+ def recv(self, segment: bytes) -> List[Union[bytes, str]]:
+ """
+ Process next segment of the stream. Return successfully deframed
+ packets as `bytes` and error messages as `str`.
+ """
+ when = time()
+ self.buffer += segment
+ if len(self.buffer) > MAXBUFFER:
+ # We are receiving junk. Let's drop it or we run out of memory.
+ self.buffer = b""
+ return [f"More than {MAXBUFFER} unparseable data, dropping"]
+ msgs: List[Union[bytes, str]] = []
+ while True:
+ framestart = self.buffer.find(b"xx")
+ if framestart == -1: # No frames, return whatever we have
+ break
+ if framestart > 0: # Should not happen, report
+ msgs.append(
+ f'Undecodable data ({framestart}) "{self.buffer[:framestart][:64].hex()}"'
+ )
+ self.buffer = self.buffer[framestart:]
+ # At this point, buffer starts with a packet
+ if len(self.buffer) < 6: # no len and proto - cannot proceed
+ break
+ exp_end = self.buffer[2] + 3 # Expect '\r\n' here
+ frameend = 0
+ # Length field can legitimeely be much less than the
+ # length of the packet (e.g. WiFi positioning), but
+ # it _should not_ be greater. Still sometimes it is.
+ # Luckily, not by too much: by maybe two or three bytes?
+ # Do this embarrassing hack to avoid accidental match
+ # of some binary data in the packet against '\r\n'.
+ while True:
+ frameend = self.buffer.find(b"\r\n", frameend + 1)
+ if frameend == -1 or frameend >= (
+ exp_end - 3
+ ): # Found realistic match or none
+ break
+ if frameend == -1: # Incomplete frame, return what we have
+ break
+ packet = self.buffer[2:frameend]
+ self.buffer = self.buffer[frameend + 2 :]
+ if len(packet) < 2: # frameend comes too early
+ msgs.append(f"Packet too short: {packet.hex()}")
+ else:
+ msgs.append(packet)
+ return msgs
+
+ def close(self) -> bytes:
+ ret = self.buffer
+ self.buffer = b""
+ return ret
+
+
+### Parser/Constructor ###
+
+
+class DecodeError(Exception):
+ def __init__(self, e: Exception, **kwargs: Any) -> None:
+ super().__init__(e)
+ for k, v in kwargs.items():
+ setattr(self, k, v)
+
+
+def maybe(typ: type) -> Callable[[Any], Any]:
+ return lambda x: None if x is None else typ(x)
+
+
+def intx(x: Union[str, int]) -> int: