torsdag, juni 15, 2006

Working towards 0.9

These last days I've been focusing on fixing issues with RubyGems and Rails, so that JRuby 0.9 will be a really great release. It already is, of course, but all we can do to make it better feels nice. These are the things I've done since sunday.

I finally took the time to rewrite all of StringIO to Java, and also really test so that it works correctly. I managed to make the more common usage patterns between 8 and 10 times faster, which I feel is sufficient for now.

Signal and Kernel#trap
Ruby has a close ties to C, which means you can trap low level POSIX signals quite easily. This is hard to support in Java, though. One common use case that most Ruby programs do, is to trap INT so they can break the program gracefully. Rails and WEBrick does this. The current Kernel#trap and Signal was just stubbed out. I found a way to support signal handling on Sun JVM's at least, through the undocumented class sun.misc.Signal. JRuby feels if this is available, if so it uses it, otherwise trapping signals doesn't work. The implementation is really easy, I just grab the block provided and saves this in a Runnable that will be executed when the trap happens.

Zlib, IOInputStream and IOOutputStream
When working with Ruby IO-like objects from Java, it is often very convenient to wrap these in a Input/Output-stream. This isn't totally obvious how to do, though. My first implementation worked, but was intolerably slow. My last post about the plaincharset tells the tale how these things can go wrong. Suffice to say, I managed to fix the streams pretty good, and then started the real work: Reimplementing Zlib::GzipReader and Zlib::GzipWriter in Java. This wasn't as hard as I thought, once I got the IO-streams working as it should.

There was one bug which was really hard to find though, and it was caused by a minor difference between Java's read(n) and Ruby's read(n) methods. In Java, if we ask to read n bytes, we don't necessarily get all the bytes we asked for, even if there are that many bytes available. This is why those read-methods return how many bytes actually were read. But Ruby's read(n) doesn't act this way. It either reads n bytes, or to end of stream, depending on which come first. That one took a while to find.

The reimplementation of Zlib isn't complete yet, but the important classes are done. The deflater and inflater classes already use a backing Java class for performance, and the checksum classes don't need that kind of speed. The performance improvement from reimplementing GzipReader into Java was great, though. It seems to be between 15 and 20 times faster, most often. RubyGems is really useful now.

What's left?
Now, these things are quite minor. They improve different parts of Ruby that are used quite often. RubyGems seem to work more or less perfectly. Rails generation works too. The server-script for Rails almost works, but there is something strange going on with WEBrick yet. I'm wondering if this has something to do with our Socket-code, which I'm not totally into yet. But these are the issues I'll be looking at before 0.9.

In the long (longer at least), I have two main points that interest me. First I want to complete JvYAML, and integrate it with JRuby. And secondly I'm thinking about ways to byte compile (to some Ruby bytecode) parts of the AST tree, much in the same way Charles have been toying with compiling parts of it to Java bytecode. This is mostly just ideas in my head yet, but that's probably something I'll write more about quite soon here.

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