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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 "mozilla/Try.h"
#include "nsCOMPtr.h"
#include "nsIWeakReferenceUtils.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:
nsMaybeWeakPtr() = default;
MOZ_IMPLICIT nsMaybeWeakPtr(T* aRef) : mPtr(aRef), mWeak(false) {}
MOZ_IMPLICIT nsMaybeWeakPtr(const nsCOMPtr<nsIWeakReference>& aRef)
: mPtr(aRef), mWeak(true) {}
nsMaybeWeakPtr<T>& operator=(T* aRef) {
mPtr = aRef;
mWeak = false;
return *this;
}
nsMaybeWeakPtr<T>& operator=(const nsCOMPtr<nsIWeakReference>& aRef) {
mPtr = aRef;
mWeak = true;
return *this;
}
bool operator==(const nsMaybeWeakPtr<T>& other) const {
return mPtr == other.mPtr;
}
nsISupports* GetRawValue() const { return mPtr.get(); }
bool IsWeak() const { return mWeak; }
const nsCOMPtr<T> GetValue() const;
private:
nsCOMPtr<nsISupports> mPtr;
bool mWeak;
};
// 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 CopyableTArray<nsMaybeWeakPtr<T>> {
typedef nsTArray<nsMaybeWeakPtr<T>> MaybeWeakArray;
nsresult SetMaybeWeakPtr(nsMaybeWeakPtr<T>& aRef, T* aElement,
bool aOwnsWeak) {
nsresult rv = NS_OK;
if (aOwnsWeak) {
aRef = do_GetWeakReference(aElement, &rv);
} else {
aRef = aElement;
}
return rv;
}
public:
nsresult AppendWeakElement(T* aElement, bool aOwnsWeak) {
nsMaybeWeakPtr<T> ref;
MOZ_TRY(SetMaybeWeakPtr(ref, aElement, aOwnsWeak));
MaybeWeakArray::AppendElement(ref);
return NS_OK;
}
nsresult AppendWeakElementUnlessExists(T* aElement, bool aOwnsWeak) {
nsMaybeWeakPtr<T> ref;
MOZ_TRY(SetMaybeWeakPtr(ref, aElement, aOwnsWeak));
if (MaybeWeakArray::Contains(ref)) {
return NS_ERROR_INVALID_ARG;
}
MaybeWeakArray::AppendElement(ref);
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);
if (!supWeakRef) {
return 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;
}
nsCOMPtr<T> ref;
nsresult rv;
if (mWeak) {
nsCOMPtr<nsIWeakReference> weakRef = do_QueryInterface(mPtr);
if (NS_WARN_IF(!weakRef)) {
return nullptr;
}
ref = do_QueryReferent(weakRef, &rv);
NS_WARNING_ASSERTION(NS_SUCCEEDED(rv) || rv == NS_ERROR_NULL_POINTER,
"QueryReferent failed with non-null pointer");
} else {
ref = do_QueryInterface(mPtr, &rv);
NS_WARNING_ASSERTION(NS_SUCCEEDED(rv),
"QueryInterface failed with non-null pointer");
}
return ref;
}
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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