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<pre><a name="line-1"></a><span class='hs-comment'>{-# LANGUAGE FlexibleContexts #-}</span>
<a name="line-2"></a><span class='hs-comment'>-- | Defines the types for a source, which is a producer of data.</span>
<a name="line-3"></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'>Types</span><span class='hs-varop'>.</span><span class='hs-conid'>Source</span>
<a name="line-4"></a> <span class='hs-layout'>(</span> <span class='hs-conid'>SourceResult</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span>
<a name="line-5"></a> <span class='hs-layout'>,</span> <span class='hs-conid'>Source</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span>
<a name="line-6"></a> <span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-7"></a>
<a name="line-8"></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-9"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Monoid</span> <span class='hs-layout'>(</span><span class='hs-conid'>Monoid</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-10"></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-11"></a>
<a name="line-12"></a><a name="SourceResult"></a><span class='hs-comment'>-- | Result of pulling from a source. Either a new piece of data (@Open@), or</span>
<a name="line-13"></a><a name="SourceResult"></a><span class='hs-comment'>-- indicates that the source is now @Closed@.</span>
<a name="line-14"></a><a name="SourceResult"></a><span class='hs-comment'>--</span>
<a name="line-15"></a><a name="SourceResult"></a><span class='hs-comment'>-- The @Open@ constructor returns both a new value, as well as a new @Source@,</span>
<a name="line-16"></a><a name="SourceResult"></a><span class='hs-comment'>-- which should be used in place of the previous @Source@.</span>
<a name="line-17"></a><a name="SourceResult"></a><span class='hs-comment'>--</span>
<a name="line-18"></a><a name="SourceResult"></a><span class='hs-comment'>-- Since 0.2.0</span>
<a name="line-19"></a><a name="SourceResult"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>SourceResult</span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Open</span> <span class='hs-layout'>(</span><span class='hs-conid'>Source</span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>Closed</span>
<a name="line-20"></a>
<a name="line-21"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Functor</span> <span class='hs-layout'>(</span><span class='hs-conid'>SourceResult</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-22"></a> <span class='hs-varid'>fmap</span> <span class='hs-varid'>f</span> <span class='hs-layout'>(</span><span class='hs-conid'>Open</span> <span class='hs-varid'>p</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Open</span> <span class='hs-layout'>(</span><span class='hs-varid'>fmap</span> <span class='hs-varid'>f</span> <span class='hs-varid'>p</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>f</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-23"></a> <span class='hs-varid'>fmap</span> <span class='hs-keyword'>_</span> <span class='hs-conid'>Closed</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Closed</span>
<a name="line-24"></a>
<a name="line-25"></a><a name="Source"></a><span class='hs-comment'>-- | A @Source@ has two operations on it: pull some data, and close the</span>
<a name="line-26"></a><a name="Source"></a><span class='hs-comment'>-- @Source@. Since @Source@ is built on top of 'ResourceT', all acquired</span>
<a name="line-27"></a><a name="Source"></a><span class='hs-comment'>-- resources should be automatically released anyway. Closing a @Source@ early</span>
<a name="line-28"></a><a name="Source"></a><span class='hs-comment'>-- is merely an optimization to free scarce resources as soon as possible.</span>
<a name="line-29"></a><a name="Source"></a><span class='hs-comment'>--</span>
<a name="line-30"></a><a name="Source"></a><span class='hs-comment'>-- A @Source@ is should free any resources it allocated when either</span>
<a name="line-31"></a><a name="Source"></a><span class='hs-comment'>-- @sourceClose@ is called or a @Closed@ is returned. However, based on the</span>
<a name="line-32"></a><a name="Source"></a><span class='hs-comment'>-- usage of @ResourceT@, this is simply an optimization.</span>
<a name="line-33"></a><a name="Source"></a><span class='hs-comment'>--</span>
<a name="line-34"></a><a name="Source"></a><span class='hs-comment'>-- Since 0.2.0</span>
<a name="line-35"></a><a name="Source"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>Source</span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Source</span>
<a name="line-36"></a> <span class='hs-layout'>{</span> <span class='hs-varid'>sourcePull</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'>SourceResult</span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-37"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>sourceClose</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>ResourceT</span> <span class='hs-varid'>m</span> <span class='hs-conid'>()</span>
<a name="line-38"></a> <span class='hs-layout'>}</span>
<a name="line-39"></a>
