SleekXMPP/sleekxmpp/xmlstream/tostring.py

# -*- coding: utf-8 -*-
"""
    sleekxmpp.xmlstream.tostring
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    This module converts XML objects into Unicode strings and
    intelligently includes namespaces only when necessary to
    keep the output readable.

    Part of SleekXMPP: The Sleek XMPP Library

    :copyright: (c) 2011 Nathanael C. Fritz
    :license: MIT, see LICENSE for more details
"""

import sys

if sys.version_info < (3, 0):
    import types


def tostring(xml=None, xmlns='', stanza_ns='', stream=None,
             outbuffer='', top_level=False):
    """Serialize an XML object to a Unicode string.

    If namespaces are provided using ``xmlns`` or ``stanza_ns``, then
    elements that use those namespaces will not include the xmlns attribute
    in the output.

    :param XML xml: The XML object to serialize.
    :param string xmlns: Optional namespace of an element wrapping the XML
                         object.
    :param string stanza_ns: The namespace of the stanza object that contains
                             the XML object.
    :param stream: The XML stream that generated the XML object.
    :param string outbuffer: Optional buffer for storing serializations
                             during recursive calls.
    :param bool top_level: Indicates that the element is the outermost
                           element.


    :type xml: :py:class:`~xml.etree.ElementTree.Element`
    :type stream: :class:`~sleekxmpp.xmlstream.xmlstream.XMLStream`

    :rtype: Unicode string
    """
    # Add previous results to the start of the output.
    output = [outbuffer]

    # Extract the element's tag name.
    tag_name = xml.tag.split('}', 1)[-1]

    # Extract the element's namespace if it is defined.
    if '}' in xml.tag:
        tag_xmlns = xml.tag.split('}', 1)[0][1:]
    else:
        tag_xmlns = ''

    default_ns = ''
    stream_ns = ''
    if stream:
        default_ns = stream.default_ns
        stream_ns = stream.stream_ns

    # Output the tag name and derived namespace of the element.
    namespace = ''
    if top_level and tag_xmlns not in ['', default_ns, stream_ns] or \
            tag_xmlns not in ['', xmlns, stanza_ns, stream_ns]:
        namespace = ' xmlns="%s"' % tag_xmlns
    if stream and tag_xmlns in stream.namespace_map:
        mapped_namespace = stream.namespace_map[tag_xmlns]
        if mapped_namespace:
            tag_name = "%s:%s" % (mapped_namespace, tag_name)
    output.append("<%s" % tag_name)
    output.append(namespace)

    # Output escaped attribute values.
    for attrib, value in xml.attrib.items():
        value = xml_escape(value)
        if '}' not in attrib:
            output.append(' %s="%s"' % (attrib, value))
        else:
            attrib_ns = attrib.split('}')[0][1:]
            attrib = attrib.split('}')[1]
            if stream and attrib_ns in stream.namespace_map:
                mapped_ns = stream.namespace_map[attrib_ns]
                if mapped_ns:
                    output.append(' %s:%s="%s"' % (mapped_ns,
                                                   attrib,
                                                   value))

    if len(xml) or xml.text:
        # If there are additional child elements to serialize.
        output.append(">")
        if xml.text:
            output.append(xml_escape(xml.text))
        if len(xml):
            for child in xml.getchildren():
                output.append(tostring(child, tag_xmlns, stanza_ns, stream))
        output.append("</%s>" % tag_name)
    elif xml.text:
        # If we only have text content.
        output.append(">%s</%s>" % (xml_escape(xml.text), tag_name))
    else:
        # Empty element.
        output.append(" />")
    if xml.tail:
        # If there is additional text after the element.
        output.append(xml_escape(xml.tail))
    return ''.join(output)


def xml_escape(text):
    """Convert special characters in XML to escape sequences.

    :param string text: The XML text to convert.
    :rtype: Unicode string
    """
    if sys.version_info < (3, 0):
        if type(text) != types.UnicodeType:
            text = unicode(text, 'utf-8', 'ignore')

    text = list(text)
    escapes = {'&': '&amp;',
               '<': '&lt;',
               '>': '&gt;',
               "'": '&apos;',
               '"': '&quot;'}
    for i, c in enumerate(text):
        text[i] = escapes.get(c, c)
    return ''.join(text)