coordinate shared datastructure teardown

ext/v8/isolate.cc

@@ -4,42 +4,39 @@
 
 namespace rr {
 
+  VALUE Isolate::Class;
+
   void Isolate::Init() {
     rb_eval_string("require 'v8/retained_objects'");
     ClassBuilder("Isolate").
       defineSingletonMethod("New", &New).
 
       defineMethod("Dispose", &Isolate::Dispose).
-      defineMethod("Equals", &rr::Isolate::PointerEquals).
 
       store(&Class);
   }
 
-
   VALUE Isolate::New(VALUE self) {
     Isolate::IsolateData* data = new IsolateData();
+
     VALUE rb_cRetainedObjects = rb_eval_string("V8::RetainedObjects");
     data->retained_objects = rb_funcall(rb_cRetainedObjects, rb_intern("new"), 0);
 
     v8::Isolate::CreateParams create_params;
     create_params.array_buffer_allocator = &data->array_buffer_allocator;
+    v8::Isolate* isolate = v8::Isolate::New(create_params);
+
 
-    Isolate isolate(v8::Isolate::New(create_params));
     isolate->SetData(0, data);
     isolate->AddGCPrologueCallback(&clearReferences);
 
-    return isolate;
+    data->isolate = isolate;
+    return Isolate(isolate);
   }
 
   VALUE Isolate::Dispose(VALUE self) {
     Isolate isolate(self);
-    delete isolate.data();
     isolate->Dispose();
     return Qnil;
   }
-
-  template <>
-  void Pointer<v8::Isolate>::unwrap(VALUE value) {
-    Data_Get_Struct(value, class v8::Isolate, pointer);
-  }
 }

ext/v8/isolate.h

@@ -23,15 +23,60 @@ namespace rr {
    * Note: You must call `Dispose()` on the isolate for its resources
    * to be released, otherwise, it will be leaked.
    */
-  class Isolate : public Pointer<v8::Isolate> {
+  class Isolate  {
   public:
     struct IsolateData;
+    static VALUE Class;
     static void Init();
 
     static VALUE New(VALUE self);
 
-    inline Isolate(v8::Isolate* isolate) : Pointer<v8::Isolate>(isolate) {}
-    inline Isolate(VALUE value) : Pointer<v8::Isolate>(value) {}
+    inline Isolate(IsolateData* data_) : data(data_) {}
+    inline Isolate(v8::Isolate* isolate) :
+      data((IsolateData*)isolate->GetData(0)) {}
+    inline Isolate(VALUE value) {
+      Data_Get_Struct(value, struct IsolateData, data);
+    }
+
+    /**
+     * Called, when Ruby no longer has any more references to this
+     * instance of `V8::C::Isolate`. However, this does not
+     * necessarily mean that we can delete the isolate data because there
+     * could be outstanding objects... things like a V8::C::String
+     * that are part of this isolate that have yet to be garbage
+     * collected. The last object in the isolate, including the
+     * isolate itself is responsible for deleting the isolate data.
+     *
+     */
+    static void destroy(IsolateData* data) {
+      Isolate isolate(data);
+      isolate.decrementTotalReferences();
+    }
+
+    /**
+     * Every time we take out a reference to a V8 object, call this
+     * method.
+     */
+    inline void incrementTotalReferences() {
+      char counter(0);
+      data->total_ruby_references_queue.enqueue(counter);
+    }
+
+    /**
+     * Every time a Ruby reference to a V8 object is garbage
+     * collected, call this method. If this is the last object
+     * associated with this isolate, then the isolate data can, and
+     * will, be safely deleted.
+     */
+    inline bool decrementTotalReferences() {
+      char counter(0);
+      if (data->total_ruby_references_queue.try_dequeue(counter)) {
+        return true;
+      } else {
+        delete data;
+        return false;
+      }
+    }
 
     /**
      * Converts the v8::Isolate into a Ruby Object, while setting up
@@ -39,17 +84,25 @@ namespace rr {
      * VALUE rubyObject = Isolate(v8::Isolate::New());
      */
     virtual operator VALUE() {
-      return Data_Wrap_Struct(Class, &releaseAndMarkRetainedObjects, 0, pointer);
+      return Data_Wrap_Struct(Class, &releaseAndMarkRetainedObjects, &destroy, data);
     }
 
     /**
-     * Access the book-keeping data. e.g.
+     * Convert this into a v8::Isolate* for those areas of the API
+     * that call for it: E.g.
      *
-     *   Isolate(self).data();
+     *   v8::Context::New(Isolate(self));
      */
-    inline IsolateData* data() {
-      return (IsolateData*)pointer->GetData(0);
-    }
+    inline operator v8::Isolate*() { return data->isolate; }
+
+    /**
+     * Dereference the underlying v8::Isolate so that we can call methods
+     * on it. E.g.
+     *
+     *   Isolate(self)->IsDead();
+     */
+
+    inline v8::Isolate* operator ->() { return data->isolate; }
 
     /**
      * Schedule a v8::Persistent reference to be be deleted with the next
@@ -59,7 +112,9 @@ namespace rr {
      */
     template <class T>
     inline void scheduleReleaseObject(v8::Persistent<T>* cell) {
-      data()->v8_release_queue.enqueue((v8::Persistent<void>*)cell);
+      if (this->decrementTotalReferences()) {
+        data->v8_release_queue.enqueue((v8::Persistent<void>*)cell);
+      }
     }
 
