JezK
Edit File: parser.py
"""A parser for HTML and XHTML.""" # This file is based on sgmllib.py, but the API is slightly different. # 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 _markupbase import re # Regular expressions used for parsing interesting_normal = re.compile('[&<]') incomplete = re.compile('&[a-zA-Z#]') entityref = re.compile('&([a-zA-Z][-.a-zA-Z0-9]*)[^a-zA-Z0-9]') charref = re.compile('&#(?:[0-9]+|[xX][0-9a-fA-F]+)[^0-9a-fA-F]') starttagopen = re.compile('<[a-zA-Z]') piclose = re.compile('>') commentclose = re.compile(r'--\s*>') tagfind = re.compile('([a-zA-Z][-.a-zA-Z0-9:_]*)(?:\s|/(?!>))*') # see http://www.w3.org/TR/html5/tokenization.html#tag-open-state # and http://www.w3.org/TR/html5/tokenization.html#tag-name-state tagfind_tolerant = re.compile('[a-zA-Z][^\t\n\r\f />\x00]*') # Note: # 1) the strict attrfind isn't really strict, but we can't make it # correctly strict without breaking backward compatibility; # 2) if you change attrfind remember to update locatestarttagend too; # 3) if you change attrfind and/or locatestarttagend the parser will # explode, so don't do it. attrfind = re.compile( r'\s*([a-zA-Z_][-.:a-zA-Z_0-9]*)(\s*=\s*' r'(\'[^\']*\'|"[^"]*"|[^\s"\'=<>`]*))?') attrfind_tolerant = re.compile( r'((?<=[\'"\s/])[^\s/>][^\s/=>]*)(\s*=+\s*' r'(\'[^\']*\'|"[^"]*"|(?![\'"])[^>\s]*))?(?:\s|/(?!>))*') locatestarttagend = re.compile(r""" <[a-zA-Z][-.a-zA-Z0-9:_]* # tag name (?:\s+ # whitespace before attribute name (?:[a-zA-Z_][-.:a-zA-Z0-9_]* # attribute name (?:\s*=\s* # value indicator (?:'[^']*' # LITA-enclosed value |\"[^\"]*\" # LIT-enclosed value |[^'\">\s]+ # bare value ) )? ) )* \s* # trailing whitespace """, re.VERBOSE) locatestarttagend_tolerant = re.compile(r""" <[a-zA-Z][-.a-zA-Z0-9:_]* # tag name (?:[\s/]* # optional whitespace before attribute name (?:(?<=['"\s/])[^\s/>][^\s/=>]* # attribute name (?:\s*=+\s* # value indicator (?:'[^']*' # LITA-enclosed value |"[^"]*" # LIT-enclosed value |(?!['"])[^>\s]* # bare value ) (?:\s*,)* # possibly followed by a comma )?(?:\s|/(?!>))* )* )? \s* # trailing whitespace """, re.VERBOSE) endendtag = re.compile('>') # the HTML 5 spec, section 8.1.2.2, doesn't allow spaces between # </ and the tag name, so maybe this should be fixed endtagfind = re.compile('</\s*([a-zA-Z][-.a-zA-Z0-9:_]*)\s*>') class HTMLParseError(Exception): """Exception raised for all parse errors.""" def __init__(self, msg, position=(None, None)): assert msg self.msg = msg self.lineno = position[0] self.offset = position[1] def __str__(self): result = self.msg if self.lineno is not None: result = result + ", at line %d" % self.lineno if self.offset is not None: result = result + ", column %d" % (self.offset + 1) return result class HTMLParser(_markupbase.ParserBase): """Find tags and other markup and call handler functions. Usage: p = HTMLParser() p.feed(data) ... p.close() Start tags are handled by calling self.handle_starttag() or self.handle_startendtag(); end tags by self.handle_endtag(). The data between tags is passed from the parser to the derived class by calling self.handle_data() with the data as argument (the data may be split up in arbitrary chunks). Entity references are passed by calling self.handle_entityref() with the entity reference as the argument. Numeric character references are passed to self.handle_charref() with the string containing the reference as the argument. """ CDATA_CONTENT_ELEMENTS = ("script", "style") def __init__(self, strict=True): """Initialize and reset this instance. If strict is set to True (the default), errors are raised when invalid HTML is encountered. If set to False, an attempt is instead made to continue parsing, making "best guesses" about