From: intc_ctor@... (Phil Tomson)
Date: 2004-01-13T08:21:39+09:00
Subject: Re: Ruby and Swig -- creating Pointers (typedef)

RubyQuestions@yahoo.com (RubyQuestions) wrote in message news:<599e9746.0401121052.61a0520c@posting.google.com>...
> I have been using Swig for the first time since Lyle mentioned Phil
> Tomson's article in C/C++ Users Journal (http://www.cuj.com)
> 
> My goal is to use my company's C/C++ API with Ruby.
> I think it would add a great deal of flexibility to my current
> programming.
> 
> I let Swig automatically create the wrapper for me (using the "truly
> lazy way" interface...just pointing it to the header file.)
> 
> Amazingly, everything is working.
> I'm able to load the shared library into Ruby.
> I can see all the methods, constants, etc...
> 
> However, some of the methods I want to use require pointers.
> Sorry for my ignorance, but I have only programmed in Java and Ruby...
> so I don't have any true exposure to C/C++ or the concept of pointers.
> 
> In the header file (API) I have are some typedef statments:
> 
> /********************************/
> /*    */    
> /*  Global Data Types  */  
> /*    */    
> /********************************/
>     typedef char  CoolBoolean;
>     typedef char*  CoolString;
>     typedef int   CoolClientHandle;
>     typedef int   CoolTableHandle;
> 
> 
> 
> Now I want use the following connect method.
> 
> /****************************************************************/
> /*        */
> /*  Opening and Closing Connection               */
> /*        */
> /****************************************************************/
> 
>     extern DllDecl CoolReturnCode CoolConnect
>  PROTO((char   *srvHostName,
>         int   serverNumber,
>         CoolClientHandle  *handle));
> 
> 
> How do I create a pointer of type "CoolClientHandle" in Ruby?
> Am I thinking about this incorrectly?
> 
> I have read over the pointer documentation, however I have been unable
> to make it work.
> 
> Any advice would be appreciated.
> 
> Thanks.

You need to include the typedefs in the declaration portion of the .i file
(or you need to include the .h file where the typedef is defined).

for example, let's say you have the typedef in the file foo.h:

//foo.h
typedef int   CoolClientHandle;
typedef int   CoolTableHandle;
///end of file///

You need to include it in your .i file like:

%{
/*this get's put in your wrapper code*/
#include "foo.h"
%}
/*no you've got to tell SWIG about it*/
typedef int   CoolClientHandle;
typedef int   CoolTableHandle;  //yeah, I know it seems redundant



You should be able to pass in an integer from the Ruby side, swig will take 
care of the pointer referencing/dereferencing.

If it's still not working, please post your .i file.

Phil