Notes on Generating Bindings

Swig generates bindings for a whole lot of languages, including python. Once you get one figured out, someone should be able to tell SWIG to generate java/perl/ruby etc with very minimal effort.

This repo is for learning SWIG, getting it as automated as possible, and learning how SWIG want's you to handle pointers. (From what I can tell so far, you declare how to cast the pointers in the *.i files)

To download SWIG

Go to http://www.swig.org/download.html.

Then install the latest:

tar -zxf swig-4.0.2.tar.gz
cd swig-4.0.2
./configure
make
sudo make install
# DONE!!

Generate Python Bindings

<cd to root of this repo>
cmake .
make all

Then you can run python!

from mypackage import cameron
cameron.add3(6)
>>> 9
# NOTE: there's cameron.getArray(), which should return something like [0,1,2,3,4,5,6,7,8,9]. Haven't got pointers figured out yet though. Basic functions like the one above work great.

Developers: To add another file to the library

If you need to add another .h and .c pair to mypackage:

1. Create a file.i file with it. Same name as the .c and .h, with these contents:

   I think this is where casting a pointer logic goes, so we might not be able to generate these files automatically:

   %module <name>
   %{                // This adds the include to the generated wrapper.
   #include "<name>.h"
   %}
   %include "<name>.h"    // This *processes* the include and makes wrappers.

2. Add this block to the end of the CMakeLists.txt

   NOTE: There HAS to be a way to automate/for-loop this, based on a include list. I just haven't looked.

   swig_add_library(<name> TYPE SHARED LANGUAGE python SOURCES mypackage/<name>.i mypackage/<name>.c)
   # NOTE the underscore before the name!!!
   set_target_properties(_<name> PROPERTIES LIBRARY_OUTPUT_DIRECTORY "mypackage/")
   SWIG_LINK_LIBRARIES(<name> ${PYTHON_LIBRARIES})

Main TODO's to figure out

• How to handle C pointers, and declare how to cast them in SWIG.

• How to simplify CMakeLists.txt, so you don't need 3 lines of code for each .c/.h pair.

• Add another mypackage directory, along with a shared directory they both import from. Make sure SWIG can handle libvnc's use case of a common dir that two libraries import from.

Useful links to do so

• Swig official documentation: http://www.swig.org/Doc4.0/Python.html
• Slideshow (around pg 32 talks about pointers): http://www.swig.org/papers/PyTutorial98/PyTutorial98.pdf