Class: Rack::Deflater

Inherits:
Object
  • Object
show all
Defined in:
lib/rack/deflater.rb

Overview

This middleware enables compression of http responses.

Currently supported compression algorithms:

* gzip
* identity (no transformation)

The middleware automatically detects when compression is supported and allowed. For example no transformation is made when a cache directive of ‘no-transform’ is present, or when the response status code is one that doesn’t allow an entity body.

Defined Under Namespace

Classes: GzipStream

Instance Method Summary collapse

Constructor Details

#initialize(app, options = {}) ⇒ Deflater

Creates Rack::Deflater middleware.

app

rack app instance

options

hash of deflater options, i.e. ‘if’ - a lambda enabling / disabling deflation based on returned boolean value

e.g use Rack::Deflater, :if => lambda { |*, body| sum=0; body.each { |i| sum += i.length }; sum > 512 }

‘include’ - a list of content types that should be compressed ‘sync’ - 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 `true'.



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# File 'lib/rack/deflater.rb', line 36

def initialize(app, options = {})
  @app = app

  @condition = options[:if]
  @compressible_types = options[:include]
  @sync = options[:sync] == false ? false : true
end

Instance Method Details

#call(env) ⇒ Object 



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# File 'lib/rack/deflater.rb', line 44

def call(env)
  status, headers, body = @app.call(env)
  headers = Utils::HeaderHash.new(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["Vary"].to_s.split(",").map(&:strip)
  unless vary.include?("*") || vary.include?("Accept-Encoding")
    headers["Vary"] = vary.push("Accept-Encoding").join(",")
  end

  case encoding
  when "gzip"
    headers['Content-Encoding'] = "gzip"
    headers.delete('Content-Length')
    mtime = headers["Last-Modified"]
    mtime = Time.httpdate(mtime).to_i if mtime
    [status, headers, GzipStream.new(body, mtime, @sync)]
  when "identity"
    [status, headers, body]
  when nil
    message = "An acceptable encoding for the requested resource #{request.fullpath} could not be found."
    bp = Rack::BodyProxy.new([message]) { body.close if body.respond_to?(:close) }
    [406, { 'Content-Type' => "text/plain", 'Content-Length' => message.length.to_s }, bp]
  end
end