190 lines
6.2 KiB
Python
190 lines
6.2 KiB
Python
"""
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A collection of Printers.
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It has methods to discover printers, and provides an interface for
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the methods expected from printers.
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"""
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from collections.abc import Set
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import time
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import threading
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import usb.core
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import usb.util
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from printer import Printer, EscPosPrinter, BrotherPrinter
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class Printers:
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"""
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Finds and creates a set of Printer that can be used by the Workers to print.
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"""
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def __init__(self, app):
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"""
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Discovers printers connected to the computer
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"""
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self.app = app
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self.printers = list(self._discover_printers())
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self._lock = threading.Lock()
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def _discover_printers(self) -> Set[Printer]:
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"""
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Gets connected USB printer devices using the pyusb library.
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We analyse the USB devices, get the ones that match
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the printer class ( 7 ) and for Brother and EPSON printers,
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try to create a Printer object that can be used by the Worker class
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to execute prints.
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Returns a set of Printer
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"""
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self.app.logger.debug("Discovering USB Devices connected to this system")
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printers = set()
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# TODO : this could go in the config ?
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waiting_time_for_printer = 5
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while True:
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# Find all connected USB devices
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# the find() fnc returns a generator
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devices = list(
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usb.core.find(
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find_all=True,
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custom_match=_FindClass(self.app,7)
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)
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)
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if devices:
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break
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if waiting_time_for_printer <= 0:
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self.app.logger.warning(
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"No USB devices of class 7 ( printers ) found or pyusb could not access the bus."
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)
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raise RuntimeError(
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"No USB devices of class 7 ( printers ) found or pyusb could not access the bus."
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)
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self.app.logger.warning(
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"No printers found; waiting for a printer to connect..."
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)
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time.sleep(1)
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waiting_time_for_printer -= 1
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for dev in devices:
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# Attempt to get the manufacturer and product strings
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try:
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manufacturer = usb.util.get_string(dev, dev.iManufacturer)
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except Exception:
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manufacturer = "Unknown"
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try:
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product = usb.util.get_string(dev, dev.iProduct)
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except Exception:
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product = "Unknown"
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self.app.logger.debug(
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"Looking at %s %s (%s:%s)",
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manufacturer,
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product,
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hex(dev.idVendor),
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hex(dev.idProduct),
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)
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if manufacturer == "EPSON":
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try:
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# We create a new EscPosPrinter()
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self.app.logger.debug("Trying to create a new EPSON printer")
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prid = dev.idProduct
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vendir = dev.idVendor
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escpos_printer = EscPosPrinter(
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self.app, vendor_id=vendir, device_id=prid
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)
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except Exception as e:
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raise e
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# If the object creation is successfull, we add it to the list of Printers
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printers.add(escpos_printer)
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self.app.logger.debug("Found a %s printer", manufacturer)
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# We already found the type of printer,
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# we don't need an extra comparaison.
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continue
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# or a Brother Printer
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if manufacturer == "Brother":
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try:
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# We create a new BrotherPrinter()
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self.app.logger.debug("Trying to create a new BROTHER printer")
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brother_printer = BrotherPrinter(
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self.app, vendor_id=dev.idVendor, device_id=dev.idProduct)
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except Exception as e:
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self.app.logger.error(
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"Could not create a %s printer class with %s:%s" , product,
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dev.idVendor,
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dev.idProduct,
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)
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raise e
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# If the object creation is successfull, we add it to the list of Printers
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printers.add(brother_printer)
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self.app.logger.debug("Found a %s printer" , manufacturer)
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self.app.logger.debug("Found %s printers" , len(printers))
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if len(printers) < 1:
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self.app.logger.warning("Not printers found ! Please plug in a Printer and restart the program.")
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raise RuntimeError("No printers found")
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return printers
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def acquire_available_printer(self, start_index=0):
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"""Atomically acquire and return an available printer, or None."""
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printers = self.printers
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if not printers:
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self.app.logger.error("No printers available for acquisition")
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return None
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with self._lock:
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for offset in range(len(printers)):
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index = (start_index + offset) % len(printers)
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printer = printers[index]
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if not printer.used:
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printer.use_printer()
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return index, printer
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return None
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def printers_info(self):
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"""Return the current list of printers"""
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return self.printers
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class _FindClass:
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"""
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Use by usb.core to modify the way USB devices are found
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Taken from pyUSB documentation on Github
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"""
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def __init__(self, app, class_):
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self._class = class_
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self.app = app
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def __call__(self, device):
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# first, let's check the device
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self.app.logger.debug("Found a USB device of class %s", str(device.bDeviceClass))
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if device.bDeviceClass == self._class:
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return True
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# ok, transverse all devices to find an
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# interface that matches our class
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for configuration in device:
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# Every device can have one or more configuration,
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interface = usb.util.find_descriptor(configuration, bInterfaceClass=self._class)
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# each config can have several interfaces
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if interface is not None:
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return True
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return False
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