Re: [linux-minidisc] another way to send SCSI commands

[manner.moe@gmx.de]

>Betreff : Re: [linux-minidisc] another way to send SCSI commands
>Gesendet: 04.12.2010 18:23:41
>An : "Thomas Arp <manner.moe@gmx.de>"
>Von: "Michael Karcher <Michael.Karcher@fu-berlin.de>"

>----- Originale Nachricht -----

>Am Samstag, den 04.12.2010, 14:33 +0100 schrieb Thomas Arp:
>> I´m rewriting himdscsitest.c using the dvd-rw-tools headers for
>> testing.
>That's great!

O.K., here is the new source code.
 
>> As far as i have tested yet when cmd.transport() has finished the
>> Scsi_Command structure will be closed automatically.
>As far as I can see, this is neither the case for Windows nor for Linux.
>Can you point out the code you think it closes the file descriptor? I
>see closing only in the destructor of Scsi_Command, so the device is
>closed only when the Scsi_Command structure goes out of scope.

>But I *do* see a potential problem that causes early closes: The
>Scsi_Command structure must never be copied, as it violates the C++
>"rule of three":
> http://en.wikipedia.org/wiki/Rule_of_three_%28C%2B%2B_programming%29
>"must never be copied" is *not* talking about DRM here (SCNR), but means
>that you can not pass a "Scsi_Command" as value to a subfunction,
>because pass-by-value copies the data (and that includes the handle) to
>local storage of the subfunction, and if that subfunction terminates,
>the local copy is destructed, closing the handle, although the object it
>was copied from in the caller still is alive. Also hell will break loose
>(i.e. you will get early closed fds/double-closed fds/leaked fds) if you
>assign one Scsi_Command object to another one. So do only pass the
>Scsi_Command structure by reference or pointer!

Yes, this was exactly my problem.

Thomas

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