/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ /* 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 nsMaybeWeakPtr_h_ #define nsMaybeWeakPtr_h_ #include "mozilla/Attributes.h" #include "nsCOMPtr.h" #include "nsWeakReference.h" #include "nsTArray.h" #include "nsCycleCollectionNoteChild.h" // nsMaybeWeakPtr is a helper object to hold a strong-or-weak reference // to the template class. It's pretty minimal, but sufficient. template<class T> class nsMaybeWeakPtr { public: MOZ_IMPLICIT nsMaybeWeakPtr(nsISupports* aRef) : mPtr(aRef) {} MOZ_IMPLICIT nsMaybeWeakPtr(const nsCOMPtr<nsIWeakReference>& aRef) : mPtr(aRef) {} MOZ_IMPLICIT nsMaybeWeakPtr(const nsCOMPtr<T>& aRef) : mPtr(aRef) {} bool operator==(const nsMaybeWeakPtr<T> &other) const { return mPtr == other.mPtr; } nsISupports* GetRawValue() const { return mPtr.get(); } const nsCOMPtr<T> GetValue() const; private: nsCOMPtr<nsISupports> mPtr; }; // nsMaybeWeakPtrArray is an array of MaybeWeakPtr objects, that knows how to // grab a weak reference to a given object if requested. It only allows a // given object to appear in the array once. template<class T> class nsMaybeWeakPtrArray : public nsTArray<nsMaybeWeakPtr<T>> { typedef nsTArray<nsMaybeWeakPtr<T>> MaybeWeakArray; public: nsresult AppendWeakElement(T* aElement, bool aOwnsWeak) { nsCOMPtr<nsISupports> ref; if (aOwnsWeak) { ref = do_GetWeakReference(aElement); } else { ref = aElement; } if (MaybeWeakArray::Contains(ref.get())) { return NS_ERROR_INVALID_ARG; } if (!MaybeWeakArray::AppendElement(ref)) { return NS_ERROR_OUT_OF_MEMORY; } return NS_OK; } nsresult RemoveWeakElement(T* aElement) { if (MaybeWeakArray::RemoveElement(aElement)) { return NS_OK; } // Don't use do_GetWeakReference; it should only be called if we know // the object supports weak references. nsCOMPtr<nsISupportsWeakReference> supWeakRef = do_QueryInterface(aElement); NS_ENSURE_TRUE(supWeakRef, NS_ERROR_INVALID_ARG); nsCOMPtr<nsIWeakReference> weakRef; nsresult rv = supWeakRef->GetWeakReference(getter_AddRefs(weakRef)); NS_ENSURE_SUCCESS(rv, rv); if (MaybeWeakArray::RemoveElement(weakRef)) { return NS_OK; } return NS_ERROR_INVALID_ARG; } }; template<class T> const nsCOMPtr<T> nsMaybeWeakPtr<T>::GetValue() const { if (!mPtr) { return nullptr; } nsresult rv; nsCOMPtr<T> ref = do_QueryInterface(mPtr, &rv); if (NS_SUCCEEDED(rv)) { return ref; } nsCOMPtr<nsIWeakReference> weakRef = do_QueryInterface(mPtr); if (weakRef) { ref = do_QueryReferent(weakRef, &rv); if (NS_SUCCEEDED(rv)) { return ref; } } return nullptr; } template <typename T> inline void ImplCycleCollectionUnlink(nsMaybeWeakPtrArray<T>& aField) { aField.Clear(); } template <typename E> inline void ImplCycleCollectionTraverse(nsCycleCollectionTraversalCallback& aCallback, nsMaybeWeakPtrArray<E>& aField, const char* aName, uint32_t aFlags = 0) { aFlags |= CycleCollectionEdgeNameArrayFlag; size_t length = aField.Length(); for (size_t i = 0; i < length; ++i) { CycleCollectionNoteChild(aCallback, aField[i].GetRawValue(), aName, aFlags); } } // Call a method on each element in the array, but only if the element is // non-null. #define ENUMERATE_WEAKARRAY(array, type, method) \ for (uint32_t array_idx = 0; array_idx < array.Length(); ++array_idx) { \ const nsCOMPtr<type> &e = array.ElementAt(array_idx).GetValue(); \ if (e) \ e->method; \ } #endif