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e123d48043
We specialize `Optional<T>` for value types that inherently support some kind of "empty" value or whose value range allow for a unlikely to be useful sentinel value that can mean "empty", instead of the boolean flag a regular Optional<T> needs to store. Because of padding, this often means saving 4 to 8 bytes per instance. By extending the new `SentinelOptional<T, Traits>`, these specializations are significantly simplified to just having to define what the sentinel value is, and how to identify a sentinel value.
55 lines
1.4 KiB
C++
55 lines
1.4 KiB
C++
/*
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* Copyright (c) 2021, 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/DistinctNumeric.h>
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#include <AK/Utf16FlyString.h>
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#include <AK/Vector.h>
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namespace JS::Bytecode {
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struct IdentifierTableIndex {
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static constexpr u32 invalid = 0xffffffffu;
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bool is_valid() const { return value != invalid; }
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u32 value { 0 };
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};
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class IdentifierTable {
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AK_MAKE_NONMOVABLE(IdentifierTable);
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AK_MAKE_NONCOPYABLE(IdentifierTable);
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public:
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IdentifierTable() = default;
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IdentifierTableIndex insert(Utf16FlyString);
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Utf16FlyString const& get(IdentifierTableIndex) const;
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void dump() const;
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bool is_empty() const { return m_identifiers.is_empty(); }
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ReadonlySpan<Utf16FlyString const> identifiers() const { return m_identifiers; }
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private:
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Vector<Utf16FlyString> m_identifiers;
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};
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}
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namespace AK {
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template<>
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struct SentinelOptionalTraits<JS::Bytecode::IdentifierTableIndex> {
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static constexpr JS::Bytecode::IdentifierTableIndex sentinel_value() { return { JS::Bytecode::IdentifierTableIndex::invalid }; }
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static constexpr bool is_sentinel(JS::Bytecode::IdentifierTableIndex const& value) { return !value.is_valid(); }
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};
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template<>
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class Optional<JS::Bytecode::IdentifierTableIndex> : public SentinelOptional<JS::Bytecode::IdentifierTableIndex> {
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public:
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using SentinelOptional::SentinelOptional;
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};
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}
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