def _recv_packet(self, allow_recovery_skip=False):
buf_1 = self._link.recv(1 + protocol.LEN_FIELD_SIZE)
start_marker = buf_1[0]
packet_len = int.from_bytes(buf_1[1:], protocol.BO)
if start_marker != protocol.START_MARKER:
raise ClientError("got invalid frame (incorrect start marker)")
buf_2 = self._link.recv(packet_len + 2)
packet = buf_2[:-1]
end_marker = buf_2[-1]
if end_marker != protocol.END_MARKER:
if not allow_recovery_skip:
raise ClientError("got invalid frame (incorrect end marker)")
log.debug(
"got invalid frame (incorrect end marker), attempting recovery"
)
buf_2.extend(self._link.recv(1 + protocol.LEN_FIELD_SIZE))
si = 0
ei = len(buf_2)
expected_sub_len = protocol.LEN_FIELD_SIZE + packet_len + 3
while True:
si = buf_2.find(buf_1, si, ei)
if si < 0:
raise ClientError(
"got invalid frame and could not recover")
sub_len_diff = expected_sub_len - (len(buf_2) - si)
if sub_len_diff > 0:
buf_2.extend(self._link.recv(sub_len_diff))
if buf_2[-1] != protocol.END_MARKER:
log.debug("recovery attempt failed")
continue
packet = buf_2[si + 1 + protocol.LEN_FIELD_SIZE:-1]
break
log.warning("successfully recovered from corrupt frame")
return protocol.unpack_packet(packet)
def test_unpack_packet():
unpacked = ptcl.unpack_packet(pkd_reg_read_res_packet)
assert unpacked == unp_reg_read_res
