movenc: Use null buffers for measuring the amount of data to be written

Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/movenc.c

@@ -2443,13 +2443,11 @@ static int mov_write_moof_tag(AVIOContext *pb, MOVMuxContext *mov, int tracks)
 {
     AVIOContext *avio_buf;
     int ret, moof_size;
-    uint8_t *buf;
 
-    if ((ret = avio_open_dyn_buf(&avio_buf)) < 0)
+    if ((ret = ffio_open_null_buf(&avio_buf)) < 0)
         return ret;
     mov_write_moof_tag_internal(avio_buf, mov, tracks, 0);
-    moof_size = avio_close_dyn_buf(avio_buf, &buf);
-    av_free(buf);
+    moof_size = ffio_close_null_buf(avio_buf);
     return mov_write_moof_tag_internal(pb, mov, tracks, moof_size);
 }
 
@@ -2738,11 +2736,10 @@ static int mov_flush_fragment(AVFormatContext *s)
         if (i < mov->nb_streams)
             return 0;
 
-        if ((ret = avio_open_dyn_buf(&moov_buf)) < 0)
+        if ((ret = ffio_open_null_buf(&moov_buf)) < 0)
             return ret;
         mov_write_moov_tag(moov_buf, mov, s);
-        buf_size = avio_close_dyn_buf(moov_buf, &buf);
-        av_free(buf);
+        buf_size = ffio_close_null_buf(moov_buf);
         for (i = 0; i < mov->nb_streams; i++)
             mov->tracks[i].data_offset = pos + buf_size + 8;
 
@@ -3348,16 +3345,13 @@ static int mov_write_header(AVFormatContext *s)
 static int get_moov_size(AVFormatContext *s)
 {
     int ret;
-    uint8_t *buf;
     AVIOContext *moov_buf;
     MOVMuxContext *mov = s->priv_data;
 
-    if ((ret = avio_open_dyn_buf(&moov_buf)) < 0)
+    if ((ret = ffio_open_null_buf(&moov_buf)) < 0)
         return ret;
     mov_write_moov_tag(moov_buf, mov, s);
-    ret = avio_close_dyn_buf(moov_buf, &buf);
-    av_free(buf);
-    return ret;
+    return ffio_close_null_buf(moov_buf);
 }
 
 /*