gecko-dev/xpcom/base/nsCycleCollectionNoteChild.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/. */

// This header will be included by headers that define refpointer and array
// classes in order to specialize CC helpers such as ImplCycleCollectionTraverse
// for them.

#ifndef nsCycleCollectionNoteChild_h__
#define nsCycleCollectionNoteChild_h__

#include "nsCycleCollectionTraversalCallback.h"
#include "mozilla/Likely.h"
#include "mozilla/TypeTraits.h"

enum { CycleCollectionEdgeNameArrayFlag = 1 };

// Just a helper for appending "[i]". Didn't want to pull in string headers
// here.
void CycleCollectionNoteEdgeNameImpl(
    nsCycleCollectionTraversalCallback& aCallback, const char* aName,
    uint32_t aFlags = 0);

// Should be inlined so that in the no-debug-info case this is just a simple
// if().
MOZ_ALWAYS_INLINE void CycleCollectionNoteEdgeName(
    nsCycleCollectionTraversalCallback& aCallback, const char* aName,
    uint32_t aFlags = 0) {
  if (MOZ_UNLIKELY(aCallback.WantDebugInfo())) {
    CycleCollectionNoteEdgeNameImpl(aCallback, aName, aFlags);
  }
}

#define NS_CYCLE_COLLECTION_INNERCLASS cycleCollection

#define NS_CYCLE_COLLECTION_INNERNAME _cycleCollectorGlobal

#define NS_CYCLE_COLLECTION_PARTICIPANT(_class) \
  _class::NS_CYCLE_COLLECTION_INNERCLASS::GetParticipant()

template <typename T>
nsISupports* ToSupports(
    T* aPtr, typename T::NS_CYCLE_COLLECTION_INNERCLASS* aDummy = 0) {
  return T::NS_CYCLE_COLLECTION_INNERCLASS::Upcast(aPtr);
}

// The default implementation of this class template is empty, because it
// should never be used: see the partial specializations below.
template <typename T, bool IsXPCOM = mozilla::IsBaseOf<nsISupports, T>::value>
struct CycleCollectionNoteChildImpl {};

template <typename T>
struct CycleCollectionNoteChildImpl<T, true> {
  static void Run(nsCycleCollectionTraversalCallback& aCallback, T* aChild) {
    aCallback.NoteXPCOMChild(ToSupports(aChild));
  }
};

template <typename T>
struct CycleCollectionNoteChildImpl<T, false> {
  static void Run(nsCycleCollectionTraversalCallback& aCallback, T* aChild) {
    aCallback.NoteNativeChild(aChild, NS_CYCLE_COLLECTION_PARTICIPANT(T));
  }
};

// We declare CycleCollectionNoteChild in 3-argument and 4-argument variants,
// rather than using default arguments, so that forward declarations work
// regardless of header inclusion order.
template <typename T>
inline void CycleCollectionNoteChild(
    nsCycleCollectionTraversalCallback& aCallback, T* aChild, const char* aName,
    uint32_t aFlags) {
  CycleCollectionNoteEdgeName(aCallback, aName, aFlags);
  CycleCollectionNoteChildImpl<T>::Run(aCallback, aChild);
}

template <typename T>
inline void CycleCollectionNoteChild(
    nsCycleCollectionTraversalCallback& aCallback, T* aChild,
    const char* aName) {
  CycleCollectionNoteChild(aCallback, aChild, aName, 0);
}

#endif  // nsCycleCollectionNoteChild_h__