Re: Confusing illustration for 3.2.11

I'm not complaining, but this seems rather inconsistent.  We were careful
to make sure there was padding everywhere else, but now we don't care
whether the individual option elements are padded.  Seems odd.  We should
have padded everywhere or nowhere.  (Can't imagine how I missed this
before!)

Russell Butek
[email protected]


Henrik Frystyk Nielsen <[email protected]>@DISCUSS.DEVELOP.COM> on
08/28/2002 10:26:54 AM

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Subject:    Re: [DIME] Confusing illustration for 3.2.11



You are right that the illustration is not correct with respect to
representing the ELEMENT_DATA field: It is not padded and does not have
to be aligned to 4 octets. Only the overall OPTIONS element is 4 octet
aligned.

Would this diagram be better:

0                   1                   2                   3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|            ELEMENT_T          |         ELEMENT_LENGTH        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                         ELEMENT_DATA    ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ...

Henrik

>In the draft there's a illustration in section 3.2.11 showing
>the layout of ELEMENT_T, ELEMENT_LENGTH and ELEMENT_DATA.
>
>The ELEMENT_DATA block has "/" left and right borders,
>indicating a padding on a 4-byte boundry.
>
>The text that accompanies the illustration says:
>
>"....
>The length of each element does not have to be a multiple of 4
>     octets and there is no padding between elements. However, the size
>     of the OPTIONS field MUST be a multiple of 4 octets. If the length
>     of all the elements is not a multiple of 4 octets, the generator
>     MUST pad the OPTIONS field value with all zero octets. Padding is
>     not included in the OPTIONS_LENGTH field (see section 3.2.7). ..."
>
>The text *before* the illustration indicates:
>
>"The OPTIONS field contains 0 or more option elements where each
>     element follows the layout in Figure 4 (see section 2.4 for a
>     description of option elements): "
>
>If the illustration is an example of a single element (as I
>read this), then the "'/' walls" indicating padding should not
 >be there. They should only be in the illustration for 3.2.