Merge pull request #1 from stormbreakerbg/isolate-reference-queue

Isolate reference queue

ext/v8/context.cc

@@ -6,10 +6,8 @@ namespace rr {
     ClassBuilder("Context").
       defineSingletonMethod("New", &New).
 
-      defineMethod("Dispose", &Dispose).
       defineMethod("Enter", &Enter).
       defineMethod("Exit", &Exit).
-
       defineMethod("Global", &Global).
 
       store(&Class);
@@ -26,7 +24,6 @@ namespace rr {
 
     Isolate isolate(rb_isolate);
     Locker lock(isolate);
-
     return Context(v8::Context::New(
       isolate
       // TODO
@@ -37,11 +34,6 @@ namespace rr {
     ));
   }
 
-  VALUE Context::Dispose(VALUE self) {
-    Context(self).dispose();
-    return Qnil;
-  }
-
   VALUE Context::Enter(VALUE self) {
     Context context(self);
     Locker lock(context.getIsolate());

ext/v8/context.h

@@ -8,11 +8,8 @@ namespace rr {
     static void Init();
 
     static VALUE New(int argc, VALUE argv[], VALUE self);
-    static VALUE Dispose(VALUE self);
-
     static VALUE Enter(VALUE self);
     static VALUE Exit(VALUE self);
-
     static VALUE Global(VALUE self);
 
     // TODO

ext/v8/isolate.cc

@@ -14,12 +14,21 @@ namespace rr {
       store(&Class);
   }
 
+
   VALUE Isolate::New(VALUE self) {
-    return Isolate(v8::Isolate::New());
+    Isolate::IsolateData* data = new IsolateData();
+    v8::Isolate::CreateParams create_params;
+    create_params.array_buffer_allocator = &data->array_buffer_allocator;
+    Isolate isolate(v8::Isolate::New(create_params));
+    isolate->SetData(0, new IsolateData());
+    isolate->AddGCPrologueCallback(&clearReferences);
+    return isolate;
   }
 
   VALUE Isolate::Dispose(VALUE self) {
-    Isolate(self)->Dispose();
+    Isolate isolate(self);
+    delete isolate.data();
+    isolate->Dispose();
     return Qnil;
   }
 

ext/v8/isolate.h

@@ -2,6 +2,10 @@
 #ifndef RR_ISOLATE
 #define RR_ISOLATE
 
+#include "vendor/concurrentqueue.h"
+
+using namespace moodycamel;
+
 namespace rr {
   /**
    * V8::C::Isolate
@@ -9,11 +13,19 @@ namespace rr {
    * Represents a fully encapsulated V8 virtual machine. Allocated
    * from Ruby by calling `V8::C::Isolate::New()`
    *
+   * Every v8::Isolate wrapped in Ruby will have an instance of
+   * `IsolateData` embedded in it that can be used for bookkeeping
+   * between the V8 and Ruby worlds. For example, when v8 objects are
+   * no longer needed by ruby, they'll be enqueued for later release
+   * inside the V8 garbarge collection thread. This queue lives in the
+   * `IsolateData`
+   *
    * Note: You must call `Dispose()` on the isolate for its resources
-   * to be released.
+   * to be released, otherwise, it will be leaked.
    */
   class Isolate : public Pointer<v8::Isolate> {
   public:
+    struct IsolateData;
     static void Init();
 
     static VALUE New(VALUE self);
@@ -21,11 +33,84 @@ namespace rr {
     inline Isolate(v8::Isolate* isolate) : Pointer<v8::Isolate>(isolate) {}
     inline Isolate(VALUE value) : Pointer<v8::Isolate>(value) {}
 
+    /**
+     * Converts the v8::Isolate into a Ruby Object, while setting up
+     * its book keeping data. E.g.
+     * VALUE rubyObject = Isolate(v8::Isolate::New());
+     */
     inline operator VALUE() {
       return Data_Wrap_Struct(Class, 0, 0, pointer);
     }
 
