[FFmpeg-devel] [PATCH 17/38] avcodec: add internal side data wrappers

[Anton Khirnov]

From: Niklas Haas <git at haasn.dev>

The signature of ff_frame_new_side_data got more complicated due to
a need to distinguish between "failed allocating side data" and "side
data was already present".

We could do something similar to ff_frame_new_side_data_from_buf, but
most callers ignore the OOM condition on this function, which is merely
re-allocating the side data array. So preserve the return signature to
make it slightly less of a pain to use.

Signed-off-by: Anton Khirnov <anton at khirnov.net>
---
 libavcodec/decode.c | 47 +++++++++++++++++++++++++++++++++++++++++++++
 libavcodec/decode.h | 20 +++++++++++++++++++
 2 files changed, 67 insertions(+)

diff --git a/libavcodec/decode.c b/libavcodec/decode.c
index 5524e229c2..10946f208a 100644
--- a/libavcodec/decode.c
+++ b/libavcodec/decode.c
@@ -1857,6 +1857,53 @@ int ff_decode_preinit(AVCodecContext *avctx)
     return 0;
 }
 
+/**
+ * Check side data preference and clear existing side data from frame
+ * if needed.
+ *
+ * @retval 0 side data of this type can be added to frame
+ * @retval 1 side data of this type should not be added to frame
+ */
+static int side_data_pref(const AVCodecContext *avctx, AVFrame *frame,
+                          enum AVFrameSideDataType type)
+{
+    DecodeContext *dc = decode_ctx(avctx->internal);
+
+    // Note: could be skipped for `type` without corresponding packet sd
+    if (av_frame_get_side_data(frame, type)) {
+        if (dc->side_data_pref_mask & (1ULL << type))
+            return 1;
+        av_frame_remove_side_data(frame, type);
+    }
+
+    return 0;
+}
+
+
+int ff_frame_new_side_data(const AVCodecContext *avctx, AVFrame *frame,
+                           enum AVFrameSideDataType type, size_t size,
+                           AVFrameSideData **sd)
+{
+    if (side_data_pref(avctx, frame, type)) {
+        *sd = NULL;
+        return 0;
+    }
+
+    *sd = av_frame_new_side_data(frame, type, size);
+    return *sd ? 0 : AVERROR(ENOMEM);
+}
+
+AVFrameSideData *ff_frame_new_side_data_from_buf(const AVCodecContext *avctx,
+                                                 AVFrame *frame,
+                                                 enum AVFrameSideDataType type,
+                                                 AVBufferRef *buf)
+{
+    if (side_data_pref(avctx, frame, type))
+        return NULL;
+
+    return av_frame_new_side_data_from_buf(frame, type, buf);
+}
+
 int ff_copy_palette(void *dst, const AVPacket *src, void *logctx)
 {
     size_t size;
diff --git a/libavcodec/decode.h b/libavcodec/decode.h
index daf1a67444..a131b9940a 100644
--- a/libavcodec/decode.h
+++ b/libavcodec/decode.h
@@ -155,4 +155,24 @@ int ff_hwaccel_frame_priv_alloc(AVCodecContext *avctx, void **hwaccel_picture_pr
 const AVPacketSideData *ff_get_coded_side_data(const AVCodecContext *avctx,
                                                enum AVPacketSideDataType type);
 
+/**
+ * Wrapper around av_frame_new_side_data, which rejects side data overridden by
+ * the demuxer. Returns 0 on success, and a negative error code otherwise.
+ * If successful, *sd may either be a pointer to the new side data, or NULL
+ * in case the side data was already present.
+ */
+int ff_frame_new_side_data(const AVCodecContext *avctx, AVFrame *frame,
+                           enum AVFrameSideDataType type, size_t size,
+                           AVFrameSideData **sd);
+
+/**
+ * Similar to `ff_frame_new_side_data`, but using an existing buffer ref.
+ * On success, returns the newly added side data, and passes ownership
+ * of `buf` to the frame.
+ */
+AVFrameSideData *ff_frame_new_side_data_from_buf(const AVCodecContext *avctx,
+                                                 AVFrame *frame,
+                                                 enum AVFrameSideDataType type,
+                                                 AVBufferRef *buf);
+
 #endif /* AVCODEC_DECODE_H */
-- 
2.42.0