############################################################################
# #
# Copyright (c) 2017 eBay Inc. #
# Modifications copyright (c) 2019 Carl Drougge #
# #
# Licensed under the Apache License, Version 2.0 (the "License"); #
# you may not use this file except in compliance with the License. #
# You may obtain a copy of the License at #
# #
# http://www.apache.org/licenses/LICENSE-2.0 #
# #
# Unless required by applicable law or agreed to in writing, software #
# distributed under the License is distributed on an "AS IS" BASIS, #
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. #
# See the License for the specific language governing permissions and #
# limitations under the License. #
# #
############################################################################
# workarounds for sadnesses
import os
import signal
import termios
import fcntl
import atexit
from contextlib import contextmanager
class SignalWrapper(object):
"""Some misguided kernels (like Linux) feel that SIGINFO is not needed.
Perhapt some other kernels feel similarly about other signals?"""
def __init__(self, signal_names=['SIGINFO'], key_values=[20], skip_input_if_possible=True):
"""signal_names is a list of signal names, which will be listened for if they exist.
key_values is a list of (terminal input) key values, each will
be considered equivalent of a signal if pressed.
If skip_input_if_possible is True no input will be read if all signals exist.
No differentiation is made between the signals."""
self.key_values = set(key_values)
self.restore = {}
self.signal_set = False
self.clean = False
self.use_input = False
all_sigs = True
atexit.register(self.cleanup)
for name in signal_names:
sig = getattr(signal, name, None)
if sig is not None:
old = signal.signal(sig, self.signal_arrived)
self.restore[sig] = old
signal.siginterrupt(sig, False)
else:
all_sigs = False
if all_sigs and skip_input_if_possible:
return
self.tc_original = termios.tcgetattr(0)
tc_changed = list(self.tc_original)
tc_changed[3] &= ~(termios.ICANON | termios.IEXTEN)
self.use_input = True
termios.tcsetattr(0, termios.TCSADRAIN, tc_changed)
def cleanup(self):
if not self.clean:
for sig, old in self.restore.items():
if old is None:
old = signal.SIG_DFL
signal.signal(sig, old)
if self.use_input:
termios.tcsetattr(0, termios.TCSADRAIN, self.tc_original)
self.clean = True
def check(self):
if self.use_input:
with nonblocking(0):
while True:
try:
if ord(os.read(0, 1)) in self.key_values:
self.signal_set = True
except OSError:
break
if self.signal_set:
self.signal_set = False
return True
else:
return False
def signal_arrived(self, sig, frame):
self.signal_set = True
@contextmanager
def nonblocking(fd):
fl_original = fcntl.fcntl(fd, fcntl.F_GETFL)
fl_changed = fl_original | os.O_NONBLOCK
fcntl.fcntl(fd, fcntl.F_SETFL, fl_changed)
try:
yield
finally:
fcntl.fcntl(fd, fcntl.F_SETFL, fl_original)
