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| -rw-r--r-- | xpcom/ds/nsTHashtable.h | 966 |
1 files changed, 966 insertions, 0 deletions
diff --git a/xpcom/ds/nsTHashtable.h b/xpcom/ds/nsTHashtable.h new file mode 100644 index 0000000000..d4a385551f --- /dev/null +++ b/xpcom/ds/nsTHashtable.h @@ -0,0 +1,966 @@ +/* -*- 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/. */ + +// See the comment at the top of mfbt/HashTable.h for a comparison between +// PLDHashTable and mozilla::HashTable. + +#ifndef nsTHashtable_h__ +#define nsTHashtable_h__ + +#include <iterator> +#include <new> +#include <type_traits> +#include <utility> + +#include "PLDHashTable.h" +#include "mozilla/Assertions.h" +#include "mozilla/Attributes.h" +#include "mozilla/Maybe.h" +#include "mozilla/MemoryReporting.h" +#include "mozilla/OperatorNewExtensions.h" +#include "mozilla/PodOperations.h" +#include "mozilla/fallible.h" +#include "nsPointerHashKeys.h" +#include "nsTArrayForwardDeclare.h" + +template <class EntryType> +class nsTHashtable; + +namespace detail { +class nsTHashtableIteratorBase { + public: + using EndIteratorTag = PLDHashTable::Iterator::EndIteratorTag; + + nsTHashtableIteratorBase(nsTHashtableIteratorBase&& aOther) = default; + + nsTHashtableIteratorBase& operator=(nsTHashtableIteratorBase&& aOther) { + // User-defined because the move assignment operator is deleted in + // PLDHashtable::Iterator. + return operator=(static_cast<const nsTHashtableIteratorBase&>(aOther)); + } + + nsTHashtableIteratorBase(const nsTHashtableIteratorBase& aOther) + : mIterator{aOther.mIterator.Clone()} {} + nsTHashtableIteratorBase& operator=(const nsTHashtableIteratorBase& aOther) { + // Since PLDHashTable::Iterator has no assignment operator, we destroy and + // recreate mIterator. + mIterator.~Iterator(); + new (&mIterator) PLDHashTable::Iterator(aOther.mIterator.Clone()); + return *this; + } + + explicit nsTHashtableIteratorBase(PLDHashTable::Iterator aFrom) + : mIterator{std::move(aFrom)} {} + + explicit nsTHashtableIteratorBase(const PLDHashTable& aTable) + : mIterator{&const_cast<PLDHashTable&>(aTable)} {} + + nsTHashtableIteratorBase(const PLDHashTable& aTable, EndIteratorTag aTag) + : mIterator{&const_cast<PLDHashTable&>(aTable), aTag} {} + + bool operator==(const nsTHashtableIteratorBase& aRhs) const { + return mIterator == aRhs.mIterator; + } + bool operator!=(const nsTHashtableIteratorBase& aRhs) const { + return !(*this == aRhs); + } + + protected: + PLDHashTable::Iterator mIterator; +}; + +// STL-style iterators to allow the use in range-based for loops, e.g. +template <typename T> +class nsTHashtableEntryIterator : public nsTHashtableIteratorBase { + friend class nsTHashtable<std::remove_const_t<T>>; + + public: + using iterator_category = std::forward_iterator_tag; + using value_type = T; + using difference_type = int32_t; + using pointer = value_type*; + using reference = value_type&; + + using iterator_type = nsTHashtableEntryIterator; + using const_iterator_type = nsTHashtableEntryIterator<const T>; + + using nsTHashtableIteratorBase::nsTHashtableIteratorBase; + + value_type* operator->() const { + return static_cast<value_type*>(mIterator.Get()); + } + value_type& operator*() const { + return *static_cast<value_type*>(mIterator.Get()); + } + + iterator_type& operator++() { + mIterator.Next(); + return *this; + } + iterator_type operator++(int) { + iterator_type it = *this; + ++*this; + return it; + } + + operator const_iterator_type() const { + return const_iterator_type{mIterator.Clone()}; + } +}; + +template <typename EntryType> +class nsTHashtableKeyIterator : public nsTHashtableIteratorBase { + friend class