Re: [Lzip-bug] bug in error output with corrupted lzip files

[Lloyd Hilaiel]

On Feb 9, 2009, at 8:30 AM, Antonio Diaz Diaz wrote:

> Hello,
>
> Lloyd Hilaiel wrote:
> >  foo.tar.1.lz: trailer truncated at trailer position 0; some  
> > checks  may fail.
> > bad crc for uncompressed data; expected 00000000, obtained E44173E6.
> > bad uncompressed size; expected 0, obtained 297944.
> > lzip: Deleting output file `foo.tar.1', if it exists.
> > I'm guessing that the expected and obtained values are flipped?
>
> I think not. The compressor stores in the member trailer the CRC and  
> size of the uncompressed data. Then the decompressor compares the  
> CRC and size "obtained" during decompression with those stored in  
> the trailer (the "expected" ones).
>
> If the trailer is corrupt, the "expected" values will be wrong.

Aha, I had thought the decompressor would "expect" a certain CRC and  
size based on its presence in the trailer, and then compare then with  
values "obtained" while decompressing the stream.  Silly me.  Perhaps  
'calculated' is clearer than 'obtained'?

best,
lloyd


> Best regards,
> Antonio.