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Dear all,

In programming terminology, what is a wrapper and where is it used?

Regards

Hi

-


"utab" <> wrote in message
news: ups.com...
> Dear all,
>
> In programming terminology, what is a wrapper and where is it used?
Well for instance you could use a C++ wrapper class around regular C code.

For instance in my personal generic library I have a wrapper class around
the pnglib libary I can the open an ifstream of a .png file and read it with
operator>> or write png files with operator<<. This also works for memory
streams etc. The C++ wrapper takes care of memory allocation and freeing the
memory and of the complexity of setting the pointers to static members to
replace the standard C FILE oriented operations.

i.e. the complexity is inside the C++ wrapper class. The wrapper class
itself is extremely simple to use. Instead of looking in the manual of png
everytime I can now load and save png in a very simple way.
>
> Regards
>

Regards, Ron AF Greve

http://moonlit.xs4all.nl

Moonlit wrote:
> Hi
>
> -
>
>
> "utab" <> wrote in message
> news: ups.com...
> > Dear all,
> >
> > In programming terminology, what is a wrapper and where is it used?
> Well for instance you could use a C++ wrapper class around regular C code.
>
> For instance in my personal generic library I have a wrapper class around
> the pnglib libary I can the open an ifstream of a .png file and read it with
> operator>> or write png files with operator<<. This also works for memory
> streams etc. The C++ wrapper takes care of memory allocation and freeing the
> memory and of the complexity of setting the pointers to static members to
> replace the standard C FILE oriented operations.
>
> i.e. the complexity is inside the C++ wrapper class. The wrapper class
> itself is extremely simple to use. Instead of looking in the manual of png
> everytime I can now load and save png in a very simple way.
> >
> > Regards
> >
>
> Regards, Ron AF Greve
>
> http://moonlit.xs4all.nl

Thanks Ron,

So in a simple manner, it is a code block to make things easier for
mixed-language programming(for the original C library in your case.).
Then briefly speaking, this is related to using more than one language
in your code. Am I correct?

Regards,

"utab" <> wrote in message
news: ups.com...
>
> Moonlit wrote:
>> Hi
>>
>> -
>>
>>
>> "utab" <> wrote in message
>> news: ups.com...
>> > Dear all,
>> >
>> > In programming terminology, what is a wrapper and where is it used?
>> Well for instance you could use a C++ wrapper class around regular C
>> code.
>>
>> For instance in my personal generic library I have a wrapper class around
>> the pnglib libary I can the open an ifstream of a .png file and read it
>> with
>> operator>> or write png files with operator<<. This also works for memory
>> streams etc. The C++ wrapper takes care of memory allocation and freeing
>> the
>> memory and of the complexity of setting the pointers to static members to
>> replace the standard C FILE oriented operations.
>>
>> i.e. the complexity is inside the C++ wrapper class. The wrapper class
>> itself is extremely simple to use. Instead of looking in the manual of
>> png
>> everytime I can now load and save png in a very simple way.
>> >
>> > Regards
>> >
>>
>> Regards, Ron AF Greve
>>
>> http://moonlit.xs4all.nl
>
> Thanks Ron,
>
> So in a simple manner, it is a code block to make things easier for
> mixed-language programming(for the original C library in your case.).
> Then briefly speaking, this is related to using more than one language
> in your code. Am I correct?

I think it is indeed mostly ( if not always ) used to make things easier.

The second statement is a bit more difficult to answer since C is for the
most part also C++. But all of my wrapper classes are indeed around regular
C functions/ libraries and not around C++ libraries. But I could imagine
that when you have a complex C++ library and you only want to use part of it
you might still want to write a wrapper class around it (then again maybe
the library itself should have been redesigned) . But from a practical point
of view I think that is right.
>
> Regards,
>

--


Regards, Ron AF Greve

http://moonlit.xs4all.nl

utab posted:

> In programming terminology, what is a wrapper and where is it used?


I'm not sure if this is a generally accepted meaning of the term, but I
take "wrapper" to mean anything which erects a 20-foot-tall wall around
something and provides a nice simple interface to the outside world. For
instance, we might create a wrapper for working with individual bits in
memory:

#include <climits>

class BitHandle {
private:

char unsigned *p;
unsigned index;

public:

operator bool() const
{
return *p & 1U<<index;
}

BitHandle &operator=(bool const val)
{
if(val) *p |= 1U<<index;
else *p &= ~(1U<<index);

return *this;
}

BitHandle &operator++() const
{
if(CHAR_BIT == index) ++p, index = 0;
else ++index;

return *this;
}
};

--

Frederick Gotham

Frederick Gotham posted:

> BitHandle &operator++() const


Of course, that shouldn't be const (but then again it wasn't a full example
to start off with).

