OpenEuphoria

RE: Previous Message All Messages Next Message Re: Checking file integrity

• Posted by rforno at tutopia.com Apr 24, 2003
• 399 views

Pete:
The CD I was speaking of is not protected, as far as I know. Once upon a
time it was completely readable, but later on it developed a scratch. As a
matter of fact, I have good copies of it.
My aim was to develop a program that detects unreadable files in a medium,
like hard disks, CD-ROMs, diskettes or whatever. Believe it or not, at this
very moment I have no bad diskettes at hand, so I can't test it. But I hope
to have one soon...
Regards.
----- Original Message -----
From: Pete Lomax <petelomax at blueyonder.co.uk>
Subject: Re: Previous Message All Messages Next Message Re: Checking file
integrity


> a
> a
> a
> a
> a
> a
> a
> a
> a
> a
> a
>
>
> On Tue, 22 Apr 2003 14:24:24 -0300, rforno at tutopia.com wrote:
>
> >
> >Bernie:
> >But I'm not asking that Euphoria performs data *recovery*. I only am
> >wondering if Euphoria can tell us about any data *error* that the OS or
the
> >hardware driver detects.
> I did a quick search on nero read error and found:
> that nero is validating the checksums and deliberately refusing to
> continue if it suspects copy protection is in use, almost certainly
> for legal reasons.
> "Neros complex read error handling", (in the advert blurb)
> "Not all drives are capable of returning error information"
> which suggests that nero specifically has code to get additional error
> info from more modern drives in a way DOS etc would not.
> "Now go to the Copy Options tab.
> ...Click Read Options.
> ...Number of Retries before error: "
>
> Anyway, have a look at this:
> http://www.phoenix.com/resources/specs-cdrom.pdf
> It may not be what you expect, but it shows how int 13 is used to make
> the cd drive emulate a normal drive, presumably if you use an int 13
> call to switch this off it would be possible to read the actual disk
> image where there may be some hidden checksums. I suspect
> there may be a few dog-eared copies of that at the nero offices.
>
> One trick we employed back in the days when distributing software on
> diskette was to make a bad block in a temporary file, fill the rest of
> the disk and then delete the temporary file. All the visible files
> would verify just fine, but copying the disk gave a read error.
> I hadn't made that connection before, but it is reasonable to assume a
> similar scheme could be used on cds. I know the penny will have
> dropped by now but I'll say it anyway: your program may not even be
> reading the part of the cd where the error lies.
>
> Pete
>
>
>
> TOPICA - Start your own email discussion group. FREE!
>
>