xmlutils.py at 7c7962b ⋅ nipy/nibabel

# emacs: -*- mode: python-mode; py-indent-offset: 4; indent-tabs-mode: nil -*-
# vi: set ft=python sts=4 ts=4 sw=4 et:
### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
#
#   See COPYING file distributed along with the NiBabel package for the
#   copyright and license terms.
#
### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
"""
Thin layer around xml.etree.ElementTree, to abstract nibabel xml support.
"""

from io import BytesIO
from xml.etree.ElementTree import Element, SubElement, tostring  # noqa
from xml.parsers.expat import ParserCreate

from .filebasedimages import FileBasedHeader


class XmlSerializable(object):
    """ Basic interface for serializing an object to xml"""

    def _to_xml_element(self):
        """ Output should be a xml.etree.ElementTree.Element"""
        raise NotImplementedError()

    def to_xml(self, enc='utf-8'):
        """ Output should be an xml string with the given encoding.
        (default: utf-8)"""
        ele = self._to_xml_element()
        return '' if ele is None else tostring(ele, enc)


class XmlBasedHeader(FileBasedHeader, XmlSerializable):
    """ Basic wrapper around FileBasedHeader and XmlSerializable."""


class XmlParser(object):
    """ Base class for defining how to parse xml-based image snippets.

    Image-specific parsers should define:
        StartElementHandler
        EndElementHandler
        CharacterDataHandler
    """

    HANDLER_NAMES = ['StartElementHandler',
                     'EndElementHandler',
                     'CharacterDataHandler']

    def __init__(self, encoding='utf-8', buffer_size=35000000, verbose=0):
        """
        Parameters
        ----------
        encoding : str
            string containing xml document

        buffer_size: None or int, optional
            size of read buffer. None uses default buffer_size
            from xml.parsers.expat.

        verbose : int, optional
            amount of output during parsing (0=silent, by default).
        """
        self.encoding = encoding
        self.buffer_size = buffer_size
        self.verbose = verbose

    def _create_parser(self):
        """Internal function that allows subclasses to mess
        with the underlying parser, if desired."""

        parser = ParserCreate(encoding=self.encoding)  # from xml package
        parser.buffer_text = True
        if self.buffer_size is not None:
            parser.buffer_size = self.buffer_size
        return parser

    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 documents
        """
        if int(string 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 = BytesIO(string)
        elif fname is not None:
            fptr = open(fname, 'r')

        parser = self._create_parser()
        for name in self.HANDLER_NAMES:
            setattr(parser, name, getattr(self, name))
        parser.ParseFile(fptr)

    def StartElementHandler(self, name, attrs):
        raise NotImplementedError

    def EndElementHandler(self, name):
        raise NotImplementedError

    def CharacterDataHandler(self, data):
        raise NotImplementedError

Read our documentation on viewing source code .

1		# emacs: -- mode: python-mode; py-indent-offset: 4; indent-tabs-mode: nil --
2		# vi: set ft=python sts=4 ts=4 sw=4 et:
3		### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
4		#
5		# See COPYING file distributed along with the NiBabel package for the
6		# copyright and license terms.
7		#
8		### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
9	33	"""
10		Thin layer around xml.etree.ElementTree, to abstract nibabel xml support.
11		"""
12
13	33	from io import BytesIO
14	33	from xml.etree.ElementTree import Element, SubElement, tostring # noqa
15	33	from xml.parsers.expat import ParserCreate
16
17	33	from .filebasedimages import FileBasedHeader
18
19
20	33	class XmlSerializable(object):
21		""" Basic interface for serializing an object to xml"""
22
23	33	def _to_xml_element(self):
24		""" Output should be a xml.etree.ElementTree.Element"""
25	0	raise NotImplementedError()
26
27	33	def to_xml(self, enc='utf-8'):
28		""" Output should be an xml string with the given encoding.
29		(default: utf-8)"""
30	33	ele = self._to_xml_element()
31	33	return '' if ele is None else tostring(ele, enc)
32
33
34	33	class XmlBasedHeader(FileBasedHeader, XmlSerializable):
35		""" Basic wrapper around FileBasedHeader and XmlSerializable."""
36
37
38	33	class XmlParser(object):
39		""" Base class for defining how to parse xml-based image snippets.
40
41		Image-specific parsers should define:
42		StartElementHandler
43		EndElementHandler
44		CharacterDataHandler
45		"""
46
47	33	HANDLER_NAMES = ['StartElementHandler',
48		'EndElementHandler',
49		'CharacterDataHandler']
50
51	33	def __init__(self, encoding='utf-8', buffer_size=35000000, verbose=0):
52		"""
53		Parameters
54		----------
55		encoding : str
56		string containing xml document
57
58		buffer_size: None or int, optional
59		size of read buffer. None uses default buffer_size
60		from xml.parsers.expat.
61
62		verbose : int, optional
63		amount of output during parsing (0=silent, by default).
64		"""
65	33	self.encoding = encoding
66	33	self.buffer_size = buffer_size
67	33	self.verbose = verbose
68
69	33	def _create_parser(self):
70		"""Internal function that allows subclasses to mess
71		with the underlying parser, if desired."""
72
73	33	parser = ParserCreate(encoding=self.encoding) # from xml package
74	33	parser.buffer_text = True
75	33	if self.buffer_size is not None:
76	33	parser.buffer_size = self.buffer_size
77	33	return parser
78
79	33	def parse(self, string=None, fname=None, fptr=None):
80		"""
81		Parameters
82		----------
83		string : str
84		string containing xml document
85
86		fname : str
87		file name of an xml document.
88
89		fptr : file pointer
90		open file pointer to an xml documents
91		"""
92	33	if int(string is not None) + int(fptr is not None) + int(fname is not None) != 1:
93	33	raise ValueError('Exactly one of fptr, fname, string must be specified.')
94
95	33	if string is not None:
96	33	fptr = BytesIO(string)
97	33	elif fname is not None:
98	0	fptr = open(fname, 'r')
99
100	33	parser = self._create_parser()
101	33	for name in self.HANDLER_NAMES:
102	33	setattr(parser, name, getattr(self, name))
103	33	parser.ParseFile(fptr)
104
105	33	def StartElementHandler(self, name, attrs):
106	0	raise NotImplementedError
107
108	33	def EndElementHandler(self, name):
109	0	raise NotImplementedError
110
111	33	def CharacterDataHandler(self, data):
112	0	raise NotImplementedError

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