Detailed Description

Message protocol handling class.

This class' purpose is to get valid messages according to its protocol from the raw data that is supplied to it. The default implementation (ProtocolHandler) implements the Xsens message protocol. To use a different protocol, overload the findMessage function.

The class is intended to be state-less with respect to the data it handles.

Definition at line 16 of file protocolhandler.h.

#include <xSens_MT4/xcommunication/include/xsens/protocolhandler.h>

Inheritance diagram for ProtocolHandler:

Public Member Functions
	ProtocolHandler ()
	Default constructor. More...

	~ProtocolHandler () override
	Destructor. More...

MessageLocation	findMessage (XsMessage &rcv, const XsByteArray &raw) const override
	Find the first message in the raw byte stream. More...

int	minimumMessageSize () const override
	Returns the minimum size of a valid message of this protocol including preambles and checksums. More...

int	maximumMessageSize () const override
	Returns the maximum size of a valid message of this protocol including preambles and checksums. More...

int	type () const override
	Returns the type of the protocol handler. More...

Static Public Member Functions
static int	composeMessage (XsByteArray &raw, const XsMessage &msg)
	Compose a message for transmission. More...

Constructor & Destructor Documentation

◆ ProtocolHandler()

ProtocolHandler::ProtocolHandler ( )

Default constructor.

Definition at line 28 of file protocolhandler.cpp.

◆ ~ProtocolHandler()

ProtocolHandler::~ProtocolHandler ( )

override

Destructor.

Definition at line 30 of file protocolhandler.cpp.

Member Function Documentation

◆ composeMessage()

int ProtocolHandler::composeMessage	(	XsByteArray &	raw,
		const XsMessage &	msg
	)

static

Compose a message for transmission.

Parameters

raw	The raw byte array to be constructed from the message
msg	The message to translate into a raw byte array

Returns: The size of the generated byte array

Todo:: Generalize this method -> IProtocolHandler

Definition at line 211 of file protocolhandler.cpp.

◆ findMessage()

MessageLocation ProtocolHandler::findMessage	(	XsMessage &	rcv,
		const XsByteArray &	raw
	)		const

overridevirtual

Find the first message in the raw byte stream.

This function scans raw for a sequence of bytes that it can convert into an XsMessage object. It returns the location and total byte size of the message so that the caller can remove those bytes from the stream. The return value can also describe that a partial message has been found. Return values:

startpos >= 0 and size > 0: A full message with size has been found at startpos.
startpos >= 0 and size == 0: The start of a message has been found at startpos, but the size could not yet be determined.
startpos >= 0 and size < 0: The start of a message has been found at startpos, and the size of the full message is at least -size.
startpos < 0: No messages have been found.

Parameters

rcv	If a message is read, it will be put in this object.
raw	The raw byte stream to analyze.

Returns: A MessageLocation object that describes what was found.

Todo:: Since the assumption is that we receive a stream of valid messages without garbage, the scan is implemented in a rather naive and simple way. If we can expect lots of garbage in the data stream, this should probably be looked into.

Implements IProtocolHandler.

Definition at line 67 of file protocolhandler.cpp.

References expectedMessageSize(), JLALERT, JLTRACE, MessageLocation::m_size, MessageLocation::m_startPos, XS_EXTLENCODE, XS_LEN_MSGEXTHEADERCS, XS_LEN_MSGHEADERCS, XS_MAXDATALEN, and XS_PREAMBLE.

Here is the call graph for this function: