diff mbox

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

Message ID 20191207215712.10137-1-cus@passwd.hu
State New
Headers show

Commit Message

Marton Balint Dec. 7, 2019, 9:57 p.m. UTC
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@passwd.hu>
---
 doc/APIchanges      |  3 +++
 libavutil/buffer.c  |  6 ++++++
 libavutil/buffer.h  | 13 +++++++++++++
 libavutil/version.h |  4 ++--
 4 files changed, 24 insertions(+), 2 deletions(-)

Comments

Marton Balint Dec. 14, 2019, 7:08 p.m. UTC | #1
On Sat, 7 Dec 2019, 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).

Ping. Will apply soon.

Thanks,
Marton

>
> Signed-off-by: Marton Balint <cus@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;
> +}
> 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, \
> -- 
> 2.16.4
>
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel@ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
James Almer Dec. 14, 2019, 10:12 p.m. UTC | #2
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@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.

> +}
> 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, \
>
Marton Balint Dec. 14, 2019, 10:50 p.m. UTC | #3
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@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?

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, \
>> 
>
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel@ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
James Almer Dec. 14, 2019, 10:58 p.m. UTC | #4
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@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.

> 
> 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, \
>>>
>>
>> _______________________________________________
>> ffmpeg-devel mailing list
>> ffmpeg-devel@ffmpeg.org
>> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>>
>> To unsubscribe, visit link above, or email
>> ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel@ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> 
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
Marton Balint Dec. 14, 2019, 11:07 p.m. UTC | #5
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@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, \
>>>>
>>>
>>> _______________________________________________
>>> ffmpeg-devel mailing list
>>> ffmpeg-devel@ffmpeg.org
>>> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>>>
>>> To unsubscribe, visit link above, or email
>>> ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
>> _______________________________________________
>> ffmpeg-devel mailing list
>> ffmpeg-devel@ffmpeg.org
>> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>> 
>> To unsubscribe, visit link above, or email
>> ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
>
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel@ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
Nicolas George Dec. 15, 2019, 2:24 p.m. UTC | #6
James Almer (12019-12-14):
> 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.

This is true, but I do not consider it that big of a problem. It makes
no sense to access the opaque pointer unless you know precisely where
the buffer comes from and what the opaque pointer contains. This is only
expanding on this a bit.

There are already several places in FFmpeg's API where parameters have a
constraint that cannot be expressed with the imperfect type system of
the C language. There are in the standard C library too: realloc() vs.
free(), pclose() vs. fclose(), etc.

Regards,
James Almer Dec. 15, 2019, 2:27 p.m. UTC | #7
On 12/15/2019 11:24 AM, Nicolas George wrote:
> James Almer (12019-12-14):
>> 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.
> 
> This is true, but I do not consider it that big of a problem. It makes
> no sense to access the opaque pointer unless you know precisely where
> the buffer comes from and what the opaque pointer contains. This is only
> expanding on this a bit.
> 
> There are already several places in FFmpeg's API where parameters have a
> constraint that cannot be expressed with the imperfect type system of
> the C language. There are in the standard C library too: realloc() vs.
> free(), pclose() vs. fclose(), etc.
> 
> Regards,

Ok, if that's preferred then just adding a check for buf != NULL before
dereferencing it should be enough.
diff mbox

Patch

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;
+}
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, \