text: # -*- coding: utf-8 -*-
  #
  # Copyright (C) 2006-2009 Edgewall Software
  # All rights reserved.
  #
  # This software is licensed as described in the file COPYING, which
  # you should have received as part of this distribution. The terms
  # are also available at http://genshi.edgewall.org/wiki/License.
  #
  # This software consists of voluntary contributions made by many
  # individuals. For the exact contribution history, see the revision
  # history and logs, available at http://genshi.edgewall.org/log/.
  
  """This module provides different kinds of serialization methods for XML event
  streams.
  """
  
  from itertools import chain
  import re
  
  from genshi.core import escape, Attrs, Markup, Namespace, QName, StreamEventKind
  from genshi.core import START, END, TEXT, XML_DECL, DOCTYPE, START_NS, END_NS, \
                          START_CDATA, END_CDATA, PI, COMMENT, XML_NAMESPACE
  
  __all__ = ['encode', 'get_serializer', 'DocType', 'XMLSerializer',
             'XHTMLSerializer', 'HTMLSerializer', 'TextSerializer']
  __docformat__ = 'restructuredtext en'
  
  
  def encode(iterator, method='xml', encoding='utf-8', out=None):
      """Encode serializer output into a string.
      
      :param iterator: the iterator returned from serializing a stream (basically
                       any iterator that yields unicode objects)
      :param method: the serialization method; determines how characters not
                     representable in the specified encoding are treated
      :param encoding: how the output string should be encoded; if set to `None`,
                       this method returns a `unicode` object
      :param out: a file-like object that the output should be written to
                  instead of being returned as one big string; note that if
                  this is a file or socket (or similar), the `encoding` must
                  not be `None` (that is, the output must be encoded)
      :return: a `str` or `unicode` object (depending on the `encoding`
               parameter), or `None` if the `out` parameter is provided
      
      :since: version 0.4.1
      :note: Changed in 0.5: added the `out` parameter
      """
      if encoding is not None:
          errors = 'replace'
          if method != 'text' and not isinstance(method, TextSerializer):
              errors = 'xmlcharrefreplace'
          _encode = lambda string: string.encode(encoding, errors)
      else:
          _encode = lambda string: string
      if out is None:
          return _encode(''.join(list(iterator)))
      for chunk in iterator:
          out.write(_encode(chunk))
  
  
  def get_serializer(method='xml', **kwargs):
      """Return a serializer object for the given method.
      
      :param method: the serialization method; can be either "xml", "xhtml",
                     "html", "text", or a custom serializer class
  
      Any additional keyword arguments are passed to the serializer, and thus
      depend on the `method` parameter value.
      
      :see: `XMLSerializer`, `XHTMLSerializer`, `HTMLSerializer`, `TextSerializer`
      :since: version 0.4.1
      """
      if isinstance(method, basestring):
          method = {'xml':   XMLSerializer,
                    'xhtml': XHTMLSerializer,
                    'html':  HTMLSerializer,
                    'text':  TextSerializer}[method.lower()]
      return method(**kwargs)
  
  
  class DocType(object):
      """Defines a number of commonly used DOCTYPE declarations as constants."""
  
      HTML_STRICT = (
          'html', '-//W3C//DTD HTML 4.01//EN',
          'http://www.w3.org/TR/html4/strict.dtd'
      )
      HTML_TRANSITIONAL = (
          'html', '-//W3C//DTD HTML 4.01 Transitional//EN',
          'http://www.w3.org/TR/html4/loose.dtd'
      )
      HTML_FRAMESET = (
          'html', '-//W3C//DTD HTML 4.01 Frameset//EN',
          'http://www.w3.org/TR/html4/frameset.dtd'
      )
      HTML = HTML_STRICT
  
      HTML5 = ('html', None, None)
  
      XHTML_STRICT = (
          'html', '-//W3C//DTD XHTML 1.0 Strict//EN',
          'http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd'
      )
      XHTML_TRANSITIONAL = (
          'html', '-//W3C//DTD XHTML 1.0 Transitional//EN',
          'http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd'
      )
      XHTML_FRAMESET = (
          'html', '-//W3C//DTD XHTML 1.0 Frameset//EN',
          'http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd'
      )
      XHTML = XHTML_STRICT
  
