[FFmpeg-devel] [PATCH 2/3] nutdec: stop skipping bytes at EOF

[Andreas Cadhalpun]

On 20.05.2015 03:15, Michael Niedermayer wrote:
> On Wed, May 20, 2015 at 12:49:55AM +0200, Andreas Cadhalpun wrote:
>> This can unnecessarily waste a lot of time.
>>
>> Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.com>
>> ---
>>  libavformat/nutdec.c | 8 +++++---
>>  1 file changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/libavformat/nutdec.c b/libavformat/nutdec.c
>> index a75587f..e979ee6 100644
>> --- a/libavformat/nutdec.c
>> +++ b/libavformat/nutdec.c
>> @@ -47,6 +47,8 @@ static int get_str(AVIOContext *bc, char *string, unsigned int maxlen)
>>      while (len > maxlen) {
>>          avio_r8(bc);
>>          len--;
>> +        if (bc->eof_reached)
>> +            len = maxlen;
>>      }
> 
> maybe this would be better as avio_skip()
> but ok either way

I prefer to avoid the additional complexity of avio_skip (see below...).

>>      if (maxlen)
>> @@ -211,7 +213,7 @@ static int skip_reserved(AVIOContext *bc, int64_t pos)
>>          avio_seek(bc, pos, SEEK_CUR);
>>          return AVERROR_INVALIDDATA;
>>      } else {
>> -        while (pos--)
>> +        while (pos-- && !bc->eof_reached)
>>              avio_r8(bc);
>>          return 0;
>>      }
>> @@ -291,7 +293,7 @@ static int decode_main_header(NUTContext *nut)
>>          if (tmp_fields > 7)
>>              tmp_head_idx = ffio_read_varlen(bc);
>>  
>> -        while (tmp_fields-- > 8)
>> +        while (tmp_fields-- > 8 && !bc->eof_reached)
>>              ffio_read_varlen(bc);
>>  
>>          if (count <= 0 || count > 256 - (i <= 'N') - i) {
>> @@ -990,7 +992,7 @@ static int decode_frame_header(NUTContext *nut, int64_t *pts, int *stream_id,
>>          *header_idx = ffio_read_varlen(bc);
>>      if (flags & FLAG_RESERVED)
>>          reserved_count = ffio_read_varlen(bc);
>> -    for (i = 0; i < reserved_count; i++)
>> +    for (i = 0; i < reserved_count && !bc->eof_reached; i++)
>>          ffio_read_varlen(bc);
> 
> these should return an error in the eof case

OK, patch updated.

> the first of the 3 could use a seek/skip as well possibly

I tried this, but it caused weird crashes in av_crc, so I reverted that.

> also if you want some of these things could also be limited by te
> packet end from get_packetheader and not just EOF

I'm not sure this would help much, because get_packetheader reads the
size from the file, so it could be an arbitrary value as well. 

Best regards,
Andreas
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