bus::IBusMessage Class Reference

Abstract base class representing a generic bus message. More...

#include "bus/ibusmessage.h"

Inheritance diagram for bus::IBusMessage:

Public Member Functions
	IBusMessage (BusMessageType type)
virtual void	ToRaw (std::vector< uint8_t > &dest) const
	Serialize the message.
virtual void	FromRaw (const std::vector< uint8_t > &source)
	Deserialize the message.
BusMessageType	Type () const
	Returns type of message.
void	Version (uint16_t version)
	Sets the vewrsion number for a message.
uint16_t	Version () const
	Returns the version number of the message.
uint32_t	Size () const
	Returns the total size of the message.
bool	Valid () const
	Returns true if the message is valid.
void	Timestamp (uint64_t timestamp)
	Sets the absolute time.
uint64_t	Timestamp () const
	Retuns the timestampe.
void	BusChannel (uint16_t channel)
	Sets the source channel.
uint16_t	BusChannel () const
	Returns the bus channel number.

Static Public Member Functions
static std::shared_ptr< IBusMessage >	Create (BusMessageType type)
	Creates a message by its type.

Protected Member Functions
void	Size (uint32_t size) const
	Sets the total size of the message.
void	Valid (bool valid) const
	Sets the message valid or invalid.

Detailed Description

This abstract base class is used to implement generic bus messages. A message must have a specific type and a version. The type and version, defines how the message is serialized. The serialization are done with the ToRaw() and FromRaw() functions. These functions are abstract and have to be implemented by the derived class.

The serialization of a bus message have a header which has the same length. The header is according to table below and uses little endian byte order.

Bus Message Header

Byte (Bits) Offset	Description	Size
0	Type of Message (enumerate)	uint16_t
2	Version Number	uint16_t
4	Length of the message	uint32_t
8	Timestamp ns since 1970	uint64_t
16	Bus Channel	uint16_t

Constructor & Destructor Documentation

IBusMessage()

bus::IBusMessage::IBusMessage ( BusMessageType type )

explicit

Contructor that creates a type of message.

This constructor should not be used by end-user but it is used for testing purpose.

Parameters

type	Type of message

Member Function Documentation

BusChannel() [1/2]

uint16_t bus::IBusMessage::BusChannel ( ) const

inlinenodiscard

The bus channel is a number that defines the source of the message. The source is typical a physical driver channel and not defining any ECU device.

Note that many manufactures of CAN communication cards, name the first channel as 'Channel 1' but uses channel 0 in its software. This causes a lot of problems and it doesn't help that the channel number randomly changes between computer restarts. It is recommended to start the channel number at 1 and assign the first channel, the 'Channel 1' name. The channel name should be assoiated with the device driver serial number instead of its internal channel number.

Returns

Bus channel number.

BusChannel() [2/2]

void bus::IBusMessage::BusChannel ( uint16_t channel )

inline

The bus channel is a number that defines the source of the message. The source is typical a physical driver channel and not defining any ECU device.

Note that many manufactures of CAN communication card, name the first channel as 'Channel 1' but uses channel 0 in its software. This causes a lot of problems and it doesn't help that the channel number randomly changes between computer restarts. It is recommended to start the channel number at 1 and assign the first channel, the 'Channel 1' name. The channel name should be assoiated with the device driver serial number instead of its internal channel number.

Parameters

channel

Bus channel number.

Create()

std::shared_ptr< IBusMessage > bus::IBusMessage::Create ( BusMessageType type )

static

Creates a message by its type. This fucntion is used by subscriber when deserialize a message.

Parameters

type	Type of message.

Returns

Smart pointer to IBussMessage object.

FromRaw()

virtual void bus::IBusMessage::FromRaw ( const std::vector< uint8_t > & source )

virtual

This function desrialize a message from an byte array.

Parameters

source

Source buffer.

Reimplemented in bus::CanDataFrame.

Size() [1/2]

uint32_t bus::IBusMessage::Size ( ) const

inlinenodiscard

The function return number of total message bytes, not the paylod data size.

Returns

Number of total message bytes.

Size() [2/2]

void bus::IBusMessage::Size ( uint32_t size ) const

inlineprotected

This function set the messsage size when serialize and deserialize the message.

Parameters

size	Message size (butes).

Timestamp() [1/2]

uint64_t bus::IBusMessage::Timestamp ( ) const

inlinenodiscard

The timestamp is defined as nanoseconds since midnight 1970-01-01. The timezone is always UTC.

Returns

Time since 1970.

Timestamp() [2/2]

void bus::IBusMessage::Timestamp ( uint64_t timestamp )

inline

Sets the timestamp for the message. The time is number of nanoseconds from midnight 1970-01-01. The timezone is always UTC.

Parameters

timestamp

Nanoseconds sinncs 1970.

ToRaw()

virtual void bus::IBusMessage::ToRaw ( std::vector< uint8_t > & dest ) const

virtual

The function serialize a message to a byte array. This array is later used by the communication interfaces for transfer the message in shared ememroy or TCP/IP. The destination array is sized by the function.

Parameters

dest	Destination buffer.

Reimplemented in bus::CanDataFrame.

Type()

BusMessageType bus::IBusMessage::Type ( ) const

inlinenodiscard

Returns

Type of message.

Valid() [1/2]

bool bus::IBusMessage::Valid ( ) const

inlinenodiscard

The message can be set invalid if the serialization or deserialization fails. olle

Returns

True if the message is valid.

Valid() [2/2]

void bus::IBusMessage::Valid ( bool valid ) const

inlineprotected

Sets the message valid or invalid. By default the message is set valid (true).

Parameters

valid

Valid is true while invalid is false.

Version() [1/2]

uint16_t bus::IBusMessage::Version ( ) const

inlinenodiscard

Rarely used function but used by the serialization and deserialization functions.

Returns

Version number.

Version() [2/2]

void bus::IBusMessage::Version ( uint16_t version )

inline

This function should rarely be used but defines the version of the message. This is used by the serialization and deserialization functions. The version is changed when properties are added.

Parameters

version

Version number.

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The documentation for this class was generated from the following file:

• include/bus/ibusmessage.h