     /**
@@ -68,7 +123,7 @@ namespace rr {
      * where you do not hold any Ruby locks (such as the V8 GC thread)
      */
     inline void scheduleReleaseObject(VALUE object) {
-      data()->rb_release_queue.enqueue(object);
+      data->rb_release_queue.enqueue(object);
     }
 
     /**
@@ -80,7 +135,7 @@ namespace rr {
      * Note: should be called from a place where Ruby locks are held.
      */
     inline void retainObject(VALUE object) {
-      rb_funcall(data()->retained_objects, rb_intern("add"), 1, object);
+      rb_funcall(data->retained_objects, rb_intern("add"), 1, object);
     }
 
     /**
@@ -91,18 +146,15 @@ namespace rr {
      * Note: should be called from a place where Ruby locks are held.
      */
     inline void releaseObject(VALUE object) {
-      rb_funcall(data()->retained_objects, rb_intern("remove"), 1, object);
+      rb_funcall(data->retained_objects, rb_intern("remove"), 1, object);
     }
 
-
     /**
      * The `gc_mark()` callback for this Isolate's
      * Data_Wrap_Struct. It releases all pending Ruby objects.
      */
-
-    static void releaseAndMarkRetainedObjects(v8::Isolate* isolate_) {
-      Isolate isolate(isolate_);
-      IsolateData* data = isolate.data();
+    static void releaseAndMarkRetainedObjects(IsolateData* data) {
+      Isolate isolate(data);
       VALUE object;
       while (data->rb_release_queue.try_dequeue(object)) {
         isolate.releaseObject(object);
@@ -118,7 +170,7 @@ namespace rr {
     static void clearReferences(v8::Isolate* i, v8::GCType type, v8::GCCallbackFlags flags) {
       Isolate isolate(i);
       v8::Persistent<void>* cell;
-      while (isolate.data()->v8_release_queue.try_dequeue(cell)) {
+      while (isolate.data->v8_release_queue.try_dequeue(cell)) {
         cell->Reset();
         delete cell;
       }
@@ -148,6 +200,11 @@ namespace rr {
      */
     struct IsolateData {
 
+      /**
+       * The actual Isolate
+       */
+      v8::Isolate* isolate;
+
       /**
        * An instance of `V8::RetainedObjects` that contains all
        * references held from from V8. As long as they are in this
@@ -157,7 +214,7 @@ namespace rr {
 
       /**
        * A custom ArrayBufferAllocator for this isolate. Why? because
-       * if you don't, it will segfault when you try and create an
+       * if you don't, it will segfault when you try and create a
        * Context. That's why.
        */
       ArrayBufferAllocator array_buffer_allocator;
@@ -176,7 +233,21 @@ namespace rr {
        * needs it.
        */
       ConcurrentQueue<VALUE> rb_release_queue;
+
+      /**
+       * Contains a number of tokens representing all of the live Ruby
+       * references that are currently active in this Isolate. Every
+       * time a Ruby reference to a V8 object is added, an item is
+       * added to this queue. Every time a ruby reference is garbage
+       * collected, an item is pulled out of the queue. Whenever this
+       * queue reaches 0, then it is time to delete the isolate data
+       * since there are no more object associated with it.
+       */
+      ConcurrentQueue<int> total_ruby_references_queue;
+
     };
+
+    IsolateData* data;
   };
 }
 

ext/v8/ref.h

@@ -38,8 +38,8 @@ namespace rr {
       Holder* holder = unwrapHolder();
 
       if (holder) {
-        this->isolate = holder->isolate;
-        this->handle = v8::Local<T>::New(holder->isolate, *holder->cell);
+        this->isolate = holder->data->isolate;
+        this->handle = v8::Local<T>::New(holder->data->isolate, *holder->cell);
       } else {
         this->isolate = NULL;
         this->handle = v8::Local<T>();
@@ -94,13 +94,15 @@ namespace rr {
 
     struct Holder {
       Holder(v8::Isolate* isolate, v8::Handle<T> handle) :
-        isolate(isolate), cell(new v8::Persistent<T>(isolate, handle)) {}
-
-      virtual ~Holder() {
-        Isolate(isolate).scheduleReleaseObject<T>(cell);
+        data((Isolate::IsolateData*)isolate->GetData(0)), cell(new v8::Persistent<T>(isolate, handle)) {
+        Isolate(data).incrementTotalReferences();
       }
 
-      v8::Isolate* isolate;
+      virtual ~Holder() {
+        Isolate(data).scheduleReleaseObject<T>(cell);
+      }
+
+      Isolate::IsolateData* data;
       v8::Persistent<T>* cell;
     };
 

spec/c/isolate_spec.rb

@@ -7,11 +7,6 @@ describe V8::C::Isolate do
     expect(isolate).to be
   end
 
-  it 'can be tested for equality' do
-    expect(isolate.Equals(isolate)).to eq true
-    expect(isolate.Equals(V8::C::Isolate::New())).to eq false
-  end
-
   it "can be disposed of" do
     isolate.Dispose()
   end

spec/c_spec_helper.rb

@@ -22,6 +22,8 @@ module V8ContextHelpers
         @ctx.Exit
       end
     end
+  ensure
+    @isolate.Dispose()
   end
 end