      XHTML11 = (
          'html', '-//W3C//DTD XHTML 1.1//EN',
          'http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd'
      )
  
      SVG_FULL = (
          'svg', '-//W3C//DTD SVG 1.1//EN',
          'http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd'
      )
      SVG_BASIC = (
          'svg', '-//W3C//DTD SVG Basic 1.1//EN',
          'http://www.w3.org/Graphics/SVG/1.1/DTD/svg11-basic.dtd'
      )
      SVG_TINY = (
          'svg', '-//W3C//DTD SVG Tiny 1.1//EN',
          'http://www.w3.org/Graphics/SVG/1.1/DTD/svg11-tiny.dtd'
      )
      SVG = SVG_FULL
  
      @classmethod
      def get(cls, name):
          """Return the ``(name, pubid, sysid)`` tuple of the ``DOCTYPE``
          declaration for the specified name.
          
          The following names are recognized in this version:
           * "html" or "html-strict" for the HTML 4.01 strict DTD
           * "html-transitional" for the HTML 4.01 transitional DTD
           * "html-frameset" for the HTML 4.01 frameset DTD
           * "html5" for the ``DOCTYPE`` proposed for HTML5
           * "xhtml" or "xhtml-strict" for the XHTML 1.0 strict DTD
           * "xhtml-transitional" for the XHTML 1.0 transitional DTD
           * "xhtml-frameset" for the XHTML 1.0 frameset DTD
           * "xhtml11" for the XHTML 1.1 DTD
           * "svg" or "svg-full" for the SVG 1.1 DTD
           * "svg-basic" for the SVG Basic 1.1 DTD
           * "svg-tiny" for the SVG Tiny 1.1 DTD
          
          :param name: the name of the ``DOCTYPE``
          :return: the ``(name, pubid, sysid)`` tuple for the requested
                   ``DOCTYPE``, or ``None`` if the name is not recognized
          :since: version 0.4.1
          """
          return {
              'html': cls.HTML, 'html-strict': cls.HTML_STRICT,
              'html-transitional': DocType.HTML_TRANSITIONAL,
              'html-frameset': DocType.HTML_FRAMESET,
              'html5': cls.HTML5,
              'xhtml': cls.XHTML, 'xhtml-strict': cls.XHTML_STRICT,
              'xhtml-transitional': cls.XHTML_TRANSITIONAL,
              'xhtml-frameset': cls.XHTML_FRAMESET,
              'xhtml11': cls.XHTML11,
              'svg': cls.SVG, 'svg-full': cls.SVG_FULL,
              'svg-basic': cls.SVG_BASIC,
              'svg-tiny': cls.SVG_TINY
          }.get(name.lower())
  
  
  class XMLSerializer(object):
      """Produces XML text from an event stream.
      
      >>> from genshi.builder import tag
      >>> elem = tag.div(tag.a(href='foo'), tag.br, tag.hr(noshade=True))
      >>> print(''.join(XMLSerializer()(elem.generate())))
      <div><a href="foo"/><br/><hr noshade="True"/></div>
      """
  
      _PRESERVE_SPACE = frozenset()
  
      def __init__(self, doctype=None, strip_whitespace=True,
                   namespace_prefixes=None, cache=True):
          """Initialize the XML serializer.
          
          :param doctype: a ``(name, pubid, sysid)`` tuple that represents the
                          DOCTYPE declaration that should be included at the top
                          of the generated output, or the name of a DOCTYPE as
                          defined in `DocType.get`
          :param strip_whitespace: whether extraneous whitespace should be
                                   stripped from the output
          :param cache: whether to cache the text output per event, which
                        improves performance for repetitive markup
          :note: Changed in 0.4.2: The  `doctype` parameter can now be a string.
          :note: Changed in 0.6: The `cache` parameter was added
          """
          self.filters = [EmptyTagFilter()]
          if strip_whitespace:
              self.filters.append(WhitespaceFilter(self._PRESERVE_SPACE))
          self.filters.append(NamespaceFlattener(prefixes=namespace_prefixes,
                                                 cache=cache))
          if doctype:
              self.filters.append(DocTypeInserter(doctype))
          self.cache = cache
  
