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#!/usr/bin/env python
"""
Helpers for the subpackage brother_ql.backends
* device discovery
* printing
"""
import logging, time
from brother_ql.backends import backend_factory, guess_backend
from brother_ql.reader import interpret_response
logger = logging.getLogger(__name__)
def discover(backend_identifier='linux_kernel'):
be = backend_factory(backend_identifier)
list_available_devices = be['list_available_devices']
BrotherQLBackend = be['backend_class']
available_devices = list_available_devices()
return available_devices
def send(instructions, printer_identifier=None, backend_identifier=None, blocking=True):
"""
Send instruction bytes to a printer.
:param bytes instructions: The instructions to be sent to the printer.
:param str printer_identifier: Identifier for the printer.
:param str backend_identifier: Can enforce the use of a specific backend.
:param bool blocking: Indicates whether the function call should block while waiting for the completion of the printing.
"""
status = {
'instructions_sent': True, # The instructions were sent to the printer.
'outcome': 'unknown', # String description of the outcome of the sending operation like: 'unknown', 'sent', 'printed', 'error'
'printer_state': None, # If the selected backend supports reading back the printer state, this key will contain it.
'did_print': False, # If True, a print was produced. It defaults to False if the outcome is uncertain (due to a backend without read-back capability).
'ready_for_next_job': False, # If True, the printer is ready to receive the next instructions. It defaults to False if the state is unknown.
}
selected_backend = None
if backend_identifier:
selected_backend = backend_identifier
else:
try:
selected_backend = guess_backend(printer_identifier)
except:
logger.info("No backend stated. Selecting the default linux_kernel backend.")
selected_backend = 'linux_kernel'
be = backend_factory(selected_backend)
list_available_devices = be['list_available_devices']
BrotherQLBackend = be['backend_class']
printer = BrotherQLBackend(printer_identifier)
start = time.time()
logger.info('Sending instructions to the printer. Total: %d bytes.', len(instructions))
printer.write(instructions)
status['outcome'] = 'sent'
if not blocking:
return status
if selected_backend == 'network':
""" No need to wait for completion. The network backend doesn't support readback. """
return status
while time.time() - start < 10:
data = printer.read()
if not data:
time.sleep(0.005)
continue
try:
result = interpret_response(data)
except ValueError:
logger.error("TIME %.3f - Couln't understand response: %s", time.time()-start, data)
continue
status['printer_state'] = result
logger.debug('TIME %.3f - result: %s', time.time()-start, result)
if result['errors']:
logger.error('Errors occured: %s', result['errors'])
status['outcome'] = 'error'
break
if result['status_type'] == 'Printing completed':
status['did_print'] = True
status['outcome'] = 'printed'
if result['status_type'] == 'Phase change' and result['phase_type'] == 'Waiting to receive':
status['ready_for_next_job'] = True
if status['did_print'] and status['ready_for_next_job']:
break
if not status['did_print']:
logger.warning("'printing completed' status not received.")
if not status['ready_for_next_job']:
logger.warning("'waiting to receive' status not received.")
if (not status['did_print']) or (not status['ready_for_next_job']):
logger.warning('Printing potentially not successful?')
if status['did_print'] and status['ready_for_next_job']:
logger.info("Printing was successful. Waiting for the next job.")
return status
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