/src/node/deps/v8/include/cppgc/heap.h

Source
// Copyright 2020 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef INCLUDE_CPPGC_HEAP_H_
#define INCLUDE_CPPGC_HEAP_H_

#include <cstddef>
#include <cstdint>
#include <memory>
#include <vector>

#include "cppgc/common.h"
#include "cppgc/custom-space.h"
#include "cppgc/platform.h"
#include "v8config.h"  // NOLINT(build/include_directory)

/**
 * cppgc - A C++ garbage collection library.
 */
namespace cppgc {

class AllocationHandle;
class HeapHandle;

/**
 * Implementation details of cppgc. Those details are considered internal and
 * may change at any point in time without notice. Users should never rely on
 * the contents of this namespace.
 */
namespace internal {
class Heap;
}  // namespace internal

class V8_EXPORT Heap {
 public:
  /**
   * Specifies the stack state the embedder is in.
   */
  using StackState = EmbedderStackState;

  /**
   * Specifies whether conservative stack scanning is supported.
   */
  enum class StackSupport : uint8_t {
    /**
     * Conservative stack scan is supported.
     */
    kSupportsConservativeStackScan,
    /**
     * Conservative stack scan is not supported. Embedders may use this option
     * when using custom infrastructure that is unsupported by the library.
     */
    kNoConservativeStackScan,
  };

  /**
   * Specifies supported marking types.
   */
  enum class MarkingType : uint8_t {
    /**
     * Atomic stop-the-world marking. This option does not require any write
     * barriers but is the most intrusive in terms of jank.
     */
    kAtomic,
    /**
     * Incremental marking interleaves marking with the rest of the application
     * workload on the same thread.
     */
    kIncremental,
    /**
     * Incremental and concurrent marking.
     */
    kIncrementalAndConcurrent
  };

  /**
   * Specifies supported sweeping types.
   */
  enum class SweepingType : uint8_t {
    /**
     * Atomic stop-the-world sweeping. All of sweeping is performed at once.
     */
    kAtomic,
    /**
     * Incremental sweeping interleaves sweeping with the rest of the
     * application workload on the same thread.
     */
    kIncremental,
    /**
     * Incremental and concurrent sweeping. Sweeping is split and interleaved
     * with the rest of the application.
     */
    kIncrementalAndConcurrent
  };

  /**
   * Constraints for a Heap setup.
   */
  struct ResourceConstraints {
    /**
     * Allows the heap to grow to some initial size in bytes before triggering
     * garbage collections. This is useful when it is known that applications
     * need a certain minimum heap to run to avoid repeatedly invoking the
     * garbage collector when growing the heap.
     */
    size_t initial_heap_size_bytes = 0;
  };

  /**
   * Options specifying Heap properties (e.g. custom spaces) when initializing a
   * heap through `Heap::Create()`.
   */
  struct HeapOptions {
    /**
     * Creates reasonable defaults for instantiating a Heap.
     *
     * \returns the HeapOptions that can be passed to `Heap::Create()`.
     */
    static HeapOptions Default() { return {}; }

    /**
     * Custom spaces added to heap are required to have indices forming a
     * numbered sequence starting at 0, i.e., their `kSpaceIndex` must
     * correspond to the index they reside in the vector.
     */
    std::vector<std::unique_ptr<CustomSpaceBase>> custom_spaces;

    /**
     * Specifies whether conservative stack scan is supported. When conservative
     * stack scan is not supported, the collector may try to invoke
     * garbage collections using non-nestable task, which are guaranteed to have
     * no interesting stack, through the provided Platform. If such tasks are
     * not supported by the Platform, the embedder must take care of invoking
     * the GC through `ForceGarbageCollectionSlow()`.
     */
    StackSupport stack_support = StackSupport::kSupportsConservativeStackScan;

    /**
     * Specifies which types of marking are supported by the heap.
     */
    MarkingType marking_support = MarkingType::kIncrementalAndConcurrent;