      def __call__(self, stream):
          have_decl = have_doctype = False
          in_cdata = False
  
          cache = {}
          cache_get = cache.get
          if self.cache:
              def _emit(kind, input, output):
                  cache[kind, input] = output
                  return output
          else:
              def _emit(kind, input, output):
                  return output
  
          for filter_ in self.filters:
              stream = filter_(stream)
          for kind, data, pos in stream:
              cached = cache_get((kind, data))
              if cached is not None:
                  yield cached
  
              elif kind is START or kind is EMPTY:
                  tag, attrib = data
                  buf = ['<', tag]
                  for attr, value in attrib:
                      buf += [' ', attr, '="', escape(value), '"']
                  buf.append(kind is EMPTY and '/>' or '>')
                  yield _emit(kind, data, Markup(''.join(buf)))
  
              elif kind is END:
                  yield _emit(kind, data, Markup('</%s>' % data))
  
              elif kind is TEXT:
                  if in_cdata:
                      yield _emit(kind, data, data)
                  else:
                      yield _emit(kind, data, escape(data, quotes=False))
  
              elif kind is COMMENT:
                  yield _emit(kind, data, Markup('<!--%s-->' % data))
  
              elif kind is XML_DECL and not have_decl:
                  version, encoding, standalone = data
                  buf = ['<?xml version="%s"' % version]
                  if encoding:
                      buf.append(' encoding="%s"' % encoding)
                  if standalone != -1:
                      standalone = standalone and 'yes' or 'no'
                      buf.append(' standalone="%s"' % standalone)
                  buf.append('?>\n')
                  yield Markup(''.join(buf))
                  have_decl = True
  
              elif kind is DOCTYPE and not have_doctype:
                  name, pubid, sysid = data
                  buf = ['<!DOCTYPE %s']
                  if pubid:
                      buf.append(' PUBLIC "%s"')
                  elif sysid:
                      buf.append(' SYSTEM')
                  if sysid:
                      buf.append(' "%s"')
                  buf.append('>\n')
                  yield Markup(''.join(buf)) % tuple([p for p in data if p])
                  have_doctype = True
  
              elif kind is START_CDATA:
                  yield Markup('<![CDATA[')
                  in_cdata = True
  
              elif kind is END_CDATA:
                  yield Markup(']]>')
                  in_cdata = False
  
              elif kind is PI:
                  yield _emit(kind, data, Markup('<?%s %s?>' % data))
  
  
  class XHTMLSerializer(XMLSerializer):
      """Produces XHTML text from an event stream.
      
      >>> from genshi.builder import tag
      >>> elem = tag.div(tag.a(href='foo'), tag.br, tag.hr(noshade=True))
      >>> print(''.join(XHTMLSerializer()(elem.generate())))
      <div><a href="foo"></a><br /><hr noshade="noshade" /></div>
      """
  
      _EMPTY_ELEMS = frozenset(['area', 'base', 'basefont', 'br', 'col', 'frame',
                                'hr', 'img', 'input', 'isindex', 'link', 'meta',
                                'param'])
      _BOOLEAN_ATTRS = frozenset(['selected', 'checked', 'compact', 'declare',
                                  'defer', 'disabled', 'ismap', 'multiple',
                                  'nohref', 'noresize', 'noshade', 'nowrap'])
      _PRESERVE_SPACE = frozenset([
          QName('pre'), QName('http://www.w3.org/1999/xhtml}pre'),
          QName('textarea'), QName('http://www.w3.org/1999/xhtml}textarea')
      ])
  
      def __init__(self, doctype=None, strip_whitespace=True,
                   namespace_prefixes=None, drop_xml_decl=True, cache=True):
          super(XHTMLSerializer, self).__init__(doctype, False)
          self.filters = [EmptyTagFilter()]
          if strip_whitespace:
              self.filters.append(WhitespaceFilter(self._PRESERVE_SPACE))
          namespace_prefixes = namespace_prefixes or {}
          namespace_prefixes['http://www.w3.org/1999/xhtml'] = ''
          self.filters.append(NamespaceFlattener(prefixes=namespace_prefixes,
                                                 cache=cache))
          if doctype:
              self.filters.append(DocTypeInserter(doctype))
          self.drop_xml_decl = drop_xml_decl
          self.cache = cache
  
