Combined Python & Ruby extension module

Question

I have a C extension module for Python and I want to make it available to Rubyists.

The source has a number of C modules, with only one being Python-dependent. The rest depend only on each other and the standard library. I can build it with python setup.py build in the usual way.

I've been experimenting with adding Ruby support using newgem and I can build a version of the extension with rake gem. However, the combined source has an ugly directory layout (mixing Gem-style and Setuptools-style structures) and the build process is a kludge.

I can't just keep all the sources in the same directory because mkmf automatically picks up the Python-dependent module and tries to build that, and users shouldn't have to install Python to compile a module that won't be used. My current hack is for extconf.rb to copy the Python-independent source-files into the same directory as the Ruby-dependent extension module.

Is there a saner way to make the code available to both languages? Should I just duplicate the Python-independent code in a separate Gem? Should I release the independent code as a separate lib built with autotools? Is there a version of mkmf that can skip the unwanted module?

Answer 1

One way to solve it is to create three different projects:

• The library itself, independent on python & ruby
• Python bindings
• Ruby bindings

That's probably the cleanest solution, albeit it requires a bit more work when doing releases, but it has the advantage that you can release a new version of the Ruby bindings without having to ship a new library/python bindings version.

Answer 2

Complimenting on what Johan said, I've used a couple c/c++ support libraries in Python thanks to swig. You write your code in c/c++ then make an intermediary template for each language that you want to support. Its rather painless for Python, but some considerations must be made for Ruby... namely I don't think pthread support is to happy with ruby or vice versa.

http://www.swig.org/ It's got a somewhat steep learning curve so it might be best to find an example project out there that demonstrates how to use the wrapper for your target languages.

This is definitely a useful tool as it makes your code a lot cleaner while still providing robust bindings to multiple languages (PHP, Python, Ruby, and I believe c#)