v8  10.1.124 (node 18.2.0)
V8 is Google's open source JavaScript engine
v8-weak-callback-info.h
Go to the documentation of this file.
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 be
3 // 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 "v8config.h" // NOLINT(build/include_directory)
9 
10 namespace v8 {
11 
12 class Isolate;
13 
14 namespace api_internal {
16 } // namespace api_internal
17 
18 static const int kInternalFieldsInWeakCallback = 2;
19 static const int kEmbedderFieldsInWeakCallback = 2;
20 
21 template <typename T>
23  public:
24  using Callback = void (*)(const WeakCallbackInfo<T>& data);
25 
26  WeakCallbackInfo(Isolate* isolate, T* parameter,
27  void* embedder_fields[kEmbedderFieldsInWeakCallback],
28  Callback* callback)
29  : isolate_(isolate), parameter_(parameter), callback_(callback) {
30  for (int i = 0; i < kEmbedderFieldsInWeakCallback; ++i) {
31  embedder_fields_[i] = embedder_fields[i];
32  }
33  }
34 
35  V8_INLINE Isolate* GetIsolate() const { return isolate_; }
36  V8_INLINE T* GetParameter() const { return parameter_; }
37  V8_INLINE void* GetInternalField(int index) const;
38 
39  // When first called, the embedder MUST Reset() the Global which triggered the
40  // callback. The Global itself is unusable for anything else. No v8 other api
41  // calls may be called in the first callback. Should additional work be
42  // required, the embedder must set a second pass callback, which will be
43  // called after all the initial callbacks are processed.
44  // Calling SetSecondPassCallback on the second pass will immediately crash.
45  void SetSecondPassCallback(Callback callback) const { *callback_ = callback; }
46 
47  private:
48  Isolate* isolate_;
49  T* parameter_;
50  Callback* callback_;
51  void* embedder_fields_[kEmbedderFieldsInWeakCallback];
52 };
53 
54 /**
55  * Weakness type for weak handles.
56  */
57 enum class WeakCallbackType {
58  /**
59  * Passes a user-defined void* parameter back to the callback.
60  */
61  kParameter,
62  /**
63  * Passes the first two internal fields of the object back to the callback.
64  */
66  /**
67  * Passes a user-defined void* parameter back to the callback. Will do so
68  * before the object is actually reclaimed, allowing it to be resurrected. In
69  * this case it is not possible to set a second-pass callback.
70  */
71  kFinalizer V8_ENUM_DEPRECATE_SOON("Resurrecting finalizers are deprecated "
72  "and will not be supported going forward.")
73 };
74 
75 template <class T>
76 void* WeakCallbackInfo<T>::GetInternalField(int index) const {
77 #ifdef V8_ENABLE_CHECKS
78  if (index < 0 || index >= kEmbedderFieldsInWeakCallback) {
79  api_internal::InternalFieldOutOfBounds(index);
80  }
81 #endif
82  return embedder_fields_[index];
83 }
84 
85 } // namespace v8
86 
87 #endif // INCLUDE_V8_WEAK_CALLBACK_INFO_H_