def openSubscribeEvent(subtype, event):
    """
    Return details from a subscribe event, or None if it is not a subscribe event.

    'subtype' is a function that tests if the supplied event type is a 
    subscription event type.
    
    Returns a list: [subscribe event type, 
                     subscriber URI, 
                     interval, subscribed event type, subscribed event source]
    
    For unsubscribe, interval=0
    """
    if subtype(event.getType()):
        evsrc = event.getSource()
        evsub = event.getPayload()
        if evsub != None: return [event.getType(),evsrc]+evsub
    return None