/src/node/deps/v8/include/cppgc/custom-space.h
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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 be |
3 | | // 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 | | |
10 | | namespace cppgc { |
11 | | |
12 | | /** |
13 | | * Index identifying a custom space. |
14 | | */ |
15 | | struct CustomSpaceIndex { |
16 | 0 | constexpr CustomSpaceIndex(size_t value) : value(value) {} // NOLINT |
17 | | size_t value; |
18 | | }; |
19 | | |
20 | | /** |
21 | | * Top-level base class for custom spaces. Users must inherit from CustomSpace |
22 | | * below. |
23 | | */ |
24 | | class 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 inheriting |
33 | | * from `CustomSpace` must define `kSpaceIndex` as unique space index. These |
34 | | * indices need for form a sequence starting at 0. |
35 | | * |
36 | | * Example: |
37 | | * \code |
38 | | * 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 | | * \endcode |
47 | | */ |
48 | | template <typename ConcreteCustomSpace> |
49 | | class CustomSpace : public CustomSpaceBase { |
50 | | public: |
51 | | /** |
52 | | * Compaction is only supported on spaces that manually manage slots |
53 | | * 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 | | */ |
68 | | template <typename T, typename = void> |
69 | | struct SpaceTrait { |
70 | | using Space = void; |
71 | | }; |
72 | | |
73 | | namespace internal { |
74 | | |
75 | | template <typename CustomSpace> |
76 | | struct IsAllocatedOnCompactableSpaceImpl { |
77 | | static constexpr bool value = CustomSpace::kSupportsCompaction; |
78 | | }; |
79 | | |
80 | | template <> |
81 | | struct IsAllocatedOnCompactableSpaceImpl<void> { |
82 | | // Non-custom spaces are by default not compactable. |
83 | | static constexpr bool value = false; |
84 | | }; |
85 | | |
86 | | template <typename T> |
87 | | struct IsAllocatedOnCompactableSpace { |
88 | | public: |
89 | | static constexpr bool value = |
90 | | IsAllocatedOnCompactableSpaceImpl<typename SpaceTrait<T>::Space>::value; |
91 | | }; |
92 | | |
93 | | } // namespace internal |
94 | | |
95 | | } // namespace cppgc |
96 | | |
97 | | #endif // INCLUDE_CPPGC_CUSTOM_SPACE_H_ |