etl/docs/Messaging/message-packet.md
John Wellbelove 4a88884b39
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---------

Co-authored-by: Roland Reichwein <Roland.Reichwein@bmw.de>
Co-authored-by: John Wellbelove <john.wellbelove@etlcpp.com>
Co-authored-by: John Wellbelove <john.wellbelove@etlcpp.co.uk>
2026-06-06 13:12:44 +01:00

3.6 KiB

title
message_packet

{{< callout type="info">}} Header: message_packet.h
{{< /callout >}}

A container for more than one type of message.
The messages must have been derived from etl::imessage.

The messages types that the packet may contain are listed as template parameters.
e.g. etl::message_packet<Message1, Message2, Message3>

From 20.40.0 message types are not required to have a virtual destructor.


message_packet()

Default constructs a message packet.
is_valid() returns false.


explicit message_packet(const etl::imessage&)

Constructs a message packet from an etl::imessage reference.
Asserts an etl::unhandled_message_exception error if the parameter is not one listed in the template parameter list.


explicit message_packet(etl::imessage&&) C++11

Move constructs a message packet from an etl::imessage rvalue reference.
Emits an etl::unhandled_message_exception error if the parameter is not one listed in the template parameter list.


template <typename TMessage>
explicit message_packet(const TMessage&)

Constructs a message packet from a TMessage reference. Emits a compile time static assert if the parameter is not one listed in the template parameter list.
From: 20.22.0


template <typename TMessage>
explicit message_packet(TMessage&&)

Move constructs a message packet from a TMessage rvalue reference. Emits a compile time static assert if the parameter is not one listed in the template parameter list.
From: 20.22.0


message_packet(const message_packet&)

Constructs a message packet from an message_packet reference.
Emits an etl::unhandled_message_exception error if the parameter is not one listed in the template parameter list.


message_packet(message_packet&&)

Move constructs a message packet from an message_packet rvalue reference.
Emits an etl::unhandled_message_exception if the parameter is not one listed in the template parameter list.


message_packet& operator =(const message_packet&)

Assigns a message packet from an message_packet reference.
Emits an etl::unhandled_message_exception error if the parameter is not one listed in the template parameter list.


message_packet& operator =(message_packet&&)

Move assigns a message packet from an message_packet rvalue reference.
Emits an etl::unhandled_message_exception error if the parameter is not one listed in the template parameter list.


etl::imessage& get()
const etl::imessage& get() const

Returns a reference to an etl::imessage.


bool is_valid() const

Returns true if the packet contains a valid message, otherwise false.


Constants

SIZE The size of the largest message. ALIGNMENT The largest message alignment.


Example

enum
{
  MESSAGE1,
  MESSAGE2,
  MESSAGE3
};

struct Message1 : public etl::message<MESSAGE1>
{
};

struct Message2 : public etl::message<MESSAGE2>
{
};

struct Message3 : public etl::message<MESSAGE3>
{
};

using Packet = etl::message_packet<Message1, Message2>

Message1 message1;
Message2 message2;
Message3 message3;

Packet packet1(message1);
Packet packet2(message2);
Packet packet3(message3); // Runtime time error! Packet does not support Message3 type.

etl::imessage& m1 = message1;
Packet packet4(m1); // Construct from an etl::imessage reference.

etl::imessage& m3 = message3;
Packet packet4(m3); // Asserts etl::unhandled_message_exception! Packet does not support Message3 type.

etl::imessage& m = packet2.get(); // Get a reference to an etl::imessage from the packet.