Get 32 most or least significant bits of a MAC address - format a MAC address as a 32 bit integer.

mackie.py

#!/usr/bin/env python2.7
# -*- coding: utf-8 -*-

from math import floor, log


def binary_macaddress(macaddress):
    """Convert a mac address into a 48-bit integer."""
    binary = 0

    for octet in map(lambda a: int(a, 16), macaddress.split(':')):
        binary = binary << 8
        binary = binary | octet

    return binary


def get_min_bits(numb):
    """
    Returns the minimum amount of bits necessary to represent an arbitrary
    number.
    """
    return int(floor(log(numb) / log(2)))


def get_32bit_mac_left(macaddress):
    """Get the left-most 32 bits of a MAC address in constant time, baby."""
    b = binary_macaddress(macaddress)
    # shift right by 16 bits no matter what
    return b >> 16


def get_32bit_mac_right(macaddress):
    """Get the right-most 32 bits of a MAC address, still constant time."""
    b = binary_macaddress(macaddress)
    # by anding it against the max 32-bit integer, we take the 32 right-most
    # bits
    return b & (2**32 - 1)


def binfmt(v):
    return bin(v)[2:]


def zfillfmt_l(v, size=48):
    s = binfmt(v)
    return ((size - len(s)) * '0') + s


def zfillfmt_r(v, size=48):
    s = binfmt(v)
    return s + ((size - (len(s) + 1)) * '0')


def test(macaddress):
    b = binary_macaddress(macaddress)
    l = get_32bit_mac_left(macaddress)
    r = get_32bit_mac_right(macaddress)

    print("Test Case: {}".format(macaddress))
    print("--------------------------------------------------------")
    print("Binary: %048s" % (zfillfmt_l(b), ))
    print("Right:  %48s" % (zfillfmt_r(r, 32), ))
    print("Left:   %-48s" % (zfillfmt_l(l, 32), ))
    print


test("ff:ff:ff:ff:ff:ff")
test("01:23:45:67:89:ab")
test("00:00:00:00:00:00")