def _encode_(self, encodeValue, inProcessPacket):
"""Encodes the provided value into a signed integer fit within the specified number of bytes.
encodeValue -- the signed integer to be encoded.
"""
twosComplementRepresentation = utilities.signedIntegerToTwosComplement(encodeValue, self.bitSize) #note that function handles both pos and neg numbers.
return utilities.unsignedIntegerToBytes(twosComplementRepresentation, self.size) # convert to byte list.
def _encode_(self, encodeValue, inProcessPacket):
"""Encodes the provided value into a signed fixed-point decimal."""
bitShiftedValue = encodeValue * 2**self.fractionalBits #fixed-point encoding is as simple as left-shifting by the fractional bits.
if self.integerBits > 0: #signed value
twosComplementRepresentation = utilities.signedIntegerToTwosComplement(int(bitShiftedValue), self.bitSize) # convert to twos complement
else: #no integer bits, unsigned value
twosComplementRepresentation = bitShiftedValue
return utilities.unsignedIntegerToBytes(twosComplementRepresentation, self.size) #convert to byte list
def _encode_(self, encodeValue, inProcessPacket):
"""Returns the length of the inProcessPacket, either including or nor itself.
inProcessPacket -- contains a second-pass in-process packet whose length should be measured.
NOTES:
-Assumes that there are not multiple length tokens in a single packet.
-Because checksums are encoded last, they are not counted in the length value reported by this function.
"""
if len(inProcessPacket)>0: #an inProcess packet has been provided
#create and count a list only containing integers from the flattened inProcessPacket
length = len(list(itertools.ifilter(lambda token: type(token) == int, utilities.flattenList(inProcessPacket))))
if self.countSelf: length += 1
return utilities.unsignedIntegerToBytes(length, self.size) #convert to integer of lenth self.size
else: return self #no in-process packet has been provided.
def _encode_(self, encodeDictionary, inProcessPacket):
"""Encodes the provided inputValue into a bitfield.
encodeDictionary -- a dictionary containing bitName:bitValue pairs to encode into the bitfield
"""
outputValue = 0 #default bit field is zeroed out.
for bitName in self.bitNameBitPositionDictionary: #iterate thru stored bitfield definition
bitPosition = self.bitNameBitPositionDictionary[bitName] #get bit position
if bitName in encodeDictionary: #check if bitName is in the provided encode dictionary
bitValue = encodeDictionary[bitName] #bitName is in encodeDictionary, set bitValue from encodeDictionary
elif self.bitPositionDefaultValueDictionary[bitPosition] != None: #check if a default bit value was provided on token creation
bitValue = self.bitPositionDefaultValueDictionary[bitPosition] #Bit value not specified in input, use default value instead
else:
bitValue = False #by default set to 0
outputValue = utilities.changeBitInInteger(outputValue, bitPosition, bitValue)
return utilities.unsignedIntegerToBytes(outputValue, self.size)
def _encode_(self, encodeValue, inProcessPacket):
"""Converts an unsigned integer into a sequence of bytes.
encodeValue -- contains an unsigned integer.
"""
return utilities.unsignedIntegerToBytes(encodeValue, self.size)