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<title>Network/Wai/Middleware/Gzip.hs</title>
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<pre><a name="line-1"></a><span class='hs-comment'>{-# LANGUAGE Rank2Types #-}</span>
<a name="line-2"></a><span class='hs-comment'>{-# LANGUAGE ScopedTypeVariables #-}</span>
<a name="line-3"></a><span class='hs-comment'>{-# LANGUAGE OverloadedStrings #-}</span>
<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 : Network.Wai.Middleware.Gzip</span>
<a name="line-7"></a><span class='hs-comment'>-- Copyright : Michael Snoyman</span>
<a name="line-8"></a><span class='hs-comment'>-- License : BSD3</span>
<a name="line-9"></a><span class='hs-comment'>--</span>
<a name="line-10"></a><span class='hs-comment'>-- Maintainer : Michael Snoyman <michael@snoyman.com></span>
<a name="line-11"></a><span class='hs-comment'>-- Stability : Unstable</span>
<a name="line-12"></a><span class='hs-comment'>-- Portability : portable</span>
<a name="line-13"></a><span class='hs-comment'>--</span>
<a name="line-14"></a><span class='hs-comment'>-- Automatic gzip compression of responses.</span>
<a name="line-15"></a><span class='hs-comment'>--</span>
<a name="line-16"></a><span class='hs-comment'>---------------------------------------------------------</span>
<a name="line-17"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Network</span><span class='hs-varop'>.</span><span class='hs-conid'>Wai</span><span class='hs-varop'>.</span><span class='hs-conid'>Middleware</span><span class='hs-varop'>.</span><span class='hs-conid'>Gzip</span> <span class='hs-layout'>(</span><span class='hs-varid'>gzip</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-18"></a>
<a name="line-19"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Network</span><span class='hs-varop'>.</span><span class='hs-conid'>Wai</span>
<a name="line-20"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Network</span><span class='hs-varop'>.</span><span class='hs-conid'>Wai</span><span class='hs-varop'>.</span><span class='hs-conid'>Zlib</span>
<a name="line-21"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Maybe</span> <span class='hs-layout'>(</span><span class='hs-varid'>fromMaybe</span><span class='hs-layout'>)</span>
<a name="line-22"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Enumerator</span> <span class='hs-layout'>(</span><span class='hs-layout'>(</span><span class='hs-varop'>$$</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-varid'>joinI</span><span class='hs-layout'>)</span>
<a name="line-23"></a><span class='hs-keyword'>import</span> <span class='hs-keyword'>qualified</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span><span class='hs-varop'>.</span><span class='hs-conid'>Char8</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>S8</span>
<a name="line-24"></a><span class='hs-keyword'>import</span> <span class='hs-keyword'>qualified</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>S</span>
<a name="line-25"></a>
<a name="line-26"></a><a name="gzip"></a><span class='hs-comment'>-- | Use gzip to compress the body of the response.</span>
<a name="line-27"></a><span class='hs-comment'>--</span>
<a name="line-28"></a><span class='hs-comment'>-- Analyzes the \"Accept-Encoding\" header from the client to determine</span>
<a name="line-29"></a><span class='hs-comment'>-- if gzip is supported.</span>
<a name="line-30"></a><span class='hs-comment'>--</span>
<a name="line-31"></a><span class='hs-comment'>-- Possible future enhancements:</span>
<a name="line-32"></a><span class='hs-comment'>--</span>
<a name="line-33"></a><span class='hs-comment'>-- * Only compress if the response is above a certain size.</span>
<a name="line-34"></a><span class='hs-comment'>--</span>
<a name="line-35"></a><span class='hs-comment'>-- * I've read that IE can\'t support compression for Javascript files.</span>
<a name="line-36"></a><span class='hs-definition'>gzip</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Bool</span> <span class='hs-comment'>-- ^ should we gzip files?</span>
<a name="line-37"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Middleware</span>
<a name="line-38"></a><span class='hs-definition'>gzip</span> <span class='hs-varid'>files</span> <span class='hs-varid'>app</span> <span class='hs-varid'>env</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-39"></a> <span class='hs-varid'>res</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>app</span> <span class='hs-varid'>env</span>
<a name="line-40"></a> <span class='hs-varid'>return</span> <span class='hs-varop'>$</span>
<a name="line-41"></a> <span class='hs-keyword'>case</span> <span class='hs-varid'>res</span> <span class='hs-keyword'>of</span>
<a name="line-42"></a> <span class='hs-conid'>ResponseFile</span><span class='hs-layout'>{</span><span class='hs-layout'>}</span> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>not</span> <span class='hs-varid'>files</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>res</span>
<a name="line-43"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>if</span> <span class='hs-str'>"gzip"</span> <span class='hs-varop'>`elem`</span> <span class='hs-varid'>enc</span> <span class='hs-varop'>&&</span> <span class='hs-varid'>not</span> <span class='hs-varid'>isMSIE6</span>
