Re: [FFmpeg-devel] [PATCH v6 06/13] avutil/frame: add helper for adding existing side data to set

[James Almer <jamrial@gmail.com>]

On 2/27/2024 7:12 PM, Jan Ekström wrote:
> ---
>   libavutil/frame.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++
>   libavutil/frame.h | 19 ++++++++++++++++++
>   2 files changed, 68 insertions(+)
> 
> diff --git a/libavutil/frame.c b/libavutil/frame.c
> index d9741240e7..99c9ce4119 100644
> --- a/libavutil/frame.c
> +++ b/libavutil/frame.c
> @@ -110,6 +110,23 @@ static void remove_side_data(AVFrameSideData ***sd, int *nb_side_data,
>       }
>   }
>   
> +static void remove_side_data_by_entry(AVFrameSideData ***sd, int *nb_sd,
> +                                      const AVFrameSideData *target)
> +{
> +    for (int i = *nb_sd - 1; i >= 0; i--) {
> +        AVFrameSideData *entry = ((*sd)[i]);
> +        if (entry != target)
> +            continue;
> +
> +        free_side_data(&entry);
> +
> +        ((*sd)[i]) = ((*sd)[*nb_sd - 1]);
> +        (*nb_sd)--;
> +
> +        return;
> +    }
> +}
> +
>   AVFrame *av_frame_alloc(void)
>   {
>       AVFrame *frame = av_malloc(sizeof(*frame));
> @@ -872,6 +889,38 @@ AVFrameSideData *av_frame_side_data_new(AVFrameSideData ***sd, int *nb_sd,
>       return ret;
>   }
>   
> +int av_frame_side_data_from_sd(AVFrameSideData ***sd, int *nb_sd,
> +                               const AVFrameSideData *src,
> +                               unsigned int flags)
> +{
> +    if (!sd || !src || !nb_sd || (*nb_sd && !*sd))
> +        return AVERROR(EINVAL);
> +
> +    {
> +        AVBufferRef           *buf    = av_buffer_ref(src->buf);
> +        AVFrameSideData       *sd_dst = NULL;
> +
> +        if (flags & AV_FRAME_SIDE_DATA_SET_FLAG_NO_DUPLICATES)
> +            remove_side_data(sd, nb_sd, src->type);
> +
> +        sd_dst = add_side_data_to_set_from_buf(sd, nb_sd, src->type, buf);
> +        if (!sd_dst) {
> +            av_buffer_unref(&buf);
> +            return AVERROR(ENOMEM);
> +        }
> +
> +        {
> +            int ret = av_dict_copy(&sd_dst->metadata, src->metadata, 0);
> +            if (ret < 0) {
> +                remove_side_data_by_entry(sd, nb_sd, sd_dst);
> +                return ret;
> +            }
> +        }
> +
> +        return 0;
> +    }
> +}
> +
>   AVFrameSideData *av_frame_get_side_data(const AVFrame *frame,
>                                           enum AVFrameSideDataType type)
>   {
> diff --git a/libavutil/frame.h b/libavutil/frame.h
> index 726ca19a03..47d0096bc4 100644
> --- a/libavutil/frame.h
> +++ b/libavutil/frame.h
> @@ -1081,6 +1081,25 @@ 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 a set based on existing side data, taking
> + * a reference towards the contained AVBufferRef.
> + *
> + * @param sd    pointer to array of side data to which to add another entry.
> + * @param nb_sd pointer to an integer containing the number of entries in
> + *              the array.
> + * @param src   side data which should be added to the set
> + * @param flags Some combination of AV_FRAME_SIDE_DATA_SET_FLAG_* flags, or 0.
> + *
> + * @return negative error code on failure, >=0 on success. In case of
> + *         AV_FRAME_SIDE_DATA_SET_FLAG_NO_DUPLICATES being set, entries
> + *         of matching AVFrameSideDataType will be removed before the
> + *         addition is attempted.
> + */
> +int av_frame_side_data_from_sd(AVFrameSideData ***sd, int *nb_sd,
> +                               const AVFrameSideData *src,
> +                               unsigned int flags);

This is pretty limiting as it works only with already existing 
AVFrameSideData entries. If you have a buffer that you want to insert to 
an array as a new AVFrameSideData entry, then this will not do.
I think it would be better to make it take an AVBufferRef as input, like 
the existing av_frame_new_side_data_from_buf() does, which can then work 
in any case.

int av_frame_side_data_add(AVFrameSideData ***sd, int *nb_sd,
                            enum AVFrameSideDataType type,
                            AVBufferRef *buf,
                            unsigned int flags);

And such a function should create a new ref to buf rather than taking 
ownership of it like av_frame_new_side_data_from_buf() does, which is a 
bit awkward.

> +
>   /**
>    * @}
>    */
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