def _extract_extras(env=None):

    """

    Extracts the Kallithea extras data from os.environ, and wraps it into named

    AttributeDict object

    """

    if not env:

        env = os.environ

    try:

        extras = json.loads(env['KALLITHEA_EXTRAS'])

    except KeyError:

        extras = {}

    try:

        for k in ['username', 'repository', 'locked_by', 'scm', 'make_lock',

                  'action', 'ip']:

            extras[k]

    except KeyError as e:

        raise Exception('Missing key %s in os.environ %s' % (e, extras))

    return AttributeDict(extras)

def _set_extras(extras):

    os.environ['KALLITHEA_EXTRAS'] = os.environ['RC_SCM_DATA'] = json.dumps(extras)

def unique_id(hexlen=32):

    alphabet = "23456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghjklmnpqrstuvwxyz"

    return suuid(truncate_to=hexlen, alphabet=alphabet)

def suuid(url=None, truncate_to=22, alphabet=None):

    """

    Generate and return a short URL safe UUID.

    If the url parameter is provided, set the namespace to the provided

    URL and generate a UUID.

    :param url to get the uuid for

    :truncate_to: truncate the basic 22 UUID to shorter version

    The IDs won't be universally unique any longer, but the probability of

    a collision will still be very low.

    """

    # Define our alphabet.

    _ALPHABET = alphabet or "23456789ABCDEFGHJKLMNPQRSTUVWXYZ"