source: TI12-security/trunk/NDG_XACML/ndg/xacml/parsers/__init__.py @ 6740

"""NDG XACML parsers package 

NERC DataGrid Project
"""
__author__ = "P J Kershaw"
__date__ = "15/03/10"
__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: $"
import logging
log = logging.getLogger(__name__)
from abc import ABCMeta, abstractmethod

from xml.etree import ElementTree


class AbstractReader:
    """Abstract base class for ElementTree implementation of XACML reader"""
    __metaclass__ = ABCMeta
    
    @classmethod
    def __subclasshook__(cls, C):
        """Derived class must implement __call__"""
        if cls is AbstractReader:
            if any("__call__" in B.__dict__ for B in C.__mro__):
                return True
            
        return NotImplemented
        
    @abstractmethod
    def __call__(self, obj):
        """Abstract Parse XACML method
        @raise NotImplementedError: 
        """
        raise NotImplementedError()
    
    @classmethod
    def parse(cls, obj):
        """Parse from input object and return new XACML object
        @param obj: input source - file name, stream object or other
        @type obj: string, stream or other
        @return: new XACML object
        @rtype: PolicyComponent sub type
        """
        reader = cls()
        return reader(obj)