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# Copyright (c) 2015, Nordic Semiconductor
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# * Redistributions of source code must retain the above copyright notice, this
# list of conditions and the following disclaimer.
#
# * Redistributions in binary form must reproduce the above copyright notice,
# this list of conditions and the following disclaimer in the documentation
# and/or other materials provided with the distribution.
#
# * Neither the name of Nordic Semiconductor ASA nor the names of its
# contributors may be used to endorse or promote products derived from
# this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
import logging
logger = logging.getLogger(__name__)
class Slip(object):
def __init__(self):
self.SLIP_END = '\xc0'
self.SLIP_ESC = '\xdb'
self.SLIP_ESC_END = '\xdc'
self.SLIP_ESC_ESC = '\xdd'
self.started = False
self.escaped = False
self.stream = ''
self.packet = ''
def append(self, data):
"""
Append a new
:param data: Append a new block of data to do decoding on when calling decode.
The developer may add more than one SLIP packet before calling decode.
:return:
"""
self.stream += data
def decode(self):
"""
Decodes a package according to http://en.wikipedia.org/wiki/Serial_Line_Internet_Protocol
:return Slip: A list of decoded slip packets
"""
packet_list = list()
for char in self.stream:
if char == self.SLIP_END:
if self.started:
if len(self.packet) > 0:
self.started = False
packet_list.append(self.packet)
self.packet = ''
else:
self.started = True
self.packet = ''
elif char == self.SLIP_ESC:
self.escaped = True
elif char == self.SLIP_ESC_END:
if self.escaped:
self.packet += self.SLIP_END
self.escaped = False
else:
self.packet += char
elif char == self.SLIP_ESC_ESC:
if self.escaped:
self.packet += self.SLIP_ESC
self.escaped = False
else:
self.packet += char
else:
if self.escaped:
logging.error("Error in SLIP packet, ignoring error.")
self.packet = ''
self.escaped = False
else:
self.packet += char
self.stream = ''
return packet_list
def encode(self, packet):
"""
Encode a packet according to SLIP.
:param packet: A str array that represents the package
:return: str array with an encoded SLIP packet
"""
encoded = self.SLIP_END
for char in packet:
if char == self.SLIP_END:
encoded += self.SLIP_ESC + self.SLIP_ESC_END
elif char == self.SLIP_ESC:
encoded += self.SLIP_ESC + self.SLIP_ESC_ESC
else:
encoded += char
encoded += self.SLIP_END
return encoded
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