[Webkit-unassigned] [Bug 33213] Make png image decoder work with segmented SharedBuffer

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=33213





--- Comment #5 from Yong Li <yong.li.webkit at gmail.com>  2010-01-05 12:17:37 PST ---
(In reply to comment #4)
> (From update of attachment 45911 [details])
> > +    const char* contents;
> > +    unsigned length = data.getSomeData(contents, 0);
> > +
> >      // We need at least 4 bytes to figure out what kind of image we're dealing with.
> > -    int length = data.size();
> >      if (length < 4)
> >          return 0;
> 
> This seems a bit subtle and non-obvious. I guess the class guarantees that the
> first four bytes will all be in a single segment even if they come in one byte
> at a time, but nothing in the SharedBuffer header comments makes that clear.
> 

You're right. To make it safe, I'll rewrite this code for the corner case, so
that we won't have a hard-to-debug problem if the assumption becomes false in
the future.

> > +        virtual void setData(SharedBuffer* data, bool allDataReceived)
> > +        {
> > +            m_data = data;
> > +            m_isAllDataReceived = allDataReceived;
> > +        }
> 
> It's not optimal style to have a virtual function defined in a header. The old
> code had that, but it would be better not to do it that way.

Not sure if any derived class has implemented different setData(). If not, I'll
remove "virtual"
> 
> > +        , m_jobComplete(false)
> 
> For booleans data members and function members it's best to name them so they
> work in a sentence "image decoder <xxx>". So hasAlpha is a pretty good name but
> jobComplete is not as good. Maybe hasFinishedDecoding or hasReceivedAllData?

will use hasFinishedDecoding

> 
> > +            if (!segmentLength) {
> > +                if (!m_jobComplete) {
> > +                    if (decoder->isAllDataReceived())
> > +                        decoder->pngComplete();
> > +                }
> > +                break;
> > +            }
> 
> I suggest putting the other code outside the loop. It seems we should just
> break when done and then finish the ob after the loop.

Agree, and actually the 2 "if" can be merged.

> 
> I'll say r=me even though I normally don't review code in this file. Seems
> fine.

thanks a lot. but I'll post a new patch regarding to above issues.

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