nsTHashtable<EntryType>; + + public: + using iterator_category = std::forward_iterator_tag; + using value_type = const std::decay_t<typename EntryType::KeyType>; + using difference_type = int32_t; + using pointer = value_type*; + using reference = value_type&; + + using iterator_type = nsTHashtableKeyIterator; + using const_iterator_type = nsTHashtableKeyIterator; + + using nsTHashtableIteratorBase::nsTHashtableIteratorBase; + + value_type* operator->() const { + return &static_cast<const EntryType*>(mIterator.Get())->GetKey(); + } + decltype(auto) operator*() const { + return static_cast<const EntryType*>(mIterator.Get())->GetKey(); + } + + iterator_type& operator++() { + mIterator.Next(); + return *this; + } + iterator_type operator++(int) { + iterator_type it = *this; + ++*this; + return it; + } +}; + +template <typename EntryType> +class nsTHashtableKeyRange { + public: + using IteratorType = nsTHashtableKeyIterator<EntryType>; + using iterator = IteratorType; + + explicit nsTHashtableKeyRange(const PLDHashTable& aHashtable) + : mHashtable{aHashtable} {} + + auto begin() const { return IteratorType{mHashtable}; } + auto end() const { + return IteratorType{mHashtable, typename IteratorType::EndIteratorTag{}}; + } + auto cbegin() const { return begin(); } + auto cend() const { return end(); } + + uint32_t Count() const { return mHashtable.EntryCount(); } + + private: + const PLDHashTable& mHashtable; +}; + +template <typename EntryType> +auto RangeSize(const ::detail::nsTHashtableKeyRange<EntryType>& aRange) { + return aRange.Count(); +} + +} // namespace detail + +/** + * a base class for templated hashtables. + * + * Clients will rarely need to use this class directly. Check the derived + * classes first, to see if they will meet your needs. + * + * @param EntryType the templated entry-type class that is managed by the + * hashtable. <code>EntryType</code> must extend the following declaration, + * and <strong>must not declare any virtual functions or derive from classes + * with virtual functions.</strong> Any vtable pointer would break the + * PLDHashTable code. + *<pre> class EntryType : public PLDHashEntryHdr + * { + * public: or friend nsTHashtable<EntryType>; + * // KeyType is what we use when Get()ing or Put()ing this entry + * // this should either be a simple datatype (uint32_t, nsISupports*) or + * // a const reference (const nsAString&) + * typedef something KeyType; + * // KeyTypePointer is the pointer-version of KeyType, because + * // PLDHashTable.h requires keys to cast to <code>const void*</code> + * typedef const something* KeyTypePointer; + * + * EntryType(KeyTypePointer aKey); + * + * // A copy or C++11 Move constructor must be defined, even if + * // AllowMemMove() == true, otherwise you will cause link errors. + * EntryType(const EntryType& aEnt); // Either this... + * EntryType(EntryType&& aEnt); // ...or this + * + * // the destructor must be defined... or you will cause link errors! + * ~EntryType(); + * + * // KeyEquals(): does this entry match this key? + * bool KeyEquals(KeyTypePointer aKey) const; + * + * // KeyToPointer(): Convert KeyType to KeyTypePointer + * static KeyTypePointer KeyToPointer(KeyType aKey); + * + * // HashKey(): calculate the hash number + * static PLDHashNumber HashKey(KeyTypePointer aKey); + * + * // ALLOW_MEMMOVE can we move this class with memmove(), or do we have + * // to use the copy constructor? + * enum { ALLOW_MEMMOVE = true/false }; + * }</pre> + * + * @see nsInterfaceHashtable + * @see nsClassHashtable + * @see nsTHashMap + * @author "Benjamin Smedberg <bsmedberg@covad.net>" + */ + +template <class EntryType> +class MOZ_NEEDS_NO_VTABLE_TYPE nsTHashtable { + typedef