source: sasview/src/sans/dataloader/readers/xml_reader.py @ f44b076

"""
    Generic XML reader
"""
############################################################################
#This software was developed by the University of Tennessee as part of the
#Distributed Data Analysis of Neutron Scattering Experiments (DANSE)
#project funded by the US National Science Foundation. 
#If you use DANSE applications to do scientific research that leads to 
#publication, we ask that you acknowledge the use of the software with the 
#following sentence:
#This work benefited from DANSE software developed under NSF award DMR-0520547. 
#copyright 2008,2009 University of Tennessee
#############################################################################

from lxml import etree
parser = etree.ETCompatXMLParser(remove_comments=True, remove_pis=False)

class XMLreader():
    
    xml = None
    xmldoc = None
    xmlroot = None
    schema = None
    schemadoc = None
    processingInstructions = None
    
    def __init__(self, xml = None, schema = None, root = None):
        self.xml = xml
        self.schema = schema
        self.processingInstructions = {}
        if xml is not None:
            self.setXMLFile(xml, root)
        else:
            self.xmldoc = None
            self.xmlroot = None
        if schema is not None:
            self.setSchema(schema)
        else:
            self.schemadoc = None
    
    def reader(self):
        """
        Read in an XML file into memory and return an lxml dictionary
        """
        if self.validateXML():
            self.xmldoc = etree.parse(self.xml, parser = parser)
        else:
            raise etree.ValidationError(self, self.findInvalidXML())
        return self.xmldoc
    
    def setXMLFile(self, xml, root = None):
        """
        Set the XML file and parse
        """
        try:
            self.xml = xml
            self.xmldoc = etree.parse(self.xml, parser = parser)
            self.xmlroot = self.xmldoc.getroot()
        except Exception:
            self.xml = None
            self.xmldoc = None
            self.xmlroot = None
    
    def setSchema(self, schema):
        """
        Set the schema file and parse
        """
        try:
            self.schema = schema
            self.schemadoc = etree.parse(self.schema, parser = parser)
        except Exception:
            self.schema = None
            self.schemadoc = None
    
    def validateXML(self):
        """
        Checks to see if the XML file meets the schema
        """
        valid = True
        if self.schema is not None:
            self.parseSchemaAndDoc()
            schemaCheck = etree.XMLSchema(self.schemadoc)
            valid = schemaCheck.validate(self.xmldoc)
        return valid
    
    def findInvalidXML(self):
        """
        Finds the first offending element that should not be present in XML file
        """
        firstError = ""
        self.parseSchemaAndDoc()
        schema = etree.XMLSchema(self.schemadoc)
        try:
            firstError = schema.assertValid(self.xmldoc)
        except etree.DocumentInvalid as e:
            firstError = str(e)
        return firstError
    
    def parseSchemaAndDoc(self):
        """
        Creates a dictionary of the parsed schema and xml files.
        """
        self.setXMLFile(self.xml)
        self.setSchema(self.schema)
        
    def toString(self, etreeElement):
        """
        Converts and etree element into a string
        """
        return etree.tostring(etreeElement)
    
    def setProcessingInstructions(self):
        """
        Take out all processing instructions and create a dictionary from them
        """
        dic = {}
        pi = self.xmlroot.getprevious()
        while pi is not None:
            attr = {}
            pi_name = ""
            pi_string = self.toString(pi)
            if isinstance(pi_string, str):
                pi_string = pi_string.replace("<?", "").replace("?>", "")
                split = pi_string.split(" ", 1)
                pi_name = split[0]
                attr = split[1]
            new_pi_name = self._create_unique_key(dic, pi_name)
            dic[new_pi_name] = attr
            pi = pi.getprevious()
        self.processingInstructions = dic
        
    def _create_unique_key(self, dictionary, name, i = 0):
        """
        Create a unique key value for any dictionary to prevent overwriting
        Recurses until a unique key value is found.
        
        :param dictionary: A dictionary with any number of entries
        :param name: The index of the item to be added to dictionary
        :param i: The number to be appended to the name, starts at 0
        """
        if dictionary.get(name) is not None:
            i += 1
            name = name.split("_")[0]
            name += "_{0}".format(i)
            name = self._create_unique_key(dictionary, name, i)
        return name
    
    def create_tree(self, root):
        """
        Create an element tree for processing from an XML string
        
        :param root: XML string 
        """
        return etree.ElementTree(root)
    
    def create_element(self, name):
        """
        Create an XML element for writing to file
        
        :param name: The name of the element to be created
        """
        return etree.Element(name)
    
    def write_text(self, elem, text):
        """
        Write text to an etree Element
        
        :param elem: etree.Element object
        :param text: text to write to the element
        """
        elem.text = text
        return elem
    
    def write_attribute(self, elem, attr_name, attr_value):
        """
        Write attributes to an Element
        
        :param elem: etree.Element object
        :param attr_name: attribute name to write
        :param attr_value: attribute value to set
        """
        attr = elem.attrib
        attr[attr_name] = attr_value