[FFmpeg-devel] [PATCH 1/2] avutil/buffer: add av_buffer_pool_buffer_get_opaque

[Marton Balint]

On Sat, 14 Dec 2019, James Almer wrote:

> On 12/14/2019 7:50 PM, Marton Balint wrote:
>> 
>> 
>> On Sat, 14 Dec 2019, James Almer wrote:
>> 
>>> On 12/7/2019 6:57 PM, Marton Balint wrote:
>>>> In order to access the original opaque parameter of a buffer in the
>>>> buffer
>>>> pool. (The buffer pool implementation overrides the normal opaque
>>>> parameter but
>>>> also saves it so it is accessible).
>>>>
>>>> Signed-off-by: Marton Balint <cus at passwd.hu>
>>>> ---
>>>>  doc/APIchanges      |  3 +++
>>>>  libavutil/buffer.c  |  6 ++++++
>>>>  libavutil/buffer.h  | 13 +++++++++++++
>>>>  libavutil/version.h |  4 ++--
>>>>  4 files changed, 24 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/doc/APIchanges b/doc/APIchanges
>>>> index 401c65a753..5b8d801f06 100644
>>>> --- a/doc/APIchanges
>>>> +++ b/doc/APIchanges
>>>> @@ -15,6 +15,9 @@ libavutil:     2017-10-21
>>>>
>>>>  API changes, most recent first:
>>>>
>>>> +2019-12-xx - xxxxxxxxxx - lavu 56.37.100 - buffer.h
>>>> +  Add av_buffer_pool_buffer_get_opaque().
>>>> +
>>>>  2019-11-17 - 1c23abc88f - lavu 56.36.100 - eval API
>>>>    Add av_expr_count_vars().
>>>>
>>>> diff --git a/libavutil/buffer.c b/libavutil/buffer.c
>>>> index f0034b026a..ec00fb22ec 100644
>>>> --- a/libavutil/buffer.c
>>>> +++ b/libavutil/buffer.c
>>>> @@ -355,3 +355,9 @@ AVBufferRef *av_buffer_pool_get(AVBufferPool *pool)
>>>>
>>>>      return ret;
>>>>  }
>>>> +
>>>> +void *av_buffer_pool_buffer_get_opaque(AVBufferRef *ref)
>>>> +{
>>>> +    BufferPoolEntry *buf = ref->buffer->opaque;
>>>> +    return buf->opaque;
>>>
>>> I'm not sure if this is a good idea. It takes any AVBufferRef as input,
>>> so it will crash on pretty much every one not created by an AVBufferPool
>>> (unless it checks that buf is not NULL before dereferencing it), or
>>> return something unrelated otherwise.
>> 
>> It is documented below that the buffer has to be part of the pool, so I
>> don't really see this as an issue.
>> 
>> An alternative approach might be to introduce
>> AVBufferRef *av_buffer_pool_get2(AVBufferPool *pool, void **opaque);
>> which returns the original opauqe value of the allocated buffer in
>> addition to returning the buffer.
>> 
>> Do you prefer this? Or maybe something entirely different?
>
> I'd like to hear other devs opinions, but that suggestion does sound
> good. It complements av_buffer_pool_init2(), the pool init function that
> allows this scenario to being with.

Ok, I'll wait a few days then.

Thanks,
Marton

>>>
>>>> +}
>>>> diff --git a/libavutil/buffer.h b/libavutil/buffer.h
>>>> index 73b6bd0b14..e0f94314f4 100644
>>>> --- a/libavutil/buffer.h
>>>> +++ b/libavutil/buffer.h
>>>> @@ -284,6 +284,19 @@ void av_buffer_pool_uninit(AVBufferPool **pool);
>>>>   */
>>>>  AVBufferRef *av_buffer_pool_get(AVBufferPool *pool);
>>>>
>>>> +/**
>>>> + * Query the original opaque parameter of an allocated buffer in the
>>>> pool.
>>>> + *
>>>> + * @param ref a buffer reference to a buffer returned by
>>>> av_buffer_pool_get.
>>>> + * @return the opaque parameter set by the buffer allocator function
>>>> of the
>>>> + *         buffer pool.
>>>> + *
>>>> + * @note the opaque parameter of ref is used by the buffer pool
>>>> implementation,
>>>> + * therefore you have to use this function to access the original
>>>> opaque
>>>> + * parameter of an allocated buffer.
>>>> + */
>>>> +void *av_buffer_pool_buffer_get_opaque(AVBufferRef *ref);
>>>> +
>>>>  /**
>>>>   * @}
>>>>   */
>>>> diff --git a/libavutil/version.h b/libavutil/version.h
>>>> index e18163388d..4de0fa1fc3 100644
>>>> --- a/libavutil/version.h
>>>> +++ b/libavutil/version.h
>>>> @@ -79,8 +79,8 @@
>>>>   */
>>>>
>>>>  #define LIBAVUTIL_VERSION_MAJOR  56
>>>> -#define LIBAVUTIL_VERSION_MINOR  36
>>>> -#define LIBAVUTIL_VERSION_MICRO 101
>>>> +#define LIBAVUTIL_VERSION_MINOR  37
>>>> +#define LIBAVUTIL_VERSION_MICRO 100
>>>>
>>>>  #define LIBAVUTIL_VERSION_INT  
>>>> AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
>>>>                                                
>>>> LIBAVUTIL_VERSION_MINOR, \
>>>>
>>>
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