avcodec/hevcdec: Add pointers to logctx and parent ctx to HEVCLocalCtx

It is safe for a slice thread to read the main context
and therefore it is safe to add a pointer to const HEVCContext
(namely the parent context) to each HEVCLocalContext.
It is also safe (and actually redundant) to add a pointer
to a logcontext to HEVCLocalContext.

Doing so allows to pass the HEVCLocalContext as context in
the parts of the code that is run slice-threaded when slice-threading
is in use (currently these parts of the code use ordinary
HEVCContext*). This way one is not tempted to modify
the main context from the slice contexts.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavcodec/hevcdec.c

@@ -2662,6 +2662,8 @@ static int hls_slice_data_wpp(HEVCContext *s, const H2645NAL *nal)
             res = AVERROR(ENOMEM);
             goto error;
         }
+        s->HEVClcList[i]->logctx = s->avctx;
+        s->HEVClcList[i]->parent = s->sList[i];
     }
 
     offset = (lc->gb.index >> 3);
@@ -3643,6 +3645,8 @@ static av_cold int hevc_init_context(AVCodecContext *avctx)
     s->sList = av_mallocz(sizeof(HEVCContext*) * s->threads_number);
     if (!s->HEVClc || !s->HEVClcList || !s->sList)
         return AVERROR(ENOMEM);
+    s->HEVClc->parent = s;
+    s->HEVClc->logctx = avctx;
     s->HEVClcList[0] = s->HEVClc;
     s->sList[0] = s;
 

libavcodec/hevcdec.h

@@ -428,6 +428,9 @@ typedef struct HEVCLocalContext {
 
     uint8_t first_qp_group;
 
+    void *logctx;
+    const struct HEVCContext *parent;
+
     GetBitContext gb;
     CABACContext cc;