class HDLCMsgParser(MsgParser):
"""This class is responsible for taking raw serial bytes and searching them for valid SLIP messages.
Attributes:
crc: CRC calculator.
msg: Parsed HDLC message with HDLC bytes extracted.
"""
def __init__(self, config):
MsgParser.__init__(self, config)
self.crc = crcmod.mkCrcFun(0x11021,
initCrc=0xFFFF,
xorOut=0,
rev=False) # CRC-16
self.crcLength = 2
self.msg = HDLCMsg(2058)
def parseSerialMsg(self, msgBytes, msgStart):
"""Searches raw serial data for HDLC messages and then validates message integrity by comparing a computed CRC to the CRC found in the message. Valid messages are then stored for processing.
Args:
msgBytes: Raw serial data to be parsed.
msgStart: Start location to begin looking for serial message in msgBytes data array.
"""
if len(msgBytes) > 0:
# Process serial message
self.msg.decodeMsg(msgBytes, msgStart)
if self.msg.msgFound == True: # Message start found
if self.msg.msgEnd != -1: # entire msg found
# Check msg CRC
crc = self.crc(self.msg.msg[:-self.crcLength])
if self.msg.msg[-self.crcLength:] == packData(
crc,
self.crcLength): # CRC matches - valid message
#print("CRC matches")
self.parsedMsgs.append(self.msg.msg[:-self.crcLength])
return self.msg.msgEnd
else: # partial msg found
pass
else: # No message found
pass
return len(
msgBytes) # all bytes parsed so return length of input message
else:
return 0
def encodeMsg(self, msgBytes):
if msgBytes: # Add CRC
crc = self.crc(msgBytes)
msgBytes = msgBytes + packData(crc, self.crcLength)
self.msg.encodeMsg(msgBytes)
return self.msg.hdlc
return msgBytes
class TestHDLCMsg:
def setup_method(self, method):
self.hdlcMsg = HDLCMsg(256)
pass
def test_encodeMsg(self):
"""Test encodeMsg method of HDLCMsg."""
self.hdlcMsg.encodeMsg(testMsg)
assert (self.hdlcMsg.hdlc == truthHDLCMsg)
def test_decodeMsg(self):
"""Test decodeMsg method of HDLCMsg. Will also test decodeMsgContents."""
# Test clearing of partial message
self.hdlcMsg = HDLCMsg(256)
self.hdlcMsg.msgFound = True
self.hdlcMsg.msg = b'123'
self.hdlcMsg.msgEnd = 5
self.hdlcMsg.msgLength = 10
self.hdlcMsg.decodeMsg(b'12345', 0)
assert (self.hdlcMsg.msgFound == False)
assert (self.hdlcMsg.msg == b'')
assert (self.hdlcMsg.msgLength == 0)
assert (self.hdlcMsg.msgEnd == -1)
# Test decoding entire message contents
self.hdlcMsg = HDLCMsg(256)
self.hdlcMsg.encodeMsg(testMsg)
assert (self.hdlcMsg.msgEnd == -1)
self.hdlcMsg.decodeMsg(self.hdlcMsg.hdlc, 0)
assert (self.hdlcMsg.msg == testMsg) # verify message contents
assert (self.hdlcMsg.msgLength == len(testMsg)
) # verify message length
assert (self.hdlcMsg.msgEnd == len(truthHDLCMsg) - 1
) # verify message end location
# Test decoding partial message
self.hdlcMsg = HDLCMsg(256)
self.hdlcMsg.encodeMsg(testMsg)
self.hdlcMsg.decodeMsg(self.hdlcMsg.hdlc[:-1], 0)
assert (self.hdlcMsg.msgEnd == -1) # message end not found
self.hdlcMsg.decodeMsg(self.hdlcMsg.hdlc[-1:],
0) # parse remaining message
assert (self.hdlcMsg.msg == testMsg) # verify message contents
assert (self.hdlcMsg.msgLength == len(testMsg)
) # verify message length
# Test decoding partial message in middle of escape sequence
self.hdlcMsg = HDLCMsg(256)
msg = b'123' + HDLC_ESC + b'456'
self.hdlcMsg.encodeMsg(msg)
self.hdlcMsg.decodeMsg(self.hdlcMsg.hdlc[0:4],
0) # length prior to escape sequence
msgLen = self.hdlcMsg.msgLength
self.hdlcMsg.decodeMsg(self.hdlcMsg.hdlc[4:5], 0) # parse HDLC_ESC
assert (
msgLen == self.hdlcMsg.msgLength
) # message length should be unchanged until entire escape sequence read
self.hdlcMsg.decodeMsg(self.hdlcMsg.hdlc[5:6],
0) # read entire escape sequence
assert (self.hdlcMsg.msgLength == msgLen + 1)
self.hdlcMsg.decodeMsg(
self.hdlcMsg.hdlc[6:],
0) # test successful parsing of remainder of message
assert (self.hdlcMsg.msg == msg) # verify message contents
assert (self.hdlcMsg.msgLength == len(msg)) # verify message length
class TestHDLCMsg:
def setup_method(self, method):
self.hdlcMsg = HDLCMsg(256)
self.truthCRC = packData(self.hdlcMsg.crc(testMsg),
self.hdlcMsg.crcLength)
pass
def test_encodeMsg(self):
"""Test encodeMsg method of HDLCMsg."""
