Vorbis dev - Nov 2005 - buffer overruns for small files

I wonder if anyone would have a comment on an experiment I have pretty much
completed in my MFC/C++ project.  With my simple libvorbis implementation, ogg
decoding works just fine for files that are 10kb or larger.  For anything
smaller (actually, I don't have a 9kb file, so <= 8), it seems that I get
an inaccurate value for ov_pcm_total.  Though ov_read returns zero, I overflow
the buffer and crash on ov_clear.  These are my TRACE statements:
>= 10kb:
Opening Audio File 'no_0.ogg'
vi->channels = '2'
vi->rate = '44100'
pcmTotal = '15341'
pcmTotal * vi->channels * 2 = '61364'
BufferSize = '61364'
dwBufferLength = '61364'
BufferSize = '61364'
dwBufferLength - BufferSize = '0'
------------
< 10kb:

Opening Audio File 'Steel guitar_4.ogg'
vi->channels = '2'
vi->rate = '44100'
pcmTotal = '9876'
pcmTotal * vi->channels * 2 = '39504'
BufferSize = '39504'
dwBufferLength = '43264'
BufferSize = '39504'
dwBufferLength - BufferSize = '3760'
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Not a clue, but since this hasn't been picked up:
How do the reference and example decoders handle these files?
Is dwBufferLength the allocated length or the attempted write
length?  Can you trace into vorbis_synthesis and see how
much is being allocated?

imalone


Steve Russell wrote:
> I wonder if anyone would have a comment on an experiment I have pretty much
completed in my MFC/C++ project.  With my simple libvorbis implementation, ogg
decoding works just fine for files that are 10kb or larger.  For anything
smaller (actually, I don't have a 9kb file, so <= 8), it seems that I get
an inaccurate value for ov_pcm_total.  Though ov_read returns zero, I overflow
the buffer and crash on ov_clear.  These are my TRACE statements:
> 
> 
>>= 10kb:
> 
> 
> Opening Audio File 'no_0.ogg'
> vi->channels = '2'
> vi->rate = '44100'
> pcmTotal = '15341'
> pcmTotal * vi->channels * 2 = '61364'
> BufferSize = '61364'
> dwBufferLength = '61364'
> BufferSize = '61364'
> dwBufferLength - BufferSize = '0'
> ------------
> < 10kb:
> 
> Opening Audio File 'Steel guitar_4.ogg'
> vi->channels = '2'
> vi->rate = '44100'
> pcmTotal = '9876'
> pcmTotal * vi->channels * 2 = '39504'
> BufferSize = '39504'
> dwBufferLength = '43264'
> BufferSize = '39504'
> dwBufferLength - BufferSize = '3760'
> 
> 
> ------------------------------------------------------------------------
> 
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