# File lib/net/sftp/protocol/01/attributes.rb, line 120
    def to_s
      flags = 0

      flags |= F_SIZE if @size
      flags |= F_UIDGID if @uid && @gid
      flags |= F_PERMISSIONS if @permissions
      flags |= F_ACMODTIME if @atime && @mtime
      flags |= F_EXTENDED if @extended

      buffer = buffers.writer
      buffer.write_long flags
      buffer.write_int64 @size if @size
      buffer.write_long @uid, @gid if @uid && @gid
      buffer.write_long @permissions if @permissions
      buffer.write_long @atime, @mtime if @atime && @mtime

      if @extended
        buffer.write_long @extended.size
        @extended.each { |k,v| buffer.write_string k, v }
      end

      buffer.to_s
    end