mozilla::fallible_t fallible_t; + static_assert(std::is_pointer_v<typename EntryType::KeyTypePointer>, + "KeyTypePointer should be a pointer"); + + public: + // Separate constructors instead of default aInitLength parameter since + // otherwise the default no-arg constructor isn't found. + nsTHashtable() + : mTable(Ops(), sizeof(EntryType), PLDHashTable::kDefaultInitialLength) {} + explicit nsTHashtable(uint32_t aInitLength) + : mTable(Ops(), sizeof(EntryType), aInitLength) {} + + /** + * destructor, cleans up and deallocates + */ + ~nsTHashtable() = default; + + nsTHashtable(nsTHashtable<EntryType>&& aOther); + nsTHashtable<EntryType>& operator=(nsTHashtable<EntryType>&& aOther); + + nsTHashtable(const nsTHashtable<EntryType>&) = delete; + nsTHashtable& operator=(const nsTHashtable<EntryType>&) = delete; + + /** + * Return the generation number for the table. This increments whenever + * the table data items are moved. + */ + uint32_t GetGeneration() const { return mTable.Generation(); } + + /** + * KeyType is typedef'ed for ease of use. + */ + typedef typename EntryType::KeyType KeyType; + + /** + * KeyTypePointer is typedef'ed for ease of use. + */ + typedef typename EntryType::KeyTypePointer KeyTypePointer; + + /** + * Return the number of entries in the table. + * @return number of entries + */ + uint32_t Count() const { return mTable.EntryCount(); } + + /** + * Return true if the hashtable is empty. + */ + bool IsEmpty() const { return Count() == 0; } + + /** + * Get the entry associated with a key. + * @param aKey the key to retrieve + * @return pointer to the entry class, if the key exists; nullptr if the + * key doesn't exist + */ + EntryType* GetEntry(KeyType aKey) const { + return static_cast<EntryType*>( + mTable.Search(EntryType::KeyToPointer(aKey))); + } + + /** + * Return true if an entry for the given key exists, false otherwise. + * @param aKey the key to retrieve + * @return true if the key exists, false if the key doesn't exist + */ + bool Contains(KeyType aKey) const { return !!GetEntry(aKey); } + + /** + * Infallibly get the entry associated with a key, or create a new entry, + * @param aKey the key to retrieve + * @return pointer to the entry retrieved; never nullptr + */ + EntryType* PutEntry(KeyType aKey) { + // Infallible WithEntryHandle. + return WithEntryHandle( + aKey, [](auto entryHandle) { return entryHandle.OrInsert(); }); + } + + /** + * Fallibly get the entry associated with a key, or create a new entry, + * @param aKey the key to retrieve + * @return pointer to the entry retrieved; nullptr only if memory can't + * be allocated + */ + [[nodiscard]] EntryType* PutEntry(KeyType aKey, const fallible_t& aFallible) { + return WithEntryHandle(aKey, aFallible, [](auto maybeEntryHandle) { + return maybeEntryHandle ? maybeEntryHandle->OrInsert() : nullptr; + }); + } + + /** + * Get the entry associated with a key, or create a new entry using infallible + * allocation and insert that. + * @param aKey the key to retrieve + * @param aEntry will be assigned (if non-null) to the entry that was + * found or created + * @return true if a new entry was created, or false if an existing entry + * was found + */ + [[nodiscard]] bool EnsureInserted(KeyType aKey, + EntryType** aEntry = nullptr) { + auto oldCount = Count(); + EntryType* entry = PutEntry(aKey); + if (aEntry) { + *aEntry = entry; + } + return oldCount != Count(); + } + + /** + * Remove the entry associated with a key. + * @param aKey of the entry to remove + */ + void RemoveEntry(KeyType aKey) { + mTable.Remove(EntryType::KeyToPointer(aKey)); + } + + /** + * Lookup the entry associated with aKey and remove it if found, otherwise + * do