Today’s embedding exercise was allowing a MOO server to execute arbitrary Python code:

;py_runfunction({"import math", "return math.sqrt(2*2*2)"})
> 2.8284271247461903

Of course, a MOO server can already do square roots… that wasn’t the point. There was no point. Anyways, here are a few ideas that might help other people embed Python in a useful way.

>>> eval("x = 2")
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "<string>", line 1
    x = 2
      ^
SyntaxError: invalid syntax

def f():
    import math
    class Cylinder:
        def _calcVolume(self):
            return math.pi * 
                self.radius**2 * 
                self.height
        volume = property(_calcVolume)
    c = Cylinder()
    c.radius = 12.2
    c.height = 16.12
    return c.volume

Py_Initialize();
PyObject* module = PyImport_AddModule("__main__");
PyObject* moduleDict = PyModule_GetDict(module);
PyObject* compileRetval = PyRun_String(code, Py_file_input,
    moduleDict, moduleDict);
...
Py_Finalize();

PyObject* dict = PyDict_New();
PyObject* compileRetval = PyRun_String(code, Py_file_input,
    dict, dict);

// Check for __builtins__...
if (PyDict_GetItemString(dict, "__builtins__") == NULL)
{
    // Hm... no __builtins__ eh?
    PyObject* builtinMod = PyImport_ImportModule("__builtin__");
    if (builtinMod == NULL ||
        PyDict_SetItemString(dict, "__builtins__", builtinMod) != 0)
    {
        Py_DECREF(dict);
        Py_XDECREF(dict);
        // error handling
        return;
    }
    Py_DECREF(builtinMod);
}

char* getPythonTraceback()
{
    // Python equivilant:
    // import traceback, sys
    // return "".join(traceback.format_exception(sys.exc_type,
    //    sys.exc_value, sys.exc_traceback))

    PyObject *type, *value, *traceback;
    PyObject *tracebackModule;
    char *chrRetval;

    PyErr_Fetch(&type, &value, &traceback);

    tracebackModule = PyImport_ImportModule("traceback");
    if (tracebackModule != NULL)
    {
        PyObject *tbList, *emptyString, *strRetval;

        tbList = PyObject_CallMethod(
            tracebackModule,
            "format_exception",
            "OOO",
            type,
            value == NULL ? Py_None : value,
            traceback == NULL ? Py_None : traceback);

        emptyString = PyString_FromString("");
        strRetval = PyObject_CallMethod(emptyString, "join",
            "O", tbList);

        chrRetval = strdup(PyString_AsString(strRetval));

        Py_DECREF(tbList);
        Py_DECREF(emptyString);
        Py_DECREF(strRetval);
        Py_DECREF(tracebackModule);
    }
    else
    {
        chrRetval = strdup("Unable to import traceback module.");
    }

    Py_DECREF(type);
    Py_XDECREF(value);
    Py_XDECREF(traceback);

    return chrRetval;
}

XPCOM is a lightweight cross-platform implementation of the concepts behind Microsoft’s COM. It has been implemented in the process of the development of Mozilla. XPCOM is essentially COM, but cross-platform, hence the XP.

The integration inside the MOO server is not necessarily for any specific purpose, but I have a few plans in mind for what this integration will permit:

• XPCOM can be used to allow builtin functions to be compiled into shared modules and dropped into the MOO ‘components’. These builtin functions will be registered with the ‘regxpcom’ program, and be accessible from inside the MOO instantly. There are multiple advantages over doing this rather than the traditional way of modifying the MOO server to add builtin functions. The most major advantage is that XPCOM components can be written in languages other than C. It’s useful to program in an object-oriented language like C++ when you’re programming a builtin function that will be used in an object-oriented environment in the first place. Additionally, plug-in DLLs can be isolated in such a way that the crash of a builtin function will not affect the running of the MOO server.

  This has been implemented and is currently undergoing testing. The implementation involved the creation of an ‘IBuiltinFunction’ interface. The plug-in DLL exports an IBuiltinFunction derived interface. The MOO server allows access to its data to the XPCOM component via a set of ‘IMOOData’-derived interfaces.

