[FFmpeg-devel] [PATCH 4/6 v2] avutil/mastering_display_metadata: add a new allocator function that returns a size

[James Almer]

On 3/25/2024 5:40 PM, Andreas Rheinhardt wrote:
> James Almer:
>> av_mastering_display_metadata_alloc() is not useful in scenarios where you need to
>> know the runtime size of AVMasteringDisplayMetadata.
>>
>> Signed-off-by: James Almer <jamrial at gmail.com>
>> ---
>>   libavutil/mastering_display_metadata.c | 13 +++++++++++++
>>   libavutil/mastering_display_metadata.h |  9 +++++++++
>>   2 files changed, 22 insertions(+)
>>
>> diff --git a/libavutil/mastering_display_metadata.c b/libavutil/mastering_display_metadata.c
>> index 6069347617..ea41f13f9d 100644
>> --- a/libavutil/mastering_display_metadata.c
>> +++ b/libavutil/mastering_display_metadata.c
>> @@ -18,6 +18,7 @@
>>    * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
>>    */
>>   
>> +#include <stddef.h>
>>   #include <stdint.h>
>>   #include <string.h>
>>   
>> @@ -29,6 +30,18 @@ AVMasteringDisplayMetadata *av_mastering_display_metadata_alloc(void)
>>       return av_mallocz(sizeof(AVMasteringDisplayMetadata));
>>   }
>>   
>> +AVMasteringDisplayMetadata *av_mastering_display_metadata_alloc_size(size_t *size)
>> +{
>> +    AVMasteringDisplayMetadata *mastering = av_mallocz(sizeof(AVMasteringDisplayMetadata));
>> +    if (!mastering)
>> +        return NULL;
>> +
>> +    if (size)
>> +        *size = sizeof(*mastering);
>> +
>> +    return mastering;
>> +}
>> +
>>   AVMasteringDisplayMetadata *av_mastering_display_metadata_create_side_data(AVFrame *frame)
>>   {
>>       AVFrameSideData *side_data = av_frame_new_side_data(frame,
>> diff --git a/libavutil/mastering_display_metadata.h b/libavutil/mastering_display_metadata.h
>> index c23b07c3cd..52fcef9e37 100644
>> --- a/libavutil/mastering_display_metadata.h
>> +++ b/libavutil/mastering_display_metadata.h
>> @@ -77,6 +77,15 @@ typedef struct AVMasteringDisplayMetadata {
>>    */
>>   AVMasteringDisplayMetadata *av_mastering_display_metadata_alloc(void);
>>   
>> +/**
>> + * Allocate an AVMasteringDisplayMetadata structure and set its fields to
>> + * default values. The resulting struct can be freed using av_freep().
>> + *
>> + * @return An AVMasteringDisplayMetadata filled with default values or NULL
>> + *         on failure.
>> + */
>> +AVMasteringDisplayMetadata *av_mastering_display_metadata_alloc_size(size_t *size);
>> +
>>   /**
>>    * Allocate a complete AVMasteringDisplayMetadata and add it to the frame.
>>    *
> 
> Instead of this we should have a generic allocator like
> void *av_frame_side_data_allocate(enum AVFrameSideDataType, size_t
> *size, size_t elem_count), with the latter being used for the allocators
> that allocate arrays (like AVRegionOfInterest); it has to be set to zero
> for the others. This will also avoid creating new
> av_*_create_side_data() functions.

I don't mind a function like that being added to simplify future 
additions, but this API is orthogonal to the frame side data one. It's 
also used in packets, for example, and right now lavf is using 
sizeof(AVMasteringDisplayMetadata) because 
av_mastering_display_metadata_alloc() is not useful.

> 
> - Andreas
> 
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> 
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".