src/cobalt/script/mozjs/referenced_object_map.h

// 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
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef COBALT_SCRIPT_MOZJS_REFERENCED_OBJECT_MAP_H_
#define COBALT_SCRIPT_MOZJS_REFERENCED_OBJECT_MAP_H_

#include "base/hash_tables.h"
#include "base/threading/thread_checker.h"
#include "cobalt/script/mozjs/weak_heap_object.h"
#include "cobalt/script/wrappable.h"
#include "third_party/mozjs/js/src/jsapi.h"

namespace cobalt {
namespace script {
namespace mozjs {

// Maintains a set of JSObjects that are reachable from a given object. This
// relationship is registered by mapping a key to a JSObject. The calling code
// should ensure that a key uniquely identifies the entity that holds a
// reference to the JSObjects.
// During garbage collection, supply a key to TraceReferencedObjects to trace
// all objects that are registered as being reachable from the object
// represented by that key.
class ReferencedObjectMap {
 public:
  explicit ReferencedObjectMap(JSContext* context);

  // Reinterpret the pointer as an integer to be used as a key for tracking
  // referenced objects.
  static intptr_t GetKeyForWrappable(const Wrappable* wrappable) {
    return reinterpret_cast<intptr_t>(wrappable);
  }

  void AddReferencedObject(intptr_t key, JS::HandleValue referee);
  void RemoveReferencedObject(intptr_t key, JS::HandleValue referee);

  // Trace all objects referenced from this WrapperPrivate*.
  void TraceReferencedObjects(JSTracer* trace, intptr_t key);

  // Remove any referenced objects that are NULL. It may be the case that a
  // weak reference to an object was garbage collected, so remove it from the
  // internal list.
  void RemoveNullReferences();

 private:
  typedef base::hash_multimap<intptr_t, WeakHeapObject>
      ReferencedObjectMultiMap;

  base::ThreadChecker thread_checker_;
  JSContext* context_;
  ReferencedObjectMultiMap referenced_objects_;
};

}  // namespace mozjs
}  // namespace script
}  // namespace cobalt

#endif  // COBALT_SCRIPT_MOZJS_REFERENCED_OBJECT_MAP_H_