ephemeron.cc

//  http://wiki.ecmascript.org/doku.php?id=harmony:ephemeron_tables
//	node-overload
//	@exports
//		EphemeronTable()
//        get(key)
//        set(key,value)
//

#include <v8.h>
#include <stdio.h>
using namespace v8;
using namespace std;

void Noop(
		Persistent<Value> object
		, void* parameter
	) {
	object.Dispose();
}

void OurWeakReferenceCallback(
		Persistent<Value> object
		, void* parameter
	) {
	HandleScope scope;
	Handle<Function> callback = Handle<Function>((Function*)parameter);

	Handle<Value> values[0];
	//ERROR: SegFault / Bus Error
	printf("obj : %d : invoking collector\n",(int)&object);
	callback->Call(Context::GetCurrent()->Global(),0,values);
	object.Dispose();
	scope.Close(Undefined());
}

void KeepingWeakReferenceCallback(
		Persistent<Value> callback
		, void* parameter
	) {
	HandleScope scope;
	Handle<Object> object = Handle<Object>((Object*)parameter);
	//ERROR points to different space?
	printf("obj : %d : testing revival need\n",(int)&object);
	if(object.IsEmpty()) {
		callback.Dispose();
	}
	else {
		//Revive this object so long as there is a dependant weak reference
		Persistent<Value>::New(callback).MakeWeak(parameter,OurWeakReferenceCallback);
	}
	scope.Close(Undefined());
}

Handle<Value> Weak(
		const Arguments& args
	) {
	HandleScope scope;
	Handle<Value> obj = args[0];
	if(!obj->IsObject() || obj->IsNull() || obj->IsUndefined()) {
		return scope.Close(ThrowException(Exception::Error(String::New("First argument must be an object"))));
	}
	Handle<Value> onCollect = args[1];
	if(onCollect->IsFunction()) {
		Persistent<Object> persistent_obj = Persistent<Object>::New(Handle<Object>::Cast(obj));
		Persistent<Function> persistent_cb = Persistent<Function>::New(Handle<Function>::Cast(onCollect));

		printf("obj : %d : making weak\n",(int)&persistent_obj);
		persistent_obj.MakeWeak(
			&persistent_cb
			, OurWeakReferenceCallback
		);
		//bind a weak ref of cb to the obj
		persistent_cb.MakeWeak(
			&persistent_obj
			, KeepingWeakReferenceCallback
		);
		return scope.Close(persistent_obj);
	}
	else {
		return scope.Close(ThrowException(Exception::Error(String::New("Collect callback must be a function"))));
	}
}

extern "C" void init (Handle<Object> target)
{
	HandleScope scope;
	Local<FunctionTemplate> weak_template = FunctionTemplate::New(Weak);
	Local<Function> weak = weak_template->GetFunction();
	//Export
	target->Set(String::New("Weak"),weak);
}

test.js

var Weak = require("../lib/ephemeron_table").Weak
  , gc = require("../node-gc/gc")
  , GC = new gc.GC();
var a={toString:function(){return "not deleted"}}

Weak(a,function a(){
  //console.log("Weak Callback Invoked")
  //a="deleted"
})

setInterval(function(){GC.collect()},500)