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// 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 V8_HEAP_ARRAY_BUFFER_SWEEPER_H_
#define V8_HEAP_ARRAY_BUFFER_SWEEPER_H_
#include <memory>
#include "src/base/logging.h"
#include "src/base/platform/mutex.h"
#include "src/objects/js-array-buffer.h"
#include "src/tasks/cancelable-task.h"
namespace v8 {
namespace internal {
class ArrayBufferExtension;
class Heap;
// Singly linked-list of ArrayBufferExtensions that stores head and tail of the
// list to allow for concatenation of lists.
struct ArrayBufferList final {
bool IsEmpty() const;
size_t ApproximateBytes() const { return bytes_; }
size_t BytesSlow() const;
void Append(ArrayBufferExtension* extension);
void Append(ArrayBufferList* list);
V8_EXPORT_PRIVATE bool ContainsSlow(ArrayBufferExtension* extension) const;
private:
ArrayBufferExtension* head_ = nullptr;
ArrayBufferExtension* tail_ = nullptr;
// Bytes are approximate as they may be subtracted eagerly, while the
// `ArrayBufferExtension` is still in the list. The extension will only be
// dropped on next sweep.
size_t bytes_ = 0;
friend class ArrayBufferSweeper;
};
// The ArrayBufferSweeper iterates and deletes ArrayBufferExtensions
// concurrently to the application.
class ArrayBufferSweeper final {
public:
enum class SweepingType { kYoung, kFull };
explicit ArrayBufferSweeper(Heap* heap);
~ArrayBufferSweeper();
void RequestSweep(SweepingType sweeping_type);
void EnsureFinished();
// Track the given ArrayBufferExtension for the given JSArrayBuffer.
void Append(JSArrayBuffer object, ArrayBufferExtension* extension);
// Detaches an ArrayBufferExtension from a JSArrayBuffer.
void Detach(JSArrayBuffer object, ArrayBufferExtension* extension);
const ArrayBufferList& young() const { return young_; }
const ArrayBufferList& old() const { return old_; }
// Bytes accounted in the young generation. Rebuilt during sweeping.
size_t YoungBytes() const { return young().ApproximateBytes(); }
// Bytes accounted in the old generation. Rebuilt during sweeping.
size_t OldBytes() const { return old().ApproximateBytes(); }
private:
struct SweepingJob;
enum class SweepingState { kInProgress, kDone };
bool sweeping_in_progress() const { return job_.get(); }
// Finishes sweeping if it is already done.
void FinishIfDone();
// Increments external memory counters outside of ArrayBufferSweeper.
// Increment may trigger GC.
void IncrementExternalMemoryCounters(size_t bytes);
void DecrementExternalMemoryCounters(size_t bytes);
void Prepare(SweepingType type);
void Finalize();
void ReleaseAll(ArrayBufferList* extension);
Heap* const heap_;
std::unique_ptr<SweepingJob> job_;
base::Mutex sweeping_mutex_;
base::ConditionVariable job_finished_;
ArrayBufferList young_;
ArrayBufferList old_;
};
} // namespace internal
} // namespace v8
#endif // V8_HEAP_ARRAY_BUFFER_SWEEPER_H_
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