Source Code for Module ndg.xacml.core.expression

 1  """NDG Security Expression type definition 
 2   
 3  NERC DataGrid 
 4  """ 
 5  __author__ = "P J Kershaw" 
 6  __date__ = "25/02/10" 
 7  __copyright__ = "(C) 2010 Science and Technology Facilities Council" 
 8  __contact__ = "Philip.Kershaw@stfc.ac.uk" 
 9  __license__ = "BSD - see LICENSE file in top-level directory" 
10  __contact__ = "Philip.Kershaw@stfc.ac.uk" 
11  __revision__ = "$Id: expression.py 8010 2012-01-30 16:24:06Z rwilkinson $" 
12  from abc import ABCMeta, abstractmethod 
13   
14  from ndg.xacml.core import XacmlCoreBase 
15   
16   
17 -class Expression(XacmlCoreBase): 
18      """XACML Expression type 
19       
20      @cvar ELEMENT_LOCAL_NAME: XML local name for this element 
21      @type ELEMENT_LOCAL_NAME: string 
22      @cvar DATA_TYPE_ATTRIB_NAME: XML attribute name for data type 
23      @type DATA_TYPE_ATTRIB_NAME: string 
24       
25      @ivar __dataType: data type for this expression 
26      @type __dataType: None / basestring 
27      """ 
28      __metaclass__ = ABCMeta 
29      ELEMENT_LOCAL_NAME = None 
30      DATA_TYPE_ATTRIB_NAME = 'DataType' 
31       
32      __slots__ = ('__dataType', ) 
33       
34 -    def __init__(self): 
35          super(Expression, self).__init__() 
36          self.__dataType = None 
37           
38 -    def _get_dataType(self): 
39          return self.__dataType 
40   
41 -    def _set_dataType(self, value): 
42          if not isinstance(value, basestring): 
43              raise TypeError('Expecting %r type for "dataType" ' 
44                              'attribute; got %r' % (basestring, type(value))) 
45               
46          self.__dataType = value    
47   
48      dataType = property(_get_dataType, _set_dataType, None,  
49                          "expression value data type")   
50       
51      @abstractmethod 
52 -    def evaluate(self, context): 
53          """Evaluate the result of the expression in a condition.  Derived  
54          classes must implement 
55           
56          @param context: the request context 
57          @type context: ndg.xacml.core.context.request.Request 
58          @return: attribute value(s) resulting from execution of this expression 
59          in a condition 
60          @rtype: AttributeValue/NoneType 
61          """ 
62          raise NotImplementedError() 
63   
64 -    def __getstate__(self): 
65          '''Enable pickling 
66           
67          @return: object's attribute dictionary 
68          @rtype: dict 
69          ''' 
70          _dict = super(Expression, self).__getstate__() 
71          for attrName in Expression.__slots__: 
72              # Ugly hack to allow for derived classes setting private member 
73              # variables 
74              if attrName.startswith('__'): 
75                  attrName = "_Expression" + attrName 
76                   
77              _dict[attrName] = getattr(self, attrName) 
78               
79          return _dict 
80