nothing. + * @param aKey of the entry to remove + * @return true if an entry was found and removed, or false if no entry + * was found for aKey + */ + bool EnsureRemoved(KeyType aKey) { + auto* entry = GetEntry(aKey); + if (entry) { + RemoveEntry(entry); + return true; + } + return false; + } + + /** + * Remove the entry associated with a key. + * @param aEntry the entry-pointer to remove (obtained from GetEntry) + */ + void RemoveEntry(EntryType* aEntry) { mTable.RemoveEntry(aEntry); } + + /** + * Remove the entry associated with a key, but don't resize the hashtable. + * This is a low-level method, and is not recommended unless you know what + * you're doing. If you use it, please add a comment explaining why you + * didn't use RemoveEntry(). + * @param aEntry the entry-pointer to remove (obtained from GetEntry) + */ + void RawRemoveEntry(EntryType* aEntry) { mTable.RawRemove(aEntry); } + + protected: + class EntryHandle { + public: + EntryHandle(EntryHandle&& aOther) = default; + ~EntryHandle() = default; + + EntryHandle(const EntryHandle&) = delete; + EntryHandle& operator=(const EntryHandle&) = delete; + EntryHandle& operator=(const EntryHandle&&) = delete; + + KeyType Key() const { return mKey; } + + bool HasEntry() const { return mEntryHandle.HasEntry(); } + + explicit operator bool() const { return mEntryHandle.operator bool(); } + + EntryType* Entry() { return static_cast<EntryType*>(mEntryHandle.Entry()); } + + void Insert() { InsertInternal(); } + + EntryType* OrInsert() { + if (!HasEntry()) { + Insert(); + } + return Entry(); + } + + void Remove() { mEntryHandle.Remove(); } + + void OrRemove() { mEntryHandle.OrRemove(); } + + protected: + template <typename... Args> + void InsertInternal(Args&&... aArgs) { + MOZ_RELEASE_ASSERT(!HasEntry()); + mEntryHandle.Insert([&](PLDHashEntryHdr* entry) { + new (mozilla::KnownNotNull, entry) EntryType( + EntryType::KeyToPointer(mKey), std::forward<Args>(aArgs)...); + }); + } + + private: + friend class nsTHashtable; + + EntryHandle(KeyType aKey, PLDHashTable::EntryHandle&& aEntryHandle) + : mKey(aKey), mEntryHandle(std::move(aEntryHandle)) {} + + KeyType mKey; + PLDHashTable::EntryHandle mEntryHandle; + }; + + template <class F> + auto WithEntryHandle(KeyType aKey, F&& aFunc) + -> std::invoke_result_t<F, EntryHandle&&> { + return this->mTable.WithEntryHandle( + EntryType::KeyToPointer(aKey), + [&aKey, &aFunc](auto entryHandle) -> decltype(auto) { + return std::forward<F>(aFunc)( + EntryHandle{aKey, std::move(entryHandle)}); + }); + } + + template <class F> + auto WithEntryHandle(KeyType aKey, const mozilla::fallible_t& aFallible, + F&& aFunc) + -> std::invoke_result_t<F, mozilla::Maybe<EntryHandle>&&> { + return this->mTable.WithEntryHandle( + EntryType::KeyToPointer(aKey), aFallible, + [&aKey, &aFunc](auto maybeEntryHandle) { + return std::forward<F>(aFunc)( + maybeEntryHandle + ? mozilla::Some(EntryHandle{aKey, maybeEntryHandle.extract()}) + : mozilla::Nothing()); + }); + } + + public: + class ConstIterator { + public: + explicit ConstIterator(nsTHashtable* aTable) + : mBaseIterator(&aTable->mTable) {} + ~ConstIterator() = default; + + KeyType Key() const { return Get()->GetKey(); } + + const EntryType* Get() const { + return static_cast<const EntryType*>(mBaseIterator.Get()); + } + + bool Done() const { return mBaseIterator.Done(); } + void Next() { mBaseIterator.Next(); } + + ConstIterator() = delete; + ConstIterator(const ConstIterator&) = delete; + ConstIterator(ConstIterator&& aOther) = delete; + ConstIterator& operator=(const ConstIterator&) = delete; + ConstIterator& operator=(ConstIterator&&) = delete; + + protected: + PLDHashTable::Iterator mBaseIterator; + }; + + // This