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// Copyright 2016 Google Inc. All Rights Reserved.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
#include <vector>
#include "base/memory/ref_counted.h"
#include "base/memory/scoped_vector.h"
#include "base/memory/weak_ptr.h"
#include "cobalt/base/polymorphic_downcast.h"
#include "cobalt/script/mozjs/wrapper_factory.h"
#include "cobalt/script/wrappable.h"
#include "third_party/mozjs/js/src/jsapi.h"
namespace cobalt {
namespace script {
namespace mozjs {
// Our mozjs specific implementation of |script::Tracer|. Tracing sessions
// will be initiated from a |Wrapper| of SpiderMonkey's choice, and then it
// will be the |mozjs::Tracer|'s job to assist SpiderMonkey's garbage
// collector in traversing the graph of |Wrapper|s and |Wrappable|s.
// |Wrappable|s will inform us about what they can reach through their
// |TraceMembers| implementation, and then we will pass the reachable
// |Wrappable|'s |Wrapper| to SpiderMonkey GC if it exists, and otherwise
// continue traversing ourselves from |Wrappable| to (the unwrapped)
// |Wrappable|.
class Tracer : public ::cobalt::script::Tracer {
explicit Tracer(JSTracer* js_tracer) : js_tracer_(js_tracer) {}
void Trace(Wrappable* wrappable) OVERRIDE;
void TraceFrom(Wrappable* wrappable);
JSTracer* js_tracer_;
// Pending |Wrappable|s that we must traverse ourselves, since they did not
// have a |Wrapper|.
std::vector<Wrappable*> frontier_;
// Contains private data associated with a JSObject representing a JS wrapper
// for a Cobalt platform object. There should be a one-to-one mapping of such
// JSObjects and WrapperPrivate instances, and the corresponding WrapperPrivate
// must be destroyed when its JSObject is garbage collected.
class WrapperPrivate : public base::SupportsWeakPtr<WrapperPrivate> {
typedef std::vector<Wrappable*> WrappableVector;
template <typename T>
scoped_refptr<T> wrappable() const {
return base::polymorphic_downcast<T*>(wrappable_.get());
JSObject* js_object_proxy() const { return wrapper_proxy_; }
// Create a new WrapperPrivate instance and associate it with the wrapper.
static void AddPrivateData(JSContext* context, JS::HandleObject wrapper_proxy,
const scoped_refptr<Wrappable>& wrappable);
// Return true if the object has wrapper private.
static bool HasWrapperPrivate(JSContext* context, JS::HandleObject object);
// Get the WrapperPrivate associated with the given Wrappable. A new JSObject
// and WrapperPrivate object may be created.
static WrapperPrivate* GetFromWrappable(
const scoped_refptr<Wrappable>& wrappable, JSContext* context,
WrapperFactory* wrapper_factory);
// Get the WrapperPrivate instance associated with this Wrapper object.
static WrapperPrivate* GetFromWrapperObject(JS::HandleObject object);
// Get the WrapperPrivate instance associated with the target of this proxy.
static WrapperPrivate* GetFromProxyObject(JSContext* context,
JS::HandleObject proxy_object);
// Get the WrapperPrivate instance associated with the object, which may
// be a proxy or a proxy target.
static WrapperPrivate* GetFromObject(JSContext* context,
JS::HandleObject object);
// Called when the wrapper object is about to be deleted by the GC.
static void Finalizer(JSFreeOp* /* free_op */, JSObject* object);
// Trace callback called during garbage collection.
static void Trace(JSTracer* trace, JSObject* object);
WrapperPrivate(JSContext* context, const scoped_refptr<Wrappable>& wrappable,
JS::HandleObject wrapper_proxy);
JSContext* context_;
scoped_refptr<Wrappable> wrappable_;
JS::Heap<JSObject*> wrapper_proxy_;
friend Tracer;
} // namespace mozjs
} // namespace script
} // namespace cobalt