<a name="line-44"></a> <span class='hs-keyword'>then</span> <span class='hs-conid'>ResponseEnumerator</span> <span class='hs-varop'>$</span> <span class='hs-varid'>compressE</span> <span class='hs-varop'>$</span> <span class='hs-varid'>responseEnumerator</span> <span class='hs-varid'>res</span>
<a name="line-45"></a> <span class='hs-keyword'>else</span> <span class='hs-varid'>res</span>
<a name="line-46"></a> <span class='hs-keyword'>where</span>
<a name="line-47"></a> <span class='hs-varid'>enc</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>fromMaybe</span> <span class='hs-conid'>[]</span> <span class='hs-varop'>$</span> <span class='hs-layout'>(</span><span class='hs-varid'>splitCommas</span> <span class='hs-varop'>.</span> <span class='hs-conid'>S8</span><span class='hs-varop'>.</span><span class='hs-varid'>unpack</span><span class='hs-layout'>)</span>
<a name="line-48"></a> <span class='hs-varop'>`fmap`</span> <span class='hs-varid'>lookup</span> <span class='hs-str'>"Accept-Encoding"</span> <span class='hs-layout'>(</span><span class='hs-varid'>requestHeaders</span> <span class='hs-varid'>env</span><span class='hs-layout'>)</span>
<a name="line-49"></a> <span class='hs-varid'>ua</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>fromMaybe</span> <span class='hs-str'>""</span> <span class='hs-varop'>$</span> <span class='hs-varid'>lookup</span> <span class='hs-str'>"user-agent"</span> <span class='hs-varop'>$</span> <span class='hs-varid'>requestHeaders</span> <span class='hs-varid'>env</span>
<a name="line-50"></a> <span class='hs-varid'>isMSIE6</span> <span class='hs-keyglyph'>=</span> <span class='hs-str'>"MSIE 6"</span> <span class='hs-varop'>`</span><span class='hs-conid'>S</span><span class='hs-varop'>.</span><span class='hs-varid'>isInfixOf</span><span class='hs-varop'>`</span> <span class='hs-varid'>ua</span>
<a name="line-51"></a>
<a name="line-52"></a><a name="compressE"></a><span class='hs-definition'>compressE</span> <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-conid'>ResponseEnumerator</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-53"></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-conid'>ResponseEnumerator</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-54"></a><span class='hs-definition'>compressE</span> <span class='hs-varid'>re</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span>
<a name="line-55"></a> <span class='hs-varid'>re</span> <span class='hs-varid'>f'</span>
<a name="line-56"></a> <span class='hs-comment'>--e s hs'</span>
<a name="line-57"></a> <span class='hs-keyword'>where</span>
<a name="line-58"></a> <span class='hs-varid'>f'</span> <span class='hs-varid'>s</span> <span class='hs-varid'>hs</span> <span class='hs-keyglyph'>=</span>
<a name="line-59"></a> <span class='hs-varid'>joinI</span> <span class='hs-varop'>$</span> <span class='hs-varid'>compress</span> <span class='hs-varop'>$$</span> <span class='hs-varid'>f</span> <span class='hs-varid'>s</span> <span class='hs-varid'>hs'</span>
<a name="line-60"></a> <span class='hs-keyword'>where</span>
<a name="line-61"></a> <span class='hs-comment'>-- Remove Content-Length header, since we will certainly have a</span>
<a name="line-62"></a> <span class='hs-comment'>-- different length after gzip compression.</span>
<a name="line-63"></a> <span class='hs-varid'>hs'</span> <span class='hs-keyglyph'>=</span> <span class='hs-layout'>(</span><span class='hs-str'>"Content-Encoding"</span><span class='hs-layout'>,</span> <span class='hs-str'>"gzip"</span><span class='hs-layout'>)</span> <span class='hs-conop'>:</span> <span class='hs-varid'>filter</span> <span class='hs-varid'>notLength</span> <span class='hs-varid'>hs</span>
<a name="line-64"></a> <span class='hs-varid'>notLength</span> <span class='hs-layout'>(</span><span class='hs-varid'>x</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>x</span> <span class='hs-varop'>/=</span> <span class='hs-str'>"content-length"</span>
<a name="line-65"></a>
<a name="line-66"></a><a name="splitCommas"></a><span class='hs-definition'>splitCommas</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>String</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>String</span><span class='hs-keyglyph'>]</span>
<a name="line-67"></a><span class='hs-definition'>splitCommas</span> <span class='hs-conid'>[]</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>[]</span>
<a name="line-68"></a><span class='hs-definition'>splitCommas</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span>
<a name="line-69"></a> <span class='hs-keyword'>let</span> <span class='hs-layout'>(</span><span class='hs-varid'>y</span><span class='hs-layout'>,</span> <span class='hs-varid'>z</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>break</span> <span class='hs-layout'>(</span><span class='hs-varop'>==</span> <span class='hs-chr'>','</span><span class='hs-layout'>)</span> <span class='hs-varid'>x</span>
<a name="line-70"></a> <span class='hs-keyword'>in</span> <span class='hs-varid'>y</span> <span class='hs-conop'>:</span> <span class='hs-varid'>splitCommas</span> <span class='hs-layout'>(</span><span class='hs-varid'>dropWhile</span> <span class='hs-layout'>(</span><span class='hs-varop'>==</span> <span class='hs-chr'>' '</span><span class='hs-layout'>)</span> <span class='hs-varop'>$</span> <span class='hs-varid'>drop</span> <span class='hs-num'>1</span> <span class='hs-varid'>z</span><span class='hs-layout'>)</span>
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