      def __call__(self, stream):
          boolean_attrs = self._BOOLEAN_ATTRS
          empty_elems = self._EMPTY_ELEMS
          drop_xml_decl = self.drop_xml_decl
          have_decl = have_doctype = False
          in_cdata = False
  
          cache = {}
          cache_get = cache.get
          if self.cache:
              def _emit(kind, input, output):
                  cache[kind, input] = output
                  return output
          else:
              def _emit(kind, input, output):
                  return output
  
          for filter_ in self.filters:
              stream = filter_(stream)
          for kind, data, pos in stream:
              cached = cache_get((kind, data))
              if cached is not None:
                  yield cached
  
              elif kind is START or kind is EMPTY:
                  tag, attrib = data
                  buf = ['<', tag]
                  for attr, value in attrib:
                      if attr in boolean_attrs:
                          value = attr
                      elif attr == 'xml:lang' and 'lang' not in attrib:
                          buf += [' lang="', escape(value), '"']
                      elif attr == 'xml:space':
                          continue
                      buf += [' ', attr, '="', escape(value), '"']
                  if kind is EMPTY:
                      if tag in empty_elems:
                          buf.append(' />')
                      else:
                          buf.append('></%s>' % tag)
                  else:
                      buf.append('>')
                  yield _emit(kind, data, Markup(''.join(buf)))
  
              elif kind is END:
                  yield _emit(kind, data, Markup('</%s>' % data))
  
              elif kind is TEXT:
                  if in_cdata:
                      yield _emit(kind, data, data)
                  else:
                      yield _emit(kind, data, escape(data, quotes=False))
  
              elif kind is COMMENT:
                  yield _emit(kind, data, Markup('<!--%s-->' % data))
  
              elif kind is DOCTYPE and not have_doctype:
                  name, pubid, sysid = data
                  buf = ['<!DOCTYPE %s']
                  if pubid:
                      buf.append(' PUBLIC "%s"')
                  elif sysid:
                      buf.append(' SYSTEM')
                  if sysid:
                      buf.append(' "%s"')
                  buf.append('>\n')
                  yield Markup(''.join(buf)) % tuple([p for p in data if p])
                  have_doctype = True
  
              elif kind is XML_DECL and not have_decl and not drop_xml_decl:
                  version, encoding, standalone = data
                  buf = ['<?xml version="%s"' % version]
                  if encoding:
                      buf.append(' encoding="%s"' % encoding)
                  if standalone != -1:
                      standalone = standalone and 'yes' or 'no'
                      buf.append(' standalone="%s"' % standalone)
                  buf.append('?>\n')
                  yield Markup(''.join(buf))
                  have_decl = True
  
              elif kind is START_CDATA:
                  yield Markup('<![CDATA[')
                  in_cdata = True
  
              elif kind is END_CDATA:
                  yield Markup(']]>')
                  in_cdata = False
  
              elif kind is PI:
                  yield _emit(kind, data, Markup('<?%s %s?>' % data))
  
  
  class HTMLSerializer(XHTMLSerializer):
      """Produces HTML text from an event stream.
      
      >>> from genshi.builder import tag
      >>> elem = tag.div(tag.a(href='foo'), tag.br, tag.hr(noshade=True))
      >>> print(''.join(HTMLSerializer()(elem.generate())))
      <div><a href="foo"></a><br><hr noshade></div>
      """
  
      _NOESCAPE_ELEMS = frozenset([
          QName('script'), QName('http://www.w3.org/1999/xhtml}script'),
          QName('style'), QName('http://www.w3.org/1999/xhtml}style')
      ])
  
      def __init__(self, doctype=None, strip_whitespace=True, cache=True):
          """Initialize the HTML serializer.
          
