xpcom/base/nsCycleCollectionNoteChild.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 // This header will be included by headers that define refpointer and array
   8 // classes in order to specialize CC helpers such as ImplCycleCollectionTraverse
   9 // for them.
  10
  11 #ifndef nsCycleCollectionNoteChild_h__
  12 #define nsCycleCollectionNoteChild_h__
  13
  14 #include "nsCycleCollectionTraversalCallback.h"
  15 #include "mozilla/Likely.h"
  16
  17 enum { CycleCollectionEdgeNameArrayFlag = 1 };
  18
  19 // Just a helper for appending "[i]". Didn't want to pull in string headers
  20 // here.
  21 void CycleCollectionNoteEdgeNameImpl(
  22     nsCycleCollectionTraversalCallback& aCallback, const char* aName,
  23     uint32_t aFlags = 0);
  24
  25 // Should be inlined so that in the no-debug-info case this is just a simple
  26 // if().
  27 MOZ_ALWAYS_INLINE void CycleCollectionNoteEdgeName(
  28     nsCycleCollectionTraversalCallback& aCallback, const char* aName,
  29     uint32_t aFlags = 0) {
  30   if (MOZ_UNLIKELY(aCallback.WantDebugInfo())) {
  31     CycleCollectionNoteEdgeNameImpl(aCallback, aName, aFlags);
  32   }
  33 }
  34
  35 #define NS_CYCLE_COLLECTION_INNERCLASS cycleCollection
  36
  37 #define NS_CYCLE_COLLECTION_INNERNAME _cycleCollectorGlobal
  38
  39 #define NS_CYCLE_COLLECTION_PARTICIPANT(_class) \
  40   _class::NS_CYCLE_COLLECTION_INNERCLASS::GetParticipant()
  41
  42 template <typename T>
  43 nsISupports* ToSupports(
  44     T* aPtr, typename T::NS_CYCLE_COLLECTION_INNERCLASS* aDummy = 0) {
  45   return T::NS_CYCLE_COLLECTION_INNERCLASS::Upcast(aPtr);
  46 }
  47
  48 // The default implementation of this class template is empty, because it
  49 // should never be used: see the partial specializations below.
  50 template <typename T, bool IsXPCOM = std::is_base_of<nsISupports, T>::value>
  51 struct CycleCollectionNoteChildImpl {};
  52
  53 template <typename T>
  54 struct CycleCollectionNoteChildImpl<T, true> {
  55   static void Run(nsCycleCollectionTraversalCallback& aCallback, T* aChild) {
  56     aCallback.NoteXPCOMChild(ToSupports(aChild));
  57   }
  58 };
  59
  60 template <typename T>
  61 struct CycleCollectionNoteChildImpl<T, false> {
  62   static void Run(nsCycleCollectionTraversalCallback& aCallback, T* aChild) {
  63     aCallback.NoteNativeChild(aChild, NS_CYCLE_COLLECTION_PARTICIPANT(T));
  64   }
  65 };
  66
  67 // We declare CycleCollectionNoteChild in 3-argument and 4-argument variants,
  68 // rather than using default arguments, so that forward declarations work
  69 // regardless of header inclusion order.
  70 template <typename T>
  71 inline void CycleCollectionNoteChild(
  72     nsCycleCollectionTraversalCallback& aCallback, T* aChild, const char* aName,
  73     uint32_t aFlags) {
  74   CycleCollectionNoteEdgeName(aCallback, aName, aFlags);
  75   CycleCollectionNoteChildImpl<T>::Run(aCallback, aChild);
  76 }
  77
  78 template <typename T>
  79 inline void CycleCollectionNoteChild(
  80     nsCycleCollectionTraversalCallback& aCallback, T* aChild,
  81     const char* aName) {
  82   CycleCollectionNoteChild(aCallback, aChild, aName, 0);
  83 }
  84
  85 #endif  // nsCycleCollectionNoteChild_h__