avformat/matroskaenc: Avoid allocation for Cues

Up until now, the Matroska muxer would allocate a structure containing
three members: The segment offset, a pointer to an array containing Cue
(index) entries and a counter for said array. It is unnecessary to
allocate it separately and it is unnecessary to contain the segment
offset in said structure, as it duplicates another field contained in
the MatroskaMuxContext. This commit implements the corresponding
changes.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

libavformat/matroskaenc.c

@@ -88,7 +88,6 @@ typedef struct mkv_cuepoint {
 } mkv_cuepoint;
 
 typedef struct mkv_cues {
-    int64_t         segment_offset;
     mkv_cuepoint    *entries;
     int             num_entries;
 } mkv_cues;
@@ -139,7 +138,7 @@ typedef struct MatroskaMuxContext {
     int64_t         duration_offset;
     int64_t         duration;
     mkv_seekhead    seekhead;
-    mkv_cues        *cues;
+    mkv_cues        cues;
     mkv_track       *tracks;
     mkv_attachments *attachments;
 
@@ -398,10 +397,7 @@ static void mkv_deinit(AVFormatContext *s)
     ffio_free_dyn_buf(&mkv->tracks_bc);
     ffio_free_dyn_buf(&mkv->tags_bc);
 
-    if (mkv->cues) {
-        av_freep(&mkv->cues->entries);
-        av_freep(&mkv->cues);
-    }
+    av_freep(&mkv->cues.entries);
     if (mkv->attachments) {
         av_freep(&mkv->attachments->entries);
         av_freep(&mkv->attachments);
@@ -483,19 +479,10 @@ static int mkv_write_seekhead(AVIOContext *pb, MatroskaMuxContext *mkv,
     return 0;
 }
 
-static mkv_cues *mkv_start_cues(int64_t segment_offset)
-{
-    mkv_cues *cues = av_mallocz(sizeof(mkv_cues));
-    if (!cues)
-        return NULL;
-
-    cues->segment_offset = segment_offset;
-    return cues;
-}
-
-static int mkv_add_cuepoint(mkv_cues *cues, int stream, int tracknum, int64_t ts,
+static int mkv_add_cuepoint(MatroskaMuxContext *mkv, int stream, int tracknum, int64_t ts,
                             int64_t cluster_pos, int64_t relative_pos, int64_t duration)
 {
+    mkv_cues *cues = &mkv->cues;
     mkv_cuepoint *entries = cues->entries;
 
     if (ts < 0)
@@ -509,7 +496,7 @@ static int mkv_add_cuepoint(mkv_cues *cues, int stream, int tracknum, int64_t ts
     cues->entries[cues->num_entries].pts           = ts;
     cues->entries[cues->num_entries].stream_idx    = stream;
     cues->entries[cues->num_entries].tracknum      = tracknum;
-    cues->entries[cues->num_entries].cluster_pos   = cluster_pos - cues->segment_offset;
+    cues->entries[cues->num_entries].cluster_pos   = cluster_pos - mkv->segment_offset;
     cues->entries[cues->num_entries].relative_pos  = relative_pos;
     cues->entries[cues->num_entries++].duration    = duration;
 
@@ -1930,11 +1917,6 @@ static int mkv_write_header(AVFormatContext *s)
             return ret;
     }
 
-    mkv->cues = mkv_start_cues(mkv->segment_offset);
-    if (!mkv->cues) {
-        return AVERROR(ENOMEM);
-    }
-
     if (s->metadata_header_padding > 0) {
         if (s->metadata_header_padding == 1)
             s->metadata_header_padding++;
@@ -2353,7 +2335,8 @@ static int mkv_write_packet_internal(AVFormatContext *s, AVPacket *pkt, int add_
         if (ret < 0)
             return ret;
         if ((s->pb->seekable & AVIO_SEEKABLE_NORMAL) && (par->codec_type == AVMEDIA_TYPE_VIDEO && keyframe || add_cue)) {
-            ret = mkv_add_cuepoint(mkv->cues, pkt->stream_index, tracknum, ts, mkv->cluster_pos, relative_packet_pos, -1);
+            ret = mkv_add_cuepoint(mkv, pkt->stream_index, tracknum, ts,
+                                   mkv->cluster_pos, relative_packet_pos, -1);
             if (ret < 0) return ret;
         }
     } else {
@@ -2378,7 +2361,7 @@ FF_ENABLE_DEPRECATION_WARNINGS
         }
 
         if (s->pb->seekable & AVIO_SEEKABLE_NORMAL) {
-            ret = mkv_add_cuepoint(mkv->cues, pkt->stream_index, tracknum, ts,
+            ret = mkv_add_cuepoint(mkv, pkt->stream_index, tracknum, ts,
                                    mkv->cluster_pos, relative_packet_pos, duration);
             if (ret < 0)
                 return ret;
@@ -2508,14 +2491,14 @@ static int mkv_write_trailer(AVFormatContext *s)
 
 
     if ((pb->seekable & AVIO_SEEKABLE_NORMAL) && !mkv->is_live) {
-        if (mkv->cues->num_entries) {
+        if (mkv->cues.num_entries) {
             if (mkv->reserve_cues_space) {
                 int64_t cues_end;
 
                 currentpos = avio_tell(pb);
                 avio_seek(pb, mkv->cues_pos, SEEK_SET);
 
-                cuespos  = mkv_write_cues(s, mkv->cues, mkv->tracks, s->nb_streams);
+                cuespos  = mkv_write_cues(s, &mkv->cues, mkv->tracks, s->nb_streams);
                 cues_end = avio_tell(pb);
                 if (cues_end > cuespos + mkv->reserve_cues_space) {
                     av_log(s, AV_LOG_ERROR,
@@ -2531,7 +2514,7 @@ static int mkv_write_trailer(AVFormatContext *s)
 
                 avio_seek(pb, currentpos, SEEK_SET);
             } else {
-                cuespos = mkv_write_cues(s, mkv->cues, mkv->tracks, s->nb_streams);
+                cuespos = mkv_write_cues(s, &mkv->cues, mkv->tracks, s->nb_streams);
             }
 
             mkv_add_seekhead_entry(mkv, MATROSKA_ID_CUES, cuespos);