[FFmpeg-devel] [PATCH 3/6] avcodec/pictordec: Optimize picmemset() for single plane full lines

[Peter Ross]

On Sat, Aug 03, 2019 at 01:49:54AM +0200, Michael Niedermayer wrote:
> Fixes: Timeout (72sec -> 1sec)
> Fixes: 15512/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_PICTOR_fuzzer-5663942342344704
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> ---
>  libavcodec/pictordec.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/libavcodec/pictordec.c b/libavcodec/pictordec.c
> index 2e6fcdca52..5beb03cd5d 100644
> --- a/libavcodec/pictordec.c
> +++ b/libavcodec/pictordec.c
> @@ -66,6 +66,7 @@ static void picmemset(PicContext *s, AVFrame *frame, unsigned value, int run,
>      int xl = *x;
>      int yl = *y;
>      int planel = *plane;
> +    int pixels_per_value = 8/bits_per_plane;
>      value   <<= shift;
>  
>      d = frame->data[0] + yl * frame->linesize[0];
> @@ -74,7 +75,7 @@ static void picmemset(PicContext *s, AVFrame *frame, unsigned value, int run,
>          for (j = 8-bits_per_plane; j >= 0; j -= bits_per_plane) {
>              d[xl] |= (value >> j) & mask;
>              xl += 1;
> -            if (xl == s->width) {
> +            while (xl == s->width) {
>                  yl -= 1;
>                  xl = 0;
>                  if (yl < 0) {
> @@ -86,6 +87,19 @@ static void picmemset(PicContext *s, AVFrame *frame, unsigned value, int run,
>                     mask  <<= bits_per_plane;
>                  }
>                  d = frame->data[0] + yl * frame->linesize[0];
> +                if (s->nb_planes == 1 &&
> +                    run*pixels_per_value >= s->width &&
> +                    pixels_per_value < s->width) {
> +                    int j;
> +                    for (j = 8-bits_per_plane; j >= 0; j -= bits_per_plane) {

suggest naming it 'k' to avoid confusion with earlier for loop.

> +                        d[xl] |= (value >> j) & mask;
> +                        xl += 1;
> +                    }
> +                    av_assert0(xl == pixels_per_value);

ok.

> +                    av_memcpy_backptr(d+xl, pixels_per_value, s->width - xl);
> +                    run -= (s->width + pixels_per_value - 1) / pixels_per_value;
> +                    xl = s->width;
> +                }
>              }
>          }
>          run--;
> -- 
> 2.22.0

otherwise patch is good.

-- Peter
(A907 E02F A6E5 0CD2 34CD 20D2 6760 79C5 AC40 DD6B)
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