gistfile1.rb

    def from_url(url)
      raise "No url specified" if url.nil?
      easy = Curl::Easy.perform(url) do |c|
        c.headers["If-Modified-Since"] = @last_modified unless @last_modified.nil?
        c.headers["If-None-Match"] = @etag unless @etag.nil?
        c.follow_location = true
      end
      if easy.response_code == 200
        @source_url = url
        parse_response(easy)
      elsif easy.response_code != 304 #not modified is fine
        raise
      end

      easy.response_code
    end