Synnefo

from synnefo import settings

def get_available_bridge(orm):

    try:

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

        entry.available = False

        entry.save()

        return entry

    except IndexError:

        try:

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

            index = last.index + 1

        except IndexError:

            index = 1

        if index <= settings.PRIVATE_PHYSICAL_VLAN_MAX_NUMBER:

            create_bridge = orm.BridgePool.objects.create

            return create_bridge(index=index,

                                 value=value_from_index(index),

                                 available=False)

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

                        ' allocate bridge')

def value_from_index(index):

    return settings.PRIVATE_PHYSICAL_VLAN_BRIDGE_PREFIX + str(index)

                entry = get_available_bridge(orm)

                bridge = entry