1// Copyright 2016 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 V8_WASM_MANAGED_H_
6#define V8_WASM_MANAGED_H_
7
8#include "src/factory.h"
9#include "src/global-handles.h"
10#include "src/handles.h"
11#include "src/isolate.h"
12
13namespace v8 {
14namespace internal {
15// An object that wraps a pointer to a C++ object and manages its lifetime.
16// The C++ object will be deleted when the managed wrapper object is
17// garbage collected, or, last resort, if the isolate is torn down before GC,
18// as part of Isolate::Dispose().
19// Managed<CppType> may be used polymorphically as Foreign, where the held
20// address is typed as CppType**. The double indirection is due to the
21// use, by Managed, of Isolate::ManagedObjectFinalizer, which has a CppType*
22// first field.
23template <class CppType>
24class Managed : public Foreign {
25 public:
26  V8_INLINE CppType* get() {
27    return *(reinterpret_cast<CppType**>(foreign_address()));
28  }
29
30  static Managed<CppType>* cast(Object* obj) {
31    SLOW_DCHECK(obj->IsForeign());
32    return reinterpret_cast<Managed<CppType>*>(obj);
33  }
34
35  static Handle<Managed<CppType>> New(Isolate* isolate, CppType* ptr) {
36    Isolate::ManagedObjectFinalizer* node =
37        isolate->RegisterForReleaseAtTeardown(ptr,
38                                              Managed<CppType>::NativeDelete);
39    Handle<Managed<CppType>> handle = Handle<Managed<CppType>>::cast(
40        isolate->factory()->NewForeign(reinterpret_cast<Address>(node)));
41    RegisterWeakCallbackForDelete(isolate, handle);
42    return handle;
43  }
44
45 private:
46  static void RegisterWeakCallbackForDelete(Isolate* isolate,
47                                            Handle<Managed<CppType>> handle) {
48    Handle<Object> global_handle = isolate->global_handles()->Create(*handle);
49    GlobalHandles::MakeWeak(global_handle.location(), global_handle.location(),
50                            &Managed<CppType>::GCDelete,
51                            v8::WeakCallbackType::kFinalizer);
52  }
53
54  static void GCDelete(const v8::WeakCallbackInfo<void>& data) {
55    Managed<CppType>** p =
56        reinterpret_cast<Managed<CppType>**>(data.GetParameter());
57
58    Isolate::ManagedObjectFinalizer* finalizer = (*p)->GetFinalizer();
59
60    Isolate* isolate = reinterpret_cast<Isolate*>(data.GetIsolate());
61    finalizer->Dispose();
62    isolate->UnregisterFromReleaseAtTeardown(&finalizer);
63
64    (*p)->set_foreign_address(static_cast<Address>(nullptr));
65    GlobalHandles::Destroy(reinterpret_cast<Object**>(p));
66  }
67
68  static void NativeDelete(void* value) {
69    CppType* typed_value = reinterpret_cast<CppType*>(value);
70    delete typed_value;
71  }
72
73  Isolate::ManagedObjectFinalizer* GetFinalizer() {
74    return reinterpret_cast<Isolate::ManagedObjectFinalizer*>(
75        foreign_address());
76  }
77};
78}  // namespace internal
79}  // namespace v8
80
81#endif  // V8_WASM_MANAGED_H_
82