What is encapsulation?

E. Robert Tisdale

Marshall Cline wrote:

http://www.parashift.com/c++-faq-lit...s.html#faq-7.4

"Preventing unauthorized access
to some piece of information or functionality."

That's *data hiding* -- not encapsulation.
A C struct *encapsulates* data members
but C does not support any mechanism
for hiding the actual data representation
except *opaque* data structures.

"Inheritanc e can also be used as a form of encapsulation."

Yes, but public inheritance does not "hide" the base class.

"Designing a clean interface
and separating that interface from its implementation
merely allows users to use the interface.
But encapsulating (putting "in a capsule") the implementation
forces users to use the interface."

No. It does *not* force the "user" to use the interface.
A determined hacker will find a way to "reach around" the interface
and access the data members directly.
Data hiding is *not* encryption.
It merely prevents unwary application programmers
from *accidently* accessing data members directly.

Sep 13 '05 #1

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10860

John Fullman

Ohhh... a philisophical question.

Encapsulation is probably best defined as one of the quotes above that
said:
(putting "in a capsule") <--- I like that :)

It's not hiding things from the developer (although that can be part of
it)... and it's not forcing people to use an interface (it's allowing
people to use an interface)

Ultimatley, it's taking an idea, task, or entity and packing it up in
code to make coding other things easier.

Sep 13 '05 #2

Peter Jansson

E. Robert Tisdale wrote:

No. It does *not* force the "user" to use the interface.
A determined hacker will find a way to "reach around" the interface
and access the data members directly.

Could you please give an example of how a determined coder may "reach
around" the interface?

Regards,
Peter Jansson

Sep 13 '05 #3

mlimber

Peter Jansson wrote:

E. Robert Tisdale wrote:
No. It does *not* force the "user" to use the interface.
A determined hacker will find a way to "reach around" the interface
and access the data members directly.

Could you please give an example of how a determined coder may "reach
around" the interface?

#define private public

Sep 13 '05 #4

John Fullman

lol... I'll have to try that one of these days :p

Sep 13 '05 #5

Mogens Heller Jensen

"mlimber" <ml*****@gmail. com> wrote in message
news:11******** **************@ f14g2000cwb.goo glegroups.com.. .

Peter Jansson wrote:
E. Robert Tisdale wrote:
> No. It does *not* force the "user" to use the interface.
> A determined hacker will find a way to "reach around" the interface
> and access the data members directly.

Could you please give an example of how a determined coder may "reach
around" the interface?

#define private public

If you can do that, it means you have access to the source code.... then you
might as well dive in and change the whole thing :o) or did I miss some
crucial point here?

Sep 13 '05 #6

John Fullman

All you need is access to the header files, not the full source, to do
that.
And any application that wants someone to use an interface has to fork
over the header files.
Otherwise, the interface won't be defined.

Sep 13 '05 #7

Peter Jansson

mlimber wrote:

#define private public

Can this be prevented if the interface code contains the following?

#ifdef private
#undef private
#endif

Regards,
Peter Jansson

Sep 13 '05 #8

John Fullman

It could, but it would be just as easy to remove that protection code
from any header file.
That would only work if the header files were somehow write protected.

Sep 13 '05 #9

Peter Jansson

John Fullman wrote:

It could, but it would be just as easy to remove that protection code
from any header file.
That would only work if the header files were somehow write protected.

I agree.

I believe this to be of little importance since the "attacker" still has
access to the headers so that person could easily change private into
public anyway.

Regards,
Peter

Sep 13 '05 #10

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