    /**
     * Specifies which types of sweeping are supported by the heap.
     */
    SweepingType sweeping_support = SweepingType::kIncrementalAndConcurrent;

    /**
     * Resource constraints specifying various properties that the internal
     * GC scheduler follows.
     */
    ResourceConstraints resource_constraints;
  };

  /**
   * Creates a new heap that can be used for object allocation.
   *
   * \param platform implemented and provided by the embedder.
   * \param options HeapOptions specifying various properties for the Heap.
   * \returns a new Heap instance.
   */
  static std::unique_ptr<Heap> Create(
      std::shared_ptr<Platform> platform,
      HeapOptions options = HeapOptions::Default());

  virtual ~Heap() = default;

  /**
   * Forces garbage collection.
   *
   * \param source String specifying the source (or caller) triggering a
   *   forced garbage collection.
   * \param reason String specifying the reason for the forced garbage
   *   collection.
   * \param stack_state The embedder stack state, see StackState.
   */
  void ForceGarbageCollectionSlow(
      const char* source, const char* reason,
      StackState stack_state = StackState::kMayContainHeapPointers);

  /**
   * \returns the opaque handle for allocating objects using
   * `MakeGarbageCollected()`.
   */
  AllocationHandle& GetAllocationHandle();

  /**
   * \returns the opaque heap handle which may be used to refer to this heap in
   *   other APIs. Valid as long as the underlying `Heap` is alive.
   */
  HeapHandle& GetHeapHandle();

 private:
  Heap() = default;

  friend class internal::Heap;
};

