# File lib/fog/google/storage.rb, line 205
        def signature(params)
          string_to_sign =
"\#{params[:method]}\n\#{params[:headers]['Content-MD5']}\n\#{params[:headers]['Content-Type']}\n\#{params[:headers]['Date']}\n"

          google_headers, canonical_google_headers = {}, ''
          for key, value in params[:headers]
            if key[0..6] == 'x-goog-'
              google_headers[key] = value
            end
          end

          google_headers = google_headers.sort {|x, y| x[0] <=> y[0]}
          for key, value in google_headers
            canonical_google_headers << "#{key}:#{value}\n"
          end
          string_to_sign << "#{canonical_google_headers}"

          subdomain = params[:host].split(".#{@host}").first
          unless subdomain =~ /^(?:[a-z]|\d(?!\d{0,2}(?:\.\d{1,3}){3}$))(?:[a-z0-9]|\.(?![\.\-])|\-(?![\.])){1,61}[a-z0-9]$/
            Fog::Logger.warning("fog: the specified google storage bucket name(#{subdomain}) is not a valid dns name.  See: http://code.google.com/apis/storage/docs/developer-guide.html#naming")
            params[:host] = params[:host].split("#{subdomain}.")[-1]
            if params[:path]
              params[:path] = "#{subdomain}/#{params[:path]}"
            else
              params[:path] = "#{subdomain}"
            end
            subdomain = nil
          end

          canonical_resource  = "/"
          unless subdomain.nil? || subdomain == @host
            canonical_resource << "#{CGI.escape(subdomain).downcase}/"
          end
          canonical_resource << "#{params[:path]}"
          canonical_resource << '?'
          for key in (params[:query] || {}).keys
            if ['acl', 'location', 'logging', 'requestPayment', 'torrent', 'versions', 'versioning'].include?(key)
              canonical_resource << "#{key}&"
            end
          end
          canonical_resource.chop!
          string_to_sign << "#{canonical_resource}"

          signed_string = @hmac.sign(string_to_sign)
          signature = Base64.encode64(signed_string).chomp!
        end