James Almer (12025-01-22):
> Ok, will implement a new struct.
Thanks.
I think this code would work:
typedef struct AVSideDataParamChange
…
intmax_t end_padding;
} AVSideDataSomethingType;
static const AVSideDataParamChange default = { ... };
AVSideDataParamChange pc;
av_assert0(sd->size > sizeof(pc.end_padding));
size_t s = FFMIN(sd->size - sizeof(pc.end_padding), sizeof(pc));
memcpy(&pc, sd->data, s);
memcpy((char *)&pc + s, (char *)&default + s, sizeof(pc) - s);
After this code, pc contains the fields from the side data if they are
present in the version known by the caller and the fields from default
otherwise.
I am rather sure this is valid C unless there we add a field with
individual size greater than end_padding, hence intmax_t.
If I can at some time start spending efforts on FFmpeg again, I intend
to use this pattern on things that need to be lightweight (no dynamic
allocations) but extensible.
Regards,
--
Nicolas George
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