public:

// Records the key and self, used by SetWeak.

struct KeyObject {

K key;

KeyWeakMap* self;

};

KeyWeakMap() {}

virtual ~KeyWeakMap() {

for (auto& p : map_)

p.second.second.ClearWeak();

}

// disable copy

KeyWeakMap(const KeyWeakMap&) = delete;

KeyWeakMap& operator=(const KeyWeakMap&) = delete;

// Sets the object to WeakMap with the given |key|.

void Set(v8::Isolate* isolate, const K& key, v8::Local<v8::Object> object) {

KeyObject key_object = {key, this};

auto& p = map_[key] =

std::make_pair(key_object, v8::Global<v8::Object>(isolate, object));

p.second.SetWeak(&(p.first), OnObjectGC, v8::WeakCallbackType::kParameter);

}

// Gets the object from WeakMap by its |key|.

v8::MaybeLocal<v8::Object> Get(v8::Isolate* isolate, const K& key) {

auto iter = map_.find(key);

if (iter == map_.end())

return v8::MaybeLocal<v8::Object>();

else

return v8::Local<v8::Object>::New(isolate, iter->second.second);

}

// Whethere there is an object with |key| in this WeakMap.

bool Has(const K& key) const { return map_.find(key) != map_.end(); }

// Returns all objects.

std::vector<v8::Local<v8::Object>> Values(v8::Isolate* isolate) const {

std::vector<v8::Local<v8::Object>> keys;

keys.reserve(map_.size());

for (const auto& it : map_)

keys.emplace_back(v8::Local<v8::Object>::New(isolate, it.second.second));

return keys;

}

// Remove object with |key| in the WeakMap.

void Remove(const K& key) {

auto iter = map_.find(key);

if (iter == map_.end())

return;

iter->second.second.ClearWeak();

map_.erase(iter);

}

private:

static void OnObjectGC(

const v8::WeakCallbackInfo<typename KeyWeakMap<K>::KeyObject>& data) {

KeyWeakMap<K>::KeyObject* key_object = data.GetParameter();

key_object->self->Remove(key_object->key);

}

// Map of stored objects.

std::unordered_map<K, std::pair<KeyObject, v8::Global<v8::Object>>> map_;