72 lines
2.7 KiB
Python
72 lines
2.7 KiB
Python
#!/usr/bin/env python
|
|
# -*- coding: utf-8 -*-
|
|
# *****************************************************************************
|
|
# This program 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 2 of the License, or (at your option) any later
|
|
# version.
|
|
#
|
|
# This program 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 program; if not, write to the Free Software Foundation, Inc.,
|
|
# 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
|
|
#
|
|
# Module authors:
|
|
# Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
|
|
#
|
|
# *****************************************************************************
|
|
"""Encoding/decoding Frames"""
|
|
|
|
from secop.protocol.framing import Framer
|
|
|
|
|
|
class RLEFramer(Framer):
|
|
data = b''
|
|
frames_to_go = 0
|
|
|
|
def encode(self, *frames):
|
|
"""add transport layer encapsulation/framing of messages"""
|
|
# format is 'number of frames:[framelengt:frme]*N'
|
|
frdata = ['%d:%s' % (len(frame), frame) for frame in frames]
|
|
return b'%d:' + b''.join(frdata)
|
|
|
|
def decode(self, data):
|
|
"""remove transport layer encapsulation/framing of messages
|
|
|
|
returns a list of messageframes which got decoded from data!
|
|
"""
|
|
self.data += data
|
|
res = []
|
|
while self.data:
|
|
if frames_to_go == 0:
|
|
if ':' in self.data:
|
|
# scan for and decode 'number of frames'
|
|
frnum, self.data = self.data.split(':', 1)
|
|
try:
|
|
self.frames_to_go = int(frnum)
|
|
except ValueError:
|
|
# can not recover, complain!
|
|
raise FramingError('invalid start of message found!')
|
|
else:
|
|
# not enough data to decode number of frames,
|
|
# return what we have
|
|
return res
|
|
while self.frames_to_go:
|
|
# there are still some (partial) frames stuck inside self.data
|
|
frlen, self.data = self.data.split(':', 1)
|
|
if len(self.data) >= frlen:
|
|
res.append(self.data[:frlen])
|
|
self.data = self.data[frlen:]
|
|
self.frames_to_go -= 1
|
|
else:
|
|
# not enough data for this frame, return what we have
|
|
return res
|
|
|
|
def reset(self):
|
|
self.data = b''
|
|
self.frames_to_go = 0
|