Lib/xmllib.py

# A parser for XML, using the derived class as static DTD.
# Author: Sjoerd Mullender.

import re
import string


# Regular expressions used for parsing

_S = '[ \t\r\n]+'
_opS = '[ \t\r\n]*'
_Name = '[a-zA-Z_:][-a-zA-Z0-9._:]*'
interesting = re.compile('[&<]')
incomplete = re.compile('&(' + _Name + '|#[0-9]*|#x[0-9a-fA-F]*)?|'
			   '<([a-zA-Z_:][^<>]*|'
			      '/([a-zA-Z_:][^<>]*)?|'
			      '![^<>]*|'
			      r'\?[^<>]*)?')

ref = re.compile('&(' + _Name + '|#[0-9]+|#x[0-9a-fA-F]+);?')
entityref = re.compile('&(?P<name>' + _Name + ')[^-a-zA-Z0-9._:]')
charref = re.compile('&#(?P<char>[0-9]+[^0-9]|x[0-9a-fA-F]+[^0-9a-fA-F])')
space = re.compile(_S)
newline = re.compile('\n')

starttagopen = re.compile('<' + _Name)
endtagopen = re.compile('</')
starttagend = re.compile(_opS + '(?P<slash>/?)>')
endbracket = re.compile('>')
tagfind = re.compile(_Name)
cdataopen = re.compile(r'<!\[CDATA\[')
cdataclose = re.compile(r'\]\]>')
doctype = re.compile('<!DOCTYPE' + _S + '(?P<name>' + _Name + ')' + _S)
special = re.compile('<!(?P<special>[^<>]*)>')
procopen = re.compile(r'<\?(?P<proc>' + _Name + ')' + _S)
procclose = re.compile(_opS + r'\?>')
commentopen = re.compile('<!--')
commentclose = re.compile('-->')
doubledash = re.compile('--')
attrfind = re.compile(
    _S + '(?P<name>' + _Name + ')'
    '(' + _opS + '=' + _opS +
    '(?P<value>\'[^\']*\'|"[^"]*"|[-a-zA-Z0-9.:+*%?!()_#=~]+))')


# XML parser base class -- find tags and call handler functions.
# Usage: p = XMLParser(); p.feed(data); ...; p.close().
# The dtd is defined by deriving a class which defines methods with
# special names to handle tags: start_foo and end_foo to handle <foo>
# and </foo>, respectively.  The data between tags is passed to the
# parser by calling self.handle_data() with some data as argument (the
# data may be split up in arbutrary chunks).  Entity references are
# passed by calling self.handle_entityref() with the entity reference
# as argument.

class XMLParser:

    # Interface -- initialize and reset this instance
    def __init__(self, verbose=0):
	self.verbose = verbose
	self.reset()

    # Interface -- reset this instance.  Loses all unprocessed data
    def reset(self):
	self.rawdata = ''
	self.stack = []
	self.nomoretags = 0
	self.literal = 0
	self.lineno = 1
	self.__at_start = 1
	self.__seen_doctype = None
	self.__seen_starttag = 0

    # For derived classes only -- enter literal mode (CDATA) till EOF
    def setnomoretags(self):
	self.nomoretags = self.literal = 1

    # For derived classes only -- enter literal mode (CDATA)
    def setliteral(self, *args):
	self.literal = 1

    # Interface -- feed some data to the parser.  Call this as
    # often as you want, with as little or as much text as you
    # want (may include '\n').  (This just saves the text, all the
    # processing is done by goahead().)
    def feed(self, data):
	self.rawdata = self.rawdata + data
	self.goahead(0)

    # Interface -- handle the remaining data
    def close(self):
	self.goahead(1)

    # Interface -- translate references
    def translate_references(self, data):
	newdata = []
	i = 0
	while 1:
	    res = ref.search(data, i)
	    if res is None:
		newdata.append(data[i:])
		return string.join(newdata, '')
	    if data[res.end(0) - 1] != ';':
		self.syntax_error("`;' missing after entity/char reference")
	    newdata.append(data[i:res.start(0)])
	    str = res.group(1)
	    if str[0] == '#':
		if str[1] == 'x':
		    newdata.append(chr(string.atoi(str[2:], 16)))
		else:
		    newdata.append(chr(string.atoi(str[1:])))
	    else:
		try:
		    newdata.append(self.entitydefs[str])
		except KeyError:
		    # can't do it, so keep the entity ref in
		    newdata.append('&' + str + ';')
	    i = res.end(0)

