add preliminary support for weak backreferences.

ext/v8/v8_handle.cpp

@@ -69,7 +69,8 @@ namespace {
 
 
   VALUE MakeWeak(VALUE self) {
-    rr_v8_handle_set_internal(self,"weakref_callback", rb_block_proc());
+    VALUE callback = rb_block_given_p() ? rb_block_proc() : Qnil;
+    rr_v8_handle_set_internal(self,"weakref_callback", callback);
     rr_v8_handle<void>(self).MakeWeak((void*)self, RubyWeakReferenceCallback);
     return Qnil;
   }
@@ -83,17 +84,18 @@ namespace {
     return rr_v82rb(rr_v8_handle<void>(self).IsNearDeath());
   }
 
-  VALUE IsDead(VALUE self) {
-    return rr_v82rb(rr_v8_handle_raw(self)->dead);
-  }
-
   VALUE IsWeak(VALUE self) {
     return rr_v82rb(rr_v8_handle<void>(self).IsWeak());
   }
+
+  VALUE dead_p(VALUE self) {
+    return rr_v8_handle_raw(self)->dead ? Qtrue : Qfalse;
+  }
 }
 
 void rr_init_handle() {
   VALUE HandleClass = rr_define_class("Handle");
+  rr_define_method(HandleClass, "dead?", dead_p, 0);
   rr_define_singleton_method(HandleClass, "New", New, 1);
   rr_define_method(HandleClass, "IsEmpty", IsEmpty, 0);
   rr_define_method(HandleClass, "Clear", Clear, 0);
@@ -101,7 +103,6 @@ void rr_init_handle() {
   rr_define_method(HandleClass, "MakeWeak", MakeWeak, 0);
   rr_define_method(HandleClass, "ClearWeak", ClearWeak, 0);
   rr_define_method(HandleClass, "IsNearDeath", IsNearDeath, 0);
-  rr_define_method(HandleClass, "IsDead", IsDead, 0);
   rr_define_method(HandleClass, "IsWeak", IsWeak, 0);
 }
 
@@ -126,4 +127,3 @@ v8_handle* rr_v8_handle_raw(VALUE value) {
   Data_Get_Struct(value, struct v8_handle, handle);
   return handle;
 }
-

ext/v8/v8_object.cpp

@@ -1,4 +1,5 @@
 #include "v8_handle.h"
+#include "v8_weakref.h"
 #include "v8_object.h"
 #include "v8_value.h"
 #include "v8_template.h"
@@ -91,9 +92,26 @@ void rr_init_object() {
   rr_define_method(ObjectClass, "SetPrototype", SetPrototype, 1);
 }
 
-VALUE rr_reflect_v8_object(Handle<Value> value) {
-  Local<Object> object(Object::Cast(*value));
-  Local<Value> peer = object->GetHiddenValue(String::NewSymbol("TheRubyRacer::RubyObject"));
-  return peer.IsEmpty() ? rr_v8_handle_new(ObjectClass, object) : (VALUE)External::Unwrap(peer);
+VALUE rr_reflect_v8_object_as(Handle<Object> object, VALUE ruby_class) {
+  VALUE handle;
+  v8_weakref* backref;
+  Local<Value> holder = object->GetHiddenValue(String::NewSymbol("TheRubyRacer::Backref"));
+  if (holder.IsEmpty()) {
+    handle = rr_v8_handle_new(ruby_class, object);
+    backref = new v8_weakref(handle);
+    object->SetHiddenValue(String::NewSymbol("TheRubyRacer::Backref"), backref->external);
+  } else {
+    backref = (v8_weakref*)External::Unwrap(holder);
+    handle = backref->get();
+    if (!RTEST(handle)) {
+      handle = rr_v8_handle_new(ruby_class, object);
+      backref->set(handle);
+    }
+  }
+  return handle;
+}
+
+VALUE rr_reflect_v8_object(Handle<Value> value) {
+  return rr_reflect_v8_object_as(value->ToObject(), ObjectClass);
 }
 

ext/v8/v8_object.h

@@ -3,7 +3,6 @@
 
 #include "rr.h"
 
-
 void rr_init_object();
 VALUE rr_v8_object_class();
 VALUE rr_reflect_v8_object(v8::Handle<v8::Value> value);

ext/v8/v8_weakref.cpp

@@ -0,0 +1,33 @@
+#include "v8.h"
+#include "v8_weakref.h"
+
+using namespace v8;
+
+v8_weakref::v8_weakref(VALUE object) {
+  this->external = Persistent<External>::New(External::New((void *)this));
+  this->external.MakeWeak(this, v8_weakref_finalize);
+  this->set(object);
+}
+
+void v8_weakref::set(VALUE value) {
+  this->object_id = rb_obj_id(value);
+}
+
+VALUE v8_weakref::get() {
+  return rb_rescue((VALUE (*)(...))v8_weakref_id2ref, this->object_id, (VALUE (*)(...))v8_weakref_nil, Qnil);
+}
+
+void v8_weakref_finalize(Persistent<Value> value, void* weakref) {
+  value.Dispose();
+  value.Clear();
+  delete (v8_weakref*)weakref;
+}
+
+VALUE v8_weakref_nil(VALUE nil, VALUE exception) {
+  return nil;
+}
+
+VALUE v8_weakref_id2ref(VALUE id) {
+  return rb_funcall(rb_const_get(rb_cObject, rb_intern("ObjectSpace")), rb_intern("_id2ref"), 1, id);
+}
+

