MessageOptions: ensure decoding size

[jeanparpaillon]

See TODO:

    defp decode_extended(delta_sum, delta, length, tail) do
      {tail1, key} =
        cond do
          delta < 13 ->
            {tail, delta_sum + delta}

          delta == 13 ->
            # TODO: size here `::size(4)`?
            <<key, new_tail1::binary>> = tail
            {new_tail1, delta_sum + key + 13}

          delta == 14 ->
            <<key::size(16), new_tail1::binary>> = tail
            {new_tail1, delta_sum + key + 269}
        end

      {tail2, option_length} =
        cond do
          length < 13 ->
            {tail1, length}

          length == 13 ->
            # TODO: size here `::size(4)`?
            <<extended_option_length, new_tail2::binary>> = tail1
            {new_tail2, extended_option_length + 13}

          length == 14 ->
            <<extended_option_length::size(16), new_tail2::binary>> = tail1
            {new_tail2, extended_option_length + 269}
        end

      {key, option_length, tail2}
    end

[jeanparpaillon]

See also:

    defp encode([{key, value} | option_list], delta_sum, acc) do
      {delta, extended_number} =
        cond do
          key - delta_sum >= 269 ->
            {14, <<key - delta_sum - 269::size(16)>>}

          key - delta_sum >= 13 ->
            {13, <<key - delta_sum - 13>>}

          true ->
            {key - delta_sum, <<>>}
        end

      {length, extended_length} =
        cond do
          byte_size(value) >= 269 ->
            {14, <<byte_size(value) - 269::size(16)>>}

          byte_size(value) >= 13 ->
            {13, <<byte_size(value) - 13>>}

          true ->
            {byte_size(value), <<>>}
        end

      acc2 = <<
        acc::binary,
        delta::size(4),
        length::size(4),
        # TODO: what size should this be?
        extended_number::binary,
        extended_length::binary,
        value::binary
      >>

      encode(option_list, key, acc2)
    end