    # Internal -- handle data as far as reasonable.  May leave state
    # and data to be processed by a subsequent call.  If 'end' is
    # true, force handling all data as if followed by EOF marker.
    def goahead(self, end):
	rawdata = self.rawdata
	i = 0
	n = len(rawdata)
	while i < n:
	    if i > 0:
		self.__at_start = 0
	    if self.nomoretags:
		data = rawdata[i:n]
		self.handle_data(data)
		self.lineno = self.lineno + string.count(data, '\n')
		i = n
		break
	    res = interesting.search(rawdata, i)
	    if res:
		    j = res.start(0)
	    else:
		    j = n
	    if i < j:
		self.__at_start = 0
		data = rawdata[i:j]
		self.handle_data(data)
		self.lineno = self.lineno + string.count(data, '\n')
	    i = j
	    if i == n: break
	    if rawdata[i] == '<':
		if starttagopen.match(rawdata, i):
		    if self.literal:
			data = rawdata[i]
			self.handle_data(data)
			self.lineno = self.lineno + string.count(data, '\n')
			i = i+1
			continue
		    k = self.parse_starttag(i)
		    if k < 0: break
		    self.__seen_starttag = 1
		    self.lineno = self.lineno + string.count(rawdata[i:k], '\n')
		    i = k
		    continue
		if endtagopen.match(rawdata, i):
		    k = self.parse_endtag(i)
		    if k < 0: break
		    self.lineno = self.lineno + string.count(rawdata[i:k], '\n')
		    i =  k
		    self.literal = 0
		    continue
		if commentopen.match(rawdata, i):
		    if self.literal:
			data = rawdata[i]
			self.handle_data(data)
			self.lineno = self.lineno + string.count(data, '\n')
			i = i+1
			continue
		    k = self.parse_comment(i)
		    if k < 0: break
		    self.lineno = self.lineno + string.count(rawdata[i:k], '\n')
		    i = k
		    continue
		if cdataopen.match(rawdata, i):
		    k = self.parse_cdata(i)
		    if k < 0: break
		    self.lineno = self.lineno + string.count(rawdata[i:i], '\n')
		    i = k
		    continue
		res = procopen.match(rawdata, i)
		if res:
		    k = self.parse_proc(i)
		    if k < 0: break
		    self.lineno = self.lineno + string.count(rawdata[i:k], '\n')
		    i = k
		    continue
		res = doctype.match(rawdata, i)
		if res:
		    if self.literal:
			data = rawdata[i]
			self.handle_data(data)
			self.lineno = self.lineno + string.count(data, '\n')
			i = i+1
			continue
		    if self.__seen_doctype:
			self.syntax_error('multiple DOCTYPE elements')
		    if self.__seen_starttag:
			self.syntax_error('DOCTYPE not at beginning of document')
		    k = self.parse_doctype(res)
		    if k < 0: break
		    self.__seen_doctype = res.group('name')
		    self.lineno = self.lineno + string.count(rawdata[i:k], '\n')
		    i = k
		    continue
		res = special.match(rawdata, i)
		if res:
		    if self.literal:
			data = rawdata[i]
			self.handle_data(data)
			self.lineno = self.lineno + string.count(data, '\n')
			i = i+1
			continue
		    self.handle_special(res.group('special'))
		    self.lineno = self.lineno + string.count(res.group(0), '\n')
		    i = res.end(0)
		    continue
	    elif rawdata[i] == '&':
		res = charref.match(rawdata, i)
		if res is not None:
		    i = res.end(0)
		    if rawdata[i-1] != ';':
			self.syntax_error("`;' missing in charref")
			i = i-1
		    self.handle_charref(res.group('char')[:-1])
		    self.lineno = self.lineno + string.count(res.group(0), '\n')
		    continue
		res = entityref.match(rawdata, i)
		if res is not None:
		    i = res.end(0)
		    if rawdata[i-1] != ';':
			self.syntax_error("`;' missing in entityref")
			i = i-1
		    self.handle_entityref(res.group('name'))
		    self.lineno = self.lineno + string.count(res.group(0), '\n')
		    continue
	    else:
		raise RuntimeError, 'neither < nor & ??'
	    # We get here only if incomplete matches but
	    # nothing else
	    res = incomplete.match(rawdata, i)
	    if not res:
		data = rawdata[i]
		self.handle_data(data)
		self.lineno = self.lineno + string.count(data, '\n')
		i = i+1
		continue
	    j = res.end(0)
	    if j == n:
		break # Really incomplete
	    self.syntax_error("bogus `<' or `&'")
	    data = res.group(0)
	    self.handle_data(data)
	    self.lineno = self.lineno + string.count(data, '\n')
	    i = j
	# end while
	if end and i < n:
	    data = rawdata[i:n]
	    self.handle_data(data)
	    self.lineno = self.lineno + string.count(data, '\n')
	    i = n
	self.rawdata = rawdata[i:]
	if end:
	    if self.stack:
		self.syntax_error('missing end tags')
		while self.stack:
		    self.finish_endtag(self.stack[-1])

