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/*
* Copyright (C) 2021-2024 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include "WeakGCHashTable.h"
#include "WeakInlines.h"
#include <wtf/HashSet.h>
#include <wtf/TZoneMalloc.h>
namespace JSC {
// A HashSet with Weak<JSCell> values, which automatically removes values once they're garbage collected.
template<typename T>
struct WeakGCSetHashTraits : HashTraits<Weak<T>> {
static constexpr bool hasIsReleasedWeakValueFunction = true;
static bool isReleasedWeakValue(const Weak<T>& value)
{
return !value.isHashTableDeletedValue() && !value.isHashTableEmptyValue() && !value;
}
};
template<typename T>
struct WeakGCSetHash {
// We only prune stale entries on Full GCs so we have to handle non-Live entries in the table.
static unsigned hash(const Weak<T>& p) { return PtrHash<T*>::hash(p.get()); }
static bool equal(const Weak<T>& a, const Weak<T>& b)
{
if (!a || !b)
return false;
return a.get() == b.get();
}
static constexpr bool safeToCompareToEmptyOrDeleted = false;
};
// FIXME: This doesn't currently accept WeakHandleOwners by default... it's probably not hard to add but it's not exactly clear how to handle multiple different handle owners for the same value.
template<typename ValueArg, typename HashArg = WeakGCSetHash<ValueArg>, typename TraitsArg = WeakGCSetHashTraits<ValueArg>>
class WeakGCSet final : public WeakGCHashTable {
WTF_MAKE_TZONE_NON_HEAP_ALLOCATABLE(WeakGCSet);
using ValueType = Weak<ValueArg>;
using HashSetType = UncheckedKeyHashSet<ValueType, HashArg, TraitsArg>;
public:
using AddResult = typename HashSetType::AddResult;
using iterator = typename HashSetType::iterator;
using const_iterator = typename HashSetType::const_iterator;
inline explicit WeakGCSet(VM&);
inline ~WeakGCSet() final;
void clear()
{
m_set.clear();
}
AddResult add(ValueArg* key)
{
// Constructing a Weak shouldn't trigger a GC but add this ASSERT for good measure.
AssertNoGC assertNoGC;
return m_set.add(key);
}
template<typename HashTranslator, typename T>
ValueArg* ensureValue(T&& key, const Invocable<ValueType()> auto& functor)
{
// If functor invokes GC, GC can prune WeakGCSet, and manipulate HashSet while we are touching it in the ensure function.
// The functor must not invoke GC.
AssertNoGC assertNoGC;
auto result = m_set.template ensure<HashTranslator>(std::forward<T>(key), functor);
return result.iterator->get();
}
// It's not safe to call into the VM or allocate an object while an iterator is open.
inline iterator begin() { return m_set.begin(); }
inline const_iterator begin() const { return m_set.begin(); }
inline iterator end() { return m_set.end(); }
inline const_iterator end() const { return m_set.end(); }
// FIXME: Add support for find/contains/remove from a ValueArg* via a HashTranslator.
private:
void pruneStaleEntries() final;
HashSetType m_set;
VM& m_vm;
};
} // namespace JSC
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