added html parser and supporting cast

Lib/sgmllib.py

+# A parser for SGML, using the derived class as static DTD.
+
+# XXX This only supports those SGML features used by HTML.
+
+# XXX There should be a way to distinguish between PCDATA (parsed
+# character data -- the normal case), RCDATA (replaceable character
+# data -- only char and entity references and end tags are special)
+# and CDATA (character data -- only end tags are special).
+
+
+import regex
+import string
+
+
+# Regular expressions used for parsing
+
+incomplete = regex.compile( \
+	  '<!-?\|</[a-zA-Z][a-zA-Z0-9]*[ \t\n]*\|</?\|' + \
+	  '&#[a-zA-Z0-9]*\|&[a-zA-Z][a-zA-Z0-9]*\|&')
+entityref = regex.compile('&[a-zA-Z][a-zA-Z0-9]*[;.]')
+charref = regex.compile('&#[a-zA-Z0-9]+;')
+starttagopen = regex.compile('<[a-zA-Z]')
+endtag = regex.compile('</[a-zA-Z][a-zA-Z0-9]*[ \t\n]*>')
+commentopen = regex.compile('<!--')
+
+
+# SGML parser base class -- find tags and call handler functions.
+# Usage: p = SGMLParser(); 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, or do_foo to handle <foo> by itself.
+# (Tags are converted to lower case for this purpose.)  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 SGMLParser:
+
+	# Interface -- initialize and reset this instance
+	def __init__(self):
+		self.reset()
+
+	# Interface -- reset this instance.  Loses all unprocessed data
+	def reset(self):
+		self.rawdata = ''
+		self.stack = []
+		self.nomoretags = 0
+		self.literal = 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 process() or close().)
+	def feed(self, data):
+		self.rawdata = self.rawdata + data
+		self.goahead(0)
+
+	# Interface -- handle the remaining data
+	def close(self):
+		self.goahead(1)
+
+	# 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 self.nomoretags:
+				self.handle_data(rawdata[i:n])
+				i = n
+				break
+			j = incomplete.search(rawdata, i)
+			if j < 0: j = n
+			if i < j: self.handle_data(rawdata[i:j])
+			i = j
+			if i == n: break
+			if rawdata[i] == '<':
+				if starttagopen.match(rawdata, i) >= 0:
+					if self.literal:
+						self.handle_data(rawdata[i])
+						i = i+1
+						continue
+					k = self.parse_starttag(i)
+					if k < 0: break
+					i = i + k
+					continue
+				k = endtag.match(rawdata, i)
+				if k >= 0:
+					j = i+k
+					self.parse_endtag(rawdata[i:j])
+					i = j
+					self.literal = 0
+					continue
+				if commentopen.match(rawdata, i) >= 0:
+					if self.literal:
+						self.handle_data(rawdata[i])
+						i = i+1
+						continue
+					k = self.parse_comment(i)
+					if k < 0: break
+					i = i+k
+					continue
+			elif rawdata[i] == '&':
+				k = charref.match(rawdata, i)
+				if k >= 0:
+					j = i+k
+					self.handle_charref(rawdata[i+2:j-1])
+					i = j
+					continue
+				k = entityref.match(rawdata, i)
+				if k >= 0:
+					j = i+k
+					self.handle_entityref(rawdata[i+1:j-1])
+					i = j
+					continue
+			else:
+				raise RuntimeError, 'neither < nor & ??'
+			# We get here only if incomplete matches but
+			# nothing else
+			k = incomplete.match(rawdata, i)
+			if k < 0: raise RuntimeError, 'no incomplete match ??'
