user_message.h - mozsearch

Enable keyboard shortcuts

// Copyright 2017 The Chromium 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 MOJO_CORE_PORTS_USER_MESSAGE_H_

#define MOJO_CORE_PORTS_USER_MESSAGE_H_

#include <stddef.h>

namespace mojo {

namespace core {

namespace ports {

class UserMessageEvent;

// Base type to use for any embedder-defined user message implementation. This

// class is intentionally empty.

//

// Provides a bit of type-safety help to subclasses since by design downcasting

// from this type is a common operation in embedders.

//

// Each subclass should define a static const instance of TypeInfo named

// |kUserMessageTypeInfo| and pass its address down to the UserMessage

// constructor. The type of a UserMessage can then be dynamically inspected by

// comparing |type_info()| to any subclass's |&kUserMessageTypeInfo|.

class UserMessage {

 public:

  struct TypeInfo {};

  explicit UserMessage(const TypeInfo* type_info);

  virtual ~UserMessage();

  UserMessage(const UserMessage&) = delete;

  void operator=(const UserMessage&) = delete;

  const TypeInfo* type_info() const { return type_info_; }

  // Invoked immediately before the system asks the embedder to forward this

  // message to an external node.

//

  // The UserMessageEvent is passed in to allow ports and other such values to

  // be attached to the message before it is sent externally, in case late

  // serialization is performed.

//

  // Returns |true| if the message is OK to route externally, or |false|

  // otherwise. Returning |false| implies an unrecoverable condition, and the

  // message event will be destroyed without further routing.

  virtual bool WillBeRoutedExternally(UserMessageEvent& event);

  // Returns the size in bytes of this message iff it's serialized. Zero

  // otherwise.

  virtual size_t GetSizeIfSerialized() const;

 private:

  const TypeInfo* const type_info_;

};

}  // namespace ports

}  // namespace core

}  // namespace mojo

#endif  // MOJO_CORE_PORTS_USER_MESSAGE_H_