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Re: comments on WOFF File Format 1.0, W3C Working Draft 27 July 2010

From: Bob Hallissy <bobh528@pobox.com>
Date: Wed, 04 Aug 2010 09:04:35 -0600
Message-ID: <4C598183.5090906@pobox.com>
To: www-font <www-font@w3.org>
On 2010-08-04  at 1:44  John Daggett wrote:
> 2. Overall File Structure
>> >  Except for padding with a maximum of three null bytes in places
>> >  where 4-byte alignment of a table length or data block is specified,
>> >  there MUST NOT be any extraneous data outside the font tables and
>> >  data blocks as pointed to by the header and table directory entries.
>>      
> Change [outside the font tables and data blocks] to [between font
> tables or other data blocks].
>    

Such a change would permit extraneous data after the last valid table or 
block, and I think that should be prohibited (for security reasons).

If the word "outside" is your concern, perhaps replace that word with 
"other than"?

> Append at the end of the section:
>
> All sizes described in this document are assumed to be in bytes unless
> otherwise noted.
>    

Thanks for this suggestion. I recommend including offsets in this, i.e:

All sizes and offsets described in this document are assumed to be in bytes unless
otherwise noted.


Which brings up a question: Is "size" different from "length" and, if 
not, could the spec be consistent? For example, I see in the WOFF header 
these items:

> UInt32    totalSfntSize    Total size needed for the uncompressed font 
> data, including the sfnt header, directory, and tables.
> UInt32    metaLength    Length of compressed metadata block.
> UInt32    metaOrigLength    Uncompressed size of metadata block.
> UInt32    privLength    Length of private data block.

If these two terms are distinct, then perhaps the spec should say:

All sizes, lengths and offsets described in this document are assumed to be in bytes unless otherwise noted.


Bob
Received on Wednesday, 4 August 2010 15:05:14 UTC

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