Re: [FFmpeg-devel] [PATCH 15/38] lavu/opt: add array options

[Marton Balint <cus@passwd.hu>]

On Fri, 23 Feb 2024, Anton Khirnov wrote:

> AVOption.array_max_size is added before AVOption.unit to avoid
> increasing sizeof(AVOption).
> ---
> doc/APIchanges        |   3 +
> libavutil/opt.c       | 344 ++++++++++++++++++++++++++++++++++++------
> libavutil/opt.h       |  26 ++++
> libavutil/tests/opt.c |  34 +++++
> tests/ref/fate/opt    |  23 ++-
> 5 files changed, 385 insertions(+), 45 deletions(-)
>
[...]

> --- a/libavutil/opt.h
> +++ b/libavutil/opt.h
> @@ -288,6 +288,16 @@ enum AVOptionType{
>  */
> #define AV_OPT_FLAG_CHILD_CONSTS    (1 << 18)
> 
> +/**
> + * The option is an array.
> + *
> + * When adding array options to an object, @ref AVOption.offset should refer to
> + * a pointer corresponding to the option type. The pointer should be immediately
> + * followed by an unsigned int that will store the number of elements in the
> + * array.
> + */
> +#define AV_OPT_FLAG_ARRAY           (1 << 19)
> +
> /**
>  * AVOption
>  */
> @@ -313,6 +323,16 @@ typedef struct AVOption {
>     union {
>         int64_t i64;
>         double dbl;
> +
> +        /**
> +         * This member is always used for AV_OPT_FLAG_ARRAY options. When
> +         * non-NULL, the first character of the string must be the separator to
> +         * be used for (de)serializing lists to/from strings with av_opt_get(),

This is quite ugly. Also it breaks the assumption that if the user sets an 
option value to the default value of the option, than it will work. So 
let's just remove this feature for now.

Eventually I think some new struct should be introduced, e.g. 
AVOptionExtension, which can be used to specify additional option 
settings, such as array min/max size, and maybe separator. It would be a 
lot more clean and future proof than filling the holes in AVOption.

Regards,
Marton
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