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#! python
#
# This module implements a special URL handler that uses the port listing to
# find ports by searching the string descriptions.
#
# This file is part of pySerial. https://github.com/pyserial/pyserial
# (C) 2011-2015 Chris Liechti <cliechti@gmx.net>
#
# SPDX-License-Identifier: BSD-3-Clause
#
# URL format: hwgrep://<regexp>&<option>
#
# where <regexp> is a Python regexp according to the re module
#
# violating the normal definition for URLs, the character `&` is used to
# separate parameters from the arguments (instead of `?`, but the question mark
# is heavily used in regexp'es)
#
# options:
# n=<N> pick the N'th entry instead of the first one (numbering starts at 1)
# skip_busy tries to open port to check if it is busy, fails on posix as ports are not locked!
from __future__ import absolute_import
import serial
import serial.tools.list_ports
try:
basestring
except NameError:
basestring = str # python 3 pylint: disable=redefined-builtin
class Serial(serial.Serial):
"""Just inherit the native Serial port implementation and patch the port property."""
# pylint: disable=no-member
@serial.Serial.port.setter
def port(self, value):
"""translate port name before storing it"""
if isinstance(value, basestring) and value.startswith('hwgrep://'):
serial.Serial.port.__set__(self, self.from_url(value))
else:
serial.Serial.port.__set__(self, value)
def from_url(self, url):
"""extract host and port from an URL string"""
if url.lower().startswith("hwgrep://"):
url = url[9:]
n = 0
test_open = False
args = url.split('&')
regexp = args.pop(0)
for arg in args:
if '=' in arg:
option, value = arg.split('=', 1)
else:
option = arg
value = None
if option == 'n':
# pick n'th element
n = int(value) - 1
if n < 1:
raise ValueError('option "n" expects a positive integer larger than 1: {!r}'.format(value))
elif option == 'skip_busy':
# open to test if port is available. not the nicest way..
test_open = True
else:
raise ValueError('unknown option: {!r}'.format(option))
# use a for loop to get the 1st element from the generator
for port, desc, hwid in sorted(serial.tools.list_ports.grep(regexp)):
if test_open:
try:
s = serial.Serial(port)
except serial.SerialException:
# it has some error, skip this one
continue
else:
s.close()
if n:
n -= 1
continue
return port
else:
raise serial.SerialException('no ports found matching regexp {!r}'.format(url))
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
if __name__ == '__main__':
s = Serial(None)
s.port = 'hwgrep://ttyS0'
print(s)
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