Gin: Make it easier to implement Wrappable

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() {
+WrappableBase::WrappableBase() {
 }
 
-Wrappable::~Wrappable() {
+WrappableBase::~WrappableBase() {
   wrapper_.Reset();
 }
 
-v8::Handle<v8::Object> Wrappable::GetWrapper(v8::Isolate* isolate) {
-  if (wrapper_.IsEmpty())
-    CreateWrapper(isolate);
-  return v8::Local<v8::Object>::New(isolate, wrapper_);
+v8::Handle<v8::Object> WrappableBase::GetWrapperImpl(
+    v8::Isolate* isolate, WrapperInfo* wrapper_info) {
+    if (wrapper_.IsEmpty())
+      CreateWrapper(isolate, wrapper_info);
+    return v8::Local<v8::Object>::New(isolate, wrapper_);
 }
 
-void Wrappable::WeakCallback(
-    const v8::WeakCallbackData<v8::Object, Wrappable>& data) {
-  Wrappable* wrappable = data.GetParameter();
+void WrappableBase::WeakCallback(
+    const v8::WeakCallbackData<v8::Object, WrappableBase>& data) {
+  WrappableBase* wrappable = data.GetParameter();
   wrappable->wrapper_.Reset();
   delete wrappable;
 }
 
-v8::Handle<v8::Object> Wrappable::CreateWrapper(v8::Isolate* isolate) {
-  WrapperInfo* info = GetWrapperInfo();
+v8::Handle<v8::Object> WrappableBase::CreateWrapper(v8::Isolate* isolate,
+                                                    WrapperInfo* info) {
   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_EQ(kNumberOfInternalFields, templ->InternalFieldCount());
   v8::Handle<v8::Object> wrapper = templ->NewInstance();
   wrapper->SetAlignedPointerInInternalField(kWrapperInfoIndex, info);
   wrapper->SetAlignedPointerInInternalField(kEncodedValueIndex, this);
   wrapper_.Reset(isolate, wrapper);
   wrapper_.SetWeak(this, WeakCallback);
   return wrapper;
 }
 
+namespace internal {
+
+void* FromV8Impl(v8::Isolate* isolate, v8::Handle<v8::Value> val,
+                 WrapperInfo* wrapper_info) {
+  if (!val->IsObject())
+    return NULL;
+  v8::Handle<v8::Object> obj = v8::Handle<v8::Object>::Cast(val);
+  WrapperInfo* info = WrapperInfo::From(obj);
+
+  // If this fails, the object is not managed by Gin. It is either a normal JS
+  // object that's not wrapping any external C++ object, or it is wrapping some
+  // C++ object, but that object isn't managed by Gin (maybe Blink).
+  if (!info)
+    return NULL;
+
+  // If this fails, the object is managed by Gin, but it's not wrapping an
+  // instance of the C++ class associated with wrapper_info.
+  if (info != wrapper_info)
+    return NULL;
+
+  return obj->GetAlignedPointerFromInternalField(kEncodedValueIndex);
+}
+
+}  // namespace internal
+
 }  // namespace gin