Re: [FFmpeg-devel] [PATCH v8 07/14] avutil/frame: add helper for adding side data w/ AVBufferRef to array

[James Almer <jamrial@gmail.com>]

On 3/11/2024 5:58 PM, Jan Ekström wrote:
> This was requested to be added in review.
> ---
>   libavutil/frame.c | 43 ++++++++++++++++++++++++++++++-------------
>   libavutil/frame.h | 21 +++++++++++++++++++++
>   2 files changed, 51 insertions(+), 13 deletions(-)
> 
> diff --git a/libavutil/frame.c b/libavutil/frame.c
> index 46f976a3ed..30db83a5e5 100644
> --- a/libavutil/frame.c
> +++ b/libavutil/frame.c
> @@ -781,29 +781,46 @@ AVFrameSideData *av_frame_side_data_new(AVFrameSideData ***sd, int *nb_sd,
>       return ret;
>   }
>   
> -int av_frame_side_data_clone(AVFrameSideData ***sd, int *nb_sd,
> -                             const AVFrameSideData *src, unsigned int flags)
> +AVFrameSideData *av_frame_side_data_add(AVFrameSideData ***sd, int *nb_sd,
> +                                        enum AVFrameSideDataType type,
> +                                        const AVBufferRef *buf,
> +                                        unsigned int flags)
>   {
> -    AVBufferRef     *buf    = NULL;
> -    AVFrameSideData *sd_dst = NULL;
> -    int              ret    = AVERROR_BUG;
> +    AVBufferRef     *new_buf = NULL;
> +    AVFrameSideData *sd_dst  = NULL;
>   
> -    if (!sd || !src || !nb_sd || (*nb_sd && !*sd))
> -        return AVERROR(EINVAL);
> +    if (!sd || !buf || !nb_sd || (*nb_sd && !*sd))
> +        return NULL;
>   
> -    buf = av_buffer_ref(src->buf);
> +    new_buf = av_buffer_ref(buf);
>       if (!buf)
> -        return AVERROR(ENOMEM);
> +        return NULL;
>   
>       if (flags & AV_FRAME_SIDE_DATA_FLAG_UNIQUE)
> -        remove_side_data(sd, nb_sd, src->type);
> +        remove_side_data(sd, nb_sd, type);
>   
> -    sd_dst = add_side_data_to_set_from_buf(sd, nb_sd, src->type, buf);
> +    sd_dst = add_side_data_to_set_from_buf(sd, nb_sd, type, new_buf);
>       if (!sd_dst) {
> -        av_buffer_unref(&buf);
> -        return AVERROR(ENOMEM);
> +        av_buffer_unref(&new_buf);
> +        return NULL;
>       }
>   
> +    return sd_dst;
> +}
> +
> +int av_frame_side_data_clone(AVFrameSideData ***sd, int *nb_sd,
> +                             const AVFrameSideData *src, unsigned int flags)
> +{
> +    AVFrameSideData *sd_dst = NULL;
> +    int              ret    = AVERROR_BUG;
> +
> +    if (!src)
> +        return AVERROR(EINVAL);
> +
> +    sd_dst = av_frame_side_data_add(sd, nb_sd, src->type, src->buf, flags);
> +    if (!sd_dst)
> +        return AVERROR(ENOMEM);
> +
>       ret = av_dict_copy(&sd_dst->metadata, src->metadata, 0);
>       if (ret < 0) {
>           remove_side_data_by_entry(sd, nb_sd, sd_dst);
> diff --git a/libavutil/frame.h b/libavutil/frame.h
> index ce93421d60..a7e62ded15 100644
> --- a/libavutil/frame.h
> +++ b/libavutil/frame.h
> @@ -1021,6 +1021,27 @@ AVFrameSideData *av_frame_side_data_new(AVFrameSideData ***sd, int *nb_sd,
>                                           enum AVFrameSideDataType type,
>                                           size_t size, unsigned int flags);
>   
> +/**
> + * Add a new side data entry to an array from an existing AVBufferRef.
> + *
> + * @param sd    pointer to array of side data to which to add another entry,
> + *              or to NULL in order to start a new array.
> + * @param nb_sd pointer to an integer containing the number of entries in
> + *              the array.
> + * @param type  type of the added side data
> + * @param buf   AVBufferRef for which a new reference will be made
> + * @param flags Some combination of AV_FRAME_SIDE_DATA_FLAG_* flags, or 0.
> + *
> + * @return newly added side data on success, NULL on error. In case of
> + *         AV_FRAME_SIDE_DATA_FLAG_UNIQUE being set, entries of matching
> + *         AVFrameSideDataType will be removed before the addition is
> + *         attempted.
> + */
> +AVFrameSideData *av_frame_side_data_add(AVFrameSideData ***sd, int *nb_sd,
> +                                        enum AVFrameSideDataType type,
> +                                        const AVBufferRef *buf,
> +                                        unsigned int flags);
> +
>   /**
>    * Add a new side data entry to an array based on existing side data, taking
>    * a reference towards the contained AVBufferRef.

This also LGTM, but Anton has expressed a dislike for the function 
signature, preferring instead one that takes ownership of the buffer by 
taking a pointer to pointer, and clearing it on success.
The argument was that the user may not care about keeping a reference to 
the buffer after it's added to the side data array, but seeing how the 
very first user in this patch does, I personally think this more 
appropriate.

If others agree with him then I'll not oppose to it.
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