APRS-IS passcode generator

aprs-is-passcode-gen.py

#!/usr/bin/env python3

from itertools import zip_longest
from functools import reduce


def code(callsign):
  """Return APRS-IS passcode for callsign

  Based on aprsc's implementation at https://git.io/vrGXL
  """
  def xor_tuple(t1, t2):
    return (x ^ y for x, y in zip(t1, t2))

  seed = (0x73, 0xe2)
  ordinals = iter((ord(c) for c in callsign.upper()))
  iterable = zip_longest(ordinals, ordinals, fillvalue=0)
  hi_byte, lo_byte = reduce(xor_tuple, iterable, seed)

  return ((hi_byte & 0x7f) << 8) + lo_byte