exit_policy.py

class MicrodescriptorExitPolicy:
  def __init__(self):
    self.ports = []
    self.policy = None
    # assume it's an accepted list of ports
    self.is_accept = True
    self.is_policy = False

  def __str__(self):
    
    if self.policy:
      return self.policy
    
    self.ports.sort()
    
    port_range = []
    start_port = self.ports[0]
    
    for id, port in enumerate(self.ports):
      if port+1 == self.ports[id+1]:
        end_port = port
      else:
        if start_port == end_port:
          port_range.append(start_port)
        else:
          port_range.append("%d-%d" % start_port, end_port)
        start_port = port+1
        
    ports = ','.join(port_range)
    
    if self.is_accept: policy = 'accept %s' % ports
    else: policy = 'reject %s' % ports
    
    if len(policy) > 1000:
      #raise PolicyLengthException
      pass
  
    # it's a policy, no more changes to the rules
    if self.is_policy:
      self.policy = policy
      
    return policy
  
  def add(self, rule):
    # it's a polciy, we can't add more rules
    if self.is_policy:
      #raise PolicyException
      pass
    
    # sanitize the input a bit, cleaning up tabs and stripping quotes
    rule = rule.replace("\\t", " ").replace("\"", "")
    
    if ',' in rule:
      self.add_policy(rule)
    else:
      self.add_rule(rule)
    
  def add_policy(self):
    self.is_policy = True
    self.is_accept = rule.startswith("accept")    
    
    # remove "accept " or "reject "
    ports = rule[7:]
    
    for ports in rule.split(','):
      if '-' in port: 
        start_port, end_port = ports.split('-', 1)
        for port in range(int(start_port), int(end_port)):
          self.ports.append(int(port))
      else:
          self.ports.append(int(ports))
          
  def add_rule(self):
    is_accept = rule.startswith("accept")
    # remove "accept " or "reject "
    rule = rule[7:]
    
    # parse 'ip:port' and 'port'
    if ':' in rule: ports = rule.split(":", 1)[1]
    else: ports = rule
    
    # last entry
    if ports is "*":
      if self.is_accept is not is_accept:
        self.is_accept = not is_accept
        self.policy = True
      else:
        # we can't have accept 80 and then accept *
        # raise PolicyException
        pass
    # it's a rule
    else:
      self.is_accept = is_accept
      self.ports.append(int(ports))