self.hdlcMsg.encodeMsg(testMsg)
# assert(self.hdlcMsg.encoded == truthHDLCMsg + self.truthCRC)
minLength = len(truthHDLCMsg + self.truthCRC)
assert (
len(self.hdlcMsg.encoded) >= minLength
) # length should be at least length of encoded raw bytes plus crc (could be longer if CRC included reserved bytes)
if (len(self.hdlcMsg.encoded) == minLength
): # no reserved bytes in CRC
assert (self.hdlcMsg.encoded == (truthHDLCMsg[:-1] +
self.truthCRC +
truthHDLCMsg[-1:]))
else: # CRC contained reserved bytes
assert (self.hdlcMsg.encoded[:-(self.hdlcMsg.crcLength +
1)] == truthHDLCMsg[:-1]
) # skip over CRC
assert (self.hdlcMsg.encoded[-1] == truthHDLCMsg[-1])
def test_decodeMsg(self):
"""Test decodeMsg method of HDLCMsg. Will also test decodeMsgContents."""
# Test clearing of partial message
self.hdlcMsg = HDLCMsg(256)
self.hdlcMsg.msgFound = True
self.hdlcMsg.msg = b'123'
self.hdlcMsg.msgEnd = 5
self.hdlcMsg.msgLength = 10
self.hdlcMsg.decodeMsg(b'12345', 0)
assert (self.hdlcMsg.msgFound == False)
assert (self.hdlcMsg.msg == b'')
assert (self.hdlcMsg.msgLength == 0)
assert (self.hdlcMsg.msgEnd == -1)
def test_parseMsg(self):
"""Test parseMsg method of HLDCMsg."""
self.hdlcMsg.encodeMsg(testMsg) # encode messaging for parsing
# Parse message from encoded message
parsedMsg = self.hdlcMsg.parseMsg(self.hdlcMsg.encoded, 0)
assert (parsedMsg == testMsg)
# Parse message with surrounding bytes
inputMsg = b'9876' + self.hdlcMsg.encoded + b'1234'
parsedMsg = self.hdlcMsg.parseMsg(inputMsg, 0)
assert (parsedMsg == testMsg)
# Parse partial message
self.hdlcMsg = HDLCMsg(256)
self.hdlcMsg.encodeMsg(testMsg)
self.hdlcMsg.parseMsg(self.hdlcMsg.encoded[:-1], 0)
assert (self.hdlcMsg.msgEnd == -1) # message end not found
parsedMsg = self.hdlcMsg.parseMsg(self.hdlcMsg.encoded[-1:],
0) # parse remaining message
assert (parsedMsg == testMsg) # verify message contents
assert (len(parsedMsg) == len(testMsg)) # verify message length
# Test parsing partial message in middle of escape sequence
self.hdlcMsg = HDLCMsg(256)
msg = b'123' + HDLC_ESC + b'456'
self.hdlcMsg.encodeMsg(msg)
self.hdlcMsg.parseMsg(self.hdlcMsg.encoded[0:4],
0) # length prior to escape sequence
msgLen = self.hdlcMsg.msgLength
self.hdlcMsg.parseMsg(self.hdlcMsg.encoded[4:5], 0) # parse HDLC_ESC
assert (
msgLen == self.hdlcMsg.msgLength
) # message length should be unchanged until entire escape sequence read
self.hdlcMsg.parseMsg(self.hdlcMsg.encoded[5:6],
0) # read entire escape sequence
assert (self.hdlcMsg.msgLength == msgLen + 1)
parsedMsg = self.hdlcMsg.parseMsg(
self.hdlcMsg.encoded[6:],
0) # test successful parsing of remainder of message
assert (parsedMsg == msg) # verify message contents
assert (len(parsedMsg) == len(msg)) # verify message length