  

• Another possible use for XPCOM inside the MOO is to allow MOO-code to access XPCOM objects. I expect that originally this will be implemented by creating an XPCOM plug-in DLL that exports builtin functions providing xpcom_createinstance(), xpcom_queryinterface(), xpcom_callfunction(), xpcom_get_attribute(), xpcom_set_attribute(), xpcom_releaseinstance(), and xpcom_isvalidinstance().

  xpcom_createinstance() will create an instance of a given contract id, if possible, and return a hash string that represents that instance. Eg:

  ;xpcom_createinstance(”@mozilla.org/file/directory_service;1″)
  => “##XPCOM#bbf8cab0-d43a-11d3-8cc2-00609792278c#59e7e77a##”

  The string representing that interface is a concationation of the CID, and a pointer address to it to make it unique for each instance. A hash table of these strings will be stored in the server so that implementation of the other xpcom_*() functions is relatively efficient.

  Implementation of this idea is pending further thought.

• The MOOzilla MOO client is written in JavaScript using Mozilla, and utilizes XPCOM heavily. It should be possible to create a plug-in architecture for MOOzilla, using some kind of common interfaces that the MOO server is aware of. Using an implementation of SOAP, (implemented as an XPCOM module, of course), it should be possible for the MOO server to ’script’ MOOzilla, or vice-versa, using out-of-band binary SOAP communication streams. Woo! The purpose? … Well, why not create an XPCOM module that wraps Gtk+, and then an interface for it on the client side and an interface for message handling on the server side could allow a Gtk+ application to be MOO-server-driven. Of course, this doesn’t apply just to Gtk+, it could be used for any toolkit… theoretically.

My efforts of XPCOM integration have yield a MOO which can successfully use XPCOM component builtin functions. My work has been based upon the MOO Canada server source, which is a rather hacked up LambdaMOO 1.8.1. The source has some unfortunate usability problems. It is basically customised just for my building and use of it. It should be possible to adapt it to build on your machine. The Makefile-xpcom-lao file is my Makefile. The automake and autoconf sources are not up to date. With some modifications to the Makefile, it should be possible to get it to build for you. Currently, I don’t have any example modules that are fit for publication.

The XPCOM enabled MOO server source can also be accessed by Subversion clients, or browsed with a web browser, at http://stompstompstomp.com/svn/moo/mc/xpcom-enabled-branch.

I’ll be publishing a new unicode patch shortly which allows non-us-ascii keywords and variable names in the MOO. This means that non-english words and characters can be used as variable, verb, property, and function names in MOO code without any unnecessary escaping. Collaborating with Jason showed that there are apparently duplicates of characters in the unicode codepage, such as the semicolon, period, quotation marks, and so on, which must be recognized by the MOO in the future as having the same functionality as the us-ascii versions of these characters. This should be interesting, and I’ll look into it soon for another unicode patch.

Once that was out of the way, it became apparent that the server handles Unicode great, the only problems left were in front end programs. Jason’s native OSX MUD client was able to send text to the MOO, but could not receive it and display it properly. The ‘telnet’ command in an OSX terminal was able to receive but not send, exactly the opposite. MOOzilla was able to do both. We didn’t have the resources available to easily test whether Mooca, the Achieve Java telnet client, could do it correctly and nicely.

Jason was interested in MOOzilla as a client itself. A number of ideas and problems came out of that discussion.

The idea of somehow making seperable windows out of MOOzilla which are MOO driven came up. This has been thought of before, but the way it was discussed here was as windows that could be separated, or could be left integrated in MOOzilla. This would allow a ‘power-user’ to keep everything in one complex window, while a beginning user would have a simpler interface that they could complicate if they chose to. I need to give some thought as to how this might be implemented… but I know that MOOzilla/Mozilla have the capabilities to do it.

