[FFmpeg-devel] [PATCH] Add SUP/PGS subtitle demuxer

[Michael Niedermayer]

On Sun, Aug 31, 2014 at 09:41:49AM +0200, Reimar Döffinger wrote:
> On 30.08.2014, at 15:38, wm4 <nfxjfg at googlemail.com> wrote:
> > +    // The packet-size is stored as part of the packet.
> > +    if ((ret = avio_read(s->pb, tmp, 3)) < 0)
> > +        return ret;
> > +
> > +    len = AV_RB16(tmp + 1);
> > +
> > +    if ((ret = av_new_packet(pkt, len + 3)) < 0)
> > +        return ret;
> > +
> > +    memcpy(pkt->data, tmp, 3);
> > +
> > +    if ((ret = avio_read(s->pb, pkt->data + 3, len)) < 0) {
> > +        av_free_packet(pkt);
> > +        return ret;
> > +    }
> 
> I think this will not handle short reads correctly, retuning uninitialised data.

> My suggestion would be to read the length, then seek back (buffering should ensure this is no issue even if we read from stdin) and then use the functions to read the full packet with all the proper error handling.

note, for guranteed seekback on non seekable input
ffio_ensure_seekback() is needed


[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Complexity theory is the science of finding the exact solution to an
approximation. Benchmarking OTOH is finding an approximation of the exact
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