    # Internal -- parse comment, return length or -1 if not terminated
    def parse_comment(self, i):
	rawdata = self.rawdata
	if rawdata[i:i+4] <> '<!--':
	    raise RuntimeError, 'unexpected call to handle_comment'
	res = commentclose.search(rawdata, i+4)
	if not res:
	    return -1
	# doubledash search will succeed because it's a subset of commentclose
	if doubledash.search(rawdata, i+4).start(0) < res.start(0):
	    self.syntax_error("`--' inside comment")
	self.handle_comment(rawdata[i+4: res.start(0)])
	return res.end(0)

    # Internal -- handle DOCTYPE tag, return length or -1 if not terminated
    def parse_doctype(self, res):
	rawdata = self.rawdata
	n = len(rawdata)
	name = res.group('name')
	j = k = res.end(0)
	level = 0
	while k < n:
	    c = rawdata[k]
	    if c == '<':
		level = level + 1
	    elif c == '>':
		if level == 0:
		    self.handle_doctype(name, rawdata[j:k])
		    return k+1
		level = level - 1
	    k = k+1
	return -1

    # Internal -- handle CDATA tag, return length or -1 if not terminated
    def parse_cdata(self, i):
	rawdata = self.rawdata
	if rawdata[i:i+9] <> '<![CDATA[':
	    raise RuntimeError, 'unexpected call to handle_cdata'
	res = cdataclose.search(rawdata, i+9)
	if not res:
	    return -1
	self.handle_cdata(rawdata[i+9:res.start(0)])
	return res.end(0)

    __xml_attributes = {'version': '1.0', 'standalone': 'no', 'encoding': None}
    # Internal -- handle a processing instruction tag
    def parse_proc(self, i):
	rawdata = self.rawdata
	end = procclose.search(rawdata, i)
	if not end:
	    return -1
	j = end.start(0)
	res = tagfind.match(rawdata, i+2)
	if not res:
	    raise RuntimeError, 'unexpected call to parse_proc'
	k = res.end(0)
	name = res.group(0)
	if name == 'xml':
	    if self.__at_start:
		attrdict, k = self.parse_attributes('xml', k, j,
						    self.__xml_attributes)
		if k != j:
		    self.syntax_error('garbage at end of <?xml?>')
		if attrdict['version'] != '1.0':
		    self.syntax_error('only XML version 1.0 supported')
		self.handle_xml(attrdict.get('encoding', None),
				attrdict['standalone'])
		return end.end(0)
	    else:
		self.syntax_error("<?xml?> tag not at start of document")
	self.handle_proc(name, rawdata[k:j])
	return end.end(0)

