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

[Nuno J. Silva]

"H. Langos" <address@hidden> writes:

> Hi Nuno,

(Sorry for the delay, classes started so I've been too busy or tired to
look into this again earlier.)

> On Mon, Sep 13, 2010 at 05:01:43PM +0100, Nuno J. Silva wrote:
>> "H. Langos" <address@hidden> writes:
>> 
>> > Hi Nuno,
>> >
>> > Just a couple of questions...
>> >
>> > Which OS / distribution do those computers have.
>> 
>> Gentoo GNU/Linux. They are not both up-to-date, though, as I'm afraid
>> some upgrade might have broken this (I'll try do some step-by-step
>> updating today - basicly updates interleaved with mktunes.pl).
>
> any luck with that?

No luck. After all upgrades the computers were still generating
different DBs.

(But there is a difference I forgot: one of the computers is a dual core
(the other is single-core).)

>> 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.

I decided the best way to find out what's going on was to try with the
simplest solution possible: I made a "virtual" empty ipod, by running
the init script on an empty folder, and renamed .gnupodrc so that it is
not used.

Running mktunes on both machines with no fwguid results in equal
databases.

When I set a fwguid (I just picked the 000ba3100310abcf example from the
info manual), mktunes writes different databases, just like with the
real iPod.

Also, positions 0x30 to 0x7f are removed (and the line starting with
0x30 is replaced with zeros), as in the real db.  But the place where
some lines are added differs - maybe they're appended at the end of the
file.


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...

> Their site is down most of the time and I only get a google cached version
> of somebody's local copy that was also retrieved from google cache...

Seems like time to google cache that google cached version.

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