1// Copyright 2020 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_CPPGC_EPHEMERON_PAIR_H_
6#define INCLUDE_CPPGC_EPHEMERON_PAIR_H_
7
8#include "cppgc/liveness-broker.h"
9#include "cppgc/member.h"
10
11namespace cppgc {
12
13/**
14 * An ephemeron pair is used to conditionally retain an object.
15 * The `value` will be kept alive only if the `key` is alive.
16 */
17template <typename K, typename V>
18struct EphemeronPair {
19  EphemeronPair(K* k, V* v) : key(k), value(v) {}
20  WeakMember<K> key;
21  Member<V> value;
22
23  void ClearValueIfKeyIsDead(const LivenessBroker& broker) {
24    if (!broker.IsHeapObjectAlive(key)) value = nullptr;
25  }
26};
27
28}  // namespace cppgc
29
30#endif  // INCLUDE_CPPGC_EPHEMERON_PAIR_H_
31