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From: Martin Krischik <krischik@users.sourceforge.net>
Newsgroups: comp.lang.ada
Subject: Re: ada binding
Date: Thu, 09 Feb 2006 18:17:54 +0100
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Date: 2006-02-09T18:17:54+01:00
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Szymon Guz wrote:

> Maciej Sobczak napisa?(a):
>> Szymon Guz wrote:
>> 
>>> how to make an Ada binding for a "C++" class using this C layer ?
>> 
>> Basically, if the C++ class is not a template, but just plain "classic"
>> OO stuff, then you can write a wrapper around it in C, which will still
>> be OO, but without the syntax sugar of real class. Something along this:
>> 
>> // an existing C++ class:
>> class MyClass
>> {
>> public:
>>     void myFun();
>> };
>> 
>> // a C wrapper:
>> extern "C"
>> void * MyClass_new()
>> {
>>     return new MyClass;
>> }
>> 
>> extern "C"
>> void MyClass_delete(void *p)
>> {
>>     delete static_cast<MyClass*>(p);
>> }
>> 
>> extern "C"
>> void MyClass_myFun(void *vp)
>> {
>>     MyClass *mcp = static_cast<MyClass*>(vp);
>>     mcp->myFun();
>> }
>> 
>> // and so on.
>> 
>> Depending on the level of isolation that you want to achieve and the
>> level of type safety that you want to retain, hiding the object behind
>> void* might or might not be the best choice, but this is to give you the
>> idea. Above, MyClass_new, MyClass_delete and MyClass_myFun are plain C
>> functions (you can extract their declarations to separate header file)
>> and you can interface them from just about any sensible language in
>> existence and from Ada in particular.
>> 
>> 
> 
> OK, but what about using the class fields :
> 
> class MyClass
> {
> public:
>    int X;
>    int *p_X;
> }
> 
> and what about inheriting this from the class in Ada, is it possible ?

If you are planning to inheriting  then you need to directly bind to the C++
class. Only one compiler offers that (GNAT). Start reading here:

http://gcc.gnu.org/onlinedocs/gcc-4.0.2/gnat_rm/Pragma-CPP_005fClass.html

Martin
-- 
mailto://krischik@users.sourceforge.net
Ada programming at: http://ada.krischik.com