Re: WOFF2 failure

I updated the comment to be more aggressive in asserting which to use/not
use. Better late than never :D

On Wed, Sep 21, 2016 at 2:09 PM, Ned Holbrook <ned@apple.com> wrote:

> Thanks for the clarification. I’m pretty sure my colleague thought the new
> API was merely a convenience, otherwise we would have picked the "right"
> one before.
>
> On Sep 21, 2016, at 1:51 PM, Roderick Sheeter <rsheeter@google.com> wrote:
>
> Sorry, that's my fault. I didn't want to remove the old API as doing so
> would break anyone using it and the repo is public so it's not easy to do a
> sweeping update of all consumers.
>
> As Khaled suggests, please use this (from https://github.com/google/
> woff2/blob/master/src/woff2_dec.h):
>
> // Decompresses the font into out. Returns true on success.
> // Works even if WOFF2Header totalSfntSize is wrong.
> bool ConvertWOFF2ToTTF(const uint8_t *data, size_t length,
>                        WOFF2Out* out);
>
> And avoid this; it's more fragile:
>
> // Decompresses the font into the target buffer. The result_length should
> // be the same as determined by ComputeFinalSize(). Returns true on
> successful
> // decompression.
> bool ConvertWOFF2ToTTF(uint8_t *result, size_t result_length,
>                        const uint8_t *data, size_t length);
>
> Rod S
>
> On Wed, Sep 21, 2016 at 12:20 PM, Khaled Hosny <khaledhosny@eglug.org>
> wrote:
>
>> LOL, I actually first wrote a much detailed answer then thought it is
>> too newbish and discarded it.
>>
>> Yes, you will need to use the new API that uses the WOFF2Out object as
>> it does not suffer from the limitations of the old API WRT trusting
>> totalSfntSize and origLength.
>>
>> Regards,
>> Khaled
>>
>> On Wed, Sep 21, 2016 at 11:31:24AM -0700, Ned Holbrook wrote:
>> > Thanks, but you’ll have to be a bit more explicit for us poor
>> newcomers. :) The fix in this case would be to use the ConvertWOFF2ToTTF()
>> overload taking a WOFF2Out object?
>> >
>> > > On Sep 21, 2016, at 11:25 AM, Khaled Hosny <khaledhosny@eglug.org>
>> wrote:
>> > >
>> > > On Wed, Sep 21, 2016 at 11:11:12AM -0700, Ned Holbrook wrote:
>> > >> This is regarding <http://test.chrislewis.codes/woff2/>, found on <
>> http://typedrawers.com/discussion/1775/browser-ots-rejectio
>> ns-for-woff2-but-not-woff>; the WOFF2 for the second line of the test
>> page is not being used.
>> > >>
>> > >> I stepped through I discovered the failure is due to this code in
>> woff2_dec.cc:
>> > >>
>> > >>    if (PREDICT_FALSE(static_cast<uint64_t>(table.dst_offset +
>> table.dst_length)
>> > >>> out->Size())) {
>> > >>      return FONT_COMPRESSION_FAILURE();
>> > >>    }
>> > >>
>> > >> At the point of failure:
>> > >>    (lldb) p out->Size()
>> > >>    (size_t) $7 = 405520
>> > >>    (lldb) p table.dst_offset + table.dst_length
>> > >>    (unsigned int) $8 = 417149
>> > >>
>> > >> Now, Khaled commented on the TypeDrawers page to suggest this check
>> is
>> > >> overly strict. Does this mean the reference implementation needs to
>> be
>> > >> fixed?
>> > >
>> > > See:
>> > > https://github.com/google/woff2/pull/48
>> > >
>> > > Regards,
>> > > Khaled
>>
>>
>
>