gps303/zmsg.py

   1 """ Zeromq messages """
   2
   3 import ipaddress as ip
   4 from struct import pack, unpack
   5
   6 __all__ = "Bcast", "Resp"
   7
   8 def pack_peer(peeraddr):
   9     saddr, port = peeraddr
  10     addr = ip.ip_address(saddr)
  11     return pack("B", addr.version) + (addr.packed + b"\0\0\0\0\0\0\0\0\0\0\0\0")[:16] + pack("!H", port)
  12
  13 def unpack_peer(buffer):
  14     version = buffer[0]
  15     if version not in (4, 6):
  16         return None
  17     if version == 4:
  18         addr = ip.IPv4Address(buffer[1:5])
  19     else:
  20         addr = ip.IPv6Address(buffer[1:17])
  21     port = unpack("!H", buffer[17:19])[0]
  22     return (addr, port)
  23
  24
  25 class _Zmsg:
  26     def __init__(self, *args, **kwargs):
  27         if len(args) == 1:
  28             self.decode(args[0])
  29         elif bool(kwargs):
  30             for k, v in self.KWARGS:
  31                 setattr(self, k, kwargs.get(k, v))
  32         else:
  33             raise RuntimeError(
  34                 self.__class__.__name__
  35                 + ": both args "
  36                 + str(args)
  37                 + " and kwargs "
  38                 + str(kwargs)
  39             )
  40
  41     def decode(self, buffer):
  42         raise RuntimeError(
  43             self.__class__.__name__ + "must implement `encode()` method"
  44         )
  45
  46     @property
  47     def packed(self):
  48         raise RuntimeError(
  49             self.__class__.__name__ + "must implement `encode()` method"
  50         )
  51
  52
  53 class Bcast(_Zmsg):
  54     """Zmq message to broadcast what was received from the terminal"""
  55
  56     KWARGS = (
  57         ("proto", 256),
  58         ("imei", None),
  59         ("when", None),
  60         ("peeraddr", None),
  61         ("packet", b""),
  62     )
  63
  64     @property
  65     def packed(self):
  66         return (
  67             pack("B", self.proto)
  68             + ("0000000000000000" if self.imei is None else self.imei).encode()
  69             + (b"\0\0\0\0\0\0\0\0" if self.when is None else pack("!d", self.when))
  70             + pack_peer(self.peeraddr)
  71             + self.packet
  72         )
  73
  74     def decode(self, buffer):
  75         self.proto = buffer[0]
  76         self.imei = buffer[1:17].decode()
  77         if self.imei == "0000000000000000":
  78             self.imei = None
  79         self.when = unpack("!d", buffer[17:25])[0]
  80         self.peeraddr = unpack_peer(buffer[25:44])
  81         self.packet = buffer[44:]
  82
  83
  84 class Resp(_Zmsg):
  85     """Zmq message received from a third party to send to the terminal"""
  86
  87     KWARGS = (("imei", None), ("packet", b""))
  88
  89     @property
  90     def packed(self):
  91         return (
  92             "0000000000000000" if self.imei is None else self.imei.encode()
  93         ) + self.packet
  94
  95     def decode(self, buffer):
  96         self.imei = buffer[:16].decode()
  97         self.packet = buffer[16:]