+			j = i+k
+			if j == n: break # Really incomplete
+			self.handle_data(rawdata[i:j])
+			i = j
+		# end while
+		if end and i < n:
+			self.handle_data(rawdata[i:n])
+			i = n
+		self.rawdata = rawdata[i:]
+		# XXX if end: check for empty stack
+
+	# Internal -- parse comment, return length or -1 if not ternimated
+	def parse_comment(self, i):
+		rawdata = self.rawdata
+		if rawdata[i:i+4] <> '<!--':
+			raise RuntimeError, 'unexpected call to handle_comment'
+		try:
+			j = string.index(rawdata, '--', i+4)
+		except string.index_error:
+			return -1
+		self.handle_comment(rawdata[i+4: j])
+		j = j+2
+		n = len(rawdata)
+		while j < n and rawdata[j] in ' \t\n': j = j+1
+		if j == n: return -1 # Wait for final '>'
+		if rawdata[j] == '>':
+			j = j+1
+		else:
+			print '*** comment not terminated with >'
+			print repr(rawdata[j-5:j]), '*!*', repr(rawdata[j:j+5])
+		return j-i
+
+	# Internal -- handle starttag, return length or -1 if not terminated
+	def parse_starttag(self, i):
+		rawdata = self.rawdata
+		try:
+			j = string.index(rawdata, '>', i)
+		except string.index_error:
+			return -1
+		# Now parse the data between i+1 and j into a tag and attrs
+		attrs = []
+		tagfind = regex.compile('[a-zA-Z][a-zA-Z0-9]*')
+		attrfind = regex.compile( \
+		  '[ \t\n]+\([a-zA-Z][a-zA-Z0-9]*\)' + \
+		  '\([ \t\n]*=[ \t\n]*' + \
+		     '\(\'[^\']*\';\|"[^"]*"\|[-a-zA-Z0-9./:+*%?!()_#]+\)\)?')
+		k = tagfind.match(rawdata, i+1)
+		if k < 0:
+			raise RuntimeError, 'unexpected call to parse_starttag'
+		k = i+1+k
+		tag = string.lower(rawdata[i+1:k])
+		while k < j:
+			l = attrfind.match(rawdata, k)
+			if l < 0: break
+			regs = attrfind.regs
+			a1, b1 = regs[1]
+			a2, b2 = regs[2]
+			a3, b3 = regs[3]
+			attrname = rawdata[a1:b1]
+			if '=' in rawdata[k:k+l]:
+				attrvalue = rawdata[a3:b3]
+				if attrvalue[:1] == '\'' == attrvalue[-1:] or \
+				   attrvalue[:1] == '"' == attrvalue[-1:]:
+					attrvalue = attrvalue[1:-1]
+			else:
+				attrvalue = ''
+			attrs.append(string.lower(attrname), attrvalue)
+			k = k + l
+		j = j+1
+		try:
+			method = getattr(self, 'start_' + tag)
+		except AttributeError:
+			try:
+				method = getattr(self, 'do_' + tag)
+			except AttributeError:
+				self.unknown_starttag(tag, attrs)
+				return j-i
+			method(attrs)
+			return j-i
+		self.stack.append(tag)
+		method(attrs)
+		return j-i
+
+	# Internal -- parse endtag
+	def parse_endtag(self, data):
+		if data[:2] <> '</' or data[-1:] <> '>':
+			raise RuntimeError, 'unexpected call to parse_endtag'
+		tag = string.lower(string.strip(data[2:-1]))
+		try:
+			method = getattr(self, 'end_' + tag)
+		except AttributeError:
+			self.unknown_endtag(tag)
+			return
+		if self.stack and self.stack[-1] == tag:
+			del self.stack[-1]
+		else:
+			print '*** Unbalanced </' + tag + '>'
+			print '*** Stack:', self.stack
+			found = None
+			for i in range(len(self.stack)):
+				if self.stack[i] == tag: found = i
+			if found <> None:
+				del self.stack[found:]
+		method()
+
+	# Example -- handle character reference, no need to override
+	def handle_charref(self, name):
+		try:
+			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.__class__.entitydefs
+		name = string.lower(name)
+		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 comment, could be overridden
+	def handle_comment(self, data):
+		pass
+
+	# 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 TestSGML(SGMLParser):
+
+	def handle_data(self, data):
+		r = repr(data)
+		if len(r) > 72:
+			r = r[:35] + '...' + r[-35:]
+		print 'data:', r
+
+	def handle_comment(self, data):
+		r = repr(data)
+		if len(r) > 68:
+			r = r[:32] + '...' + r[-32:]
+		print 'comment:', r
+
+	def unknown_starttag(self, tag, attrs):
+		print 'start tag: <' + tag,
+		for name, value in attrs:
+			print name + '=' + '"' + value + '"',
+		print '>'
+
+	def unknown_endtag(self, tag):
+		print 'end tag: </' + tag + '>'
+
+	def unknown_entityref(self, ref):
+		print '*** unknown entity ref: &' + ref + ';'
+
+	def unknown_charref(self, ref):
+		print '*** unknown char ref: &#' + ref + ';'
+
+
+def test():
+	file = 'test.html'
+	f = open(file, 'r')
+	x = TestSGML()
+	while 1:
+		line = f.readline()
+		if not line:
+			x.close()
+			break
+		x.feed(line)
+
+
+#test()