3c74dc9f4d
This patch adds two macros to declare per-type allocators: - JS_DECLARE_ALLOCATOR(TypeName) - JS_DEFINE_ALLOCATOR(TypeName) When used, they add a type-specific CellAllocator that the Heap will delegate allocation requests to. The result of this is that GC objects of the same type always end up within the same HeapBlock, drastically reducing the ability to perform type confusion attacks. It also improves HeapBlock utilization, since each block now has cells sized exactly to the type used within that block. (Previously we only had a handful of block sizes available, and most GC allocations ended up with a large amount of slack in their tails.) There is a small performance hit from this, but I'm sure we can make up for it elsewhere. Note that the old size-based allocators still exist, and we fall back to them for any type that doesn't have its own CellAllocator.
118 lines
3 KiB
C++
118 lines
3 KiB
C++
/*
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* Copyright (c) 2021, Idan Horowitz <idan.horowitz@serenityos.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/HashMap.h>
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#include <AK/RedBlackTree.h>
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#include <LibJS/Runtime/GlobalObject.h>
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#include <LibJS/Runtime/Object.h>
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#include <LibJS/Runtime/Value.h>
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#include <LibJS/Runtime/ValueTraits.h>
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namespace JS {
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class Map : public Object {
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JS_OBJECT(Map, Object);
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JS_DECLARE_ALLOCATOR(Map);
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public:
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static NonnullGCPtr<Map> create(Realm&);
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virtual ~Map() override = default;
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void map_clear();
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bool map_remove(Value const&);
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Optional<Value> map_get(Value const&) const;
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bool map_has(Value const&) const;
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void map_set(Value const&, Value);
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size_t map_size() const;
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struct EndIterator {
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};
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template<bool IsConst>
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struct IteratorImpl {
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bool is_end() const
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{
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return m_map->m_keys.begin_from(m_index).is_end()
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&& m_map->m_keys.find_smallest_not_below_iterator(m_index).is_end();
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}
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IteratorImpl& operator++()
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{
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++m_index;
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return *this;
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}
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decltype(auto) operator*()
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{
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ensure_next_element();
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return *m_map->m_entries.find(*m_map->m_keys.begin_from(m_index));
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}
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decltype(auto) operator*() const
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{
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ensure_next_element();
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return *m_map->m_entries.find(*m_map->m_keys.begin_from(m_index));
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}
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bool operator==(IteratorImpl const& other) const { return m_index == other.m_index && &m_map == &other.m_map; }
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bool operator==(EndIterator const&) const { return is_end(); }
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private:
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friend class Map;
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IteratorImpl(Map const& map)
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requires(IsConst)
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: m_map(map)
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{
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ensure_index();
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}
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IteratorImpl(Map& map)
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requires(!IsConst)
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: m_map(map)
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{
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ensure_index();
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}
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void ensure_index() const
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{
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if (m_map->m_keys.is_empty())
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m_index = m_map->m_next_insertion_id;
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else
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m_index = m_map->m_keys.begin().key();
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}
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void ensure_next_element() const
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{
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if (auto it = m_map->m_keys.find_smallest_not_below_iterator(m_index); it.is_end())
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m_index = m_map->m_next_insertion_id;
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else
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m_index = it.key();
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}
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Conditional<IsConst, NonnullGCPtr<Map const>, NonnullGCPtr<Map>> m_map;
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mutable size_t m_index { 0 };
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};
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using Iterator = IteratorImpl<false>;
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using ConstIterator = IteratorImpl<true>;
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ConstIterator begin() const { return { *this }; }
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Iterator begin() { return { *this }; }
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EndIterator end() const { return {}; }
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private:
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explicit Map(Object& prototype);
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virtual void visit_edges(Visitor& visitor) override;
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size_t m_next_insertion_id { 0 };
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RedBlackTree<size_t, Value> m_keys;
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HashMap<Value, Value, ValueTraits> m_entries;
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};
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}
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