mdw@git.distorted.org.uk Git - hippotat/blob - hippotatlib/slip.py

   1 # SLIP handling
   2
   3 end = b'\300'
   4 esc = b'\333'
   5 esc_end = b'\334'
   6 esc_esc = b'\335'
   7 delimiter = end
   8
   9 def encode(packet):
  10   return (packet
  11           .replace(esc, esc + esc_esc)
  12           .replace(end, esc + esc_end))
  13
  14 def decode(data, keep_tail=False):
  15   #print('DECODE ', repr(data))
  16   out = []
  17   inp = data.split(end)
  18   tail = []
  19   if keep_tail:
  20     tail.append(inp.pop())
  21   for packet in inp:
  22     pdata = b''
  23     while True:
  24       eix = packet.find(esc)
  25       if eix == -1:
  26         pdata += packet
  27         break
  28       #print('ESC ', repr((pdata, packet, eix)))
  29       pdata += packet[0 : eix]
  30       ck = packet[eix+1]
  31       #print('ESC... %o' % ck)
  32       if   ck == esc_esc[0]: pdata += esc
  33       elif ck == esc_end[0]: pdata += end
  34       else: raise ValueError('invalid SLIP escape 0%o %#x' % (ck, ck))
  35       packet = packet[eix+2 : ]
  36     out.append(pdata)
  37   #print('DECODED ', repr(out))
  38   out += tail
  39   return out
  40 # -*- python -*-
  41