[Amarok] b18a028: Use shared memory for collection

[Maximilian Kossick]

On Sun, Nov 7, 2010 at 11:33 AM, Ralf Engels <ralf-engels at gmx.de> wrote:
>
>> Message: 1
>> Date: Sat, 06 Nov 2010 09:03:34 -0400
>> From: Jeff Mitchell <mitchell at kde.org>
>> Subject: Re: [Amarok] b18a028: Use shared memory for collection
>>       scanner to      rememb
>> To: maximilian.kossick at gmail.com, amarok-devel at kde.org
>> Cc: kde-commits at kde.org
>> Message-ID: <4CD55226.9030406 at kde.org>
>> Content-Type: text/plain; charset="utf-8"
>>
>> On 11/06/2010 05:38 AM, Maximilian Kossick wrote:
>> > One of the reasons for collection scanner as a separate executable was
>> > to prevent a crash in collectionscanner from bringing down Amarok as
>> > well. As both processes only communicated with each other via files or
>> > stdout/stdin, this was relatively safe. Is it ensured that a
>> > corrpution of the shared memory data does not crash both processes?
>>
>> This is especially important as TagLib has a history of being quite
>> crashy on corrupted files (which are quite common). (The old ScanManager
>> tried to skip such files if the scanner was crashing on a particular
>> file (with mixed success) by restarting the scanner.)
>>
>> --Jeff
>>
>
> Hi Jeff,
> the new scanner also skips the files where it crashed.
>
> I just needs to have a method to save the information about the bad
> files.
> The old version used a normal text file which might cause problems when
> the filenames have such stupid things as newlines in them.
> The my version used to use QSettings which turned out to be very slow.
> The very last version uses a shared memory which is both fast and (as
> taglib is not accessing the memory) also quite safe.
> An additional benefit is that several running scanners will not longer
> corrupt each others files.

Ok, newlines might be a problem unless properly escaped, but I do not
think that we should start using shared meory just because QSettings
is slow. I'd suggest either going back to the previous method, or
writing to a XML file using QXmlStreamWriter.

> Also while playing around with taglib I never encountered a crash
> directly caused by taglib.
> If it weren't for the batch mode I would recommend to forget about a
> seperate scanning process.
>
> Also since File.cpp and AFTUtil.cpp is directly using taglib they will
> run into the same taglib problems. So a potential crash is not prevented
> but only less likely.
>
> BR,
> Ralf
>
>
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