    # Internal -- parse attributes between i and j
    def parse_attributes(self, tag, k, j, attributes = None):
	rawdata = self.rawdata
	# Now parse the data between k and j into a tag and attrs
	attrdict = {}
	try:
	    # convert attributes list to dictionary
	    d = {}
	    for a in attributes:
		d[a] = None
	    attributes = d
	except TypeError:
	    pass
	while k < j:
	    res = attrfind.match(rawdata, k)
	    if not res: break
	    attrname, attrvalue = res.group('name', 'value')
	    if attrvalue is None:
		self.syntax_error('no attribute value specified')
		attrvalue = attrname
	    elif attrvalue[:1] == "'" == attrvalue[-1:] or \
		 attrvalue[:1] == '"' == attrvalue[-1:]:
		attrvalue = attrvalue[1:-1]
	    else:
		self.syntax_error('attribute value not quoted')
	    if attributes is not None and not attributes.has_key(attrname):
		self.syntax_error('unknown attribute %s of element %s' %
				  (attrname, tag))
	    if attrdict.has_key(attrname):
		self.syntax_error('attribute specified twice')
	    attrdict[attrname] = self.translate_references(attrvalue)
	    k = res.end(0)
	if attributes is not None:
	    # fill in with default attributes
	    for key, val in attributes.items():
		if val is not None and not attrdict.has_key(key):
		    attrdict[key] = val
	return attrdict, k

    # Internal -- handle starttag, return length or -1 if not terminated
    def parse_starttag(self, i):
	rawdata = self.rawdata
	# i points to start of tag
	end = endbracket.search(rawdata, i+1)
	if not end:
	    return -1
	j = end.start(0)
	res = tagfind.match(rawdata, i+1)
	if not res:
	    raise RuntimeError, 'unexpected call to parse_starttag'
	k = res.end(0)
	tag = res.group(0)
	if not self.__seen_starttag and self.__seen_doctype:
	    if tag != self.__seen_doctype:
		self.syntax_error('starttag does not match DOCTYPE')
	if hasattr(self, tag + '_attributes'):
	    attributes = getattr(self, tag + '_attributes')
	else:
	    attributes = None
	attrdict, k = self.parse_attributes(tag, k, j, attributes)
	res = starttagend.match(rawdata, k)
	if not res:
	    self.syntax_error('garbage in start tag')
	self.finish_starttag(tag, attrdict)
	if res and res.group('slash') == '/':
	    self.finish_endtag(tag)
	return end.end(0)

    # Internal -- parse endtag
    def parse_endtag(self, i):
	rawdata = self.rawdata
	end = endbracket.search(rawdata, i+1)
	if not end:
	    return -1
	res = tagfind.match(rawdata, i+2)
	if not res:
	    self.syntax_error('no name specified in end tag')
	    tag = ''
	    k = i+2
	else:
	    tag = res.group(0)
	    k = res.end(0)
	if k != end.start(0):
	    # check that there is only white space at end of tag
	    res = space.match(rawdata, k)
	    if res is None or res.end(0) != end.start(0):
		self.syntax_error('garbage in end tag')
	self.finish_endtag(tag)
	return end.end(0)

    # Internal -- finish processing of start tag
    # Return -1 for unknown tag, 1 for balanced tag
    def finish_starttag(self, tag, attrs):
	self.stack.append(tag)
	try:
	    method = getattr(self, 'start_' + tag)
	except AttributeError:
	    self.unknown_starttag(tag, attrs)
	    return -1
	else:
	    self.handle_starttag(tag, method, attrs)
	    return 1

    # Internal -- finish processing of end tag
    def finish_endtag(self, tag):
	if not tag:
	    self.syntax_error('name-less end tag')
	    found = len(self.stack) - 1
	    if found < 0:
		self.unknown_endtag(tag)
		return
	else:
	    if tag not in self.stack:
		self.syntax_error('unopened end tag')
		try:
		    method = getattr(self, 'end_' + tag)
		except AttributeError:
		    self.unknown_endtag(tag)
		return
	    found = len(self.stack)
	    for i in range(found):
		if self.stack[i] == tag:
		    found = i
	while len(self.stack) > found:
	    if found < len(self.stack) - 1:
		self.syntax_error('missing close tag for %s' % self.stack[-1])
	    tag = self.stack[-1]
	    try:
		method = getattr(self, 'end_' + tag)
	    except AttributeError:
		method = None
	    if method:
		self.handle_endtag(tag, method)
	    else:
		self.unknown_endtag(tag)
	    del self.stack[-1]

