not_modified?

# File lib/webrick/httpservlet/filehandler.rb, line 47
      def not_modified?(req, res, mtime, etag)
        if ir = req['if-range']
          begin
            if Time.httpdate(ir) >= mtime
              return true
            end
          rescue
            if HTTPUtils::split_header_value(ir).member?(res['etag'])
              return true
            end
          end
        end

        if (ims = req['if-modified-since']) && Time.parse(ims) >= mtime
          return true
        end

        if (inm = req['if-none-match']) &&
           HTTPUtils::split_header_value(inm).member?(res['etag'])
          return true
        end

        return false
      end