call

# File actionpack/lib/action_controller/vendor/rack-1.0/rack/deflater.rb, line 12
    def call(env)
      status, headers, body = @app.call(env)
      headers = Utils::HeaderHash.new(headers)

      # Skip compressing empty entity body responses and responses with
      # no-transform set.
      if Utils::STATUS_WITH_NO_ENTITY_BODY.include?(status) ||
          headers['Cache-Control'].to_s =~ /\bno-transform\b/
        return [status, headers, body]
      end

      request = Request.new(env)

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

      # Set the Vary HTTP header.
      vary = headers["Vary"].to_s.split(",").map { |v| v.strip }
      unless vary.include?("*") || vary.include?("Accept-Encoding")
        headers["Vary"] = vary.push("Accept-Encoding").join(",")
      end

      case encoding
      when "gzip"
        mtime = headers.key?("Last-Modified") ?
          Time.httpdate(headers["Last-Modified"]) : Time.now
        body = self.class.gzip(body, mtime)
        size = Rack::Utils.bytesize(body)
        headers = headers.merge("Content-Encoding" => "gzip", "Content-Length" => size.to_s)
        [status, headers, [body]]
      when "deflate"
        body = self.class.deflate(body)
        size = Rack::Utils.bytesize(body)
        headers = headers.merge("Content-Encoding" => "deflate", "Content-Length" => size.to_s)
        [status, headers, [body]]
      when "identity"
        [status, headers, body]
      when nil
        message = "An acceptable encoding for the requested resource #{request.fullpath} could not be found."
        [406, {"Content-Type" => "text/plain", "Content-Length" => message.length.to_s}, [message]]
      end
    end