98 lines
2.4 KiB
C
98 lines
2.4 KiB
C
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// Copyright 2020 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef INCLUDE_CPPGC_CUSTOM_SPACE_H_
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#define INCLUDE_CPPGC_CUSTOM_SPACE_H_
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#include <stddef.h>
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namespace cppgc {
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/**
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* Index identifying a custom space.
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*/
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struct CustomSpaceIndex {
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constexpr CustomSpaceIndex(size_t value) : value(value) {} // NOLINT
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size_t value;
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};
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/**
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* Top-level base class for custom spaces. Users must inherit from CustomSpace
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* below.
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*/
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class CustomSpaceBase {
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public:
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virtual ~CustomSpaceBase() = default;
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virtual CustomSpaceIndex GetCustomSpaceIndex() const = 0;
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virtual bool IsCompactable() const = 0;
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};
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/**
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* Base class custom spaces should directly inherit from. The class inheriting
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* from `CustomSpace` must define `kSpaceIndex` as unique space index. These
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* indices need for form a sequence starting at 0.
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*
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* Example:
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* \code
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* class CustomSpace1 : public CustomSpace<CustomSpace1> {
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* public:
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* static constexpr CustomSpaceIndex kSpaceIndex = 0;
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* };
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* class CustomSpace2 : public CustomSpace<CustomSpace2> {
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* public:
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* static constexpr CustomSpaceIndex kSpaceIndex = 1;
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* };
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* \endcode
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*/
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template <typename ConcreteCustomSpace>
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class CustomSpace : public CustomSpaceBase {
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public:
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/**
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* Compaction is only supported on spaces that manually manage slots
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* recording.
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*/
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static constexpr bool kSupportsCompaction = false;
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CustomSpaceIndex GetCustomSpaceIndex() const final {
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return ConcreteCustomSpace::kSpaceIndex;
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}
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bool IsCompactable() const final {
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return ConcreteCustomSpace::kSupportsCompaction;
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}
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};
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/**
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* User-overridable trait that allows pinning types to custom spaces.
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*/
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template <typename T, typename = void>
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struct SpaceTrait {
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using Space = void;
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};
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namespace internal {
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template <typename CustomSpace>
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struct IsAllocatedOnCompactableSpaceImpl {
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static constexpr bool value = CustomSpace::kSupportsCompaction;
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};
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template <>
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struct IsAllocatedOnCompactableSpaceImpl<void> {
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// Non-custom spaces are by default not compactable.
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static constexpr bool value = false;
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};
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template <typename T>
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struct IsAllocatedOnCompactableSpace {
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public:
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static constexpr bool value =
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IsAllocatedOnCompactableSpaceImpl<typename SpaceTrait<T>::Space>::value;
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};
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} // namespace internal
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} // namespace cppgc
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#endif // INCLUDE_CPPGC_CUSTOM_SPACE_H_
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