Calling C functions inside Python

In my current work, I’m developing new ways to test a Telecom framework. Firstly, I was building automation tests with cgreen to blackbox/unit test model. But the development stages were going a little more slow than I thought because write and debug C code is not so easy.

Suddenly, I though…”Hey, why do I not build these tests with python scripts ???”. And my response was: “Ctypes is your friend!”

Ctypes permits you call C functions inside python code. It’s wonderful. Let’s see how to do it in OpenSolaris environment:

First, download ctypes:

$ wget -c \
http://ufpr.dl.sourceforge.net/sourceforge/ctypes/ctypes-1.0.2.tar.gz

Install ctypes in a local path (as normal user):

$ tar -zxvf ctypes-1.0.2.tar.gz

$ cd ctypes-1.0.2

$ python setup.py install --prefix=$HOME/python

Export your PYTHONPATH environment variable:

$ export PYTHONPATH=$HOME/python/lib/python2.4/site-packages

Testing ctypes:

$ python

>>> import ctypes

OK ! Ctypes is there, but how do I use it ???

See a little example that I made to explain how to use ctypes:

• A file named test.c with a function (sum) that returns a sum of two values:

int sum (int a, int b)
{
    return (a+b);
}

• Compile it as a shared library:

$ gcc -fPIC -c test.c

$ gcc -shared -o test.o libtest.so

• Make sure that our library will be found

$ cp test.so $HOME/example

$ export LD_LIBRARY_PATH=$HOME/example

• Let’s call the function sum through a Python script

$ python

>>> from ctypes import *
>>> cdll.LoadLibrary('libtest.so')
<CDLL 'libtest.so', handle fe7806e0 at 80dfcec>
>>> libc = CDLL('libtest.so')
>>> libc.sum()
112710980
>>> libc.sum(1,2)
3

I can see a smile in your face. Yeah! Ctypes is a great trick to C programmers

Enjoy it!

Useful links:

1. http://docs.python.org/library/ctypes.html

Enabling a Marvel Yukon NIC on OpenSolaris

When I installed OpenSolaris 2008.05 in my laptop (Sony Vaio), the operating system does not recognized my ethernet card (marvel yukon), but identified my wireless NIC.

I don’t use ethernet card frequently because I have a Wireless Access Point. But, some days ago I had to enable my Marvel Yukon.

Let’s see how did I do this:

By default, snv_86 build does not come with the Marvel Yukon driver enabled in the kernel. But you can download it at:

http://homepage2.nifty.com/mrym3/taiyodo/myk-2.6.5.tar.gz

Done that, I take these steps:

1. tar -zxvf myk-2.6.5.tar.gz

2. cd myk-2.6.5

3. rm -Rf obj Makefile

4. ln -s Makefile.i386_gcc Makefile

5. ln -s i386 obj

6. export PATH=/usr/ccs/bin:$PATH

7. which gcc (/usr/ccs/bin/gcc expected)

8. which make (/usr/ccs/bin/make expected)

9. pfexec make install

10. pfexec ./adddrv.sh (should says ok!)

11. ifconfig myk0 plumb

12. ifconfig -a (wow ! I see my ethernet card!!!   )

PS: Before try my tips, please, read the installation document in tarball ’cause you can have to do different steps.

Links:

http://homepage2.nifty.com/mrym3/taiyodo/eng/