[FFmpeg-devel] [PATCH 1/2] avformat/wtvdec: Forward errors when reading packet

Andreas Rheinhardt andreas.rheinhardt at gmail.com
Tue Feb 18 14:36:00 EET 2020


Andreas Rheinhardt:
> wtvfile_read_packet did not abide by the requirements of an
> AVIOContext's read_packet-function: If it did not read anything,
> it returned zero, which currently leads to a warning in read_packet_wrapper
> in aviobuf.c. Said warning will be an av_assert2 as soon as
> FF_API_OLD_AVIO_EOF_0 is zero (probably the next major version bump).
> So instead forward the error code from the underlying protocol.
> 
> This error/assert is triggered in the wtv-demux FATE test.
> 
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
> ---
> This patch supersedes [1]. The difference to the previous version is
> that I have changed the return value from "nread ? nread : n ? :
> AVERROR_EOF" to "nread ? nread : n". This can only make a difference if
> buf_size (the size of the data to be read) is zero and I now think that
> this should simply not happen: It would be possible by calling
> avio_read_partial with a desired size of 0 and if the AVIOContext's
> write_flag is set, but avio_read_partial is not called with one of
> wtvdec's custom AVIOContexts (not to mention that if this were a
> problem, it should probably be fixed in avio_read_partial).
> 
> [1]: https://patchwork.ffmpeg.org/project/ffmpeg/patch/20190821090438.10260-4-andreas.rheinhardt@gmail.com/
> 
>  libavformat/wtvdec.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/libavformat/wtvdec.c b/libavformat/wtvdec.c
> index 67d934f074..83f510b92f 100644
> --- a/libavformat/wtvdec.c
> +++ b/libavformat/wtvdec.c
> @@ -71,7 +71,7 @@ static int wtvfile_read_packet(void *opaque, uint8_t *buf, int buf_size)
>  {
>      WtvFile *wf = opaque;
>      AVIOContext *pb = wf->pb_filesystem;
> -    int nread = 0;
> +    int nread = 0, n = 0;
>  
>      if (wf->error || pb->error)
>          return -1;
> @@ -80,7 +80,6 @@ static int wtvfile_read_packet(void *opaque, uint8_t *buf, int buf_size)
>  
>      buf_size = FFMIN(buf_size, wf->length - wf->position);
>      while(nread < buf_size) {
> -        int n;
>          int remaining_in_sector = (1 << wf->sector_bits) - (wf->position & ((1 << wf->sector_bits) - 1));
>          int read_request        = FFMIN(buf_size - nread, remaining_in_sector);
>  
> @@ -100,7 +99,7 @@ static int wtvfile_read_packet(void *opaque, uint8_t *buf, int buf_size)
>              }
>          }
>      }
> -    return nread;
> +    return nread ? nread : n;
>  }
>  
>  /**
> 

Ping.

- Andreas


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