[FFmpeg-devel] [PATCH 3/4] avutil/detection_bbox: simplify code for better readability

[lance.lmwang at gmail.com]

On Tue, Sep 28, 2021 at 03:57:27PM +0200, Andreas Rheinhardt wrote:
> lance.lmwang at gmail.com:
> > From: Limin Wang <lance.lmwang at gmail.com>
> > 
> > Signed-off-by: Limin Wang <lance.lmwang at gmail.com>
> > ---
> >  libavutil/detection_bbox.c | 24 +++++++++++++-----------
> >  1 file changed, 13 insertions(+), 11 deletions(-)
> > 
> > diff --git a/libavutil/detection_bbox.c b/libavutil/detection_bbox.c
> > index 8bfdff7..3de66ce 100644
> > --- a/libavutil/detection_bbox.c
> > +++ b/libavutil/detection_bbox.c
> > @@ -23,27 +23,29 @@ AVDetectionBBoxHeader *av_detection_bbox_alloc(uint32_t nb_bboxes, size_t *out_s
> >      size_t size;
> >      struct BBoxContext {
> >          AVDetectionBBoxHeader header;
> > -        AVDetectionBBox boxes[1];
> > -    } *ret;
> > +        AVDetectionBBox boxes;
> > +    };
> >      const size_t bboxes_offset = offsetof(struct BBoxContext, boxes);
> > +    const size_t bbox_size = sizeof(AVDetectionBBox);
> > +    AVDetectionBBoxHeader *header;
> >  
> > -    size = sizeof(*ret);
> > -    if (nb_bboxes - 1 > (SIZE_MAX - size) / sizeof(*ret->boxes))
> 
> This here is actually not a simplification, but a patch: The old code
> would not really work if nb_bboxes == 0.

OK, I'll change the comment message to "Fix the av_detection_bbox_alloc failed if nb_bboxes == 0"


> 
> > +    size = bboxes_offset;
> > +    if (nb_bboxes > (SIZE_MAX - size) / bbox_size)
> >          return NULL;
> > -    size += sizeof(*ret->boxes) * (nb_bboxes - 1);
> > +    size += bbox_size * nb_bboxes;
> >  
> > -    ret = av_mallocz(size);
> > -    if (!ret)
> > +    header = av_mallocz(size);
> > +    if (!header)
> >          return NULL;
> >  
> > -    ret->header.nb_bboxes = nb_bboxes;
> > -    ret->header.bbox_size = sizeof(*ret->boxes);
> > -    ret->header.bboxes_offset = bboxes_offset;
> > +    header->nb_bboxes     = nb_bboxes;
> > +    header->bbox_size     = bbox_size;
> > +    header->bboxes_offset = bboxes_offset;
> >  
> >      if (out_size)
> >          *out_size = size;
> >  
> > -    return &ret->header;
> > +    return header;
> >  }
> >  
> >  AVDetectionBBoxHeader *av_detection_bbox_create_side_data(AVFrame *frame, uint32_t nb_bboxes)
> > 
> 
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-- 
Thanks,
Limin Wang