Re: [FFmpeg-devel] [PATCH 14/42] avcodec/hevcdec: Use RefStruct API for RefPicListTap buffer

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

Anton Khirnov:
> Quoting Andreas Rheinhardt (2023-09-19 21:57:06)
>> avcodec/hevcdec: Use RefStruct API for RefPicListTap buffer
>                                                     ^
>                                                     b
> 
>> Given that the RefStruct API relies on the user to know
>> the size of the objects and does not provide a way to get it,
> 
> Is there a reason you decided not to provide it, or there just wasn't
> any code that would be improved by it?
> 

In this example, there would be no improvement if RefStruct recorded the
size (in bytes) and provided a getter for it.

In general, the philosophy of the RefStruct API is that the user and not
the API knows what is in the user data. So the user has to keep track of
stuff like this in cases where the user doesn't know it.

The only scenario where keeping track of the size would be advantageous
would be for using arrays-of-whatever if the callbacks provided the size
as a parameter (to be ignored by most users), because one could then
derive the number of elements from it. I pondered this, but given that
the AVBuffer API doesn't do so either, I didn't do it. Shall I change this?

>> we need to store the number of elements allocated ourselves;
>> but this is actually better than deriving it from the size
>> in bytes.
>>
>> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
>> ---
>>  libavcodec/hevc_refs.c | 14 ++++++++------
>>  libavcodec/hevcdec.c   |  5 ++---
>>  libavcodec/hevcdec.h   |  3 ++-
>>  3 files changed, 12 insertions(+), 10 deletions(-)
> 
> The actual code looks good.
> 

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