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1// Copyright 2021 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_V8_WEAK_CALLBACK_INFO_H_6#define INCLUDE_V8_WEAK_CALLBACK_INFO_H_7 8#include <cstring>9 10#include "cppgc/internal/conditional-stack-allocated.h"  // NOLINT(build/include_directory)11#include "v8config.h"  // NOLINT(build/include_directory)12 13namespace v8 {14 15class Isolate;16 17namespace api_internal {18V8_EXPORT void InternalFieldOutOfBounds(int index);19}  // namespace api_internal20 21static constexpr int kInternalFieldsInWeakCallback = 2;22static constexpr int kEmbedderFieldsInWeakCallback = 2;23 24template <typename T>25class WeakCallbackInfo26    : public cppgc::internal::ConditionalStackAllocatedBase<T> {27 public:28  using Callback = void (*)(const WeakCallbackInfo<T>& data);29 30  WeakCallbackInfo(Isolate* isolate, T* parameter,31                   void* embedder_fields[kEmbedderFieldsInWeakCallback],32                   Callback* callback)33      : isolate_(isolate), parameter_(parameter), callback_(callback) {34    memcpy(embedder_fields_, embedder_fields,35           sizeof(embedder_fields[0]) * kEmbedderFieldsInWeakCallback);36  }37 38  V8_INLINE Isolate* GetIsolate() const { return isolate_; }39  V8_INLINE T* GetParameter() const { return parameter_; }40  V8_INLINE void* GetInternalField(int index) const;41 42  /**43   * When a weak callback is first invoked the embedders _must_ Reset() the44   * handle which triggered the callback. The handle itself is unusable for45   * anything else. No other V8 API calls may be called in the first callback.46   * Additional work requires scheduling a second invocation via47   * `SetSecondPassCallback()` which will be called some time after all the48   * initial callbacks are processed.49   *50   * The second pass callback is prohibited from executing JavaScript. Embedders51   * should schedule another callback in case this is required.52   */53  void SetSecondPassCallback(Callback callback) const { *callback_ = callback; }54 55 private:56  Isolate* isolate_;57  T* parameter_;58  Callback* callback_;59  void* embedder_fields_[kEmbedderFieldsInWeakCallback];60};61 62/**63 * Weakness type for weak handles.64 */65enum class WeakCallbackType {66  /**67   * Passes a user-defined void* parameter back to the callback.68   */69  kParameter,70  /**71   * Passes the first two internal fields of the object back to the callback.72   */73  kInternalFields,74};75 76template <class T>77void* WeakCallbackInfo<T>::GetInternalField(int index) const {78#ifdef V8_ENABLE_CHECKS79  if (index < 0 || index >= kEmbedderFieldsInWeakCallback) {80    api_internal::InternalFieldOutOfBounds(index);81  }82#endif83  return embedder_fields_[index];84}85 86}  // namespace v887 88#endif  // INCLUDE_V8_WEAK_CALLBACK_INFO_H_89