Director support for PHP

SWIG is normally can be used for wrapping a C/C++ library to be accessible from other languages like Python, PHP, etc. In case the given function requires a callback, normally the callback has to be written in C/C++ as well. The director feature of SWIG allows the user to implement callback functions in the target language. The used technique is to inherit the C++ class of callback function in the target language and implement the callbacks there. The director feature is implemented for a number of languages, but PHP support is not yet done. This summer I would like to implement it.

When the project is completed, users who use SWIG to access C/C++ libraries from PHP will have the ability to implement callback functions in PHP by being able to inherit C++ classes in PHP.

I got the idea of working on this because I already used the director feature of SWIG in the libwpd project for Java, and recently the libwpd maintainer added C# support to CVS as well - based on my work. It would be nice to have PHP support as well, but currently SWIG does not allow me to do so.

Regarding implementation, I want to take the Python director support as an example and implement this feature in a similar way for PHP. I don’t know exact filenames, because I don’t know (yet) the PHP nor the SWIG internal API, but I expect the areas touched by the Python implementation will basically match the ones I want to touch because of PHP.

The typical usage of the director feature is the following: A C++ parser library provides a class of virtual functions, like:

Then normally this class is inherited in C++, the functions are implemented, and an instance of the inherited class is passed back to the parser as a pointer. The trick is to be able to inherit the class in PHP and implement these callback functions in PHP, instead of C++.

A sample about how callbacks should be implemented in PHP could be the curl PHP bindings (http://curl.haxx.se/libcurl/php/examples/callbacks.html, http://cvs.php.net/viewvc.cgi/php-src/ext/curl/).

Of course I don’t want to reinvent the wheel, so I want to first see how the Python director test-cases work, and then I can write a PHP version of them to test my code.

So I would like the first version of the PHP director code ready by the time of mid-term evaluation, then I can work out the minor problems, write documentation and if time permits - implement related other minor features in the second half of the summer. I used concrete dates so that I can be checked easily if I’m on track, but of course I may finish with a given part a bit earlier or I may have a little delay.

I’m a student in Hungary, and here the exam period is between 2009.05.18. and 2009.06.26. Sadly this has a big overlap with the Summer of Code, which starts on 2009.05.26. I’m aware of this and last year I managed to get over this as well. I plan to work on my project 40 hours a week, which permits to spend entire days on my project, then work nothing a few days before the exam. I don’t know the exact date, but probably after the mid-term evaluation I’ll have a week of holiday. I think once I returned I can work more productive on my project with a fresh mind, compared to going nowhere during the whole summer.

My experience is that IRC is handy for quick questions, but basically the primary protocol is email. If this is OK for my mentor, then I would like to use these two for this project as well.

I would like to start with trivial patches or minor bugfixes before the SoC starts, so when I start to work on my project, hopefully my name will not be unknown on the SWIG developer list. I plan to work 40 hours a week during the SoC. (Well, basically. I do not use a timer, the average is about something like this.) I don’t know the future, I hope I can do some contribution after SoC as well.

I don’t know anything about it so far, but I’m sure there will be new ideas during the implementation of the project. I’m sure I’ll at least document these ideas once the project is finished, so I or others can work on them after the end of SoC.

I used swig’s director feature when I created the Java bindings for libwpd and I used SWIG’s C#, Java, Perl and Python targets with the Pacman package manager (but the later does not use directors). So I’m familiar with SWIG as a user, but I did not contribute patches to SWIG itself so far.

I expect that I’ll need to write C/C++ and/or PHP code during the project. I contributed to various projects written in these languages (see below).

I’m a Linux guy, and I use OS X sometimes, mainly for testing purposes as well. I do not really use Windows, unless really needed (then I can install it in a virtual machine or something). I’m familiar with gcc and make, I used autotools for other projects previously as well.

I’m hanging around on #swig-gsoc, and I have talked a bit with William Fulton and Olly Betts there.

Education: Completing a B.Sc. degree in Computer Science (since 2005) at Budapest University of Technology and Economics. I work for SZTAKI (http://www.sztaki.hu/?en, part time - 1 day in a week, since 2004). I have a page with a few minor projects: http://vmiklos.hu/projects/

A have a page with links to patches I contributed to other FOSS projects: http://vmiklos.hu/portfolio/ Mostly minor code and/or documentation fixes. I contributed a few more complex patches to the pacman package manager, the bitlbee IM gateway, MPlayer, Git and wapreader (these are C and PHP projects). I’m generally a bash, C/C++ and Python guy. I know PHP very well, too. I know some perl/Java/erlang/C# as well. I’m familiar with various version control systems, including SVN and Git.

vmiklos