is an iterator that also allows entry removal. Example usage: + // + // for (auto iter = table.Iter(); !iter.Done(); iter.Next()) { + // Entry* entry = iter.Get(); + // // ... do stuff with |entry| ... + // // ... possibly call iter.Remove() once ... + // } + // + class Iterator final : public ConstIterator { + public: + using ConstIterator::ConstIterator; + + using ConstIterator::Get; + + EntryType* Get() const { + return static_cast<EntryType*>(this->mBaseIterator.Get()); + } + + void Remove() { this->mBaseIterator.Remove(); } + }; + + Iterator Iter() { return Iterator(this); } + + ConstIterator ConstIter() const { + return ConstIterator(const_cast<nsTHashtable*>(this)); + } + + using const_iterator = ::detail::nsTHashtableEntryIterator<const EntryType>; + using iterator = ::detail::nsTHashtableEntryIterator<EntryType>; + + iterator begin() { return iterator{mTable}; } + const_iterator begin() const { return const_iterator{mTable}; } + const_iterator cbegin() const { return begin(); } + iterator end() { + return iterator{mTable, typename iterator::EndIteratorTag{}}; + } + const_iterator end() const { + return const_iterator{mTable, typename const_iterator::EndIteratorTag{}}; + } + const_iterator cend() const { return end(); } + + void Remove(const_iterator& aIter) { aIter.mIterator.Remove(); } + + /** + * Return a range of the keys (of KeyType). Note this range iterates over the + * keys in place, so modifications to the nsTHashtable invalidate the range + * while it's iterated, except when calling Remove() with a key iterator + * derived from that range. + */ + auto Keys() const { + return ::detail::nsTHashtableKeyRange<EntryType>{mTable}; + } + + /** + * Remove an entry from a key range, specified via a key iterator, e.g. + * + * for (auto it = hash.Keys().begin(), end = hash.Keys().end(); + * it != end; * ++it) { + * if (*it > 42) { hash.Remove(it); } + * } + */ + void Remove(::detail::nsTHashtableKeyIterator<EntryType>& aIter) { + aIter.mIterator.Remove(); + } + + /** + * Remove all entries, return hashtable to "pristine" state. It's + * conceptually the same as calling the destructor and then re-calling the + * constructor. + */ + void Clear() { mTable.Clear(); } + + /** + * Measure the size of the table's entry storage. Does *not* measure anything + * hanging off table entries; hence the "Shallow" prefix. To measure that, + * either use SizeOfExcludingThis() or iterate manually over the entries, + * calling SizeOfExcludingThis() on each one. + * + * @param aMallocSizeOf the function used to measure heap-allocated blocks + * @return the measured shallow size of the table + */ + size_t ShallowSizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const { + return mTable.ShallowSizeOfExcludingThis(aMallocSizeOf); + } + + /** + * Like ShallowSizeOfExcludingThis, but includes sizeof(*this). + */ + size_t ShallowSizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const { + return aMallocSizeOf(this) + ShallowSizeOfExcludingThis(aMallocSizeOf); + } + + /** + * This is a "deep" measurement of the table. To use it, |EntryType| must + * define SizeOfExcludingThis, and that method will be called on all live + * entries. + */ + size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const { + size_t n = ShallowSizeOfExcludingThis(aMallocSizeOf); + for (auto iter = ConstIter(); !iter.Done(); iter.Next()) { + n += (*iter.Get()).SizeOfExcludingThis(aMallocSizeOf); + } + return n; + } + + /** + * Like SizeOfExcludingThis, but includes sizeof(*this). + */ + size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const { + return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf); + } + + /** + * Swap the