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#!/usr/bin/python3
#
# Copyright (C) 2018 Canonical, Ltd.
# Author: Mathieu Trudel-Lapierre <[email protected]>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; version 3.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
"""
Terminal / input handling
"""
import fcntl
import os
import termios
import select
import sys
class Terminal(object):
"""
Do minimal terminal mangling to prompt users for input
"""
def __init__(self, fd):
self.fd = fd
self.orig_flags = None
self.orig_term = None
self.save()
def enable_echo(self):
if sys.stdin.isatty():
attrs = termios.tcgetattr(self.fd)
attrs[3] = attrs[3] | termios.ICANON
attrs[3] = attrs[3] | termios.ECHO
termios.tcsetattr(self.fd, termios.TCSANOW, attrs)
def disable_echo(self):
if sys.stdin.isatty():
attrs = termios.tcgetattr(self.fd)
attrs[3] = attrs[3] & ~termios.ICANON
attrs[3] = attrs[3] & ~termios.ECHO
termios.tcsetattr(self.fd, termios.TCSANOW, attrs)
def enable_nonblocking_io(self):
flags = fcntl.fcntl(self.fd, fcntl.F_GETFL)
fcntl.fcntl(self.fd, fcntl.F_SETFL, flags | os.O_NONBLOCK)
def disable_nonblocking_io(self):
flags = fcntl.fcntl(self.fd, fcntl.F_GETFL)
fcntl.fcntl(self.fd, fcntl.F_SETFL, flags & ~os.O_NONBLOCK)
def get_confirmation_input(self, timeout=120, message=None): # pragma: nocover (requires user input)
"""
Get a "confirmation" input from the user, for at most (timeout)
seconds. Optionally, customize the message to be displayed.
timeout -- timeout to wait for input (default 120)
message -- optional customized message ("Press ENTER to (message)")
raises:
InputAccepted -- the user confirmed the changes
InputRejected -- the user rejected the changes
"""
print("Do you want to keep these settings?\n\n")
settings = dict()
self.save(settings)
self.disable_echo()
self.enable_nonblocking_io()
if not message:
message = "accept the new configuration"
print("Press ENTER before the timeout to {}\n\n".format(message))
timeout_now = timeout
while (timeout_now > 0):
print("Changes will revert in {:>{}} seconds".format(timeout_now, len(str(timeout))), end='\r')
# wait at most 1 second for usable input from stdin
select.select([sys.stdin], [], [], 1)
try:
# retrieve any input from the terminal. select() either has
# timed out with no input, or found something we can retrieve.
c = sys.stdin.read()
if (c == '\n'):
self.reset(settings)
# Yay, user has accepted the changes!
raise InputAccepted()
except TypeError:
# read() above is non-blocking, if there is nothing to read it
# will return TypeError, which we should ignore -- on to the
# next iteration until timeout.
pass
timeout_now -= 1
# We reached the timeout for our loop, now revert our change for
# non-blocking I/O and signal the caller the changes were essentially
# rejected.
self.reset(settings)
raise InputRejected()
def save(self, dest=None):
"""
Save the terminal's current attributes and flags
Optional argument:
- dest: if set, save settings to this dict
"""
orig_flags = fcntl.fcntl(self.fd, fcntl.F_GETFL)
orig_term = None
if sys.stdin.isatty():
orig_term = termios.tcgetattr(self.fd)
if dest is not None:
dest.update({'flags': orig_flags,
'term': orig_term})
else:
self.orig_flags = orig_flags
self.orig_term = orig_term
def reset(self, orig=None):
"""
Reset the terminal to its original attributes and flags
Optional argument:
- orig: if set, reset to settings from this dict
"""
orig_term = None
orig_flags = None
if orig is not None:
orig_term = orig.get('term')
orig_flags = orig.get('flags')
else:
orig_term = self.orig_term
orig_flags = self.orig_flags
if sys.stdin.isatty():
termios.tcsetattr(self.fd, termios.TCSAFLUSH, orig_term)
fcntl.fcntl(self.fd, fcntl.F_SETFL, orig_flags)
class InputAccepted(Exception):
""" Denotes has accepted input"""
pass
class InputRejected(Exception):
""" Denotes that the user has rejected input"""
pass
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