On 4/30/2021 10:36 AM, Lynne wrote:
Apr 30, 2021, 13:34 by br...@frogmouth.net:
Signed-off-by: Brad Hards <br...@frogmouth.net>
---
libavutil/frame.c | 31 +++++++++++++++++++++++++++++++
libavutil/frame.h | 23 +++++++++++++++++++++++
2 files changed, 54 insertions(+)
diff --git a/libavutil/frame.c b/libavutil/frame.c
index 2ec59b44b1..9f9953c2b4 100644
--- a/libavutil/frame.c
+++ b/libavutil/frame.c
@@ -625,6 +625,37 @@ AVFrameSideData *av_frame_get_side_data(const AVFrame
*frame,
return NULL;
}
+AVFrameSideData *av_frame_get_side_data_n(const AVFrame *frame,
+ enum AVFrameSideDataType type,
+ const int side_data_instance)
+{
+ int i;
+ int n = 0;
+
+ for (i = 0; i < frame->nb_side_data; i++) {
+ if (frame->side_data[i]->type == type) {
+ if (n == side_data_instance) {
+ return frame->side_data[i];
+ } else {
+ n++;
+ }
+ }
+ }
+ return NULL;
+}
_follow_the_code_style_
We have a document! We have thousands of lines of code already written with it!
We do not add brackets on one-line statements, and we allow for (int loops.
I don't like this function's name, and I don't like the way it operates.
If we do allow multiple side-data entries with the same type (my opinion is if
you can't read them
without workarounds they're just not allowed), I'd much rather have a linked
list, which would
allow us to keep the same style of _next(prev) iteration functions we've used
everywhere else.
Plus, it would mean you don't have to do a worst possible case iteration for
each lookup when you
have a million side data entries. Users have wanted to do this.
I think we should just have a av_frame_get_side_data_next(prev), where prev
will be
NULL for the first call. Users can filter by data type themselves.
av_frame_get_side_data_iterate(void **opaque), if anything, following
existing API like those iterating through AVCodecs. There's nothing in a
returned AVFrameSideData that points to the next entry.
In any case, this would require a warning about calling
av_frame_remove_side_data() invalidating the iteration state.
That way av_frame_get_side_data_nb can be removed.
I'd also like an APIchanges entry we're allowing multiple side data entries
with the same type.
This is not a small change in behavior that we're making official.
This would not be a change in behavior. We would only be adding an
official way to fetch every entry beyond the first by introducing an
iterator function, something already possible if you manually iterate
through frame->side_data entries, something we afaik never really forbid.
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