Tuesday, May 27, 2008

Proof-of-Concept Backport Invokedynamic in Groovy

It is my first day of Google Summer of Code, and here is what I've done today ;-)

I have been reading hard and trying to understand Invokedynamic EDR since last week. It is quite difficult for me, who has little background of this kind of things. However, I have got some good sources for studying how invokedynamic work from John Rose's blog, Alex Tkachman's Method Handle code, Jeroen Frijters's blog, and RĂ©mi Forax's blog.

Although, there is no something complex like Jeroen's sample, here is a working version of Hello World that uses my backport of invokedynamic APIs.

package groovy.dyn.subject.vm5;

import groovy.dyn.CallSite;
import groovy.dyn.Linkage;
import groovy.dyn.MethodHandle;
import groovy.dyn.MethodHandles;
import groovy.dyn.MethodType;
import groovy.dyn.StaticContext;
import groovy.dyn.internal.CallSiteImpl;
import groovy.dyn.internal.StaticContextImpl;

import java.io.PrintStream;
import java.lang.reflect.Method;

public class InvokeDynamicSubject {

private static CallSite[] callsites;
private static final int NUM_OF_CALLSITES = 1;

static {
try {
Method method = InvokeDynamicSubject.class
CallSite.class, Object.class, Object[].class);
MethodHandle mh = MethodHandles.unreflect(method);
Linkage.registerBootstrapMethod(InvokeDynamicSubject.class, mh);
} catch (Throwable e) {
// do nothing now

private static void initCallSites() {
callsites = new CallSite[NUM_OF_CALLSITES];
callsites[0] = new CallSiteImpl(0,
new StaticContextImpl(
MethodType.make(void.class, String.class)

private static Object bootstrapInvokeDynamic(CallSite cs,
Object receiver, Object[] args) throws Throwable {
Method method=null;
CallSiteImpl csi = (CallSiteImpl)cs; // down cast: language specific
switch(csi.index()) {
case 0: {
StaticContext sc = cs.getStaticContext();
Class<?> c = sc.getCallingClass();
method = c.getDeclaredMethod(
MethodHandle mh = MethodHandles.unreflect(method);
return mh.invoke(receiver, args);
return null;

public void test() throws Throwable {
// System.out.println("Hello World");
MethodHandle mh = callsites[0].getTarget();
if(mh == null) {
bootstrapInvokeDynamic(callsites[0], System.out, new Object[]{"Hello World"});
} else {
mh.invoke(System.out, "Hello World");

Sunday, May 18, 2008

Groovy, Bazaar and bzr-svn

In the past, I was wondering how could I manage my Groovy fork (SVN is not good to do that because it's centralized nature). I was thinking to use SVK, but failed to set it up.

Today, Russel posted to groovy-dev that he set up a branch of Groovy on Launchpad. I have heard about Launchpad, but never tried to be its user. More that 2 hours that I have tried to set everything up.

I registered to be a Launchpad user, then forked my branch from Russel's one. OK, then what's next?
I'm still on Windows XP, so I need a set of putty programs for SSH. Later, I use PUTTYGEN to generate my public key and import it into Launchpad.

The next step is to download Python 2.5, Bazaar for Windows. Then, I installed bazaar and was able to branch Russel's trunk locally.

bzr branch http://bazaar.launchpad.net/~russel/groovy/trunk

After that I pushed it back to my branch.

bzr push bzr+ssh://chanwit@bazaar.launchpad.net/~chanwit/groovy/ck1

Then, something went wrong. I did not setup SSH properly. bazaar blamed me that I forgot to set BZR_SSH.

set BZR_SSH=plink

OK, here we go. Now everything went smoothly. I can push my local codes back to Launchpad. So I did clean and re-build Groovy to see if everything was fine. But hey !, the branch of Russel is out-of-date. I need the latest patch Alex just committed. So what to do?

I checked some docs on bazaar wiki and they said it is able to merge code from SVN using bzr-svn plugin. That sounds great to me. So I downloaded bzr-svn, but thing did not go smooth again. I need Python-Subversion binding with the special patches. Come on, where on the earth it is? Alright ! It seems I got everything to run bzr-svn.

I ran this command:

bzr merge http://svn.codehaus.org/groovy/trunk/groovy/groovy-core/

but it was not successful. The document said it should be svn+http. How silly I am. I tried merging again:

bzr merge svn+http://svn.codehaus.org/groovy/trunk/groovy/groovy-core/

And it worked ! After that I did commit.

bzr commit -m "message goes here"

and push all committed code back to Launchpad again:

bzr push

Wow, it was fun and cool!. Now I can have my experiment branch without missing any new patch from the main trunk! That's great, isn't it?