[Rcpp-devel] wrap returned pointer to class

[Sebastian Weber]

Hi!

I just figured a way to deal with pointers to objects in memory which I receive by calling whatever function of a third-party library. The problem is warp it into a suitable object. My approach which does a nice job is:

  template <>
  SEXP wrap( B* const& mb ) {
    typedef result<B> ptr_wrap_t;
    return XPtr<ptr_wrap_t>(new ptr_wrap_t(mb));
  }

Here, B* is returned from a function I call. Now the idea is to create a result-object which contains the pointer and hand that to XPtr. This makes XPtr happy as it is now authoritative over the life of the result-object. How about enabling this for *all* pointers by default which get passed into R space?

Cheers,

Sebastian

Am 02.08.2011 um 11:28 schrieb romain at r-enthusiasts.com:

> Ah, 
> 
> I need to think about this. Will give you an update if i manage to deal with it.
> 
> Romain
> 
> 
> 
> Le 2 août 2011 à 11:24, Sebastian Weber <sebastian.weber at frias.uni-freiburg.de> a écrit :
> 
>> Hi!
>> 
>> The solution you point out there is exactly what I need - but without class intrusion. The class I am wrapping is not under my control, but belongs to a third party. Or does your solution apply also in a non-intrusive case which I overlooked?
>> 
>> Cheers,
>> 
>> Sebastian
>> 
>> Am 02.08.2011 um 11:10 schrieb romain at r-enthusiasts.com:
>> 
>>> Hello sebastian, 
>>> 
>>> I think what you are looking for is covered by some enhancements i added recently and described in this thread: 
>>> 
>>> http://thread.gmane.org/gmane.comp.lang.r.rcpp/2092
>>> 
>>> Romain
>>> 
>>> 
>>> Le 1 août 2011 à 18:07, Sebastian Weber <sebastian.weber at frias.uni-freiburg.de> a écrit :
>>> 
>>>> Hi,
>>>> 
>>>> first of all thank you, Dirk and Romain, so much for this great library! I was stunned when I saw the examples.
>>>> 
>>>> Hence, I started immediately a quite involved project which interfaces another library to R via C++. Currently I have the problem that I want to expose a function from a class which returns a pointer to a class. When exposing via the
>>>> 
>>>> class_<A>.method("fun", &A::fun);
>>>> 
>>>> mechanism, the compiler fails with a message saying that he cannot wrap the return type of function fun. The returned object itself is a pointer to another class B. How to solve this? I tried providing the wrap call with no success.
>>>> 
>>>> Here is some code which might not work, but explains more detailed:
>>>> 
>>>> class B {};
>>>> 
>>>> class A {
>>>> public:
>>>> B* fun();
>>>> };
>>>> 
>>>> which gives, when compiled:
>>>> 
>>>> /Library/Frameworks/R.framework/Versions/2.13/Resources/library/Rcpp/include/Rcpp/internal/wrap.h:428: error: cannot convert ‘B* const’ to ‘SEXPREC*’ in initialization
>>>> 
>>>> Any ideas how to fix this?
>>>> 
>>>> Thanks,
>>>> 
>>>> PS: Is there some bug tracking tool? I got some weird problem when the function wrapped expects a char as input. I fixed it somehow, but I am not sure if it is the right way...
>>>> 
>>>> -- 
>>>> Sebastian Weber
>>>> Group of Cell Communication and Control
>>>> Freiburg Institute for Advanced Studies - FRIAS
>>>> School of Life Sciences - LIFENET
>>>> Albert-Ludwigs-Universität Freiburg
>>>> Albertstr. 19
>>>> 79104 Freiburg
>>>> T.: +49-761-203-97237
>>>> Fax:+49-761-203-97334
>>>> 
>>>> _______________________________________________
>>>> Rcpp-devel mailing list
>>>> Rcpp-devel at lists.r-forge.r-project.org
>>>> https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel
>> 
>> -- 
>> Sebastian Weber
>> Group of Cell Communication and Control
>> Freiburg Institute for Advanced Studies - FRIAS
>> School of Life Sciences - LIFENET
>> Albert-Ludwigs-Universität Freiburg
>> Albertstr. 19
>> 79104 Freiburg
>> T.: +49-761-203-97237
>> Fax:+49-761-203-97334
>> 

-- 
Sebastian Weber
Group of Cell Communication and Control
Freiburg Institute for Advanced Studies - FRIAS
School of Life Sciences - LIFENET
Albert-Ludwigs-Universität Freiburg
Albertstr. 19
79104 Freiburg
T.: +49-761-203-97237
Fax:+49-761-203-97334