call (Rack::Deflater)

# File lib/rack/deflater.rb, line 34
    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 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"
        headers['Content-Encoding'] = "gzip"
        headers.delete(CONTENT_LENGTH)
        mtime = headers.key?("Last-Modified") ?
          Time.httpdate(headers["Last-Modified"]) : Time.now
        [status, headers, GzipStream.new(body, mtime)]
      when "deflate"
        headers['Content-Encoding'] = "deflate"
        headers.delete(CONTENT_LENGTH)
        [status, headers, DeflateStream.new(body)]
      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