          :param doctype: a ``(name, pubid, sysid)`` tuple that represents the
                          DOCTYPE declaration that should be included at the top
                          of the generated output
          :param strip_whitespace: whether extraneous whitespace should be
                                   stripped from the output
          :param cache: whether to cache the text output per event, which
                        improves performance for repetitive markup
          :note: Changed in 0.6: The `cache` parameter was added
          """
          super(HTMLSerializer, self).__init__(doctype, False)
          self.filters = [EmptyTagFilter()]
          if strip_whitespace:
              self.filters.append(WhitespaceFilter(self._PRESERVE_SPACE,
                                                   self._NOESCAPE_ELEMS))
          self.filters.append(NamespaceFlattener(prefixes={
              'http://www.w3.org/1999/xhtml': ''
          }, cache=cache))
          if doctype:
              self.filters.append(DocTypeInserter(doctype))
          self.cache = True
  
      def __call__(self, stream):
          boolean_attrs = self._BOOLEAN_ATTRS
          empty_elems = self._EMPTY_ELEMS
          noescape_elems = self._NOESCAPE_ELEMS
          have_doctype = False
          noescape = False
  
          cache = {}
          cache_get = cache.get
          if self.cache:
              def _emit(kind, input, output):
                  cache[kind, input] = output
                  return output
          else:
              def _emit(kind, input, output):
                  return output
  
          for filter_ in self.filters:
              stream = filter_(stream)
          for kind, data, _ in stream:
              output = cache_get((kind, data))
              if output is not None:
                  yield output
                  if (kind is START or kind is EMPTY) \
                          and data[0] in noescape_elems:
                      noescape = True
                  elif kind is END:
                      noescape = False
  
              elif kind is START or kind is EMPTY:
                  tag, attrib = data
                  buf = ['<', tag]
                  for attr, value in attrib:
                      if attr in boolean_attrs:
                          if value:
                              buf += [' ', attr]
                      elif ':' in attr:
                          if attr == 'xml:lang' and 'lang' not in attrib:
                              buf += [' lang="', escape(value), '"']
                      elif attr != 'xmlns':
                          buf += [' ', attr, '="', escape(value), '"']
                  buf.append('>')
                  if kind is EMPTY:
                      if tag not in empty_elems:
                          buf.append('</%s>' % tag)
                  yield _emit(kind, data, Markup(''.join(buf)))
                  if tag in noescape_elems:
                      noescape = True
  
              elif kind is END:
                  yield _emit(kind, data, Markup('</%s>' % data))
                  noescape = False
  
              elif kind is TEXT:
                  if noescape:
                      yield _emit(kind, data, data)
                  else:
                      yield _emit(kind, data, escape(data, quotes=False))
  
              elif kind is COMMENT:
                  yield _emit(kind, data, Markup('<!--%s-->' % data))
  
              elif kind is DOCTYPE and not have_doctype:
                  name, pubid, sysid = data
                  buf = ['<!DOCTYPE %s']
                  if pubid:
                      buf.append(' PUBLIC "%s"')
                  elif sysid:
                      buf.append(' SYSTEM')
                  if sysid:
                      buf.append(' "%s"')
                  buf.append('>\n')
                  yield Markup(''.join(buf)) % tuple([p for p in data if p])
                  have_doctype = True
  
              elif kind is PI:
                  yield _emit(kind, data, Markup('<?%s %s?>' % data))
  
  
  class TextSerializer(object):
      """Produces plain text from an event stream.
      
      Only text events are included in the output. Unlike the other serializer,
      special XML characters are not escaped:
      
      >>> from genshi.builder import tag
      >>> elem = tag.div(tag.a('<Hello!>', href='foo'), tag.br)
      >>> print(elem)
      <div><a href="foo">&lt;Hello!&gt;</a><br/></div>
      >>> print(''.join(TextSerializer()(elem.generate())))
      <Hello!>
  
      If text events contain literal markup (instances of the `Markup` class),
      that markup is by default passed through unchanged:
      
      >>> elem = tag.div(Markup('<a href="foo">Hello &amp; Bye!</a><br/>'))
      >>> print(elem.generate().render(TextSerializer, encoding=None))
      <a href="foo">Hello &amp; Bye!</a><br/>
      
      You can use the ``strip_markup`` to change this behavior, so that tags and
      entities are stripped from the output (or in the case of entities,
      replaced with the equivalent character):
  
      >>> print(elem.generate().render(TextSerializer, strip_markup=True,
      ...                              encoding=None))
      Hello & Bye!
      """
  
      def __init__(self, strip_markup=False):
          """Create the serializer.
          
