def message_loop(self):
loop_start_at = datetime.now()
loop_last_print_at = datetime.now()
while True:
# Two parts to loop body: 1) look for and handle any
# incoming messages, and 2) send out any outgoing
# messages.
# Hacky flag variables to avoid spinning fast if there is
# nothing coming in and nothing going out (the common
# case...)
no_inputs = True
no_outputs = True
#
# Handle any synthetic messages and loop them back to us.
#
if not self.fake_rx_queue.empty():
no_inputs = False
msg = self.fake_rx_queue.get()
self.logger.debug("Received synthetic message")
# Don't need to confirm checksum as we computed it
# ourselves!
self.handle_message(msg)
#
# Handle incoming messages.
#
if self.serial_interface.wait_for_message_start() == MSG_START:
no_inputs = False
msg_ok = True
try:
msg = self.serial_interface.read_next_message()
except CommException, ex:
self.send_nak()
self.logger.error(repr(ex))
continue
msg_time = datetime.now()
if len(msg) < 3:
# Message too short, need at least length byte,
# command byte, and checksum byte.
self.send_nak()
self.logger.error("Message too short: %r" %
encode_message_to_ascii(msg))
if validate_message_checksum(msg):
self.send_ack()
self.handle_message(msg)
else:
# Bad checksum
self.send_nak()
self.logger.error("Bad checksum for message %r" %
encode_message_to_ascii(msg))
# TODO: check here if there is pending input and handle it
# by looping again, before worrying about sending out any
# commands.
#
# If there is a pending message awaiting ack, see if it needs
# to be resent. If there is no pending message (or the
# pending message timed-out), send what's on the transmit
# queue.
#
if self.tx_pending is not None and self.tx_timeout_exceded():
no_outputs = False
self.maybe_resend_message("timeout")
if self.tx_pending is None and not self.tx_queue.empty():
no_outputs = False
msg = self.tx_queue.get()
if msg == STOP:
# Close the serial port once all the pending
# messages have been sent. Because we close it,
# we can't rerun message_loop(); we have to create
# a new AlarmPanelInterface instance.
self.serial_interface.close()
return
self.send_message(msg)
# If there was nothing to do on this pass through the
# loop, take a nap...
if no_inputs and no_outputs:
time.sleep(self.timeout_secs)
secs_since_print = total_secs(datetime.now() - loop_last_print_at)
if secs_since_print > 20:
self.logger.debug_verbose("Looping %d" % \
total_secs(datetime.now() - loop_start_at))
loop_last_print_at = datetime.now()
def tx_timeout_exceded(self):
assert self.tx_pending is not None
elapsed = datetime.now() - self.tx_time
return total_secs(elapsed) > ACK_TIMEOUT_INBOUND