Re: [FFmpeg-devel] [PATCH 01/16] avutil/buffer: add helper to allocate aligned memory

[averne <averne381@gmail.com>]

Le 30/05/2024 à 22:38, Rémi Denis-Courmont a écrit :
> Le torstaina 30. toukokuuta 2024, 22.43.03 EEST averne a écrit :
>> This is useful eg. for memory-mapped buffers that need page-aligned memory,
>> when dealing with hardware devices
>>
>> Signed-off-by: averne <averne381@gmail.com>
>> ---
>>  libavutil/buffer.c | 31 +++++++++++++++++++++++++++++++
>>  libavutil/buffer.h |  7 +++++++
>>  2 files changed, 38 insertions(+)
>>
>> diff --git a/libavutil/buffer.c b/libavutil/buffer.c
>> index e4562a79b1..b8e357f540 100644
>> --- a/libavutil/buffer.c
>> +++ b/libavutil/buffer.c
>> @@ -16,9 +16,14 @@
>>   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301
>> USA */
>>
>> +#include "config.h"
>> +
>>  #include <stdatomic.h>
>>  #include <stdint.h>
>>  #include <string.h>
>> +#if HAVE_MALLOC_H
>> +#include <malloc.h>
>> +#endif
>>
>>  #include "avassert.h"
>>  #include "buffer_internal.h"
>> @@ -100,6 +105,32 @@ AVBufferRef *av_buffer_allocz(size_t size)
>>      return ret;
>>  }
>>
>> +AVBufferRef *av_buffer_aligned_alloc(size_t size, size_t align)
>> +{
>> +    AVBufferRef *ret = NULL;
>> +    uint8_t    *data = NULL;
>> +
>> +#if HAVE_POSIX_MEMALIGN
>> +    if (posix_memalign((void **)&data, align, size))
> 
> Invalid cast.
> 

Neither gcc or clang emit a warning here, even on -Weverything.
What would be your idea of a valid cast then? First cast to intptr_t, 
then void** ?

>> +        return NULL;
>> +#elif HAVE_ALIGNED_MALLOC
>> +    data = aligned_alloc(align, size);
>> +#elif HAVE_MEMALIGN
>> +    data = memalign(align, size);
>> +#else
>> +    return NULL;
>> +#endif
>> +
>> +    if (!data)
>> +        return NULL;
>> +
>> +    ret = av_buffer_create(data, size, av_buffer_default_free, NULL, 0);
>> +    if (!ret)
>> +        av_freep(&data);
>> +
>> +    return ret;
>> +}
>> +
>>  AVBufferRef *av_buffer_ref(const AVBufferRef *buf)
>>  {
>>      AVBufferRef *ret = av_mallocz(sizeof(*ret));
>> diff --git a/libavutil/buffer.h b/libavutil/buffer.h
>> index e1ef5b7f07..8422ec3453 100644
>> --- a/libavutil/buffer.h
>> +++ b/libavutil/buffer.h
>> @@ -107,6 +107,13 @@ AVBufferRef *av_buffer_alloc(size_t size);
>>   */
>>  AVBufferRef *av_buffer_allocz(size_t size);
>>
>> +/**
>> + * Allocate an AVBuffer of the given size and alignment.
>> + *
>> + * @return an AVBufferRef of given size or NULL when out of memory
>> + */
>> +AVBufferRef *av_buffer_aligned_alloc(size_t size, size_t align);
>> +
>>  /**
>>   * Always treat the buffer as read-only, even when it has only one
>>   * reference.
> 
> 
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