Re: [Dev-C++] How to read/write directly a track/sector in a hard disk or CD

[Per W. <pw...@ia...>]

Security from snooping? That is done by strong encryption.

Security from data loss? That is done by journaling or similar for power
failures and mirrored or check-summed data to handle hardware failures.

Data recovery? Journaling, ECC, check-sum, mirroring or similar..

Reasons for thinking about direct access - or for intercepting driver
accesses might be:

- extremely high-end database using custom-optimized file system.
- cryptographic layer doing sector-by-sector encryption.
- routing layer for faking a local harddrive over the network.
- storage manager layer for glueing multiple drives dynamically or
statically into larger drives.
- software RAID.
- support for foreign file systems natively or in "user mode".
- repartitioning drives, growing/shrinking/converting file systems.
- media rotation layer for supporting media with limited write counts.
- repair of broken file system.
- ...

Most of above cases exists for free or almost free, or are so very out of
scope for real use that it isn't economical to develop a solution unless
the target application can be sold for _big_ sums of money.

www.sysinternals.com have some nice articles about file systems and how to
build your own disk defragger for example.

Anyway, to be able to give reasonable help/recommendations it very much
helps to know the why. A lot of people ask very specific questions about
problems that are not relevant. What use is it to help them to fix a bug
in an incorrectly chosen algorithm instead of telling them which algorithm
they should have used? The quality of expected answers very much depends
on the quality of the question.

/Per W

On Mon, 29 Aug 2005, Alfred P. Reaud wrote:

> IMHO, there are many reasons for doing such, including security, data recovery, etc.  However, I've never seen this done in C/C++.  As you have to access low level IO functions, this is preferentially done is assembly, as I don't believe C/C++ have this capability.  At least, I've never found the need to research it.
>
> I would recommend Googling for low level disk IO.  If you're really diligent, you can find out that there are undocumented features to disk controllers that significantly enhance data security.
>
> Per Westermark <pw...@ia...> wrote:
> Since reading/wringing directly to the drive requires access to the
> physical hardware, I have to ask exactly why you have this need. What are
> you trying to do?
>
> /Per W
>
> On Mon, 29 Aug 2005, rc...@bi... wrote:
>
> >
> > Dear sir,
> >
> > I see how to read/write to files using C. But I need to to define a track/sector that I can read and write to it under my control. Could
> > you help me pointing out documents/sites with this information or teatching me how to do this.
> >
> > Thanks for your help
> >
> > Roger
> <snip>
>
>
>
>
> Alfred P. Reaud
>
>
>