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diff --git a/xpcom/ds/nsRefCountedHashtable.h b/xpcom/ds/nsRefCountedHashtable.h
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+/* -*- 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/. */
+
+#ifndef XPCOM_DS_NSREFCOUNTEDHASHTABLE_H_
+#define XPCOM_DS_NSREFCOUNTEDHASHTABLE_H_
+
+#include "nsBaseHashtable.h"
+#include "nsHashKeys.h"
+
+/**
+ * templated hashtable class maps keys to reference pointers.
+ * See nsBaseHashtable for complete declaration.
+ * @param KeyClass a wrapper-class for the hashtable key, see nsHashKeys.h
+ * for a complete specification.
+ * @param PtrType the reference-type being wrapped
+ * @see nsClassHashtable, nsTHashMap
+ */
+template <class KeyClass, class PtrType>
+class nsRefCountedHashtable
+ : public nsBaseHashtable<
+ KeyClass, PtrType,
+ typename mozilla::detail::SmartPtrTraits<PtrType>::RawPointerType> {
+ public:
+ using KeyType = typename KeyClass::KeyType;
+ using SmartPtrTraits = mozilla::detail::SmartPtrTraits<PtrType>;
+ using PointeeType = typename SmartPtrTraits::PointeeType;
+ using RawPointerType = typename SmartPtrTraits::RawPointerType;
+ using base_type = nsBaseHashtable<KeyClass, PtrType, RawPointerType>;
+
+ using base_type::base_type;
+
+ static_assert(SmartPtrTraits::IsRefCounted);
+
+ /**
+ * @copydoc nsBaseHashtable::Get
+ * @param aData This is an XPCOM getter, so aData is already_addrefed.
+ * If the key doesn't exist, *aData will be set to nullptr.
+ */
+ bool Get(KeyType aKey, RawPointerType* aData) const;
+
+ /**
+ * @copydoc nsBaseHashtable::Get
+ */
+ [[nodiscard]] already_AddRefed<PointeeType> Get(KeyType aKey) const;
+
+ /**
+ * Gets a weak reference to the hashtable entry.
+ * @param aFound If not nullptr, will be set to true if the entry is found,
+ * to false otherwise.
+ * @return The entry, or nullptr if not found. Do not release this pointer!
+ */
+ [[nodiscard]] RawPointerType GetWeak(KeyType aKey,
+ bool* aFound = nullptr) const;
+
+ using base_type::InsertOrUpdate;
+
+ template <typename U,
+ typename = std::enable_if_t<std::is_base_of_v<PointeeType, U>>>
+ void InsertOrUpdate(
+ KeyType aKey,
+ typename SmartPtrTraits::template OtherSmartPtrType<U>&& aData);
+
+ template <typename U,
+ typename = std::enable_if_t<std::is_base_of_v<PointeeType, U>>>
+ [[nodiscard]] bool InsertOrUpdate(
+ KeyType aKey,
+ typename SmartPtrTraits::template OtherSmartPtrType<U>&& aData,
+ const mozilla::fallible_t&);
+
+ template <typename U,
+ typename = std::enable_if_t<std::is_base_of_v<PointeeType, U>>>
+ void InsertOrUpdate(KeyType aKey, already_AddRefed<U>&& aData);
+
+ template <typename U,
+ typename = std::enable_if_t<std::is_base_of_v<PointeeType, U>>>
+ [[nodiscard]] bool InsertOrUpdate(KeyType aKey, already_AddRefed<U>&& aData,
+ const mozilla::fallible_t&);
+
+ /**
+ * Remove the entry associated with aKey (if any), optionally _moving_ its
+ * current value into *aData, thereby avoiding calls to AddRef and Release.
+ * Return true if found.
+ * @param aKey the key to remove from the hashtable
+ * @param aData where to move the value (if non-null). If an entry is not
+ * found it will be set to nullptr.