--

Frederick Gotham

Moonlit wrote:
> "utab" <> wrote in message
> news: ups.com...
> >
> > Moonlit wrote:
> >> Hi
> >>
> >> -
> >>
> >>
> >> "utab" <> wrote in message
> >> news: ups.com...
> >> > Dear all,
> >> >
> >> > In programming terminology, what is a wrapper and where is it used?
> >> Well for instance you could use a C++ wrapper class around regular C
> >> code.
> >>
> >> For instance in my personal generic library I have a wrapper class around
> >> the pnglib libary I can the open an ifstream of a .png file and read it
> >> with
> >> operator>> or write png files with operator<<. This also works for memory
> >> streams etc. The C++ wrapper takes care of memory allocation and freeing
> >> the
> >> memory and of the complexity of setting the pointers to static members to
> >> replace the standard C FILE oriented operations.
> >>
> >> i.e. the complexity is inside the C++ wrapper class. The wrapper class
> >> itself is extremely simple to use. Instead of looking in the manual of
> >> png
> >> everytime I can now load and save png in a very simple way.
> >> >
> >> > Regards
> >> >
> >>
> >> Regards, Ron AF Greve
> >>
> >> http://moonlit.xs4all.nl
> >
> > Thanks Ron,
> >
> > So in a simple manner, it is a code block to make things easier for
> > mixed-language programming(for the original C library in your case.).
> > Then briefly speaking, this is related to using more than one language
> > in your code. Am I correct?
>
> I think it is indeed mostly ( if not always ) used to make things easier.
>
> The second statement is a bit more difficult to answer since C is for the
> most part also C++. But all of my wrapper classes are indeed around regular
> C functions/ libraries and not around C++ libraries. But I could imagine
> that when you have a complex C++ library and you only want to use part of it
> you might still want to write a wrapper class around it (then again maybe
> the library itself should have been redesigned) . But from a practical point
> of view I think that is right.
> >
> > Regards,
> >
>
> --
>
>
> Regards, Ron AF Greve
>
> http://moonlit.xs4all.nl

Thanks again,

What do you mean by this

"But I could imagine
that when you have a complex C++ library and you only want to use part
of it
you might still want to write a wrapper class around it "

You mean to copy the parts you like to use for a complete C
application(in a class).

Is that also related with compatibility while using two languages. I
mean type compatibility, for instance C does not have a built-in vector
type but C++ has. And while writing some code which needs to use
vectors in the code for instance, you use a proper C++ wrapper in the
proper interface to use these features of C++ in C. Am I completely
confusing or on the right way?

Regards,
Regards,

Frederick Gotham wrote:
> utab posted:
>
> > In programming terminology, what is a wrapper and where is it used?
>
>
> I'm not sure if this is a generally accepted meaning of the term, but I
> take "wrapper" to mean anything which erects a 20-foot-tall wall around
> something and provides a nice simple interface to the outside world. For
> instance, we might create a wrapper for working with individual bits in
> memory:
>
> #include <climits>
>
> class BitHandle {
> private:
>
> char unsigned *p;
> unsigned index;
>
> public:
>
> operator bool() const
> {
> return *p & 1U<<index;
> }
>
> BitHandle &operator=(bool const val)
> {
> if(val) *p |= 1U<<index;
> else *p &= ~(1U<<index);
>
> return *this;
> }
>
> BitHandle &operator++() const
> {
> if(CHAR_BIT == index) ++p, index = 0;
> else ++index;
>
> return *this;
> }
> };
>
> --
>
> Frederick Gotham

Dear Frederick,

So that is a way to make things more understantable from the
programmers point of view. Using the existing but in a fancier
interface(in a different form).

Regards

> Is that also related with compatibility while using two languages. I
> mean type compatibility, for instance C does not have a built-in vector
> type but C++ has. And while writing some code which needs to use

Does C++ implement a Vector type ?
STL maybe, but not C++ as an intrinsic type, as far as I know.



