// 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_