elements in this hashtable with the elements in aOther. + */ + void SwapElements(nsTHashtable<EntryType>& aOther) { + MOZ_ASSERT_IF(this->mTable.Ops() && aOther.mTable.Ops(), + this->mTable.Ops() == aOther.mTable.Ops()); + std::swap(this->mTable, aOther.mTable); + } + + /** + * Mark the table as constant after initialization. + * + * This will prevent assertions when a read-only hash is accessed on multiple + * threads without synchronization. + */ + void MarkImmutable() { mTable.MarkImmutable(); } + + protected: + PLDHashTable mTable; + + static PLDHashNumber s_HashKey(const void* aKey); + + static bool s_MatchEntry(const PLDHashEntryHdr* aEntry, const void* aKey); + + static void s_CopyEntry(PLDHashTable* aTable, const PLDHashEntryHdr* aFrom, + PLDHashEntryHdr* aTo); + + static void s_ClearEntry(PLDHashTable* aTable, PLDHashEntryHdr* aEntry); + + private: + // copy constructor, not implemented + nsTHashtable(nsTHashtable<EntryType>& aToCopy) = delete; + + /** + * Gets the table's ops. + */ + static const PLDHashTableOps* Ops(); + + // assignment operator, not implemented + nsTHashtable<EntryType>& operator=(nsTHashtable<EntryType>& aToEqual) = + delete; +}; + +namespace mozilla { +namespace detail { + +// Like PLDHashTable::MoveEntryStub, but specialized for fixed N (i.e. the size +// of the entries in the hashtable). Saves a memory read to figure out the size +// from the table and gives the compiler the opportunity to inline the memcpy. +// +// We define this outside of nsTHashtable so only one copy exists for every N, +// rather than separate copies for every EntryType used with nsTHashtable. +template <size_t N> +static void FixedSizeEntryMover(PLDHashTable*, const PLDHashEntryHdr* aFrom, + PLDHashEntryHdr* aTo) { + memcpy(aTo, aFrom, N); +} + +} // namespace detail +} // namespace mozilla + +// +// template definitions +// + +template <class EntryType> +nsTHashtable<EntryType>::nsTHashtable(nsTHashtable<EntryType>&& aOther) + : mTable(std::move(aOther.mTable)) {} + +template <class EntryType> +nsTHashtable<EntryType>& nsTHashtable<EntryType>::operator=( + nsTHashtable<EntryType>&& aOther) { + mTable = std::move(aOther.mTable); + return *this; +} + +template <class EntryType> +/* static */ const PLDHashTableOps* nsTHashtable<EntryType>::Ops() { + // If this variable is a global variable, we get strange start-up failures on + // WindowsCrtPatch.h (see bug 1166598 comment 20). But putting it inside a + // function avoids that problem. + static const PLDHashTableOps sOps = { + s_HashKey, s_MatchEntry, + EntryType::ALLOW_MEMMOVE + ? mozilla::detail::FixedSizeEntryMover<sizeof(EntryType)> + : s_CopyEntry, + // Simplify hashtable clearing in case our entries are trivially + // destructible. + std::is_trivially_destructible_v<EntryType> ? nullptr : s_ClearEntry, + // We don't use a generic initEntry hook because we want to allow + // initialization of data members defined in derived classes directly + // in the entry constructor (for example when a member can't be default + // constructed). + nullptr}; + return &sOps; +} + +// static definitions + +template <class EntryType> +PLDHashNumber nsTHashtable<EntryType>::s_HashKey(const void* aKey) { + return EntryType::HashKey(static_cast<KeyTypePointer>(aKey)); +} + +template <class EntryType> +bool nsTHashtable<EntryType>::s_MatchEntry(const PLDHashEntryHdr* aEntry, + const void* aKey) { + return (static_cast<const EntryType*>(aEntry)) + ->KeyEquals(static_cast<KeyTypePointer>(aKey)); +} + +template <class EntryType> +void nsTHashtable<EntryType>::s_CopyEntry(PLDHashTable* aTable, + const PLDHashEntryHdr* aFrom, + PLDHashEntryHdr* aTo) { + auto* fromEntry = const_cast<std::remove_const_t<EntryType>*>( + static_cast<const EntryType*>(aFrom)); + + new (mozilla::KnownNotNull, aTo) EntryType(std::move(*fromEntry)); + + fromEntry->~EntryType(); +} + +template <class EntryType> +void nsTHashtable<EntryType>::s_ClearEntry(PLDHashTable* aTable, + PLDHashEntryHdr* aEntry) { + static_cast<EntryType*>(aEntry)->~EntryType(); +} + +class nsCycleCollectionTraversalCallback; + +template <class EntryType> +inline void ImplCycleCollectionUnlink(nsTHashtable<EntryType>& aField) { + aField.Clear(); +} + +template <class EntryType> +inline void ImplCycleCollectionTraverse( + nsCycleCollectionTraversalCallback& aCallback, + nsTHashtable<EntryType>& aField, const char* aName, uint32_t aFlags = 0) { + for (auto iter = aField.Iter(); !iter.Done(); iter.Next()) { + EntryType* entry = iter.Get(); + ImplCycleCollectionTraverse(aCallback, *entry, aName, aFlags); + } +} + +/** + * For nsTHashtable with pointer entries, we can have a template specialization + * that layers a typed T* interface on top of a common implementation that + * works internally with void pointers. This arrangement saves code size and + * might slightly improve performance as well. + */ + +/** + * We need a separate entry type class for the inheritance structure of the + * nsTHashtable specialization below; nsVoidPtrHashKey is simply typedefed to a + * specialization of nsPtrHashKey, and the formulation: + * + * class nsTHashtable<nsPtrHashKey<T>> : + * protected nsTHashtable<nsPtrHashKey<const void> + * + * is not going to turn out very well, since we'd wind up with an nsTHashtable + * instantiation that is its own base class. + */ +namespace detail { + +class VoidPtrHashKey : public nsPtrHashKey<const void> { + typedef nsPtrHashKey<const void> Base; + + public: + explicit VoidPtrHashKey(const void* aKey) : Base(aKey) {} +}; + +} // namespace detail + +/** + * See the main nsTHashtable documentation for descriptions of this class's + * methods. + */ +template <typename T> +class nsTHashtable<nsPtrHashKey<T>> + : protected nsTHashtable<::detail::VoidPtrHashKey> { + typedef nsTHashtable<::detail::VoidPtrHashKey> Base; + typedef nsPtrHashKey<T> EntryType; + + // We play games with reinterpret_cast'ing between these two classes, so + // try to ensure that playing said games is reasonable. + static_assert(sizeof(nsPtrHashKey<T>) == sizeof(::detail::VoidPtrHashKey), + "hash keys must be the same size"); + + nsTHashtable(const nsTHashtable& aOther) = delete; + nsTHashtable& operator=(const nsTHashtable& aOther) = delete; + + public: + nsTHashtable() = default; + explicit nsTHashtable(uint32_t aInitLength) : Base(aInitLength) {} + + ~nsTHashtable() = default; + + nsTHashtable(nsTHashtable&&) = default; + + using Base::Clear; + using Base::Count; + using Base::GetGeneration; + using Base::IsEmpty; + + using Base::MarkImmutable; + using Base::ShallowSizeOfExcludingThis; + using Base::ShallowSizeOfIncludingThis; + + /* Wrapper functions */ + EntryType* GetEntry(T* aKey) const { + return reinterpret_cast<EntryType*>(Base::GetEntry(aKey)); + } + + bool Contains(T* aKey) const { return Base::Contains(aKey); } + + EntryType* PutEntry(T* aKey) { + return reinterpret_cast<EntryType*>(Base::PutEntry(aKey)); + } + + [[nodiscard]] EntryType* PutEntry(T* aKey, + const mozilla::fallible_t& aFallible) { + return reinterpret_cast<EntryType*>(Base::PutEntry(aKey, aFallible)); + } + + [[nodiscard]] bool EnsureInserted(T* aKey, EntryType** aEntry = nullptr) { + return Base::EnsureInserted( + aKey, reinterpret_cast<::detail::VoidPtrHashKey**>(aEntry)); + } + + void RemoveEntry(T* aKey) { Base::RemoveEntry(aKey); } + + bool EnsureRemoved(T* aKey) { return