[FFmpeg-devel] [PATCH] avutil/opt: add AV_OPT_FLAG_FORCE_CONST

[Marton Balint]

On Sun, 14 Apr 2024, Timo Rothenpieler wrote:

> ---
> doc/APIchanges      |  3 +++
> libavutil/opt.c     | 14 ++++++++++++++
> libavutil/opt.h     |  5 +++++
> libavutil/version.h |  2 +-
> 4 files changed, 23 insertions(+), 1 deletion(-)

Where do you intend to use this flag? So some justification or description 
of your plans is missing from the commit message.

>
> diff --git a/doc/APIchanges b/doc/APIchanges
> index 63e7a47126..da2c87909b 100644
> --- a/doc/APIchanges
> +++ b/doc/APIchanges
> @@ -2,6 +2,9 @@ The last version increases of all libraries were on 2024-03-07
>
> API changes, most recent first:
>
> +2024-04-xx - xxxxxxxxxx - lavu 59.15.101 - opt.h
> +  Add AV_OPT_FLAG_FORCE_CONST.
> +
> 2024-04-11 - xxxxxxxxxx - lavc 61.5.102 - avcodec.h
>   AVCodecContext.decoded_side_data may now be set by libavcodec after
>   calling avcodec_open2().
> diff --git a/libavutil/opt.c b/libavutil/opt.c
> index d11e9d2ac5..9e51fa47f9 100644
> --- a/libavutil/opt.c
> +++ b/libavutil/opt.c
> @@ -365,6 +365,20 @@ static int set_string_number(void *obj, void *target_obj, const AVOption *o, con
>                 if (o_named->flags & AV_OPT_FLAG_DEPRECATED)
>                     av_log(obj, AV_LOG_WARNING, "The \"%s\" option is deprecated: %s\n",
>                            o_named->name, o_named->help);
> +            } else if (o->flags & AV_OPT_FLAG_FORCE_CONST) {
> +                av_log(obj, AV_LOG_ERROR, "The \"%s\" option only accepts one of its pre-defined constant values",
> +                       o->name);
> +                buf[0] = ':'; buf[1] = ' '; buf[2] = 0;
> +                for (o_named = NULL; o_named = av_opt_next(target_obj, o_named); ) {
> +                    if (o_named->type == AV_OPT_TYPE_CONST &&
> +                        o_named->unit && o->unit &&
> +                        !strcmp(o_named->unit, o->unit)) {
> +                        av_log(obj, AV_LOG_ERROR, "%s%s", buf, o_named->name);
> +                        buf[0] = ',';
> +                    }
> +                }
> +                av_log(obj, AV_LOG_ERROR, "\n");
> +                return AVERROR(EINVAL);
>             } else {
>                 if (o->unit) {
>                     for (o_named = NULL; o_named = av_opt_next(target_obj, o_named); ) {
> diff --git a/libavutil/opt.h b/libavutil/opt.h
> index e6013662f6..67e2b687b2 100644
> --- a/libavutil/opt.h
> +++ b/libavutil/opt.h
> @@ -305,6 +305,11 @@ enum AVOptionType{
>  * Set if option constants can also reside in child objects.
>  */
> #define AV_OPT_FLAG_CHILD_CONSTS    (1 << 18)
> +/**
> + * The option will only accept AV_OPT_TYPE_CONST values.
> + * Any other user supplied values will be rejected.
> + */

What about built-in named constants, such as min/max/default?

> +#define AV_OPT_FLAG_FORCE_CONST     (1 << 19)
>
> /**
>  * May be set as default_val for AV_OPT_TYPE_FLAG_ARRAY options.
> diff --git a/libavutil/version.h b/libavutil/version.h
> index 1f2bddc022..5de2d92146 100644
> --- a/libavutil/version.h
> +++ b/libavutil/version.h
> @@ -80,7 +80,7 @@
>
> #define LIBAVUTIL_VERSION_MAJOR  59
> #define LIBAVUTIL_VERSION_MINOR  15
> -#define LIBAVUTIL_VERSION_MICRO 100
> +#define LIBAVUTIL_VERSION_MICRO 101
>
> #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
>                                                LIBAVUTIL_VERSION_MINOR, \
> -- 
> 2.34.1

Regards,
Marton