[FFmpeg-devel] [PATCH 1/3] lavu: add a template for refcounted objects.

[James Almer]

On 7/1/2020 12:05 PM, Anton Khirnov wrote:
> Quoting Nicolas George (2020-06-27 17:16:44)
>> Signed-off-by: Nicolas George <george at nsup.org>
>> ---
>>  libavutil/avrefcount_template.h | 140 ++++++++++++++++++++++++++++++++
>>  tests/ref/fate/source           |   1 +
>>  2 files changed, 141 insertions(+)
>>  create mode 100644 libavutil/avrefcount_template.h
>>
>>
>> I will need to refcount something soon. Recently, the need to stop
>> abusing AVBuffer for all refcounting was mentioned on the list. So here
>> is an attempt at isolating the refcounting itself.
>>
>> This is not the final verion, I will first work on the "something" to
>> make sure it suits the needs. But it is a first version.
>>
>> Anton, I would appreciate if you had a look at this and told me if there
>> is something you strongly dislike about before I have piled too much
>> efforts over it.
> 
> Why a template? It seems simpler to add a struct like
> typedef struct AVRefcount {
>     atomic_uint refcount;
>     void       *opaque;
>     void      (*free)(void *opaque);
> } AVRefcount;
> and then embed it in everything that wants to be refcounted. All just
> normal structs and functions, no layers of macros.

I very much prefer this approach, being clean looking, public, and free
of macros from unguarded headers, but it needs to be either easily
extensible or well defined since day 1.
For example, it could have more callbacks to be triggered by specific
actions, like when creating new references, to workaround the current
constrains of AVBufferRef.