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25a5ed94d6
This is a weak pointer that integrates with the garbage collector. It has a number of differences compared to AK::WeakPtr, including: - The "control block" is allocated from a well-packed WeakBlock owned by the GC heap, not just a generic malloc allocation. - Pointers to dead cells are nulled out by the garbage collector immediately before running destructors. - It works on any GC::Cell derived type, meaning you don't have to inherit from AK::Weakable for the ability to be weakly referenced. - The Weak always points to a control block, even when "null" (it then points to a null WeakImpl), which means one less null check when chasing pointers.
45 lines
903 B
C++
45 lines
903 B
C++
/*
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* Copyright (c) 2025, Andreas Kling <andreas@ladybird.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/IntrusiveList.h>
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#include <LibGC/Forward.h>
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#include <LibGC/Weak.h>
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namespace GC {
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class GC_API WeakBlock {
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public:
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static constexpr size_t BLOCK_SIZE = 16 * KiB;
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static WeakBlock* create();
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WeakImpl* allocate(Cell*);
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void deallocate(WeakImpl*);
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bool can_allocate() const { return m_freelist != nullptr; }
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void sweep();
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private:
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WeakBlock();
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~WeakBlock();
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IntrusiveListNode<WeakBlock> m_list_node;
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public:
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using List = IntrusiveList<&WeakBlock::m_list_node>;
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WeakImpl* m_freelist { nullptr };
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static constexpr size_t IMPL_COUNT = (BLOCK_SIZE - sizeof(m_list_node) - sizeof(WeakImpl*)) / sizeof(WeakImpl);
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WeakImpl m_impls[IMPL_COUNT];
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};
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static_assert(sizeof(WeakBlock) <= WeakBlock::BLOCK_SIZE);
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}
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