avformat/avio: privatize source of truth for AVIOContext::written

Looking at 3f75e5116b900f1428aa13041fc7d6301bf1988a, the field
was supposed to be private, but during merging the field and the
group that had the comment about it got separated.

Thus, move the actual privately utilized state of this variable
into the private FFIOContext. Additionally, name the private field
somewhat better, so that it does not get confused with the amount
of bytes written out.

2 files changed, 13 insertions, 4 deletions

diff --git a/libavformat/avio_internal.h b/libavformat/avio_internal.h
index eded38759b..467e80701f 100644
--- a/libavformat/avio_internal.h
+++ b/libavformat/avio_internal.h
@@ -66,6 +66,12 @@ typedef struct FFIOContext {
      * used after probing to ensure seekback and to reset the buffer size
      */
     int orig_buffer_size;
+
+    /**
+     * Written output size
+     * is updated each time a successful writeout ends up further position-wise
+     */
+    int64_t written_output_size;
 } FFIOContext;
 
 static av_always_inline FFIOContext *ffiocontext(AVIOContext *ctx)
diff --git a/libavformat/aviobuf.c b/libavformat/aviobuf.c
index 3d87d66091..b18a56ef19 100644
--- a/libavformat/aviobuf.c
+++ b/libavformat/aviobuf.c
@@ -164,8 +164,10 @@ static void writeout(AVIOContext *s, const uint8_t *data, int len)
         if (ret < 0) {
             s->error = ret;
         } else {
-            if (s->pos + len > s->written)
-                s->written = s->pos + len;
+            if (s->pos + len > ctx->written_output_size) {
+                ctx->written_output_size = s->pos + len;
+                s->written = ctx->written_output_size;
+            }
         }
     }
     if (ctx->current_type == AVIO_DATA_MARKER_SYNC_POINT ||
@@ -337,13 +339,14 @@ int64_t avio_skip(AVIOContext *s, int64_t offset)
 
 int64_t avio_size(AVIOContext *s)
 {
+    FFIOContext *const ctx = ffiocontext(s);
     int64_t size;
 
     if (!s)
         return AVERROR(EINVAL);
 
-    if (s->written)
-        return s->written;
+    if (ctx->written_output_size)
+        return ctx->written_output_size;
 
     if (!s->seek)
         return AVERROR(ENOSYS);