helpers.py

import sys, os, socket, errno

logprefix = ''
verbose = 0

def log(s):
    try:
        sys.stdout.flush()
        sys.stderr.write(logprefix + s)
        sys.stderr.flush()
    except IOError:
        # this could happen if stderr gets forcibly disconnected, eg. because
        # our tty closes.  That sucks, but it's no reason to abort the program.
        pass

def debug1(s):
    if verbose >= 1:
        log(s)

def debug2(s):
    if verbose >= 2:
        log(s)

def debug3(s):
    if verbose >= 3:
        log(s)


class Fatal(Exception):
    pass


EXITCODE_NEEDS_REBOOT = 111
class FatalNeedsReboot(Fatal):
    pass


def list_contains_any(l, sub):
    for i in sub:
        if i in l:
            return True
    return False


def resolvconf_nameservers():
    l = []
    for line in open('/etc/resolv.conf'):
        words = line.lower().split()
        if len(words) >= 2 and words[0] == 'nameserver':
            l.append(words[1])
    return l


def resolvconf_random_nameserver():
    l = resolvconf_nameservers()
    if l:
        if len(l) > 1:
            # don't import this unless we really need it
            import random
            random.shuffle(l)
        return l[0]
    else:
        return '127.0.0.1'
    

def islocal(ip):
    sock = socket.socket()
    try:
        try:
            sock.bind((ip, 0))
        except socket.error, e:
            if e.args[0] == errno.EADDRNOTAVAIL:
                return False  # not a local IP
            else:
                raise
    finally:
        sock.close()
    return True  # it's a local IP, or there would have been an error


def shl(n, bits):
    # we use our own implementation of left-shift because
    # results may be different between older and newer versions
    # of python for numbers like 1<<32.  We use long() because
    # int(2**32) doesn't work in older python, which has limited
    # int sizes.
    return n * long(2**bits)