gps303/zmsg.py

   1 """ Zeromq messages """
   2
   3 import ipaddress as ip
   4 from struct import pack, unpack
   5
   6 __all__ = "Bcast", "Resp", "topic"
   7
   8
   9 def pack_peer(peeraddr):
  10     try:
  11         if peeraddr is None:
  12             saddr = "::"
  13             port = 0
  14         else:
  15             saddr, port, _x, _y = peeraddr
  16         addr = ip.ip_address(saddr)
  17     except ValueError:
  18         saddr, port = peeraddr
  19         a4 = ip.ip_address(saddr)
  20         addr = ip.IPv6Address(b"\0\0\0\0\0\0\0\0\0\0\xff\xff" + a4.packed)
  21     return addr.packed + pack("!H", port)
  22
  23
  24 def unpack_peer(buffer):
  25     a6 = ip.IPv6Address(buffer[:16])
  26     port = unpack("!H", buffer[16:])[0]
  27     addr = a6.ipv4_mapped
  28     if addr is None:
  29         addr = a6
  30     return (addr, port)
  31
  32
  33 class _Zmsg:
  34     def __init__(self, *args, **kwargs):
  35         if len(args) == 1:
  36             self.decode(args[0])
  37         elif bool(kwargs):
  38             for k, v in self.KWARGS:
  39                 setattr(self, k, kwargs.get(k, v))
  40         else:
  41             raise RuntimeError(
  42                 self.__class__.__name__
  43                 + ": both args "
  44                 + str(args)
  45                 + " and kwargs "
  46                 + str(kwargs)
  47             )
  48
  49     def __repr__(self):
  50         return "{}({})".format(
  51             self.__class__.__name__,
  52             ", ".join(
  53                 [
  54                     "{}={}".format(
  55                         k,
  56                         'bytes.fromhex("{}")'.format(getattr(self, k).hex())
  57                         if isinstance(getattr(self, k), bytes)
  58                         else getattr(self, k),
  59                     )
  60                     for k, _ in self.KWARGS
  61                 ]
  62             ),
  63         )
  64
  65     def __eq__(self, other):
  66         return all(
  67             [getattr(self, k) == getattr(other, k) for k, _ in self.KWARGS]
  68         )
  69
  70     def decode(self, buffer):
  71         raise NotImplementedError(
  72             self.__class__.__name__ + "must implement `decode()` method"
  73         )
  74
  75     @property
  76     def packed(self):
  77         raise NotImplementedError(
  78             self.__class__.__name__ + "must implement `packed()` property"
  79         )
  80
  81
  82 def topic(proto, is_incoming=True, imei=None):
  83     return (
  84         pack("BB", is_incoming, proto) + b"" if imei is None else imei.encode()
  85     )
  86
  87
  88 class Bcast(_Zmsg):
  89     """Zmq message to broadcast what was received from the terminal"""
  90
  91     KWARGS = (
  92         ("is_incoming", True),
  93         ("proto", 256),
  94         ("imei", None),
  95         ("when", None),
  96         ("peeraddr", None),
  97         ("packet", b""),
  98     )
  99
 100     @property
 101     def packed(self):
 102         return (
 103             pack("BB", int(self.is_incoming), self.proto)
 104             + ("0000000000000000" if self.imei is None else self.imei).encode()
 105             + (
 106                 b"\0\0\0\0\0\0\0\0"
 107                 if self.when is None
 108                 else pack("!d", self.when)
 109             )
 110             + pack_peer(self.peeraddr)
 111             + self.packet
 112         )
 113
 114     def decode(self, buffer):
 115         self.is_incoming = bool(buffer[0])
 116         self.proto = buffer[1]
 117         self.imei = buffer[2:18].decode()
 118         if self.imei == "0000000000000000":
 119             self.imei = None
 120         self.when = unpack("!d", buffer[18:26])[0]
 121         self.peeraddr = unpack_peer(buffer[26:44])
 122         self.packet = buffer[44:]
 123
 124
 125 class Resp(_Zmsg):
 126     """Zmq message received from a third party to send to the terminal"""
 127
 128     KWARGS = (("imei", None), ("when", None), ("packet", b""))
 129
 130     @property
 131     def packed(self):
 132         return (
 133             ("0000000000000000" if self.imei is None else self.imei.encode())
 134             + (
 135                 b"\0\0\0\0\0\0\0\0"
 136                 if self.when is None
 137                 else pack("!d", self.when)
 138             )
 139             + self.packet
 140         )
 141
 142     def decode(self, buffer):
 143         self.imei = buffer[:16].decode()
 144         self.when = unpack("!d", buffer[16:24])[0]
 145         self.packet = buffer[24:]