source: TI12-security/trunk/NDG_XACML/ndg/xacml/core/__init__.py @ 6747

"""NDG XACML core package 

NERC DataGrid Project
"""
__author__ = "P J Kershaw"
__date__ = "16/03/10"
__copyright__ = "(C) 2010 Science and Technology Facilities Council"
__contact__ = "Philip.Kershaw@stfc.ac.uk"
__license__ = "BSD - see LICENSE file in top-level directory"
__contact__ = "Philip.Kershaw@stfc.ac.uk"
__revision__ = "$Id: $"
from ndg.xacml.utils import TypedList

    
class PolicyComponent(object):
    """Base class for Policy and Policy subelements"""
    XACML_2_0_XMLNS = "urn:oasis:names:tc:xacml:2.0:policy:schema:os"

    __slots__ = ('__xmlns', '__reader', '__writer')

    ELEMENT_LOCAL_NAME = None
    
    def __init__(self):
        self.__xmlns = PolicyComponent.XACML_2_0_XMLNS
        self.__reader = None
        self.__writer = None
        
    def _getXmlns(self):
        return self.__xmlns

    def _setXmlns(self, value):
        if not isinstance(value, basestring):
            raise TypeError('Expecting string type for "xmlns" '
                            'attribute; got %r' % type(value))
        self.__xmlns = value

    xmlns = property(_getXmlns, _setXmlns, 
                     doc="XML Namespace for policy the document")
    
    @property
    def isValidXmlns(self):
        return self.xmlns in PolicyComponent.XMLNS

    def read(self, obj):
        """Read using callable assinged to reader property"""
        if self.__reader is None:
            raise AttributeError('No reader set for %r' % self.__class__)
        
        self.__reader(self, obj)

    @classmethod
    def Read(cls, obj):
        """Construct a new Policy""" 
        xacmlObj = cls()
        xacmlObj.read(obj)
        return xacmlObj
    
    def write(self, obj):
        """Read using callable assinged to reader property"""
        if self.__writer is None:
            raise AttributeError('No writer set for %r' % self.__class__)
        
        self.__writer(self, obj)
        
            
class RequestPropertyBase(PolicyComponent):
    """Base type for Subject, Resource, Action and Environment types"""
    MATCH_TYPE = None
    
    __slots__ = ('__matches', )
    
    def __init__(self):
        # Derived types can specify the type for matches via the MATCH_TYPE
        # class variable
        self.__matches = TypedList(self.__class__.MATCH_TYPE)
        
    @property
    def matches(self):
        return self.__matches