avcodec: add internal side data wrappers

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

Signed-off-by: Anton Khirnov <anton@khirnov.net>

libavcodec/decode.c

@@ -1791,6 +1791,72 @@ 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 **psd)
+{
+    AVFrameSideData *sd;
+
+    if (side_data_pref(avctx, frame, type)) {
+        if (psd)
+            *psd = NULL;
+        return 0;
+    }
+
+    sd = av_frame_new_side_data(frame, type, size);
+    if (psd)
+        *psd = sd;
+
+    return sd ? 0 : AVERROR(ENOMEM);
+}
+
+int ff_frame_new_side_data_from_buf(const AVCodecContext *avctx,
+                                    AVFrame *frame, enum AVFrameSideDataType type,
+                                    AVBufferRef **buf, AVFrameSideData **psd)
+{
+    AVFrameSideData *sd = NULL;
+    int ret = 0;
+
+    if (side_data_pref(avctx, frame, type))
+        goto finish;
+
+    sd = av_frame_new_side_data_from_buf(frame, type, *buf);
+    if (sd)
+        *buf = NULL;
+    else
+        ret = AVERROR(ENOMEM);
+
+finish:
+    av_buffer_unref(buf);
+    if (psd)
+        *psd = sd;
+
+    return ret;
+}
+
 int ff_copy_palette(void *dst, const AVPacket *src, void *logctx)
 {
     size_t size;

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 and sd is not NULL, *sd may either contain 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.
+ *
+ * *buf is ALWAYS consumed by this function and NULL written in its place, even
+ * on failure.
+ */
+int ff_frame_new_side_data_from_buf(const AVCodecContext *avctx,
+                                    AVFrame *frame, enum AVFrameSideDataType type,
+                                    AVBufferRef **buf, AVFrameSideData **sd);
+
 #endif /* AVCODEC_DECODE_H */