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<title>class Rack::Deflater - rack-2.2.10 Documentation</title>

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 <h1 id="class-Rack::Deflater" class="class">
 class Rack::Deflater
 </h1>

<section class="description">
 
This middleware enables content encoding of http responses, usually for purposes of compression.

Currently supported encodings:
<ul><li>
gzip
</li><li>
identity (no transformation)
</li></ul>

This middleware automatically detects when encoding is supported and allowed. For example no encoding is made when a cache directive of &#39;no-transform&#39; is present, when the response status code is one that doesn&#39;t allow an entity body, or when the body is empty.

Note that despite the name, <a href="Deflater.html"><code>Deflater</code></a> does not support the <code>deflate</code> encoding.

</section>

<section id="public-class-5Buntitled-5D-method-details" class="method-section">
 <header>
 <h3>Public Class Methods</h3>
 </header>

<div id="method-c-new" class="method-detail ">
 
 <div class="method-heading">
 new(app, options = {})
 
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 </div>

<div class="method-description">
 
 Creates <a href="Deflater.html"><code>Rack::Deflater</code></a> middleware. Options:
<dl class="rdoc-list note-list"><dt>:if 
<dd>
a lambda enabling / disabling deflation based on returned boolean value (e.g <code>use Rack::Deflater, :if =&gt; lambda { |*, body| sum=0; body.each { |i| sum += i.length }; sum &gt; 512 }</code>). However, be aware that calling `body.each` inside the block will break cases where `body.each` is not idempotent, such as when it is an <code>IO</code> instance.
</dd><dt>:include 
<dd>
a list of content types that should be compressed. By default, all content types are compressed.
</dd><dt>:sync 
<dd>
determines if the stream is going to be flushed after every chunk. Flushing after every chunk reduces latency for time-sensitive streaming applications, but hurts compression and throughput. Defaults to <code>true</code>.
</dd></dl>

<div class="method-source-code" id="new-source">
 <pre># File lib/rack/deflater.rb, line 36
def initialize(app, options = {})
 @app = app
 @condition = options[:if]
 @compressible_types = options[:include]
 @sync = options.fetch(:sync, true)
end</pre>
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</section>
 
 <section id="public-instance-5Buntitled-5D-method-details" class="method-section">
 <header>
 <h3>Public Instance Methods</h3>
 </header>

<div id="method-i-call" class="method-detail ">
 
 <div class="method-heading">
 call(env)
 
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<div class="method-source-code" id="call-source">
 <pre># File lib/rack/deflater.rb, line 43
def call(env)
 status, headers, body = @app.call(env)
 headers = Utils::HeaderHash[headers]

unless should_deflate?(env, status, headers, body)
 return [status, headers, body]
 end

request = Request.new(env)

encoding = Utils.select_best_encoding(%w(gzip identity),
 request.accept_encoding)

# Set the Vary HTTP header.
 vary = headers[&quot;Vary&quot;].to_s.split(&quot;,&quot;).map(&amp;:strip)
 unless vary.include?(&quot;*&quot;) || vary.include?(&quot;Accept-Encoding&quot;)
 headers[&quot;Vary&quot;] = vary.push(&quot;Accept-Encoding&quot;).join(&quot;,&quot;)
 end

case encoding
 when &quot;gzip&quot;
 headers[&#39;Content-Encoding&#39;] = &quot;gzip&quot;
 headers.delete(CONTENT_LENGTH)
 mtime = headers[&quot;Last-Modified&quot;]
 mtime = Time.httpdate(mtime).to_i if mtime
 [status, headers, GzipStream.new(body, mtime, @sync)]
 when &quot;identity&quot;
 [status, headers, body]
 when nil
 message = &quot;An acceptable encoding for the requested resource #{request.fullpath} could not be found.&quot;
 bp = Rack::BodyProxy.new([message]) { body.close if body.respond_to?(:close) }
 [406, { CONTENT_TYPE =&gt; &quot;text/plain&quot;, CONTENT_LENGTH =&gt; message.length.to_s }, bp]
 end
end</pre>
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</section>
 
 <section id="private-instance-5Buntitled-5D-method-details" class="method-section">
 <header>
 <h3>Private Instance Methods</h3>
 </header>

<div id="method-i-should_deflate-3F" class="method-detail ">
 
 <div class="method-heading">
 should_deflate?(env, status, headers, body)
 
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 </div>

<div class="method-description">
 
 Whether the body should be compressed.

<div class="method-source-code" id="should_deflate-3F-source">
 <pre># File lib/rack/deflater.rb, line 122
def should_deflate?(env, status, headers, body)
 # Skip compressing empty entity body responses and responses with
 # no-transform set.
 if Utils::STATUS_WITH_NO_ENTITY_BODY.key?(status.to_i) ||
 /\bno-transform\b/.match?(headers[&#39;Cache-Control&#39;].to_s) ||
 headers[&#39;Content-Encoding&#39;]&amp;.!~(/\bidentity\b/)
 return false
 end

# Skip if @compressible_types are given and does not include request&#39;s content type
 return false if @compressible_types &amp;&amp; !(headers.has_key?(&#39;Content-Type&#39;) &amp;&amp; @compressible_types.include?(headers[&#39;Content-Type&#39;][/[^;]*/]))

# Skip if @condition lambda is given and evaluates to false
 return false if @condition &amp;&amp; !@condition.call(env, status, headers, body)

# No point in compressing empty body, also handles usage with
 # Rack::Sendfile.
 return false if headers[CONTENT_LENGTH] == &#39;0&#39;

true
end</pre>
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