text: # Copyright (C) 2003-2007, 2009-2011 Nominum, Inc.
  #
  # Permission to use, copy, modify, and distribute this software and its
  # documentation for any purpose with or without fee is hereby granted,
  # provided that the above copyright notice and this permission notice
  # appear in all copies.
  #
  # THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
  # WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  # MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
  # ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  # WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  # ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
  # OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  
  import struct
  import binascii
  
  import dns.exception
  import dns.inet
  import dns.rdata
  import dns.tokenizer
  from dns._compat import xrange
  
  
  class APLItem(object):
  
      """An APL list item.
  
      @ivar family: the address family (IANA address family registry)
      @type family: int
      @ivar negation: is this item negated?
      @type negation: bool
      @ivar address: the address
      @type address: string
      @ivar prefix: the prefix length
      @type prefix: int
      """
  
      __slots__ = ['family', 'negation', 'address', 'prefix']
  
      def __init__(self, family, negation, address, prefix):
          self.family = family
          self.negation = negation
          self.address = address
          self.prefix = prefix
  
      def __str__(self):
          if self.negation:
              return "!%d:%s/%s" % (self.family, self.address, self.prefix)
          else:
              return "%d:%s/%s" % (self.family, self.address, self.prefix)
  
      def to_wire(self, file):
          if self.family == 1:
              address = dns.inet.inet_pton(dns.inet.AF_INET, self.address)
          elif self.family == 2:
              address = dns.inet.inet_pton(dns.inet.AF_INET6, self.address)
          else:
              address = binascii.unhexlify(self.address)
          #
          # Truncate least significant zero bytes.
          #
          last = 0
          for i in xrange(len(address) - 1, -1, -1):
              if address[i] != chr(0):
                  last = i + 1
                  break
          address = address[0: last]
          l = len(address)
          assert l < 128
          if self.negation:
              l |= 0x80
          header = struct.pack('!HBB', self.family, self.prefix, l)
          file.write(header)
          file.write(address)
  
  
  class APL(dns.rdata.Rdata):
  
      """APL record.
  
      @ivar items: a list of APL items
      @type items: list of APL_Item
      @see: RFC 3123"""
  
      __slots__ = ['items']
  
      def __init__(self, rdclass, rdtype, items):
          super(APL, self).__init__(rdclass, rdtype)
          self.items = items
  
      def to_text(self, origin=None, relativize=True, **kw):
          return ' '.join(map(str, self.items))
  
      @classmethod
      def from_text(cls, rdclass, rdtype, tok, origin=None, relativize=True):
          items = []
          while 1:
              token = tok.get().unescape()
              if token.is_eol_or_eof():
                  break
              item = token.value
              if item[0] == '!':
                  negation = True
                  item = item[1:]
              else:
                  negation = False
              (family, rest) = item.split(':', 1)
              family = int(family)
              (address, prefix) = rest.split('/', 1)
              prefix = int(prefix)
              item = APLItem(family, negation, address, prefix)
              items.append(item)
  
          return cls(rdclass, rdtype, items)
  
      def to_wire(self, file, compress=None, origin=None):
          for item in self.items:
              item.to_wire(file)
  
      @classmethod
      def from_wire(cls, rdclass, rdtype, wire, current, rdlen, origin=None):
          items = []
          while 1:
              if rdlen == 0:
                  break
              if rdlen < 4:
                  raise dns.exception.FormError
              header = struct.unpack('!HBB', wire[current: current + 4])
              afdlen = header[2]
              if afdlen > 127:
                  negation = True
                  afdlen -= 128
              else:
                  negation = False
              current += 4
              rdlen -= 4
              if rdlen < afdlen:
                  raise dns.exception.FormError
              address = wire[current: current + afdlen].unwrap()
              l = len(address)
              if header[0] == 1:
                  if l < 4:
                      address += '\x00' * (4 - l)
                  address = dns.inet.inet_ntop(dns.inet.AF_INET, address)
              elif header[0] == 2:
                  if l < 16:
                      address += '\x00' * (16 - l)
                  address = dns.inet.inet_ntop(dns.inet.AF_INET6, address)
              else:
                  #
                  # This isn't really right according to the RFC, but it
                  # seems better than throwing an exception
                  #
                  address = address.encode('hex_codec')
              current += afdlen
              rdlen -= afdlen
              item = APLItem(header[0], negation, address, header[1])
              items.append(item)
          return cls(rdclass, rdtype, items)
  