          :param strip_markup: whether markup (tags and encoded characters) found
                               in the text should be removed
          """
          self.strip_markup = strip_markup
  
      def __call__(self, stream):
          strip_markup = self.strip_markup
          for event in stream:
              if event[0] is TEXT:
                  data = event[1]
                  if strip_markup and type(data) is Markup:
                      data = data.striptags().stripentities()
                  yield unicode(data)
  
  
  class EmptyTagFilter(object):
      """Combines `START` and `STOP` events into `EMPTY` events for elements that
      have no contents.
      """
  
      EMPTY = StreamEventKind('EMPTY')
  
      def __call__(self, stream):
          prev = (None, None, None)
          for ev in stream:
              if prev[0] is START:
                  if ev[0] is END:
                      prev = EMPTY, prev[1], prev[2]
                      yield prev
                      continue
                  else:
                      yield prev
              if ev[0] is not START:
                  yield ev
              prev = ev
  
  
  EMPTY = EmptyTagFilter.EMPTY
  
  
  class NamespaceFlattener(object):
      r"""Output stream filter that removes namespace information from the stream,
      instead adding namespace attributes and prefixes as needed.
      
      :param prefixes: optional mapping of namespace URIs to prefixes
      
      >>> from genshi.input import XML
      >>> xml = XML('''<doc xmlns="NS1" xmlns:two="NS2">
      ...   <two:item/>
      ... </doc>''')
      >>> for kind, data, pos in NamespaceFlattener()(xml):
      ...     print('%s %r' % (kind, data))
      START (u'doc', Attrs([('xmlns', u'NS1'), (u'xmlns:two', u'NS2')]))
      TEXT u'\n  '
      START (u'two:item', Attrs())
      END u'two:item'
      TEXT u'\n'
      END u'doc'
      """
  
      def __init__(self, prefixes=None, cache=True):
          self.prefixes = {XML_NAMESPACE.uri: 'xml'}
          if prefixes is not None:
              self.prefixes.update(prefixes)
          self.cache = cache
  
      def __call__(self, stream):
          cache = {}
          cache_get = cache.get
          if self.cache:
              def _emit(kind, input, output, pos):
                  cache[kind, input] = output
                  return kind, output, pos
          else:
              def _emit(kind, input, output, pos):
                  return output
  
          prefixes = dict([(v, [k]) for k, v in self.prefixes.items()])
          namespaces = {XML_NAMESPACE.uri: ['xml']}
          def _push_ns(prefix, uri):
              namespaces.setdefault(uri, []).append(prefix)
              prefixes.setdefault(prefix, []).append(uri)
              cache.clear()
          def _pop_ns(prefix):
              uris = prefixes.get(prefix)
              uri = uris.pop()
              if not uris:
                  del prefixes[prefix]
              if uri not in uris or uri != uris[-1]:
                  uri_prefixes = namespaces[uri]
                  uri_prefixes.pop()
                  if not uri_prefixes:
                      del namespaces[uri]
              cache.clear()
              return uri
  
          ns_attrs = []
          _push_ns_attr = ns_attrs.append
          def _make_ns_attr(prefix, uri):
              return 'xmlns%s' % (prefix and ':%s' % prefix or ''), uri
  
          def _gen_prefix():
              val = 0
              while 1:
                  val += 1
                  yield 'ns%d' % val
          _gen_prefix = _gen_prefix().next
  
          for kind, data, pos in stream:
              output = cache_get((kind, data))
              if output is not None:
                  yield kind, output, pos
  
              elif kind is START or kind is EMPTY:
                  tag, attrs = data
  
                  tagname = tag.localname
                  tagns = tag.namespace
                  if tagns:
                      if tagns in namespaces:
                          prefix = namespaces[tagns][-1]
                          if prefix:
                              tagname = '%s:%s' % (prefix, tagname)
                      else:
                          _push_ns_attr(('xmlns', tagns))
                          _push_ns('', tagns)
  
                  new_attrs = []
                  for attr, value in attrs:
                      attrname = attr.localname
                      attrns = attr.namespace
                      if attrns:
                          if attrns not in namespaces:
                              prefix = _gen_prefix()
                              _push_ns(prefix, attrns)
                              _push_ns_attr(('xmlns:%s' % prefix, attrns))
                          else:
                              prefix = namespaces[attrns][-1]
                          if prefix:
                              attrname = '%s:%s' % (prefix, attrname)
                      new_attrs.append((attrname, value))
  
