"""A parser for SGML, using the derived class as a 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 re import string # Regular expressions used for parsing interesting = re.compile('[&<]') incomplete = re.compile('&([a-zA-Z][a-zA-Z0-9]*|#[0-9]*)?|' '<([a-zA-Z][^<>]*|' '/([a-zA-Z][^<>]*)?|' '![^<>]*)?') entityref = re.compile('&([a-zA-Z][-.a-zA-Z0-9]*)[^a-zA-Z0-9]') charref = re.compile('&#([0-9]+)[^0-9]') starttagopen = re.compile('<[>a-zA-Z]') shorttagopen = re.compile('<[a-zA-Z][-.a-zA-Z0-9]*/') shorttag = re.compile('<([a-zA-Z][-.a-zA-Z0-9]*)/([^/]*)/') piopen = re.compile('<\?') piclose = re.compile('>') endtagopen = re.compile('</[<>a-zA-Z]') endbracket = re.compile('[<>]') special = re.compile('<![^<>]*>') commentopen = re.compile('<!--') commentclose = re.compile('--[%s]*>' % string.whitespace) tagfind = re.compile('[a-zA-Z][-.a-zA-Z0-9]*') attrfind = re.compile( '[%s]*([a-zA-Z_][-.a-zA-Z_0-9]*)' % string.whitespace + ('([%s]*=[%s]*' % (string.whitespace, string.whitespace)) + r'(\'[^\']*\'|"[^"]*"|[-a-zA-Z0-9./:+*%?!\(\)_#=~]*))?') # 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, verbose=0): self.verbose = verbose self.reset() # Interface -- reset this instance. Loses all unprocessed data def reset(self): self.rawdata = '' self.stack = [] self.lasttag = '???' 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 goahead().) 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 match = interesting.search(rawdata, i) if match: j = match.start(0) else: 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): if self.literal: self.handle_data(rawdata[i]) i = i+1 continue k = self.parse_starttag(i) if k < 0: break i = k continue if endtagopen.match(rawdata, i): k = self.parse_endtag(i) if k < 0: break i = k self.literal = 0 continue if commentopen.match(rawdata, i): 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 if piopen.match(rawdata, i): if self.literal: self.handle_data(rawdata[i]) i = i+1 continue k = self.parse_pi(i) if k < 0: break i = i+k continue match = special.match(rawdata, i) if match: if self.literal: self.handle_data(rawdata[i]) i = i+1 continue i = match.end(0) continue elif rawdata[i] == '&': match = charref.match(rawdata, i) if match: name = match.group(1) self.handle_charref(name) i = match.end(0) if rawdata[i-1] != ';': i = i-1 continue match = entityref.match(rawdata, i) if match: name = match.group(1) self.handle_entityref(name) i = match.end(0) if rawdata[i-1] != ';': i = i-1 continue else: raise RuntimeError, 'neither < nor & ??' # We get here only if incomplete matches but # nothing else match = incomplete.match(rawdata, i) if not match: self.handle_data(rawdata[i]) i = i+1 continue j = match.end(0) 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 terminated def parse_comment(self, i): rawdata = self.rawdata if rawdata[i:i+4] <> '<!--': raise RuntimeError, 'unexpected call to handle_comment' match = commentclose.search(rawdata, i+4) if not match: return -1 j = match.start(0) self.handle_comment(rawdata[i+4: j]) j = match.end(0) return j-i # Internal -- parse processing instr, return length or -1 if not terminated def parse_pi(self, i): rawdata = self.rawdata if rawdata[i:i+2] <> '<?': raise RuntimeError, 'unexpected call to handle_pi' match = piclose.search(rawdata, i+2) if not match: return -1 j = match.start(0) self.handle_pi(rawdata[i+2: j]) j = match.end(0) return j-i # Internal -- handle starttag, return length or -1 if not terminated def parse_starttag(self, i): rawdata = self.rawdata if shorttagopen.match(rawdata, i): # SGML shorthand: <tag/data/ == <tag>data</tag> # XXX Can data contain &... (entity or char refs)? # XXX Can data contain < or > (tag characters)? # XXX Can there be whitespace before the first /? match = shorttag.match(rawdata, i) if not match: return -1 tag, data = match.group(1, 2) tag = string.lower(tag) self.finish_shorttag(tag, data) k = match.end(0) return k # XXX The following should skip matching quotes (' or ") match = endbracket.search(rawdata, i+1) if not match: return -1 j = match.start(0) # Now parse the data between i+1 and j into a tag and attrs attrs = [] if rawdata[i:i+2] == '<>': # SGML shorthand: <> == <last open tag seen> k = j tag = self.lasttag else: match = tagfind.match(rawdata, i+1) if not match: raise RuntimeError, 'unexpected call to parse_starttag' k = match.end(0) tag = string.lower(rawdata[i+1:k]) self.lasttag = tag while k < j: match = attrfind.match(rawdata, k) if not match: break attrname, rest, attrvalue = match.group(1, 2, 3) if not rest: attrvalue = attrname elif attrvalue[:1] == '\'' == attrvalue[-1:] or \ attrvalue[:1] == '"' == attrvalue[-1:]: attrvalue = attrvalue[1:-1] attrs.append((string.lower(attrname), attrvalue)) k = match.end(0) if rawdata[j] == '>': j = j+1 self.finish_starttag(tag, attrs) return j # Internal -- parse endtag def parse_endtag(self, i): rawdata = self.rawdata match = endbracket.search(rawdata, i+1) if not match: return -1 j = match.start(0) tag = string.lower(string.strip(rawdata[i+2:j])) if rawdata[j] == '>': j = j+1 self.finish_endtag(tag) return j # Internal -- finish parsing of <tag/data/ (same as <tag>data</tag>) def finish_shorttag(self, tag, data): self.finish_starttag(tag, []) self.handle_data(data) self.finish_endtag(tag) # Internal -- finish processing of start tag # Return -1 for unknown tag, 0 for open-only tag, 1 for balanced tag def finish_starttag(self, tag, attrs): try: method = getattr(self, 'start_' + tag) except AttributeError: try: method = getattr(self, 'do_' + tag) except AttributeError: self.unknown_starttag(tag, attrs) return -1 else: self.handle_starttag(tag, method, attrs) return 0 else: self.stack.append(tag) self.handle_starttag(tag, method, attrs) return 1 # Internal -- finish processing of end tag def finish_endtag(self, tag): if not tag: found = len(self.stack) - 1 if found < 0: self.unknown_endtag(tag) return else: if tag not in self.stack: try: method = getattr(self, 'end_' + tag) except AttributeError: self.unknown_endtag(tag) else: self.report_unbalanced(tag) return found = len(self.stack) for i in range(found): if self.stack[i] == tag: found = i while len(self.stack) > found: 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 start tag def handle_starttag(self, tag, method, attrs): method(attrs) # Overridable -- handle end tag def handle_endtag(self, tag, method): method() # Example -- report an unbalanced </...> tag. def report_unbalanced(self, tag): if self.verbose: print '*** Unbalanced </' + tag + '>' print '*** Stack:', self.stack # 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.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 comment, could be overridden def handle_comment(self, data): pass # Example -- handle processing instruction, could be overridden def handle_pi(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 TestSGMLParser(SGMLParser): def __init__(self, verbose=0): self.testdata = "" SGMLParser.__init__(self, verbose) 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_comment(self, data): self.flush() r = `data` if len(r) > 68: r = r[:32] + '...' + r[-32:] print 'comment:', r 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: 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): SGMLParser.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 = SGMLParser else: klass = TestSGMLParser if args: file = args[0] else: file = 'test.html' 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()