C++ pointers to Ruby objects

Ruby
1

I’m trying to make an interface between PhysX and Ruby and I got stucked
on the very beggining. XD

I have an NxPhysicsSDK pointer, pointing to an object (duh) and I would
like to store this pointer into an Ruby VALUE object. I don’t really
need to see it’s value outside the extension class (being clear:
everything would be encapsulated), but I only find conversions from C
pointers, not C++ objects.

Does anyone have a tip?

2

You need to either build your own C wrapper around the C++ and expose
that
in Ruby as you cannot just map C++ objects to Ruby’s C-API.

Or you use a tool like Rice ( http://rice.rubyforge.org ) or SWIG to
wrap
the C++ into Ruby.

I would also recommend looking into Rb++ (
http://rbplusplus.rubyforge.org )
which IMO (though slightly biased) is easier to deal with than SWIG.

Jason

On Thu, Dec 17, 2009 at 10:42 AM, Yuri Albuquerque

3

Well, I installed Rice’s gem and when I try to run my extconf.rb it
returns:

extconf.rb:1:in `require’: no such file to load – mkmf-rice (LoadError)
from extconf.rb:1

For some reason, Ruby is not finding this file.

I’ll try with Rb++ and see what I get.

4

Yuri Albuquerque wrote:

Well, I installed Rice’s gem and when I try to run my extconf.rb it
returns:

extconf.rb:1:in `require’: no such file to load – mkmf-rice (LoadError)
from extconf.rb:1

For some reason, Ruby is not finding this file.

I’ll try with Rb++ and see what I get.

Forget it. I forgot to include require ‘rubygems’ on my extconf.rb
Thank you.
But I’ll still try Rb++, too. ^^

5

Well, I have two new doubts:

1 - When an object is created on PhysX, it’s not directly with a
constructor. For example, if I want to create an NxPhysicsSDK object, I
have to do this:
NxPhysicsSDK *sdk = NxCreatePhysicsSDK(NX_PHYSICS_SDK_VERSION, 0, 0);
What do I have to do to convert this on an initialize method on Rice?

2 - If I try to use Rb++, it asks for a namespace. PhysX does not use
namespaces. What should I do in this case? Ignore this step?

6

Yuri Albuquerque wrote:

I’m trying to make an interface between PhysX and Ruby and I got stucked
on the very beggining. XD

I have an NxPhysicsSDK pointer, pointing to an object (duh) and I would
like to store this pointer into an Ruby VALUE object. I don’t really
need to see it’s value outside the extension class (being clear:
everything would be encapsulated), but I only find conversions from C
pointers, not C++ objects.

theoretically you should be able to store a struct in a ruby object that
can contain pointers to anything.

is an example project that has pointers to a C++ object [a google hash
map].

The trick is wrapping all your ruby code in an extern “C” { } block.

GL.
-r

7

Roger P. wrote:

theoretically you should be able to store a struct in a ruby object that
can contain pointers to anything.

GitHub - rdp/google_hash: wrapper for google's hash functions, for ruby

is an example project that has pointers to a C++ object [a google hash
map].

The trick is wrapping all your ruby code in an extern “C” { } block.

GL.
-r

Thanks to your tip, I am very closer to what I want to do than ever. I
didn’t needed to make any gluecode between C and C++, I’m writing
directly gluecode between Ruby and C++.

Thank you very much.