Create a new XmlImageParser abstract class, which must be implemented and attached to each XmlBasedImage subclass.

Author: Ben Cipollini

nibabel/xmlbasedimages.py

@@ -10,6 +10,7 @@
 Thin layer around xml.etree.ElementTree, to abstract nibabel xml support.
 """
 from xml.etree.ElementTree import Element, SubElement, tostring
+from xml.parsers.expat import ParserCreate, ExpatError
 
 from .filebasedimages import FileBasedHeader, FileBasedImage
 
@@ -31,7 +32,61 @@ class XmlBasedHeader(FileBasedHeader, XmlSerializable):
     pass
 
 
+class XmlImageParser(object):
+    """ Parse XML image"""
+
+    HANDLER_NAMES = ['StartElementHandler',
+                     'EndElementHandler',
+                     'CharacterDataHandler']
+
+    def __init__(self, encoding=None):
+        self.encoding = encoding
+        self.img = None
+
+    def parse(self, string=None, fname=None, fptr=None):
+        """
+        Parameters
+        ----------
+        string : str
+            string containing xml document
+
+        fname : str
+            file name of an xml document.
+
+        fptr : file pointer
+            open file pointer to an xml document
+
+        Returns
+        -------
+        img : XmlBasedImage
+        """
+        if int(fname is not None) + int(fptr is not None) + int(fname is not None) != 1:
+            raise ValueError('Exactly one of fptr, fname, string must be specified.')
+
+        if string is not None:
+            fptr = StringIO(string)
+        elif fname is not None:
+            fptr = open(fname, 'r')
+
+        parser = ParserCreate()  # from xml package
+        for name in self.HANDLER_NAMES:
+            setattr(parser, name, getattr(self, name))
+        parser.ParseFile(fptr)
+
+        return self.img
+
+    def StartElementHandler(self, name, attrs):
+        raise NotImplementedError
+
+    def EndElementHandler(self, name):
+        raise NotImplementedError
+
+    def CharacterDataHandler(self, data):
+        raise NotImplementedError
+
+
 class XmlBasedImage(FileBasedImage, XmlSerializable):
+    parser = XmlImageParser
 
     def to_file_map(self, file_map=None):
         """ Save the current image to the specified file_map
@@ -48,3 +103,18 @@ def to_file_map(self, file_map=None):
             file_map = self.file_map
         f = file_map['image'].get_prepare_fileobj('wb')
         f.write(self.to_xml())
+
+    @classmethod
+    def from_file_map(klass, file_map):
+        """ Load a Gifti image from a file_map
+
+        Parameters
+        file_map : string
+
+        Returns
+        -------
+        img : GiftiImage
+            Returns a GiftiImage
+         """
+        return parser.parse(
+            fptr=file_map['image'].get_prepare_fileobj('rb'))