+ * @return true if an entry for aKey was found (and removed)
+ */
+ inline bool Remove(KeyType aKey, RawPointerType* aData = nullptr);
+
+ nsRefCountedHashtable Clone() const {
+ return this->template CloneAs<nsRefCountedHashtable>();
+ }
+};
+
+template <typename K, typename T>
+inline void ImplCycleCollectionUnlink(nsRefCountedHashtable<K, T>& aField) {
+ aField.Clear();
+}
+
+template <typename K, typename T>
+inline void ImplCycleCollectionTraverse(
+ nsCycleCollectionTraversalCallback& aCallback,
+ nsRefCountedHashtable<K, T>& aField, const char* aName,
+ uint32_t aFlags = 0) {
+ for (auto iter = aField.ConstIter(); !iter.Done(); iter.Next()) {
+ CycleCollectionNoteChild(aCallback, iter.UserData(), aName, aFlags);
+ }
+}
+
+//
+// nsRefCountedHashtable definitions
+//
+
+template <class KeyClass, class PtrType>
+bool nsRefCountedHashtable<KeyClass, PtrType>::Get(
+ KeyType aKey, RawPointerType* aRefPtr) const {
+ typename base_type::EntryType* ent = this->GetEntry(aKey);
+
+ if (ent) {
+ if (aRefPtr) {
+ *aRefPtr = ent->GetData();
+
+ NS_IF_ADDREF(*aRefPtr);
+ }
+
+ return true;
+ }
+
+ // if the key doesn't exist, set *aRefPtr to null
+ // so that it is a valid XPCOM getter
+ if (aRefPtr) {
+ *aRefPtr = nullptr;
+ }
+
+ return false;
+}
+
+template <class KeyClass, class PtrType>
+already_AddRefed<typename nsRefCountedHashtable<KeyClass, PtrType>::PointeeType>
+nsRefCountedHashtable<KeyClass, PtrType>::Get(KeyType aKey) const {
+ typename base_type::EntryType* ent = this->GetEntry(aKey);
+ if (!ent) {
+ return nullptr;
+ }
+
+ PtrType copy = ent->GetData();
+ return copy.forget();
+}
+
+template <class KeyClass, class PtrType>
+typename nsRefCountedHashtable<KeyClass, PtrType>::RawPointerType
+nsRefCountedHashtable<KeyClass, PtrType>::GetWeak(KeyType aKey,
+ bool* aFound) const {
+ typename base_type::EntryType* ent = this->GetEntry(aKey);
+
+ if (ent) {
+ if (aFound) {
+ *aFound = true;
+ }
+
+ return ent->GetData();
+ }
+
+ // Key does not exist, return nullptr and set aFound to false
+ if (aFound) {
+ *aFound = false;
+ }
+
+ return nullptr;
+}
+
+template <class KeyClass, class PtrType>
+template <typename U, typename>
+void nsRefCountedHashtable<KeyClass, PtrType>::InsertOrUpdate(
+ KeyType aKey,
+ typename SmartPtrTraits::template OtherSmartPtrType<U>&& aData) {
+ if (!InsertOrUpdate(aKey, std::move(aData), mozilla::fallible)) {
+ NS_ABORT_OOM(this->mTable.EntrySize() * this->mTable.EntryCount());
+ }
+}
+
+template <class KeyClass, class PtrType>
+template <typename U, typename>
+bool nsRefCountedHashtable<KeyClass, PtrType>::InsertOrUpdate(
+ KeyType aKey,
+ typename SmartPtrTraits::template OtherSmartPtrType<U>&& aData,
+ const mozilla::fallible_t&) {
+ typename base_type::EntryType* ent = this->PutEntry(aKey, mozilla::fallible);
+
+ if (!ent) {
+ return false;
+ }
+
+ ent->SetData(std::move(aData));
+
+ return true;
+}
+
+template <class KeyClass, class PtrType>
+template <typename U, typename>
+void nsRefCountedHashtable<KeyClass, PtrType>::InsertOrUpdate(
+ KeyType aKey, already_AddRefed<U>&& aData) {
+ if (!InsertOrUpdate(aKey, std::move(aData), mozilla::fallible)) {
+ NS_ABORT_OOM(this->mTable.EntrySize() * this->mTable.EntryCount());
+ }
+}
+
+template <class KeyClass, class PtrType>
+template <typename U, typename>
+bool nsRefCountedHashtable<KeyClass, PtrType>::InsertOrUpdate(
+ KeyType aKey, already_AddRefed<U>&& aData, const mozilla::fallible_t&) {
+ typename base_type::EntryType* ent = this->PutEntry(aKey, mozilla::fallible);
+
+ if (!ent) {
+ return false;
+ }
+
+ ent->SetData(std::move(aData));
+
+ return true;
+}
+
+template <class KeyClass, class PtrType>
+bool nsRefCountedHashtable<KeyClass, PtrType>::Remove(KeyType aKey,
+ RawPointerType* aRefPtr) {
+ typename base_type::EntryType* ent = this->GetEntry(aKey);
+
+ if (ent) {
+ if (aRefPtr) {
+ ent->GetModifiableData()->forget(aRefPtr);
+ }
+ this->RemoveEntry(ent);
+ return true;
+ }
+
+ if (aRefPtr) {
+ *aRefPtr = nullptr;
+ }
+ return false;
+}
+
+#endif // XPCOM_DS_NSREFCOUNTEDHASHTABLE_H_