[Gin] Add a mechanism for wrapping C++ object

gin/wrappable.cc

+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "gin/wrappable.h"
+
+#include "base/logging.h"
+#include "gin/per_isolate_data.h"
+
+namespace gin {
+
+Wrappable::Wrappable() {
+}
+
+Wrappable::~Wrappable() {
+  wrapper_.Reset();
+}
+
+void Wrappable::WeakCallback(
+    const v8::WeakCallbackData<v8::Object, Wrappable>& data) {
+  Wrappable* wrappable = data.GetParameter();
+  wrappable->wrapper_.Reset();
+  wrappable->Release();  // Balanced in Wrappable::ConfigureWrapper.
+}
+
+v8::Handle<v8::Object> Wrappable::CreateWrapper(v8::Isolate* isolate) {
+  WrapperInfo* info = GetWrapperInfo();
+  PerIsolateData* data = PerIsolateData::From(isolate);
+  v8::Local<v8::ObjectTemplate> templ = data->GetObjectTemplate(info);
+  CHECK(!templ.IsEmpty());  // Don't forget to register an object template.
+  CHECK(templ->InternalFieldCount() == kNumberOfInternalFields);
+  v8::Handle<v8::Object> wrapper = templ->NewInstance();
+  wrapper->SetAlignedPointerInInternalField(kWrapperInfoIndex, info);
+  wrapper->SetAlignedPointerInInternalField(kEncodedValueIndex, this);
+  wrapper_.Reset(isolate, wrapper);
+  AddRef();  // Balanced in Wrappable::WeakCallback.
+  wrapper_.SetWeak(this, WeakCallback);
+  return wrapper;
+}
+
+v8::Handle<v8::Value> Converter<Wrappable*>::ToV8(v8::Isolate* isolate,
+                                                  Wrappable* val) {
+  if (val->wrapper_.IsEmpty())
+    return val->CreateWrapper(isolate);
+  return v8::Local<v8::Object>::New(isolate, val->wrapper_);
+}
+
+bool Converter<Wrappable*>::FromV8(v8::Handle<v8::Value> val,
+                                   Wrappable** out) {
+  if (!val->IsObject())
+    return false;
+  v8::Handle<v8::Object> obj = v8::Handle<v8::Object>::Cast(val);
+  WrapperInfo* info = WrapperInfo::From(obj);
+  if (!info)
+    return false;
+  void* pointer = obj->GetAlignedPointerFromInternalField(kEncodedValueIndex);
+  Wrappable* wrappable = static_cast<Wrappable*>(pointer);
+  CHECK(wrappable->GetWrapperInfo() == info);  // Security check for cast above.
+  *out = wrappable;
+  return true;
+}
+
+}  // namespace gin