[FFmpeg-devel] [PATCH 1/3] ffv1dec: move slice start finding into a function

[Michael Niedermayer]

On Mon, Jan 06, 2025 at 01:05:09PM +0900, Lynne wrote:
> 
> 
> On 06/01/2025 12:40, Michael Niedermayer wrote:
> > Hi Lynne
> > 
> > On Sun, Jan 05, 2025 at 05:59:35PM +0900, Lynne wrote:
> > > This also cleans up and gives the code some much needed comments.
> > > ---
> > >   libavcodec/ffv1dec.c | 66 +++++++++++++++++++++++++++++++-------------
> > >   1 file changed, 47 insertions(+), 19 deletions(-)
> > > 
> > > diff --git a/libavcodec/ffv1dec.c b/libavcodec/ffv1dec.c
> > > index b7f235c47f..aa988571bc 100644
> > > --- a/libavcodec/ffv1dec.c
> > > +++ b/libavcodec/ffv1dec.c
> > > @@ -866,6 +866,38 @@ static av_cold int decode_init(AVCodecContext *avctx)
> > >       return 0;
> > >   }
> > > +static int find_next_slice(AVCodecContext *avctx,
> > > +                           uint8_t *buf, uint8_t *buf_end, int idx,
> > > +                           uint8_t **pos, uint32_t *len)
> > > +{
> > > +    FFV1Context *f = avctx->priv_data;
> > > +
> > > +    /* Length field */
> > > +    uint32_t v = buf_end - buf;
> > > +    if (idx || f->version > 2) {
> > > +        /* Three bytes of length, plus flush bit + CRC */
> > > +        uint32_t trailer = 3 + 5*!!f->ec;
> > > +        if (trailer > buf_end - buf)
> > > +            v = INT_MAX;
> > > +        else
> > > +            v = AV_RB24(buf_end - trailer) + trailer;
> > > +    }
> > > +
> > 
> > > +    if (buf_end - buf < v) {
> > > +        av_log(avctx, AV_LOG_ERROR, "Slice pointer chain broken\n");
> > > +        ff_progress_frame_report(&f->picture, INT_MAX);
> > > +        return AVERROR_INVALIDDATA;
> > > +    }
> > 
> > the if() can be moved into the previous if()
> 
> I'd prefer to keep it separate to make it cleaner this is a check.
>  > the v = buf_end - buf;
> > is unused in the first if() so it could be set in an else
> 
> I think its cleaner this way, plus its 3 less lines.

if you prefer, sure

thx

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Frequently ignored answer#1 FFmpeg bugs should be sent to our bugtracker. User
questions about the command line tools should be sent to the ffmpeg-user ML.
And questions about how to use libav* should be sent to the libav-user ML.
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