Synnefo

from synnefo import settings

def get_available_mac_prefix(orm):

    try:

        entry = orm.MacPrefixPool.objects.filter(available=True)[0]

        entry.available = False

        entry.save()

        return entry

    except IndexError:

        try:

            last = orm.MacPrefixPool.objects.order_by('-index')[0]

            index = last.index + 1

        except IndexError:

            index = 1

        if index <= settings.MAC_POOL_LIMIT:

            create_mac_prefix = orm.MacPrefixPool.objects.create

            return create_mac_prefix(index=index,

                                 value=value_from_index(index),

                                 available=False)

        raise Exception('Pool of mac_prefixes exhausted. Can not'

                        ' allocate mac_prefix.')

def value_from_index(index):

    """Convert number to mac prefix

    """

    base = settings.MAC_POOL_BASE

    a = hex(int(base.replace(":", ""), 16) + index).replace("0x", '')

    mac_prefix = ":".join([a[x:x + 2] for x in xrange(0, len(a), 2)])

    return mac_prefix

                network.mac_prefix = settings.MAC_POOL_BASE

                mac_prefix = get_available_mac_prefix(orm)

                network.mac_prefix = mac_prefix.value