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/*
* Copyright (C) 2011-2024 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 <wtf/Compiler.h>
WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN
#include "Handle.h"
#include "HandleSet.h"
#include "Heap.h"
#include "JSLock.h"
#include "StrongForward.h"
#include <wtf/RefTrackerMixin.h>
namespace JSC {
class VM;
#if ENABLE(REFTRACKER)
void initializeSystemForStrongRefTracker();
#endif
REFTRACKER_DECL(StrongRefTracker, {
initializeSystemForStrongRefTracker();
});
// A strongly referenced handle that prevents the object it points to from being garbage collected.
template <typename T, ShouldStrongDestructorGrabLock shouldStrongDestructorGrabLock> class Strong final : public Handle<T> {
using Handle<T>::slot;
using Handle<T>::setSlot;
template <typename U, ShouldStrongDestructorGrabLock> friend class Strong;
public:
typedef typename Handle<T>::ExternalType ExternalType;
Strong()
: Handle<T>()
{
}
inline Strong(VM&, ExternalType = ExternalType());
inline Strong(VM&, Handle<T>);
Strong(const Strong& other)
: Handle<T>()
{
if (!other.slot())
return;
setSlot(HandleSet::heapFor(other.slot())->allocate());
set(other.get());
}
template <typename U> Strong(const Strong<U>& other)
: Handle<T>()
{
if (!other.slot())
return;
setSlot(HandleSet::heapFor(other.slot())->allocate());
set(other.get());
}
enum HashTableDeletedValueTag { HashTableDeletedValue };
bool isHashTableDeletedValue() const { return slot() == hashTableDeletedValue(); }
Strong(HashTableDeletedValueTag)
: Handle<T>(hashTableDeletedValue())
{
}
enum HashTableEmptyValueTag { HashTableEmptyValue };
bool isHashTableEmptyValue() const { return slot() == hashTableEmptyValue(); }
Strong(HashTableEmptyValueTag)
: Handle<T>(hashTableEmptyValue())
{
}
~Strong() override
{
clear();
}
bool operator!() const { return !slot() || !*slot(); }
explicit operator bool() const { return !!*this; }
void swap(Strong& other)
{
Handle<T>::swap(other);
}
ExternalType get() const { return HandleTypes<T>::getFromSlot(this->slot()); }
inline void set(VM&, ExternalType);
template <typename U> Strong& operator=(const Strong<U>& other)
{
if (!other.slot()) {
clear();
return *this;
}
set(*HandleSet::heapFor(other.slot())->vm(), other.get());
return *this;
}
Strong& operator=(const Strong& other)
{
if (!other.slot()) {
clear();
return *this;
}
set(HandleSet::heapFor(other.slot())->vm(), other.get());
return *this;
}
void clear()
{
if (!slot())
return;
auto* heap = HandleSet::heapFor(slot());
if (shouldStrongDestructorGrabLock == ShouldStrongDestructorGrabLock::Yes) {
JSLockHolder holder(heap->vm());
heap->deallocate(slot());
setSlot(nullptr);
} else {
heap->deallocate(slot());
setSlot(nullptr);
}
}
private:
static HandleSlot hashTableDeletedValue() { return reinterpret_cast<HandleSlot>(-1); }
static HandleSlot hashTableEmptyValue() { return reinterpret_cast<HandleSlot>(0); }
void set(ExternalType externalType)
{
ASSERT(slot());
JSValue value = HandleTypes<T>::toJSValue(externalType);
HandleSet::heapFor(slot())->template writeBarrier<std::is_base_of_v<JSCell, T>>(slot(), value);
*slot() = value;
}
REFTRACKER_MEMBERS(StrongRefTracker);
};
template<class T> inline void swap(Strong<T>& a, Strong<T>& b)
{
a.swap(b);
}
} // namespace JSC
namespace WTF {
template<typename T> struct VectorTraits<JSC::Strong<T>> : SimpleClassVectorTraits {
static constexpr bool canCompareWithMemcmp = false;
#if ENABLE(REFTRACKER)
static constexpr bool canInitializeWithMemset = false;
static constexpr bool canMoveWithMemcpy = false;
#endif
};
template<typename P> struct HashTraits<JSC::Strong<P>> : SimpleClassHashTraits<JSC::Strong<P>> {
#if ENABLE(REFTRACKER)
using S = JSC::Strong<P>;
static constexpr bool emptyValueIsZero = false;
static S emptyValue() { return S::HashTableEmptyValue; }
template <typename>
static void constructEmptyValue(S& slot)
{
new (NotNull, std::addressof(slot)) S(S::HashTableEmptyValue);
}
static constexpr bool hasIsEmptyValueFunction = true;
static bool isEmptyValue(const S& value) { return value.isHashTableEmptyValue(); }
static void constructDeletedValue(S& slot) { new (NotNull, &slot) S(S::HashTableDeletedValue); }
static bool isDeletedValue(const S& value) { return value.isHashTableDeletedValue(); }
#endif
};
} // namespace WTF
WTF_ALLOW_UNSAFE_BUFFER_USAGE_END
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