File Explorer

1// Copyright 2020 the V8 project authors. All rights reserved.2// Use of this source code is governed by a BSD-style license that can be3// found in the LICENSE file.4 5#ifndef INCLUDE_CPPGC_CUSTOM_SPACE_H_6#define INCLUDE_CPPGC_CUSTOM_SPACE_H_7 8#include <stddef.h>9 10namespace cppgc {11 12/**13 * Index identifying a custom space.14 */15struct CustomSpaceIndex {16  constexpr CustomSpaceIndex(size_t value) : value(value) {}  // NOLINT17  size_t value;18};19 20/**21 * Top-level base class for custom spaces. Users must inherit from CustomSpace22 * below.23 */24class CustomSpaceBase {25 public:26  virtual ~CustomSpaceBase() = default;27  virtual CustomSpaceIndex GetCustomSpaceIndex() const = 0;28  virtual bool IsCompactable() const = 0;29};30 31/**32 * Base class custom spaces should directly inherit from. The class inheriting33 * from `CustomSpace` must define `kSpaceIndex` as unique space index. These34 * indices need for form a sequence starting at 0.35 *36 * Example:37 * \code38 * class CustomSpace1 : public CustomSpace<CustomSpace1> {39 *  public:40 *   static constexpr CustomSpaceIndex kSpaceIndex = 0;41 * };42 * class CustomSpace2 : public CustomSpace<CustomSpace2> {43 *  public:44 *   static constexpr CustomSpaceIndex kSpaceIndex = 1;45 * };46 * \endcode47 */48template <typename ConcreteCustomSpace>49class CustomSpace : public CustomSpaceBase {50 public:51  /**52   * Compaction is only supported on spaces that manually manage slots53   * recording.54   */55  static constexpr bool kSupportsCompaction = false;56 57  CustomSpaceIndex GetCustomSpaceIndex() const final {58    return ConcreteCustomSpace::kSpaceIndex;59  }60  bool IsCompactable() const final {61    return ConcreteCustomSpace::kSupportsCompaction;62  }63};64 65/**66 * User-overridable trait that allows pinning types to custom spaces.67 */68template <typename T, typename = void>69struct SpaceTrait {70  using Space = void;71};72 73namespace internal {74 75template <typename CustomSpace>76struct IsAllocatedOnCompactableSpaceImpl {77  static constexpr bool value = CustomSpace::kSupportsCompaction;78};79 80template <>81struct IsAllocatedOnCompactableSpaceImpl<void> {82  // Non-custom spaces are by default not compactable.83  static constexpr bool value = false;84};85 86template <typename T>87struct IsAllocatedOnCompactableSpace {88 public:89  static constexpr bool value =90      IsAllocatedOnCompactableSpaceImpl<typename SpaceTrait<T>::Space>::value;91};92 93}  // namespace internal94 95}  // namespace cppgc96 97#endif  // INCLUDE_CPPGC_CUSTOM_SPACE_H_98