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// 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_
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