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

[Michael Niedermayer]

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()

the v = buf_end - buf;
is unused in the first if() so it could be set in an else

patch LGTM otherwise

thx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

"You are 36 times more likely to die in a bathtub than at the hands of a
terrorist. Also, you are 2.5 times more likely to become a president and
2 times more likely to become an astronaut, than to die in a terrorist
attack." -- Thoughty2

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 195 bytes
Desc: not available
URL: <https://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20250106/572d5884/attachment.sig>