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Filename : debconf.py
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# Copyright:
#   Moshe Zadka (c) 2002
#   Canonical Ltd. (c) 2005 (DebconfCommunicator)
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
# 
# THIS SOFTWARE IS PROVIDED BY AUTHORS AND CONTRIBUTORS ``AS IS'' AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.

from __future__ import print_function

import sys, os
import errno
import re
import subprocess
import fcntl

class DebconfError(Exception):
    pass

LOW, MEDIUM, HIGH, CRITICAL = 'low', 'medium', 'high', 'critical'

class Debconf:

    def __init__(self, title=None, read=None, write=None):
        for command in ('capb set reset title input beginblock endblock go get'
                        ' register unregister subst fset fget previous_module'
                        ' visible purge metaget exist version settitle'
                        ' info progress data').split():
            self.setCommand(command)
        self.read = read or sys.stdin
        self.write = write or sys.stdout
        sys.stdout = sys.stderr
        self.setUp(title)

    def setUp(self, title):
        self.version = self.version(2)
        if self.version[:2] != '2.':
            raise DebconfError(256, "wrong version: %s" % self.version)
        self.capabilities = self.capb().split()
        if title:
            self.title(title)

    def setCommand(self, command):
        setattr(self, command,
               lambda *args, **kw: self.command(command, *args, **kw))

    def command(self, command, *params):
        command = command.upper()
        self.write.write("%s %s\n" % (command, ' '.join(map(str, params))))
        self.write.flush()

        while True:
            try:
                resp = self.read.readline().rstrip('\n')
                break
            except IOError as e:
                if e.errno == errno.EINTR:
                    continue
                else:
                    raise

        if ' ' in resp:
            status, data = resp.split(' ', 1)
        else:
            status, data = resp, ''
        status = int(status)
        if status == 0:
            return data
        elif status == 1:   # unescaped data
            unescaped = ''
            for chunk in re.split(r'(\\.)', data):
                if chunk.startswith('\\') and len(chunk) == 2:
                    if chunk[1] == 'n':
                        unescaped += '\n'
                    else:
                        unescaped += chunk[1]
                else:
                    unescaped += chunk
            return unescaped
        else:
            raise DebconfError(status, data)

    def stop(self):
        self.write.write('STOP\n')
        self.write.flush()

    def forceInput(self, priority, question):
        try:
            self.input(priority, question)
            return 1
        except DebconfError as e:
            if e.args[0] != 30:
                raise
        return 0

    def getBoolean(self, question):
        result = self.get(question)
        return result == 'true'

    def getString(self, question):
        return self.get(question)


class DebconfCommunicator(Debconf, object):
    def __init__(self, owner, title=None, cloexec=False):
        args = ['debconf-communicate', '-fnoninteractive', owner]
        self.dccomm = subprocess.Popen(
            args, stdin=subprocess.PIPE, stdout=subprocess.PIPE,
            close_fds=True, universal_newlines=True)
        super(DebconfCommunicator, self).__init__(title=title,
                                                  read=self.dccomm.stdout,
                                                  write=self.dccomm.stdin)
        if cloexec:
            fcntl.fcntl(self.read.fileno(), fcntl.F_SETFD, fcntl.FD_CLOEXEC)
            fcntl.fcntl(self.write.fileno(), fcntl.F_SETFD, fcntl.FD_CLOEXEC)

    def shutdown(self):
        if self.dccomm is not None:
            self.dccomm.stdin.close()
            self.dccomm.stdout.close()
            self.dccomm.wait()
            self.dccomm = None

    # Don't rely on this; call .shutdown() explicitly.
    def __del__(self):
        try:
            self.shutdown()
        except AttributeError:
            pass


if ('DEBCONF_USE_CDEBCONF' in os.environ and
    os.environ['DEBCONF_USE_CDEBCONF'] != ''):
    _frontEndProgram = '/usr/lib/cdebconf/debconf'
else:
    _frontEndProgram = '/usr/share/debconf/frontend'

def runFrontEnd():
    if 'DEBIAN_HAS_FRONTEND' not in os.environ:
        os.environ['PERL_DL_NONLAZY']='1'
        os.execv(_frontEndProgram, [_frontEndProgram, sys.executable]+sys.argv)


if __name__ == '__main__':
    runFrontEnd()
    db = Debconf()
    db.forceInput(CRITICAL, 'bsdmainutils/calendar_lib_is_not_empty')
    db.go()
    less = db.getBoolean('less/add_mime_handler')
    aptlc = db.getString('apt-listchanges/email-address')
    db.stop()
    print(db.version)
    print(db.capabilities)
    print(less)
    print(aptlc)