slixmpp/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
"""

from __future__ import unicode_literals

import sys

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


XML_NS = 'http://www.w3.org/XML/1998/namespace'


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

    If an outer xmlns is provided using ``xmlns``, then the current element's
    namespace will not be included if it matches the outer namespace. An
    exception is made for elements that have an attached stream, and appear
    at the stream root.

    :param XML xml: The XML object to serialize.
    :param string xmlns: Optional namespace of an element wrapping 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.
    :param set namespaces: Track which namespaces are in active use so
                           that new ones can be declared when needed.

    :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 = ''
    use_cdata = False

    if stream:
        default_ns = stream.default_ns
        stream_ns = stream.stream_ns
        use_cdata = stream.use_cdata

    # Output the tag name and derived namespace of the element.
    namespace = ''
    if tag_xmlns:
        if top_level and tag_xmlns not in [default_ns, xmlns, stream_ns] \
          or not top_level and tag_xmlns != xmlns:
            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.
    new_namespaces = set()
    for attrib, value in xml.attrib.items():
        value = escape(value, use_cdata)
        if '}' not in attrib:
            output.append(' %s="%s"' % (attrib, value))
        else:
            attrib_ns = attrib.split('}')[0][1:]
            attrib = attrib.split('}')[1]
            if attrib_ns == XML_NS:
                output.append(' xml:%s="%s"' % (attrib, value))
            elif stream and attrib_ns in stream.namespace_map:
                mapped_ns = stream.namespace_map[attrib_ns]
                if mapped_ns:
                    if namespaces is None:
                        namespaces = set()
                    if attrib_ns not in namespaces:
                        namespaces.add(attrib_ns)
                        new_namespaces.add(attrib_ns)
                        output.append(' xmlns:%s="%s"' % (
                            mapped_ns, attrib_ns))
                    output.append(' %s:%s="%s"' % (
                        mapped_ns, attrib, value))

    if open_only:
        # Only output the opening tag, regardless of content.
        output.append(">")
        return ''.join(output)

    if len(xml) or xml.text:
        # If there are additional child elements to serialize.
        output.append(">")
        if xml.text:
            output.append(escape(xml.text, use_cdata))
        if len(xml):
            for child in xml:
                output.append(tostring(child, tag_xmlns, stream,
                    namespaces=namespaces))
        output.append("</%s>" % tag_name)
    elif xml.text:
        # If we only have text content.
        output.append(">%s</%s>" % (escape(xml.text, use_cdata), tag_name))
    else:
        # Empty element.
        output.append(" />")
    if xml.tail:
        # If there is additional text after the element.
        output.append(escape(xml.tail, use_cdata))
    for ns in new_namespaces:
        # Remove namespaces introduced in this context. This is necessary
        # because the namespaces object continues to be shared with other
        # contexts.
        namespaces.remove(ns)
    return ''.join(output)


def escape(text, use_cdata=False):
    """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')

    escapes = {'&': '&amp;',
               '<': '&lt;',
               '>': '&gt;',
               "'": '&apos;',
               '"': '&quot;'}

    if not use_cdata:
        text = list(text)
        for i, c in enumerate(text):
            text[i] = escapes.get(c, c)
        return ''.join(text)
    else:
        escape_needed = False
        for c in text:
            if c in escapes:
                escape_needed = True
                break
        if escape_needed:
            escaped = map(lambda x : "<![CDATA[%s]]>" % x, text.split("]]>"))
            return "<![CDATA[]]]><![CDATA[]>]]>".join(escaped)
        return text