avformat/aviobuf: fix checks in ffio_ensure_seekback

The new buf_size was detemined too conservatively, maybe because of the off-by-one issue which was fixed recently in fill_buffer. We can safely substract 1 more from the new buffer size, because max_buffer_size space must only be guaranteed when we are reading the last byte of the requested window. Comparing the new buf_size against filled did not make a lot of sense, what makes sense is that we want to reallocate the buffer if the new buf_size is bigger than the old, therefore the change in the check. Signed-off-by: Marton Balint <[email protected]>
zhangxiaoben · Oct 9, 2020 · a3943c4 · a3943c4
1 parent 6d972be
commit a3943c4
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/libavformat/aviobuf.c b/libavformat/aviobuf.c
@@ -1002,9 +1002,9 @@ int ffio_ensure_seekback(AVIOContext *s, int64_t buf_size)
     if (buf_size <= s->buf_end - s->buf_ptr)
         return 0;
 
-    buf_size += s->buf_ptr - s->buffer + max_buffer_size;
+    buf_size += s->buf_ptr - s->buffer + max_buffer_size - 1;
 
-    if (buf_size < filled || s->seekable || !s->read_packet)
+    if (buf_size <= s->buffer_size || s->seekable || !s->read_packet)
         return 0;
     av_assert0(!s->write_flag);