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 {
15 V8_EXPORT void InternalFieldOutOfBounds(int index);
16 } // namespace api_internal
17
18 static const int kInternalFieldsInWeakCallback = 2;
19 static const int kEmbedderFieldsInWeakCallback = 2;
20
21 template <typename T>
22 class WeakCallbackInfo {
23 public:
24 using Callback = void (*)(const WeakCallbackInfo<T>& data);
25
WeakCallbackInfo(Isolate * isolate,T * parameter,void * embedder_fields[kEmbedderFieldsInWeakCallback],Callback * callback)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
GetIsolate()35 V8_INLINE Isolate* GetIsolate() const { return isolate_; }
GetParameter()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.
SetSecondPassCallback(Callback callback)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 // kParameter will pass a void* parameter back to the callback, kInternalFields
55 // will pass the first two internal fields back to the callback, kFinalizer
56 // will pass a void* parameter back, but is invoked before the object is
57 // actually collected, so it can be resurrected. In the last case, it is not
58 // possible to request a second pass callback.
59 enum class WeakCallbackType { kParameter, kInternalFields, kFinalizer };
60
61 template <class T>
GetInternalField(int index)62 void* WeakCallbackInfo<T>::GetInternalField(int index) const {
63 #ifdef V8_ENABLE_CHECKS
64 if (index < 0 || index >= kEmbedderFieldsInWeakCallback) {
65 api_internal::InternalFieldOutOfBounds(index);
66 }
67 #endif
68 return embedder_fields_[index];
69 }
70
71 } // namespace v8
72
73 #endif // INCLUDE_V8_WEAK_CALLBACK_INFO_H_
74