Re: [Bug-gnupod] mktunes: Same settings & version, different databases

[Nuno J. Silva]

address@hidden (Nuno J. Silva) writes:
> "H. Langos" <address@hidden> writes:
>> On Mon, Sep 13, 2010 at 05:01:43PM +0100, Nuno J. Silva wrote:

>>> They are exactly the same size:
> ...
>>>  $ diff oldtunesdb-good.ascii oldtunesdb-bad.ascii 
>>> 4,8c4
>>> < 00000030  01 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  
>>> |................|
>>> < 00000040  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  
>>> |................|
>>> < 00000050  00 00 00 00 00 00 00 00  30 69 78 e0 71 77 98 c7  
>>> |........0ix.qw..|
>>> < 00000060  c6 78 eb 38 99 ae 91 20  36 b0 f4 52 00 00 00 00  |.x.8... 
>>> 6..R....|
>>> < 00000070  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  
>>> |................|
>>> ---
>>> > 00000030  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  
>>> > |................|
>>> 207a204,206
>>> > 00001000  00 00 00 00 00 00 00 00  b0 08 68 01 86 d3 51 01  
>>> > |..........h...Q.|
>>> > 00001010  3f 79 9d e5 00 00 00 00  00 00 00 00 00 00 00 00  
>>> > |?y..............|
>>> > 00001020  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  
>>> > |................|
>>> 
>>> I don't know what the changes do, though.
>>
>> If you could send me the iTunesDB file I could take a detailed look at them.
>>
>> The difference really looks tiny. So it should be easy enough to find out
>> whats wrong. And I'll have to get a copy of the ipodlinux wiki. With the
>> format description of iTunesDB files.
...
> It seems the same version of gnupod is hashing files in a different way
> on each computer. 
>
> Sounds like time to read the gnupod source and to the operations
> directly in perl to see if there's some nasty mathematic bug under the
> hood...

I've not yet solved it, but I thought it was time for an update:

As far as I can tell, _Pretender (in hash-file.pm, the file I've been
looking at), writes at different places: in the computer which generates
the good db, it writes at the specified offsets, in the other, it
appends some values to the end of the file instead of doing it at the
given offset (but it might be doing some writes on the right place).

Strange enough, I've been using the debug technique known as
debug-by-printf and it seems the offsets are okay...

I'll dive deeper into this and then I'll say what's going on (I hope I
can find that out).

-- 
Nuno J. Silva
gopher://sdf-eu.org/1/users/njsg