}  // namespace cppgc

#endif  // INCLUDE_CPPGC_HEAP_H_

Coverage Report

Created: 2025-10-31 09:06

Line	Count	Source
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_HEAP_H_
6		#define INCLUDE_CPPGC_HEAP_H_
7
8		#include <cstddef>
9		#include <cstdint>
10		#include <memory>
11		#include <vector>
12
13		#include "cppgc/common.h"
14		#include "cppgc/custom-space.h"
15		#include "cppgc/platform.h"
16		#include "v8config.h" // NOLINT(build/include_directory)
17
18		/**
19		* cppgc - A C++ garbage collection library.
20		*/
21		namespace cppgc {
22
23		class AllocationHandle;
24		class HeapHandle;
25
26		/**
27		* Implementation details of cppgc. Those details are considered internal and
28		* may change at any point in time without notice. Users should never rely on
29		* the contents of this namespace.
30		*/
31		namespace internal {
32		class Heap;
33		} // namespace internal
34
35		class V8_EXPORT Heap {
36		public:
37		/**
38		* Specifies the stack state the embedder is in.
39		*/
40		using StackState = EmbedderStackState;
41
42		/**
43		* Specifies whether conservative stack scanning is supported.
44		*/
45		enum class StackSupport : uint8_t {
46		/**
47		* Conservative stack scan is supported.
48		*/
49		kSupportsConservativeStackScan,
50		/**
51		* Conservative stack scan is not supported. Embedders may use this option
52		* when using custom infrastructure that is unsupported by the library.
53		*/
54		kNoConservativeStackScan,
55		};
56
57		/**
58		* Specifies supported marking types.
59		*/
60		enum class MarkingType : uint8_t {
61		/**
62		* Atomic stop-the-world marking. This option does not require any write
63		* barriers but is the most intrusive in terms of jank.
64		*/
65		kAtomic,
66		/**
67		* Incremental marking interleaves marking with the rest of the application
68		* workload on the same thread.
69		*/
70		kIncremental,
71		/**
72		* Incremental and concurrent marking.
73		*/
74		kIncrementalAndConcurrent
75		};
76
77		/**
78		* Specifies supported sweeping types.
79		*/
80		enum class SweepingType : uint8_t {
81		/**
82		* Atomic stop-the-world sweeping. All of sweeping is performed at once.
83		*/
84		kAtomic,
85		/**
86		* Incremental sweeping interleaves sweeping with the rest of the
87		* application workload on the same thread.
88		*/
89		kIncremental,
90		/**
91		* Incremental and concurrent sweeping. Sweeping is split and interleaved
92		* with the rest of the application.
93		*/
94		kIncrementalAndConcurrent
95		};
96
97		/**
98		* Constraints for a Heap setup.
99		*/
100		struct ResourceConstraints {
101		/**
102		* Allows the heap to grow to some initial size in bytes before triggering
103		* garbage collections. This is useful when it is known that applications
104		* need a certain minimum heap to run to avoid repeatedly invoking the
105		* garbage collector when growing the heap.
106		*/
107		size_t initial_heap_size_bytes = 0;
108		};
109
110		/**
111		* Options specifying Heap properties (e.g. custom spaces) when initializing a
112		* heap through `Heap::Create()`.
113		*/
114		struct HeapOptions {
115		/**
116		* Creates reasonable defaults for instantiating a Heap.
117		*
118		* \returns the HeapOptions that can be passed to `Heap::Create()`.
119		*/
120	0	static HeapOptions Default() { return {}; }
121
122		/**
123		* Custom spaces added to heap are required to have indices forming a
124		* numbered sequence starting at 0, i.e., their `kSpaceIndex` must
125		* correspond to the index they reside in the vector.
126		*/
127		std::vector<std::unique_ptr<CustomSpaceBase>> custom_spaces;
128
129		/**
130		* Specifies whether conservative stack scan is supported. When conservative
131		* stack scan is not supported, the collector may try to invoke
132		* garbage collections using non-nestable task, which are guaranteed to have
133		* no interesting stack, through the provided Platform. If such tasks are
134		* not supported by the Platform, the embedder must take care of invoking
135		* the GC through `ForceGarbageCollectionSlow()`.
136		*/
137		StackSupport stack_support = StackSupport::kSupportsConservativeStackScan;
138
139		/**
140		* Specifies which types of marking are supported by the heap.
141		*/
142		MarkingType marking_support = MarkingType::kIncrementalAndConcurrent;
143
144		/**
145		* Specifies which types of sweeping are supported by the heap.
146		*/
147		SweepingType sweeping_support = SweepingType::kIncrementalAndConcurrent;
148
149		/**
150		* Resource constraints specifying various properties that the internal
151		* GC scheduler follows.
152		*/
153		ResourceConstraints resource_constraints;
154		};
155
156		/**
157		* Creates a new heap that can be used for object allocation.
158		*
159		* \param platform implemented and provided by the embedder.
160		* \param options HeapOptions specifying various properties for the Heap.
161		* \returns a new Heap instance.
162		*/
163		static std::unique_ptr<Heap> Create(
164		std::shared_ptr<Platform> platform,
165		HeapOptions options = HeapOptions::Default());
166
167		virtual ~Heap() = default;
168
169		/**
170		* Forces garbage collection.
171		*
172		* \param source String specifying the source (or caller) triggering a
173		* forced garbage collection.
174		* \param reason String specifying the reason for the forced garbage
175		* collection.
176		* \param stack_state The embedder stack state, see StackState.
177		*/
178		void ForceGarbageCollectionSlow(
179		const char* source, const char* reason,
180		StackState stack_state = StackState::kMayContainHeapPointers);
181
182		/**
183		* \returns the opaque handle for allocating objects using
184		* `MakeGarbageCollected()`.
185		*/
186		AllocationHandle& GetAllocationHandle();
187
188		/**
189		* \returns the opaque heap handle which may be used to refer to this heap in
190		* other APIs. Valid as long as the underlying `Heap` is alive.
191		*/
192		HeapHandle& GetHeapHandle();
193
194		private:
195		Heap() = default;
196
197		friend class internal::Heap;
198		};
199
200		} // namespace cppgc
201
202		#endif // INCLUDE_CPPGC_HEAP_H_