I have been working with method lookup and caching using gwt which seems
to work well.
However to get it to work I had to set up the casting in a way which was
not obvious to me.
In my Smalltalk implementation all ST objects are instances of a single
java class ( RtObject )
so I was thinking that all of my method handles would use that as a type.
But what worked was:
( full code at bottom )
First I collect all of the ST args into an array
My collector ( mh2 type is (RtObject.class, RtObject.class,
RtObject.class )
MethodHandle mh3=mh2.asCollector(RtObject[].class, site.getAirity());
At this point I enter the fallback
The type of my fallback method ( I expected the last type to be RtObject[]
).
MethodType mt=MethodType.methodType(RtObject.class, RtCallSite.class,
Object[].class);
The spreader ( I expected the first type to be RtObject[] )
MethodHandle invoke=newTarget.asSpreader(Object[].class,
site.getAirity());
The invoke ( again not sure why I needed the cast here )
result=(RtObject)invoke.invokeExact((Object[])args);
The problem area seems to be going from the collector to the fallback
call. If I make the
fallback RtObject then I start getting type error. The latest doc implies
that the type of
this array 'usually' is the same type as the args collected.
Is collector doing the cast to Object[]?
Thanks
mark
// handle the self bootstrap and lookup
public static RtCallSite bootStrapSelf(MethodHandles.Lookup
callerLookup, String name, MethodType type, Object arg) {
// return a call site for a method on self called first time
System.out.println("bootstrap " + name);
RtObject sel=new RtObject(name);
RtCallSite site=new RtCallSite(type, sel.asSymbol());
site.setAirity(type.parameterCount());
// need to set the target to the initial fallback
// needs to do a combine args based on airity, insert site and then
the lookup
MethodHandles.Lookup lookup=MethodHandles.lookup();
MethodType mt=MethodType.methodType(RtObject.class, RtCallSite.class,
Object[].class);
MethodHandle mh=null;
try {
mh=lookup.findStatic(RtCallSite.class, "fallbackSelf", mt);
}
catch (Exception e1) {
e1.printStackTrace();
}
// insert the call site
MethodHandle mh2=MethodHandles.insertArguments(mh, 0, site);
// combine the args into an array
MethodHandle mh3=mh2.asCollector(RtObject[].class, site.getAirity());
site.setTarget(mh3);
return site;
}
public static RtObject fallbackSelf(RtCallSite site, Object[] args) {
// set a new guard with test path based on test failing/;
System.out.println("fallback");
System.out.println(site.getSelector());
int last=args.length;
RtObject rcvr=(RtObject)args[last - 1];
MethodHandles.Lookup lookup=MethodHandles.lookup();
// create the gwt
MethodType mt=MethodType.methodType(boolean.class, RtObject.class,
RtObject.class);
MethodHandle test=null;
try {
test=lookup.findStatic(RtCallSite.class, "test", mt);
}
catch (Exception e1) {
e1.printStackTrace();
}
// need to insert the test at the beginning
test=MethodHandles.insertArguments(test, 0, rcvr.classField());
// now drop the excess args ( leaving first and last)
test=MethodHandles.dropArguments(test, 1, site.dropArray());
// now I need to lookup the smalltalk method
RtObject method=rcvr.lookupSelf(site.getSelector());
MethodHandle newTarget=primGetMethodHandle(method);
MethodHandle gwt=MethodHandles.guardWithTest(test, newTarget,
site.getTarget());
site.setTarget(gwt);
// now I have to invoke it
MethodHandle invoke=newTarget.asSpreader(Object[].class,
site.getAirity());
RtObject result=null;
try {
result=(RtObject)invoke.invokeExact((Object[])args);
}
catch (Throwable e) {
e.printStackTrace();
}
return result;
}_______________________________________________
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