<a name="line-40"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Functor</span> <span class='hs-layout'>(</span><span class='hs-conid'>Source</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-41"></a> <span class='hs-varid'>fmap</span> <span class='hs-varid'>f</span> <span class='hs-varid'>src</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>src</span>
<a name="line-42"></a> <span class='hs-layout'>{</span> <span class='hs-varid'>sourcePull</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>liftM</span> <span class='hs-layout'>(</span><span class='hs-varid'>fmap</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>sourcePull</span> <span class='hs-varid'>src</span><span class='hs-layout'>)</span>
<a name="line-43"></a> <span class='hs-layout'>}</span>
<a name="line-44"></a>
<a name="line-45"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Resource</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Monoid</span> <span class='hs-layout'>(</span><span class='hs-conid'>Source</span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-46"></a> <span class='hs-varid'>mempty</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Source</span>
<a name="line-47"></a> <span class='hs-layout'>{</span> <span class='hs-varid'>sourcePull</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>return</span> <span class='hs-conid'>Closed</span>
<a name="line-48"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>sourceClose</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>return</span> <span class='hs-conid'>()</span>
<a name="line-49"></a> <span class='hs-layout'>}</span>
<a name="line-50"></a> <span class='hs-varid'>mappend</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>mconcat</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-varid'>b</span><span class='hs-keyglyph'>]</span>
<a name="line-51"></a> <span class='hs-varid'>mconcat</span> <span class='hs-conid'>[]</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>mempty</span>
<a name="line-52"></a> <span class='hs-varid'>mconcat</span> <span class='hs-layout'>(</span><span class='hs-varid'>next0</span><span class='hs-conop'>:</span><span class='hs-varid'>rest0</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span>
<a name="line-53"></a> <span class='hs-varid'>src</span> <span class='hs-varid'>next0</span> <span class='hs-varid'>rest0</span>
<a name="line-54"></a> <span class='hs-keyword'>where</span>
<a name="line-55"></a> <span class='hs-varid'>src</span> <span class='hs-varid'>next</span> <span class='hs-varid'>rest</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Source</span> <span class='hs-layout'>(</span><span class='hs-varid'>pull</span> <span class='hs-varid'>next</span> <span class='hs-varid'>rest</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>close</span> <span class='hs-varid'>next</span> <span class='hs-varid'>rest</span><span class='hs-layout'>)</span>
<a name="line-56"></a>
<a name="line-57"></a> <span class='hs-varid'>pull</span> <span class='hs-varid'>current</span> <span class='hs-varid'>rest</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-58"></a> <span class='hs-varid'>res</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>sourcePull</span> <span class='hs-varid'>current</span>
<a name="line-59"></a> <span class='hs-keyword'>case</span> <span class='hs-varid'>res</span> <span class='hs-keyword'>of</span>
<a name="line-60"></a> <span class='hs-comment'>-- end of the current Source</span>
<a name="line-61"></a> <span class='hs-conid'>Closed</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>do</span>
<a name="line-62"></a> <span class='hs-keyword'>case</span> <span class='hs-varid'>rest</span> <span class='hs-keyword'>of</span>
<a name="line-63"></a> <span class='hs-comment'>-- ... and open the next one</span>
<a name="line-64"></a> <span class='hs-varid'>a</span><span class='hs-conop'>:</span><span class='hs-keyword'>as</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>pull</span> <span class='hs-varid'>a</span> <span class='hs-keyword'>as</span>
<a name="line-65"></a> <span class='hs-comment'>-- no more source, return an EOF</span>
<a name="line-66"></a> <span class='hs-conid'>[]</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>return</span> <span class='hs-conid'>Closed</span>
<a name="line-67"></a> <span class='hs-conid'>Open</span> <span class='hs-varid'>current'</span> <span class='hs-varid'>val</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-conid'>Open</span> <span class='hs-layout'>(</span><span class='hs-varid'>src</span> <span class='hs-varid'>current'</span> <span class='hs-varid'>rest</span><span class='hs-layout'>)</span> <span class='hs-varid'>val</span><span class='hs-layout'>)</span>
<a name="line-68"></a> <span class='hs-varid'>close</span> <span class='hs-varid'>current</span> <span class='hs-sel'>_rest</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-69"></a> <span class='hs-comment'>-- we only need to close the current Source, since they are opened</span>
<a name="line-70"></a> <span class='hs-comment'>-- one at a time</span>
<a name="line-71"></a> <span class='hs-varid'>sourceClose</span> <span class='hs-varid'>current</span>
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