On Sun, 4 Oct 2020, Andriy Gelman wrote:
Hi Marton,
On Tue, 29. Sep 23:10, Marton Balint wrote:
Existing code did not check if the requested seekback buffer is
already read entirely. In this case, nothing has to be done to guarantee
seekback.
Signed-off-by: Marton Balint <c...@passwd.hu>
---
libavformat/aviobuf.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/libavformat/aviobuf.c b/libavformat/aviobuf.c
index 9675425349..d94be478ac 100644
--- a/libavformat/aviobuf.c
+++ b/libavformat/aviobuf.c
@@ -999,6 +999,9 @@ int ffio_ensure_seekback(AVIOContext *s, int64_t buf_size)
int filled = s->buf_end - s->buffer;
ptrdiff_t checksum_ptr_offset = s->checksum_ptr ? s->checksum_ptr -
s->buffer : -1;
+ if (buf_size <= s->buf_end - s->buf_ptr)
+ return 0;
+
buf_size += s->buf_ptr - s->buffer + max_buffer_size;
if (buf_size < filled || s->seekable || !s->read_packet)
I was testing this set, and saw commit 53c25ee0736. It discards buffered data by
resetting s->{buf_ptr,buf_end} when we need to read more data.
Maybe I missed something, but wouldn't this mean that seekback no longer works
if
fill_buffer() is called in avio_read_partial().. so defeating the purpose of
ffio_ensure_seekback()?
I think you are right. It looks like that commit is not needed after
2ca48e466675a8a3630061cd2c15325eab8eda97, so probably it should be
reverted now to unbreak ffio_ensure_seekback().
Regards,
Marton
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