ObjectWeakCallbackState(std::shared_ptr<v8::Persistent<v8::Value>> target)

: target_(target) {}

std::shared_ptr<v8::Persistent<v8::Value>> target_;

// Links in the per-isolate registry (Caches::ObjectManagedValues) that

// teardown walks. Intrusive so that a wrapper unlinks itself in O(1) when it

// is disposed, rather than leaving an entry for a later sweep to find.

// head_ points at the owning cache's head slot so unlinking -- which happens

// in a GC finalizer -- needs no cache lookup.

ObjectWeakCallbackState** head_ = nullptr;

ObjectWeakCallbackState* prev_ = nullptr;

ObjectWeakCallbackState* next_ = nullptr;

// Set while one of the two owning sites is disposing this handle's value.

// Disposal releases the native counterpart, whose -dealloc can re-enter JS

// and reach __releaseNativeCounterpart for this very handle; retiring it

// there would free the state under the frame that owns it. Retirement

// observes the flag and leaves the handle to that frame.

bool disposing_ = false;

public:

static void Init(v8::Isolate* isolate,

v8::Local<v8::ObjectTemplate> globalTemplate);

static std::shared_ptr<v8::Persistent<v8::Value>> Register(

v8::Local<v8::Context> context, const v8::Local<v8::Value> obj);

static void FinalizerCallback(

const v8::WeakCallbackInfo<ObjectWeakCallbackState>& data);

static bool DisposeValue(v8::Isolate* isolate, v8::Local<v8::Value> value,

bool isFinalDisposal = false);

// Disposes every handle from Register() that is still alive. Replaces the

// old Isolate::VisitHandlesWithClassIds walk, which V8 removed.

static void DisposeAllRegistered(v8::Isolate* isolate);

private:

static void ReleaseNativeCounterpartCallback(

const v8::FunctionCallbackInfo<v8::Value>& info);

static long GetRetainCount(id obj);

static bool IsInstanceOf(id obj, Class clazz);