[V8] Generalize external object resources

V8 was already able to manage and finalize an external string
resource.  This change generalizes that mechanism to handle a
single generic external resource - a v8::Object::ExternalResource
derived instance - on normal JSObject's.

This is useful for mapping C++ objects to JS objects where the
C++ object's memory is effectively owned by the JS Object, and
thus needs to destroyed when the JS Object is garbage collected.
The V8 mailing list suggests using a weak persistent handle for
this purpose, but that seems to incur a fairly massive performance
penalty for short lived objects as weak persistent handle callbacks
are not called until the object has been promoted into the old
object space.

Change-Id: I83677c9d906742a2bf0596961491eecb7ee60003
Reviewed-by: Kent Hansen <kent.hansen@nokia.com>

1 files changed, 56 insertions, 0 deletions

diff --git a/src/3rdparty/v8/src/api.cc b/src/3rdparty/v8/src/api.cc
index af8cfa4..b78213c 100644
--- a/src/3rdparty/v8/src/api.cc
+++ b/src/3rdparty/v8/src/api.cc
@@ -1465,6 +1465,34 @@ void ObjectTemplate::SetInternalFieldCount(int value) {
 }
 
 
+bool ObjectTemplate::HasExternalResource()
+{
+  if (IsDeadCheck(Utils::OpenHandle(this)->GetIsolate(),
+                  "v8::ObjectTemplate::HasExternalResource()")) {
+    return 0;
+  }
+  return !Utils::OpenHandle(this)->has_external_resource()->IsUndefined();
+}
+
+
+void ObjectTemplate::SetHasExternalResource(bool value)
+{
+  i::Isolate* isolate = Utils::OpenHandle(this)->GetIsolate();
+  if (IsDeadCheck(isolate, "v8::ObjectTemplate::SetHasExternalResource()")) {
+    return;
+  }
+  ENTER_V8(isolate);
+  if (value) {
+    EnsureConstructor(this);
+  }
+  if (value) {
+      Utils::OpenHandle(this)->set_has_external_resource(i::Smi::FromInt(1));
+  } else {
+      Utils::OpenHandle(this)->set_has_external_resource(Utils::OpenHandle(this)->GetHeap()->undefined_value());
+  }
+}
+
+
 // --- S c r i p t D a t a ---
 
 
@@ -4258,6 +4286,34 @@ void v8::Object::SetPointerInInternalField(int index, void* value) {
 }
 
 
+void v8::Object::SetExternalResource(v8::Object::ExternalResource *resource) {
+  i::Isolate* isolate = Utils::OpenHandle(this)->GetIsolate();
+  ENTER_V8(isolate);
+  i::Handle<i::JSObject> obj = Utils::OpenHandle(this);
+  if (CanBeEncodedAsSmi(resource)) {
+    obj->SetExternalResourceObject(EncodeAsSmi(resource));
+  } else {
+    obj->SetExternalResourceObject(*isolate->factory()->NewForeign(static_cast<i::Address>((void *)resource)));
+  }
+  if (!obj->IsSymbol()) {
+    isolate->heap()->external_string_table()->AddObject(*obj);
+  }
+}
+
+
+v8::Object::ExternalResource *v8::Object::GetExternalResource() {
+  i::Handle<i::JSObject> obj = Utils::OpenHandle(this);
+  i::Object* value = obj->GetExternalResourceObject();
+  if (value->IsSmi()) {
+    return reinterpret_cast<v8::Object::ExternalResource*>(i::Internals::GetExternalPointerFromSmi(value));
+  } else if (value->IsForeign()) {
+    return reinterpret_cast<v8::Object::ExternalResource*>(i::Foreign::cast(value)->foreign_address());
+  } else {
+    return NULL;
+  }
+}
+
+
 // --- E n v i r o n m e n t ---