    # Overridable -- handle xml processing instruction
    def handle_xml(self, encoding, standalone):
	pass

    # Overridable -- handle DOCTYPE
    def handle_doctype(self, tag, data):
	pass

    # Overridable -- handle start tag
    def handle_starttag(self, tag, method, attrs):
	method(attrs)

    # Overridable -- handle end tag
    def handle_endtag(self, tag, method):
	method()

    # Example -- handle character reference, no need to override
    def handle_charref(self, name):
	try:
	    if name[0] == 'x':
		n = string.atoi(name[1:], 16)
	    else:
		n = string.atoi(name)
	except string.atoi_error:
	    self.unknown_charref(name)
	    return
	if not 0 <= n <= 255:
	    self.unknown_charref(name)
	    return
	self.handle_data(chr(n))

    # Definition of entities -- derived classes may override
    entitydefs = {'lt': '<', 'gt': '>', 'amp': '&', 'quot': '"', 'apos': "'"}

    # Example -- handle entity reference, no need to override
    def handle_entityref(self, name):
	table = self.entitydefs
	if table.has_key(name):
	    self.handle_data(table[name])
	else:
	    self.unknown_entityref(name)
	    return

    # Example -- handle data, should be overridden
    def handle_data(self, data):
	pass

    # Example -- handle cdata, could be overridden
    def handle_cdata(self, data):
	pass

    # Example -- handle comment, could be overridden
    def handle_comment(self, data):
	pass

    # Example -- handle processing instructions, could be overridden
    def handle_proc(self, name, data):
	pass

    # Example -- handle special instructions, could be overridden
    def handle_special(self, data):
	pass

    # Example -- handle relatively harmless syntax errors, could be overridden
    def syntax_error(self, message):
	raise RuntimeError, 'Syntax error at line %d: %s' % (self.lineno, message)

    # To be overridden -- handlers for unknown objects
    def unknown_starttag(self, tag, attrs): pass
    def unknown_endtag(self, tag): pass
    def unknown_charref(self, ref): pass
    def unknown_entityref(self, ref): pass


class TestXMLParser(XMLParser):

    def __init__(self, verbose=0):
	self.testdata = ""
	XMLParser.__init__(self, verbose)

    def handle_xml(self, encoding, standalone):
	self.flush()
	print 'xml: encoding =',encoding,'standalone =',standalone

    def handle_doctype(self, tag, data):
	self.flush()
	print 'DOCTYPE:',tag, `data`

    def handle_data(self, data):
	self.testdata = self.testdata + data
	if len(`self.testdata`) >= 70:
	    self.flush()

    def flush(self):
	data = self.testdata
	if data:
	    self.testdata = ""
	    print 'data:', `data`

    def handle_cdata(self, data):
	self.flush()
	print 'cdata:', `data`

    def handle_proc(self, name, data):
	self.flush()
	print 'processing:',name,`data`

    def handle_special(self, data):
	self.flush()
	print 'special:',`data`

    def handle_comment(self, data):
	self.flush()
	r = `data`
	if len(r) > 68:
	    r = r[:32] + '...' + r[-32:]
	print 'comment:', r

    def syntax_error(self, message):
	print 'error at line %d:' % self.lineno, message

    def unknown_starttag(self, tag, attrs):
	self.flush()
	if not attrs:
	    print 'start tag: <' + tag + '>'
	else:
	    print 'start tag: <' + tag,
	    for name, value in attrs.items():
		print name + '=' + '"' + value + '"',
	    print '>'

    def unknown_endtag(self, tag):
	self.flush()
	print 'end tag: </' + tag + '>'

    def unknown_entityref(self, ref):
	self.flush()
	print '*** unknown entity ref: &' + ref + ';'

    def unknown_charref(self, ref):
	self.flush()
	print '*** unknown char ref: &#' + ref + ';'

    def close(self):
	XMLParser.close(self)
	self.flush()

def test(args = None):
    import sys

    if not args:
	args = sys.argv[1:]

    if args and args[0] == '-s':
	args = args[1:]
	klass = XMLParser
    else:
	klass = TestXMLParser

    if args:
	file = args[0]
    else:
	file = 'test.xml'

    if file == '-':
	f = sys.stdin
    else:
	try:
	    f = open(file, 'r')
	except IOError, msg:
	    print file, ":", msg
	    sys.exit(1)

    data = f.read()
    if f is not sys.stdin:
	f.close()

    x = klass()
    for c in data:
	x.feed(c)
    x.close()


if __name__ == '__main__':
    test()