A problem that arose is MOOzilla distribution and access. A Java client is easy to access because it requires no software installation, is just right there, and is cross-platform. MOOzilla does require software installation, two pieces of software actually, and the software varies from platform to platform. This would be streamlined a bit by the proposed ‘MOOzilla Package’ which was just MOOzilla, without Mozilla cruft, but would still not be usable in Jason’s teaching environment. So… what would? Hm… if only IE supported XUL/XPCOM. Now, if someone could make a plugin for IE that would allow the running of an XUL application… it would probably be a huge plugin. Could one be made that was MOOzilla-specific? … who knows how to make an IE plugin? Need some magic glue components here…

When completed, MC will have a nice clean DOM2 implementation that is actually reference counted, not garbage collected, though a series of magic levers and spells. It’s very slick. Basically, references are only kept going up the tree, and copies of WAIFs as text are kept going down the tree. It works surprisingly well.

The surprising thing is the massive amount of groth that MOOzilla will go through for it’s next release. This documentation will eventually include colourful images of MOOzilla being used in various scary ways by people. Currently I’m writing just the section on how to use MOOzilla as a MOO/MUD client, and I already have bumped the MOOzilla size up to about 290k, from its previous 75k. The documentation for how to build with MOOzilla will be very pictureful to be as useful as possible… or at least, I guess I’d like it to be.

Maybe I could make MOOzilla mock-ups using the same HTML rendering that MOOzilla uses itself. This oughta be smaller than using pictures of the rendered text…

… something about that makes me feel uncomfortable. Well, I’ll try it out when I get to the building section of the documentation.

My current feature list for 0.9.9:

• Documentation (1-2 weeks)
• Stand-Alone MOOzilla distributions for Windows and Linux. No Mozilla installation required, just gecko and other technologies bundled together. (1-2 weeks)
• Monospaced input windows, single + multi line. (2-3 days, if possible at all w/ XUL+XBL…)
• Save log as web page (1 hour)

The biggest problem with this plan for 0.9.9 is that the stand-alone distributions will be for platforms I don’t have access to. Teehee… this means MOOzilla 0.9.9 is probably planned for release around Christmas, after I do have access to an x86 computer to do some development with.

The documentation will also be put on MOOzilla’s web site, purely in HTML. Hopefully it will be useful. I just would love to hear from people as to what would be useful in the documentation, but … everyone is dead, it seems. So I’ll just pour dozens of hours of work into this documentation with absolutely no knowledge as to whether it will be useful to the universe or not. Maybe I’m just burning my time.

Currently things are looking pretty good. Cecil is doing a lot of design work on paper, and I’ve been plowing ahead with smashing stuff. I hope I smash things like he’s planning! :)

Lego simulator development hasn’t continued at all today.

Created a MOO Transpo in the downtown of MOO Canada, but it doesn’t yet have the desired functionality of a taxi stand. It does have a transporter, at least. This is yet another project to be done now.

I seem to have spent most of the day playing with web browsers… for some reason reading articles by CodeBitch at MacEdition.net has made me spend time playing with web browsers and CSS websites. Kinda weird… to be playing around with one of the most basic tools of the Internet age and just seeing what it can do. Well, a kinda weird day I guess.

The zeroconf_browse() builtin function takes two arguments: an object representing what object will be ‘listening’ for browse finds, and an string which will be the name of the service. The given object has a verb zeroconf_browse_add called on it when a new service is located, with the arguments {server’s name, server’s address, TCP port}. zeroconf_browse_remove is called whenever a service drops off the network, but I haven’t yet hammered out details of what arguments will be given to it.

And finally, the zeroconf_unbrowse() function takes a service name and stops browsing for that service.

The browsing is all done asynchronously in the current implementation, and a hook has been put in the main server loop to allow this to occur. The current implementation of zeroconf is highly MacOS X specific, but it can be re-written or extended to support multiple operating systems, especially by embedding Apple’s mDNSResponder daemon inside the MOO server. I haven’t even touched this yet, though.

I started looking into a Mozilla bug, bug #63895, but after some smashing at it with a hammer, I decided that a more informed and subtle approach is needed. It may indeed be a significant amount of work to fix even. The code in nsCSSFrameConstructor is a bit too complex for me to sink into it enough to find out what the problem is, so I think I’ll just ignore it…

I’m considering adding a locking system of some kind to Growlmurrdurr so I could write selectively private entries… but I don’t know what the point of a weblog that people can’t read is. :P