gecko-dev/dom/bindings/SpiderMonkeyInterface.h

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef mozilla_dom_SpiderMonkeyInterface_h
#define mozilla_dom_SpiderMonkeyInterface_h

#include "jsapi.h"
#include "jsfriendapi.h"
#include "js/TracingAPI.h"

namespace mozilla {
namespace dom {

/*
 * Class that just handles the JSObject storage and tracing for spidermonkey
 * interfaces
 */
struct SpiderMonkeyInterfaceObjectStorage
{
protected:
  JSObject* mImplObj;
  JSObject* mWrappedObj;

  SpiderMonkeyInterfaceObjectStorage()
    : mImplObj(nullptr),
      mWrappedObj(nullptr)
  {
  }

  SpiderMonkeyInterfaceObjectStorage(SpiderMonkeyInterfaceObjectStorage&& aOther)
    : mImplObj(aOther.mImplObj),
      mWrappedObj(aOther.mWrappedObj)
  {
    aOther.mImplObj = nullptr;
    aOther.mWrappedObj = nullptr;
  }

public:
  inline void TraceSelf(JSTracer* trc)
  {
    JS::UnsafeTraceRoot(trc, &mImplObj, "SpiderMonkeyInterfaceObjectStorage.mImplObj");
    JS::UnsafeTraceRoot(trc, &mWrappedObj, "SpiderMonkeyInterfaceObjectStorage.mWrappedObj");
  }

  inline bool inited() const
  {
    return !!mImplObj;
  }

  inline bool WrapIntoNewCompartment(JSContext* cx)
  {
    return JS_WrapObject(cx,
      JS::MutableHandle<JSObject*>::fromMarkedLocation(&mWrappedObj));
  }

  inline JSObject *Obj() const
  {
    MOZ_ASSERT(inited());
    return mWrappedObj;
  }

private:
  SpiderMonkeyInterfaceObjectStorage(const SpiderMonkeyInterfaceObjectStorage&) = delete;
};

// A class for rooting an existing SpiderMonkey Interface struct
template<typename InterfaceType>
class MOZ_RAII SpiderMonkeyInterfaceRooter : private JS::CustomAutoRooter
{
public:
  template <typename CX>
  SpiderMonkeyInterfaceRooter(const CX& cx,
                              InterfaceType* aInterface MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
    : JS::CustomAutoRooter(cx MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT),
      mInterface(aInterface)
  {
  }

  virtual void trace(JSTracer* trc) override
  {
    mInterface->TraceSelf(trc);
  }

private:
  SpiderMonkeyInterfaceObjectStorage* const mInterface;
};

// And a specialization for dealing with nullable SpiderMonkey interfaces
template<typename Inner> struct Nullable;
template<typename InterfaceType>
class MOZ_RAII SpiderMonkeyInterfaceRooter<Nullable<InterfaceType>> :
    private JS::CustomAutoRooter
{
public:
  template <typename CX>
  SpiderMonkeyInterfaceRooter(const CX& cx,
                              Nullable<InterfaceType>* aInterface MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
    : JS::CustomAutoRooter(cx MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT),
      mInterface(aInterface)
  {
  }

  virtual void trace(JSTracer* trc) override
  {
    if (!mInterface->IsNull()) {
      mInterface->Value().TraceSelf(trc);
    }
  }

private:
  Nullable<InterfaceType>* const mInterface;
};

// Class for easily setting up a rooted SpiderMonkey interface object on the
// stack
template<typename InterfaceType>
class MOZ_RAII RootedSpiderMonkeyInterface final : public InterfaceType,
                                                   private SpiderMonkeyInterfaceRooter<InterfaceType>
{
public:
  template <typename CX>
  explicit RootedSpiderMonkeyInterface(const CX& cx MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
    : InterfaceType(),
      SpiderMonkeyInterfaceRooter<InterfaceType>(cx, this
                                                 MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT)
  {
  }

  template <typename CX>
  RootedSpiderMonkeyInterface(const CX& cx, JSObject* obj MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
    : InterfaceType(obj),
      SpiderMonkeyInterfaceRooter<InterfaceType>(cx, this
                                                 MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT)
  {
  }
};

} // namespace dom
} // namespace mozilla

#endif /* mozilla_dom_SpiderMonkeyInterface_h */