varid'>push</span> <span class='hs-varid'>close</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Processing</span>
<a name="line-108"></a> <span class='hs-layout'>(</span><span class='hs-varid'>transResourceT</span> <span class='hs-varid'>f</span> <span class='hs-varop'>.</span> <span class='hs-varid'>fmap</span> <span class='hs-layout'>(</span><span class='hs-varid'>transSinkPush</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-varop'>.</span> <span class='hs-varid'>push</span><span class='hs-layout'>)</span>
<a name="line-109"></a> <span class='hs-layout'>(</span><span class='hs-varid'>transResourceT</span> <span class='hs-varid'>f</span> <span class='hs-varid'>close</span><span class='hs-layout'>)</span>
</pre></body>
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