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/* -*- 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
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