+    /**
+     * Access the book-keeping data. e.g.
+     *
+     *   Isolate(self).data();
+     */
+    inline IsolateData* data() {
+      return (IsolateData*)pointer->GetData(0);
+    }
+
+    /**
+     * Schedule a v8::Persistent reference to be be deleted with the next
+     * invocation of the V8 Garbarge Collector
+     */
+    template <class T>
+    inline void scheduleDelete(v8::Persistent<T>* cell) {
+      data()->queue.enqueue((v8::Persistent<void>*)cell);
+    }
+
+    /**
+     * An instance of v8::GCPrologueCallback, this will run in the v8
+     * GC thread, and clear out all the references that have been
+     * released from Ruby.
+     */
+    static void clearReferences(v8::Isolate* i, v8::GCType type, v8::GCCallbackFlags flags) {
+      Isolate isolate(i);
+      v8::Persistent<void>* cell;
+      while (isolate.data()->queue.try_dequeue(cell)) {
+        cell->Reset();
+        delete cell;
+      }
+    }
+
+
     static VALUE Dispose(VALUE self);
+
+    /**
+     * Recent versions of V8 will segfault unless you pass in an
+     * ArrayBufferAllocator into the create params of an isolate. This
+     * is the simplest implementation possible.
+     */
+    class ArrayBufferAllocator : public v8::ArrayBuffer::Allocator {
+    public:
+      virtual void* Allocate(size_t length) {
+        void* data = AllocateUninitialized(length);
+        return data == NULL ? data : memset(data, 0, length);
+      }
+      virtual void* AllocateUninitialized(size_t length) { return malloc(length); }
+      virtual void Free(void* data, size_t) { free(data); }
+    };
+
+    /**
+     * Data specific to the Ruby embedding. It has the same life span
+     * as the isolate.
+     */
+    struct IsolateData {
+      /**
+       * A custom ArrayBufferAllocator for this isolate. Why? because
+       * if you don't, it will segfault when you try and create an
+       * Context. That's why.
+       */
+      ArrayBufferAllocator array_buffer_allocator;
+
+      /**
+       * Queue to hold unused references to v8 objects. Once Ruby is
+       * finished with an object it will be enqueued here so that it
+       * can be released by the v8 garbarge collector later.
+       */
+      ConcurrentQueue<v8::Persistent<void>*> queue;
+    };
   };
 }
 

ext/v8/ref.h

@@ -32,13 +32,14 @@ namespace rr {
   template <class T>
   class Ref {
   public:
+    struct Holder;
     Ref(VALUE value) {
       this->value = value;
       Holder* holder = unwrapHolder();
 
       if (holder) {
         this->isolate = holder->isolate;
-        this->handle = v8::Local<T>::New(holder->isolate, *holder->handle);
+        this->handle = v8::Local<T>::New(holder->isolate, *holder->cell);
       } else {
         this->isolate = NULL;
         this->handle = v8::Local<T>();
@@ -60,7 +61,7 @@ namespace rr {
         return Qnil;
       }
 
-      return Data_Wrap_Struct(Class, 0, &Holder::destroy, new Holder(isolate, handle));
+      return Data_Wrap_Struct(Class, 0, &destroy, new Holder(isolate, handle));
     }
 
     /*
@@ -74,10 +75,8 @@ namespace rr {
       return isolate;
     }
 
-    void dispose() {
-      Holder* holder = NULL;
-      Data_Get_Struct(this->value, class Holder, holder);
-      holder->dispose();
+    static void destroy(Holder* holder) {
+      delete holder;
     }
 
     /*
@@ -89,37 +88,16 @@ namespace rr {
     inline v8::Handle<T> operator->() const { return *this; }
     inline v8::Handle<T> operator*() const { return *this; }
 
-    class Holder {
-      friend class Ref;
-    public:
-      Holder(v8::Isolate* isolate, v8::Handle<T> handle) {
-        this->disposed_p = false;
-        this->isolate = isolate;
-        this->handle = new v8::Persistent<T>(isolate, handle);
-      }
+    struct Holder {
+      Holder(v8::Isolate* isolate, v8::Handle<T> handle) :
+        isolate(isolate), cell(new v8::Persistent<T>(isolate, handle)) {}
 
       virtual ~Holder() {
-        this->dispose();
+        Isolate(isolate).scheduleDelete<T>(cell);
       }
 
-      void dispose() {
-        if (!this->disposed_p) {
-          handle->Reset();
-          delete handle;
-          this->disposed_p = true;
-        }
-      }
-
-    protected:
       v8::Isolate* isolate;
-      v8::Persistent<T>* handle;
-      bool disposed_p;
-
-      static void destroy(Holder* holder) {
-        holder->dispose();
-
-        // TODO: Use a nonblocking queue with `AddGCPrologueCallback`
-      }
+      v8::Persistent<T>* cell;
     };
 
     static VALUE Class;
@@ -128,7 +106,7 @@ namespace rr {
     Holder* unwrapHolder() const {
       if (RTEST(this->value)) {
         Holder* holder = NULL;
-        Data_Get_Struct(this->value, class Holder, holder);
+        Data_Get_Struct(this->value, struct Holder, holder);
         return holder;
       } else {
         return NULL;

spec/c/context_spec.rb

@@ -0,0 +1,15 @@
+require 'c_spec_helper'
+
+describe V8::C::Context do
+  let(:isolate) { V8::C::Isolate::New() }
+  let(:context) { V8::C::Context::New(isolate) }
+  around do |example|
+    V8::C::HandleScope(isolate) do
+      example.run
+    end
+  end
+
+  it "can be instantiated" do
+    expect(context).to be
+  end
+end