Source/JavaScriptCore/heap/WeakSet.h

/*
 * Copyright (C) 2012-2022 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 * 1. Redistributions of source code must retain the above copyright
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 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
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 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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#pragma once

#include "CellContainer.h"
#include "WeakBlock.h"
#include <wtf/SentinelLinkedList.h>

namespace JSC {

class Heap;
class WeakImpl;

namespace Integrity {
class Analyzer;
}

class WeakSet : public BasicRawSentinelNode<WeakSet> {
    friend class LLIntOffsetsExtractor;
    friend class Integrity::Analyzer;

public:
    static WeakImpl* allocate(JSValue, WeakHandleOwner* = nullptr, void* context = nullptr);
    static void deallocate(WeakImpl*);

    WeakSet(VM&);
    ~WeakSet();
    void lastChanceToFinalize();
    
    Heap* heap() const;
    VM& vm() const;

    bool isEmpty() const;
    bool isTriviallyDestructible() const;

    template<typename Visitor> void visit(Visitor&);

    void reap();
    void sweep();
    void shrink();
    void resetAllocator();

    static ptrdiff_t offsetOfVM() { return OBJECT_OFFSETOF(WeakSet, m_vm); }

private:
    JS_EXPORT_PRIVATE WeakBlock::FreeCell* findAllocator(CellContainer);
    WeakBlock::FreeCell* tryFindAllocator();
    WeakBlock::FreeCell* addAllocator(CellContainer);
    void removeAllocator(WeakBlock*);

    WeakBlock::FreeCell* m_allocator { nullptr };
    WeakBlock* m_nextAllocator { nullptr };
    DoublyLinkedList<WeakBlock> m_blocks;
    // m_vm must be a pointer (instead of a reference) because the JSCLLIntOffsetsExtractor
    // cannot handle it being a reference.
    VM* m_vm;
};

inline WeakSet::WeakSet(VM& vm)
    : m_vm(&vm)
{
}

inline VM& WeakSet::vm() const
{
    return *m_vm;
}

inline bool WeakSet::isEmpty() const
{
    for (WeakBlock* block = m_blocks.head(); block; block = block->next()) {
        if (!block->isEmpty())
            return false;
    }

    return true;
}

inline bool WeakSet::isTriviallyDestructible() const
{
    if (!m_blocks.isEmpty())
        return false;
    if (isOnList())
        return false;
    return true;
}

inline void WeakSet::deallocate(WeakImpl* weakImpl)
{
    weakImpl->setState(WeakImpl::Deallocated);
}

inline void WeakSet::lastChanceToFinalize()
{
    for (WeakBlock* block = m_blocks.head(); block; block = block->next())
        block->lastChanceToFinalize();
}

template<typename Visitor>
inline void WeakSet::visit(Visitor& visitor)
{
    for (WeakBlock* block = m_blocks.head(); block; block = block->next())
        block->visit(visitor);
}

inline void WeakSet::reap()
{
    for (WeakBlock* block = m_blocks.head(); block; block = block->next())
        block->reap();
}

inline void WeakSet::resetAllocator()
{
    m_allocator = nullptr;
    m_nextAllocator = m_blocks.head();
}

} // namespace JSC