Base::EnsureRemoved(aKey); } + + void RemoveEntry(EntryType* aEntry) { + Base::RemoveEntry(reinterpret_cast<::detail::VoidPtrHashKey*>(aEntry)); + } + + void RawRemoveEntry(EntryType* aEntry) { + Base::RawRemoveEntry(reinterpret_cast<::detail::VoidPtrHashKey*>(aEntry)); + } + + protected: + class EntryHandle : protected Base::EntryHandle { + public: + using Base = nsTHashtable::Base::EntryHandle; + + EntryHandle(EntryHandle&& aOther) = default; + ~EntryHandle() = default; + + EntryHandle(const EntryHandle&) = delete; + EntryHandle& operator=(const EntryHandle&) = delete; + EntryHandle& operator=(const EntryHandle&&) = delete; + + using Base::Key; + + using Base::HasEntry; + + using Base::operator bool; + + EntryType* Entry() { return reinterpret_cast<EntryType*>(Base::Entry()); } + + using Base::Insert; + + EntryType* OrInsert() { + if (!HasEntry()) { + Insert(); + } + return Entry(); + } + + using Base::Remove; + + using Base::OrRemove; + + private: + friend class nsTHashtable; + + explicit EntryHandle(Base&& aBase) : Base(std::move(aBase)) {} + }; + + template <class F> + auto WithEntryHandle(KeyType aKey, F aFunc) + -> std::invoke_result_t<F, EntryHandle&&> { + return Base::WithEntryHandle(aKey, [&aFunc](auto entryHandle) { + return aFunc(EntryHandle{std::move(entryHandle)}); + }); + } + + template <class F> + auto WithEntryHandle(KeyType aKey, const mozilla::fallible_t& aFallible, + F aFunc) + -> std::invoke_result_t<F, mozilla::Maybe<EntryHandle>&&> { + return Base::WithEntryHandle( + aKey, aFallible, [&aFunc](auto maybeEntryHandle) { + return aFunc(maybeEntryHandle ? mozilla::Some(EntryHandle{ + maybeEntryHandle.extract()}) + : mozilla::Nothing()); + }); + } + + public: + class ConstIterator { + public: + explicit ConstIterator(nsTHashtable* aTable) + : mBaseIterator(&aTable->mTable) {} + ~ConstIterator() = default; + + KeyType Key() const { return Get()->GetKey(); } + + const EntryType* Get() const { + return static_cast<const EntryType*>(mBaseIterator.Get()); + } + + bool Done() const { return mBaseIterator.Done(); } + void Next() { mBaseIterator.Next(); } + + ConstIterator() = delete; + ConstIterator(const ConstIterator&) = delete; + ConstIterator(ConstIterator&& aOther) = delete; + ConstIterator& operator=(const ConstIterator&) = delete; + ConstIterator& operator=(ConstIterator&&) = delete; + + protected: + PLDHashTable::Iterator mBaseIterator; + }; + + class Iterator final : public ConstIterator { + public: + using ConstIterator::ConstIterator; + + using ConstIterator::Get; + + EntryType* Get() const { + return static_cast<EntryType*>(this->mBaseIterator.Get()); + } + + void Remove() { this->mBaseIterator.Remove(); } + }; + + Iterator Iter() { return Iterator(this); } + + ConstIterator ConstIter() const { + return ConstIterator(const_cast<nsTHashtable*>(this)); + } + + using const_iterator = ::detail::nsTHashtableEntryIterator<const EntryType>; + using iterator = ::detail::nsTHashtableEntryIterator<EntryType>; + + iterator begin() { return iterator{mTable}; } + const_iterator begin() const { return const_iterator{mTable}; } + const_iterator cbegin() const { return begin(); } + iterator end() { + return iterator{mTable, typename iterator::EndIteratorTag{}}; + } + const_iterator end() const { + return const_iterator{mTable, typename const_iterator::EndIteratorTag{}}; + } + const_iterator cend() const { return end(); } + + auto Keys() const { + return ::detail::nsTHashtableKeyRange<nsPtrHashKey<T>>{mTable}; + } + + void Remove(::detail::nsTHashtableKeyIterator<EntryType>& aIter) { + aIter.mIterator.Remove(); + } + + void SwapElements(nsTHashtable& aOther) { Base::SwapElements(aOther); } +}; + +#endif // nsTHashtable_h__ |