                  yield _emit(kind, data, (tagname, Attrs(ns_attrs + new_attrs)), pos)
                  del ns_attrs[:]
  
              elif kind is END:
                  tagname = data.localname
                  tagns = data.namespace
                  if tagns:
                      prefix = namespaces[tagns][-1]
                      if prefix:
                          tagname = '%s:%s' % (prefix, tagname)
                  yield _emit(kind, data, tagname, pos)
  
              elif kind is START_NS:
                  prefix, uri = data
                  if uri not in namespaces:
                      prefix = prefixes.get(uri, [prefix])[-1]
                      _push_ns_attr(_make_ns_attr(prefix, uri))
                  _push_ns(prefix, uri)
  
              elif kind is END_NS:
                  if data in prefixes:
                      uri = _pop_ns(data)
                      if ns_attrs:
                          attr = _make_ns_attr(data, uri)
                          if attr in ns_attrs:
                              ns_attrs.remove(attr)
  
              else:
                  yield kind, data, pos
  
  
  class WhitespaceFilter(object):
      """A filter that removes extraneous ignorable white space from the
      stream.
      """
  
      def __init__(self, preserve=None, noescape=None):
          """Initialize the filter.
          
          :param preserve: a set or sequence of tag names for which white-space
                           should be preserved
          :param noescape: a set or sequence of tag names for which text content
                           should not be escaped
          
          The `noescape` set is expected to refer to elements that cannot contain
          further child elements (such as ``<style>`` or ``<script>`` in HTML
          documents).
          """
          if preserve is None:
              preserve = []
          self.preserve = frozenset(preserve)
          if noescape is None:
              noescape = []
          self.noescape = frozenset(noescape)
  
      def __call__(self, stream, ctxt=None, space=XML_NAMESPACE['space'],
                   trim_trailing_space=re.compile('[ \t]+(?=\n)').sub,
                   collapse_lines=re.compile('\n{2,}').sub):
          mjoin = Markup('').join
          preserve_elems = self.preserve
          preserve = 0
          noescape_elems = self.noescape
          noescape = False
  
          textbuf = []
          push_text = textbuf.append
          pop_text = textbuf.pop
          for kind, data, pos in chain(stream, [(None, None, None)]):
  
              if kind is TEXT:
                  if noescape:
                      data = Markup(data)
                  push_text(data)
              else:
                  if textbuf:
                      if len(textbuf) > 1:
                          text = mjoin(textbuf, escape_quotes=False)
                          del textbuf[:]
                      else:
                          text = escape(pop_text(), quotes=False)
                      if not preserve:
                          text = collapse_lines('\n', trim_trailing_space('', text))
                      yield TEXT, Markup(text), pos
  
                  if kind is START:
                      tag, attrs = data
                      if preserve or (tag in preserve_elems or
                                      attrs.get(space) == 'preserve'):
                          preserve += 1
                      if not noescape and tag in noescape_elems:
                          noescape = True
  
                  elif kind is END:
                      noescape = False
                      if preserve:
                          preserve -= 1
  
                  elif kind is START_CDATA:
                      noescape = True
  
                  elif kind is END_CDATA:
                      noescape = False
  
                  if kind:
                      yield kind, data, pos
  
  
  class DocTypeInserter(object):
      """A filter that inserts the DOCTYPE declaration in the correct location,
      after the XML declaration.
      """
      def __init__(self, doctype):
          """Initialize the filter.
  
          :param doctype: DOCTYPE as a string or DocType object.
          """
          if isinstance(doctype, basestring):
              doctype = DocType.get(doctype)
          self.doctype_event = (DOCTYPE, doctype, (None, -1, -1))
  
      def __call__(self, stream):
          doctype_inserted = False
          for kind, data, pos in stream:
              if not doctype_inserted:
                  doctype_inserted = True
                  if kind is XML_DECL:
                      yield (kind, data, pos)
                      yield self.doctype_event
                      continue
                  yield self.doctype_event
  
              yield (kind, data, pos)
  
          if not doctype_inserted:
              yield self.doctype_event
  