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kiss.py
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kiss.py
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# Copyright 2016 Daniel Estevez <[email protected]>.
#
# This is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3, or (at your option)
# any later version.
#
# This software is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this software; see the file COPYING. If not, write to
# the Free Software Foundation, Inc., 51 Franklin Street,
# Boston, MA 02110-1301, USA.
"""KISS framing library"""
__author__ = 'Daniel Estevez'
__copyright__ = 'Copyright 2016, Daniel Estevez'
__license__ = 'GPLv3'
__maintainer__ = 'Daniel Estevez'
__email__ = '[email protected]'
import collections
class KISSDeframer():
"""
Deframe a stream of bytes into KISS frames
"""
__FEND = 0xc0
__FESC = 0xdb
__TFEND = 0xdc
__TFESC = 0xdd
def __init__(self):
"""
Initialize KISS deframer
"""
self.__kiss = collections.deque()
self.__pdu = bytearray()
self.__transpose = False
def push(self, data):
"""
Push a chunk of data bytes into the deframer
Returns a list of the frames that have being
successfully deframed (in the same order as in the stream)
Args:
data (bytes): the chunk of bytes to push
"""
pdus = list()
self.__kiss.extend(data)
while self.__kiss:
c = self.__kiss.popleft()
if c == self.__FEND:
if self.__pdu and not self.__pdu[0] & 0x0f:
pdus.append(bytes(self.__pdu[1:]))
self.__pdu = bytearray()
elif self.__transpose:
if c == self.__TFEND:
self.__pdu.append(self.__FEND)
elif c == self.__TFESC:
self.__pdu.append(self.__FESC)
self.__transpose = False
elif c == self.__FESC:
self.__transpose = True
else:
self.__pdu.append(c)
return pdus