Inside Ajoke

Here's the Ajoke internals blog that I commited to write long time ago.

1 Flatten, the world of pragramming languages is flat

I tried to use Antlr for parsing Java source files. Boy it is slow! I'm slow to learn Antlr, and the parser I wrote using Antlr is slow to run. Maybe I'm not made for that stuff.

Than I wrote flatten, a simple perl script that will do the following things (not necessarily in the order):

  1. Remove all unnecessary spaces. Only a single space between two identifiers are left alone. Because removing it will make the two identifiers turn into one.
  2. Remove all strings, or put it better, make all string literals empty. Thus printf("hello world\n"); will become printf("");
  3. Remove all comments.
  4. Put a line feed (\n) only after these three characters: {};.

And that's about all. If not, you can always refer to the code.

Using, the following nonsense code will be transformed into better shape:

aontehua eouinta (anoethu noehu, noatehu aon)/*aoenu haonhaoeu */ { "anthue an"; }asneo huanoehu anoeh{aneou haneohuanoheu; }

like this:

naoehu anteohu anteohu aontehua eouinta(anoethu noehu,noatehu aon){
asneo huanoehu anoeh{
    aneou haneohuanoheu;

2 Parsing flat java

Java is so easy to parse when it is flatten. Well, not quite if you take generic programming into question. It's a lot more difficult with it. So screw generic programming.

Flat Java is very easy to parse, you can do it with Regular Expression. First of all, for any class/interface/method, you can look for the { character on the same line. If there is a class/interface keyword, then it's a class definition; if there is a ( character, then it is a method. The whole line can be used as the prototype for the class/interface/method.

See the code at both and

3 Patching ctags-exuberant and GNU global

For some reason, if you tagged Java source code with global + ctags-exuberant, and you query for String, java.lang.String will show up as a match. But if you query for java.lang.String, then there is no match.

This is because . is a regexp meta character, and global supports regexp querying, if it saw any irregular character like ".", then the query became a regexp matching instead of simple string compare.

Besides, even if it's not ., but the c++ ":", the java::lang::String will not show up because only String is recorded as an entry, java::lang is recorded as its prefix which will be added to the front if the entry matches.

So I patched global a bit, that when it sees java.lang.String queried, it will do the right thing.

See this commit at my system-config project. Later I have moved the ctags-exuberant and global projects into their separate github repo here and here, respectively. Some changes to them have been left in the system-config project though. What a mess:-)

4 Tagging .jar files

In the beginning my ajoke system is only for Android programming where the whole source code is available, even the java.lang.String class's source code.

But to make ajoke more useful, it must be able to handle .jar files, which is the norm for java programming.

Turns out it's easy. Given a .jar file, you can unzip it to get all the .class files in it. Then you can use javap to peek what classes/interfaces/methods are there in it.

And that's all I need to put together a perl script gtagsAntlrJavaParser to parse the .jar files. Don't ask me why the name says using Antlr to parse Java. Long story and you are welcome to guess. I will someday change it to gtagsJarParser.

And the global source code for invoking this parser is completely copied from global's plugin to call ctags-exuberant. Only minor changes are done to it, check the code gtags-antlr-java.c.

5 Idea: Using Ajoke to do C# programming (with Mono)

I hope Ajoke can someday be extended to allow it being used for C# programming. Like the .jar files, the .dll files for Mono platform can be decompiled to get the classes/interfaces/methods.

But not until I have the need again to do Mono programming. My beagrep.git project is the only place I used C#, and I'm not doing it recently.