chromium/v8/include/cppgc/liveness-broker.h

// Copyright 2020 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef INCLUDE_CPPGC_LIVENESS_BROKER_H_
#define INCLUDE_CPPGC_LIVENESS_BROKER_H_

#include "cppgc/heap.h"
#include "cppgc/member.h"
#include "cppgc/sentinel-pointer.h"
#include "cppgc/trace-trait.h"
#include "v8config.h"  // NOLINT(build/include_directory)

namespace cppgc {

namespace internal {
class LivenessBrokerFactory;
}  // namespace internal

/**
 * The broker is passed to weak callbacks to allow (temporarily) querying
 * the liveness state of an object. References to non-live objects must be
 * cleared when `IsHeapObjectAlive()` returns false.
 *
 * \code
 * class GCedWithCustomWeakCallback final
 *   : public GarbageCollected<GCedWithCustomWeakCallback> {
 *  public:
 *   UntracedMember<Bar> bar;
 *
 *   void CustomWeakCallbackMethod(const LivenessBroker& broker) {
 *     if (!broker.IsHeapObjectAlive(bar))
 *       bar = nullptr;
 *   }
 *
 *   void Trace(cppgc::Visitor* visitor) const {
 *     visitor->RegisterWeakCallbackMethod<
 *         GCedWithCustomWeakCallback,
 *         &GCedWithCustomWeakCallback::CustomWeakCallbackMethod>(this);
 *   }
 * };
 * \endcode
 */
class V8_EXPORT LivenessBroker final { … };

}  // namespace cppgc

#endif  // INCLUDE_CPPGC_LIVENESS_BROKER_H_