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From: Maciej Sobczak <no.spam@no.spam.com>
Newsgroups: comp.lang.ada
Subject: Re: ada binding
Date: Thu, 09 Feb 2006 15:31:56 +0100
Organization: CERN - European Laboratory for Particle Physics
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Xref: g2news1.google.com comp.lang.ada:2819
Date: 2006-02-09T15:31:56+01:00
List-Id: <comp.lang.ada>

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.


-- 
Maciej Sobczak : http://www.msobczak.com/
Programming    : http://www.msobczak.com/prog/