ext/v8/v8_weakref.h

@@ -0,0 +1,22 @@
+#ifndef _RR_V8_WEAKREF_
+#define _RR_V8_WEAKREF_ 
+
+#include <v8.h>
+#include "ruby.h"
+
+struct v8_weakref  {
+  v8_weakref(VALUE object);
+  VALUE get();
+  void set(VALUE object);
+  void retain();
+  void release();
+
+  VALUE object_id;
+  v8::Persistent<v8::External> external;
+};
+
+void  v8_weakref_finalize(v8::Persistent<v8::Value> value, void* weakref);
+VALUE v8_weakref_nil(VALUE nil, VALUE exception);
+VALUE v8_weakref_id2ref(VALUE id);
+
+#endif

spec/ext/ext_spec_helper.rb

@@ -0,0 +1,37 @@
+
+module V8::ExtSpec
+  
+  def self.included(object)
+    object.class_eval do
+      before(:all) {c::V8::SetFlagsFromString("--expose-gc")}
+      before do
+        @cxt = c::Context::New()
+        @cxt.Enter()
+      end
+      after do
+        @cxt.Exit()
+      end
+    end
+  end
+  
+  def v8_eval(script)
+    c::Script::New(c::String::New(script), c::String::New('<eval>')).Run()
+  end
+
+  def c
+    V8::C
+  end
+  
+  def ruby_gc
+    current = GC.stress
+    GC.stress = true
+    yield
+  ensure
+    GC.stress = current
+  end
+
+  def v8_gc
+    c::Script::New(c::String::New("gc()"), c::String::New("gc.js")).Run()
+  end
+
+end

spec/ext/handle_spec.rb

@@ -1,18 +0,0 @@
-
-require 'spec_helper'
-
-describe V8::C::Handle do
-
-  before(:all) do
-    V8::C::V8::SetFlagsFromString("--expose-gc")
-    @cxt = V8::Context.new
-  end
-
-  def c
-    V8::C
-  end
-  
-  def gc
-    @cxt.eval('gc()');
-  end
-end

spec/ext/mem_spec.rb

@@ -2,53 +2,43 @@
 require 'spec_helper'
 
 describe "Memory:" do
-  context "A JavaScript Object reflected into ruby" do
-    before(:all) {c::V8::SetFlagsFromString("--expose-gc")}
+  include V8::ExtSpec
+  context "A JavaScript Object reflected into Ruby" do
+
     before do
-      @cxt = c::Context::New()
-      @cxt.Enter()
-    end
-    
-    after do
-      @cxt.Exit()
+      @weakref_callback = WeakrefCallback.new
     end
 
-    it "has a strong reference from the ruby side" do
+    it "has a strong reference from the ruby side, which is not released until the Ruby reference goes away" do
       handle = c::Handle::New(object = c::Object::New())
-      collected = false
-      handle.MakeWeak() {collected = true; puts "yo"}
-      v8_gc
-      collected.should_not be_true
-      handle.IsDead().should be_false
-    end
-    
-    it "will be garbarge collected if there are no more ruby references and is weakly reachable from V8" do
-      handle = c::Handle::New(object = c::Object::New())
-      object = nil
-      collected = false
-      handle.MakeWeak() {collected = true}
+      handle.MakeWeak(&@weakref_callback)
       ruby_gc do
         v8_gc
-        collected.should be_true
-        handle.IsDead().should be_true
+        @weakref_callback.should_not have_been_invoked
+        handle.should_not be_dead
+      end
+      ruby_gc do
+        object = nil
+        v8_gc
+        @weakref_callback.should have_been_invoked
+        handle.should be_dead
       end
     end
-    
-    private 
 
-    def v8_gc
-      c::Script::New(c::String::New("gc()"), c::String::New("gc.js")).Run()
-    end
-    
-    def ruby_gc
-      GC.stress = true
-      yield if block_given?
-    ensure
-      GC.stress = false
-    end
-    
-    def c
-      V8::C
+    private
+
+    class WeakrefCallback
+      def to_proc
+        method(:invoke).to_proc
+      end
+
+      def invoke
+        @invoked = true
+      end
+
+      def has_been_invoked?
+        @invoked
+      end
     end
   end
 end

spec/ext/object_spec.rb

@@ -0,0 +1,21 @@
+require 'spec_helper'
+
+describe V8::C::Object do
+  include V8::ExtSpec
+
+  it "always returns a copy of the same object if it is the same object" do
+    v8_eval('var o = new Object()')
+    v8_eval('o').should be(v8_eval('o'))
+  end
+
+  it "will return a new peer and not barf if the old peer has been garbage collected" do
+    v8_eval('var o = {foo: "bar"}')
+    o = v8_eval('o')
+    old_id = o.object_id
+    ruby_gc do
+      o = nil
+      v8_eval('o').Get(c::String::New("foo")).Utf8Value().should == "bar"
+      v8_eval('o').object_id.should_not be(old_id)
+    end
+  end
+end

spec/spec_helper.rb

@@ -1,7 +1,7 @@
 
 require 'v8'
-
 require 'erb'
+require Pathname(__FILE__).dirname.join('ext/ext_spec_helper')
 def rputs(msg)
   puts "<pre>#{ERB::Util.h(msg)}</pre>"
   $stdout.flush