"utab" <> wrote in message
news: oups.com...
>
> Moonlit wrote:
>> "utab" <> wrote in message
>> news: ups.com...
>> >
>> > Moonlit wrote:
>> >> Hi
>> >>
>> >> -
>> >>
>> >>
>> >> "utab" <> wrote in message
>> >> news: ups.com...
>> >> > Dear all,
>> >> >
>> >> > In programming terminology, what is a wrapper and where is it used?
>> >> Well for instance you could use a C++ wrapper class around regular C
>> >> code.
>> >>
>> >> For instance in my personal generic library I have a wrapper class
>> >> around
>> >> the pnglib libary I can the open an ifstream of a .png file and read
>> >> it
>> >> with
>> >> operator>> or write png files with operator<<. This also works for
>> >> memory
>> >> streams etc. The C++ wrapper takes care of memory allocation and
>> >> freeing
>> >> the
>> >> memory and of the complexity of setting the pointers to static members
>> >> to
>> >> replace the standard C FILE oriented operations.
>> >>
>> >> i.e. the complexity is inside the C++ wrapper class. The wrapper class
>> >> itself is extremely simple to use. Instead of looking in the manual of
>> >> png
>> >> everytime I can now load and save png in a very simple way.
>> >> >
>> >> > Regards
>> >> >
>> >>
>> >> Regards, Ron AF Greve
>> >>
>> >> http://moonlit.xs4all.nl
>> >
>> > Thanks Ron,
>> >
>> > So in a simple manner, it is a code block to make things easier for
>> > mixed-language programming(for the original C library in your case.).
>> > Then briefly speaking, this is related to using more than one language
>> > in your code. Am I correct?
>>
>> I think it is indeed mostly ( if not always ) used to make things easier.
>>
>> The second statement is a bit more difficult to answer since C is for the
>> most part also C++. But all of my wrapper classes are indeed around
>> regular
>> C functions/ libraries and not around C++ libraries. But I could imagine
>> that when you have a complex C++ library and you only want to use part of
>> it
>> you might still want to write a wrapper class around it (then again maybe
>> the library itself should have been redesigned) . But from a practical
>> point
>> of view I think that is right.
>> >
>> > Regards,
>> >
>>
>> --
>>
>>
>> Regards, Ron AF Greve
>>
>> http://moonlit.xs4all.nl
>
> Thanks again,
>
> What do you mean by this
>
> "But I could imagine
> that when you have a complex C++ library and you only want to use part
> of it
> you might still want to write a wrapper class around it "
>
> You mean to copy the parts you like to use for a complete C
> application(in a class).
>
> Is that also related with compatibility while using two languages. I
> mean type compatibility, for instance C does not have a built-in vector
> type but C++ has. And while writing some code which needs to use
> vectors in the code for instance, you use a proper C++ wrapper in the
> proper interface to use these features of C++ in C. Am I completely
> confusing or on the right way?
>
> Regards,
> Regards,
>

Arve Sollie wrote:
> > Is that also related with compatibility while using two languages. I
> > mean type compatibility, for instance C does not have a built-in vector
> > type but C++ has. And while writing some code which needs to use
>
> Does C++ implement a Vector type ?
> STL maybe, but not C++ as an intrinsic type, as far as I know.
>
>
>
> "utab" <> wrote in message
> news: oups.com...
> >
> > Moonlit wrote:
> >> "utab" <> wrote in message
> >> news: ups.com...
> >> >
> >> > Moonlit wrote:
> >> >> Hi
> >> >>
> >> >> -
> >> >>
> >> >>
> >> >> "utab" <> wrote in message
> >> >> news: ups.com...
> >> >> > Dear all,
> >> >> >
> >> >> > In programming terminology, what is a wrapper and where is it used?
> >> >> Well for instance you could use a C++ wrapper class around regular C
> >> >> code.
> >> >>
> >> >> For instance in my personal generic library I have a wrapper class
> >> >> around
> >> >> the pnglib libary I can the open an ifstream of a .png file and read
> >> >> it
> >> >> with
> >> >> operator>> or write png files with operator<<. This also works for
> >> >> memory
> >> >> streams etc. The C++ wrapper takes care of memory allocation and
> >> >> freeing
> >> >> the
> >> >> memory and of the complexity of setting the pointers to static members
> >> >> to
> >> >> replace the standard C FILE oriented operations.
> >> >>
> >> >> i.e. the complexity is inside the C++ wrapper class. The wrapper class
> >> >> itself is extremely simple to use. Instead of looking in the manual of
> >> >> png
> >> >> everytime I can now load and save png in a very simple way.
> >> >> >
> >> >> > Regards
> >> >> >
> >> >>
> >> >> Regards, Ron AF Greve
> >> >>
> >> >> http://moonlit.xs4all.nl
> >> >
> >> > Thanks Ron,
> >> >
> >> > So in a simple manner, it is a code block to make things easier for
> >> > mixed-language programming(for the original C library in your case.).
> >> > Then briefly speaking, this is related to using more than one language
> >> > in your code. Am I correct?
> >>
> >> I think it is indeed mostly ( if not always ) used to make things easier.
> >>
> >> The second statement is a bit more difficult to answer since C is for the
> >> most part also C++. But all of my wrapper classes are indeed around
> >> regular
> >> C functions/ libraries and not around C++ libraries. But I could imagine
> >> that when you have a complex C++ library and you only want to use part of
> >> it
> >> you might still want to write a wrapper class around it (then again maybe
> >> the library itself should have been redesigned) . But from a practical
> >> point
> >> of view I think that is right.
> >> >
> >> > Regards,
> >> >
> >>
> >> --
> >>
> >>
> >> Regards, Ron AF Greve
> >>
> >> http://moonlit.xs4all.nl
> >
> > Thanks again,
> >
> > What do you mean by this
> >
> > "But I could imagine
> > that when you have a complex C++ library and you only want to use part
> > of it
> > you might still want to write a wrapper class around it "
> >
> > You mean to copy the parts you like to use for a complete C
> > application(in a class).
> >
> > Is that also related with compatibility while using two languages. I
> > mean type compatibility, for instance C does not have a built-in vector
> > type but C++ has. And while writing some code which needs to use
> > vectors in the code for instance, you use a proper C++ wrapper in the
> > proper interface to use these features of C++ in C. Am I completely
> > confusing or on the right way?
> >
> > Regards,
> > Regards,
> >

Of course STL, thanks for the warning