chromium/third_party/perfetto/include/perfetto/protozero/message_handle.h

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef INCLUDE_PERFETTO_PROTOZERO_MESSAGE_HANDLE_H_
#define INCLUDE_PERFETTO_PROTOZERO_MESSAGE_HANDLE_H_

#include <functional>

#include "perfetto/base/export.h"
#include "perfetto/protozero/message.h"
#include "perfetto/protozero/scattered_stream_writer.h"

namespace protozero {

class Message;

class PERFETTO_EXPORT_COMPONENT MessageFinalizationListener { … };

// MessageHandle allows to decouple the lifetime of a proto message
// from the underlying storage. It gives the following guarantees:
// - The underlying message is finalized (if still alive) if the handle goes
//   out of scope.
// - In Debug / DCHECK_ALWAYS_ON builds, the handle becomes null once the
//   message is finalized. This is to enforce the append-only API. For instance
//   when adding two repeated messages, the addition of the 2nd one forces
//   the finalization of the first.
// Think about this as a WeakPtr<Message> which calls
// Message::Finalize() when going out of scope.

class PERFETTO_EXPORT_COMPONENT MessageHandleBase { … };

template <typename T>
class MessageHandle : public MessageHandleBase { … };

}  // namespace protozero

#endif  // INCLUDE_PERFETTO_PROTOZERO_MESSAGE_HANDLE_H_