Re: WOFF2 failure

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 <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 <mailto: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 <mailto: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/ <http://test.chrislewis.codes/woff2/>>, found on <http://typedrawers.com/discussion/1775/browser-ots-rejections-for-woff2-but-not-woff <http://typedrawers.com/discussion/1775/browser-ots-rejections-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 <https://github.com/google/woff2/pull/48>
> > >
> > > Regards,
> > > Khaled
> 
>