the intended meaning, in a fashion similar to what browsers typically do. """ self.strict = strict self.reset() def reset(self): """Reset this instance. Loses all unprocessed data.""" self.rawdata = '' self.lasttag = '???' self.interesting = interesting_normal self.cdata_elem = None _markupbase.ParserBase.reset(self) def feed(self, data): r"""Feed data to the parser. Call this as often as you want, with as little or as much text as you want (may include '\n'). """ self.rawdata = self.rawdata + data self.goahead(0) def close(self): """Handle any buffered data.""" self.goahead(1) def error(self, message): raise HTMLParseError(message, self.getpos()) __starttag_text = None def get_starttag_text(self): """Return full source of start tag: '<...>'.""" return self.__starttag_text def set_cdata_mode(self, elem): self.cdata_elem = elem.lower() self.interesting = re.compile(r'</\s*%s\s*>' % self.cdata_elem, re.I) def clear_cdata_mode(self): self.interesting = interesting_normal self.cdata_elem = None # 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: match = self.interesting.search(rawdata, i) # < or & if match: j = match.start() else: if self.cdata_elem: break j = n if i < j: self.handle_data(rawdata[i:j]) i = self.updatepos(i, j) if i == n: break startswith = rawdata.startswith if startswith('<', i): if starttagopen.match(rawdata, i): # < + letter k = self.parse_starttag(i) elif startswith("</", i): k = self.parse_endtag(i) elif startswith("<!--", i): k = self.parse_comment(i) elif startswith("<?", i): k = self.parse_pi(i) elif startswith("<!", i): if self.strict: k = self.parse_declaration(i) else: k = self.parse_html_declaration(i) elif (i + 1) < n: self.handle_data("<") k = i + 1 else: break if k < 0: if not end: break if self.strict: self.error("EOF in middle of construct") k = rawdata.find('>', i + 1) if k < 0: k = rawdata.find('<', i + 1) if k < 0: k = i + 1 else: k += 1 self.handle_data(rawdata[i:k]) i = self.updatepos(i, k) elif startswith("&#", i): match = charref.match(rawdata, i) if match: name = match.group()[2:-1] self.handle_charref(name) k = match.end() if not startswith(';', k-1): k = k - 1 i = self.updatepos(i, k) continue else: if ";" in rawdata[i:]: #bail by consuming &# self.handle_data(rawdata[0:2]) i = self.updatepos(i, 2) break elif startswith('&', i): match = entityref.match(rawdata, i) if match: name = match.group(1) self.handle_entityref(name) k = match.end() if not startswith(';', k-1): k = k - 1 i = self.updatepos(i, k) continue match = incomplete.match(rawdata, i) if match: # match.group() will contain at least 2 chars if end and match.group() == rawdata[i:]: if self.strict: self.error("EOF in middle of entity or char ref") else: if k <= i: k = n i = self.updatepos(i, i + 1) # incomplete break elif (i + 1) < n: # not the end of the buffer, and can't be confused # with some other construct self.handle_data("&") i = self.updatepos(i, i + 1) else: break else: assert 0, "interesting.search() lied" # end while if end and i < n and not self.cdata_elem: self.handle_data(rawdata[i:n]) i = self.updatepos(i, n) self.rawdata = rawdata[i:] # Internal -- parse html declarations, return length or -1 if not terminated # See w3.org/TR/html5/tokenization.html#markup-declaration-open-state # See also parse_declaration in _markupbase def parse_html_declaration(self, i): rawdata = self.rawdata if rawdata[i:i+2] != '<!': self.error('unexpected call to parse_html_declaration()') if rawdata[i:i+4] == '<!--': # this case is actually already handled in goahead() return self.parse_comment(i) elif rawdata[i:i+3] == '<![': return self.parse_marked_section(i) elif rawdata[i:i+9].lower() == '<!doctype': # find the closing > gtpos = rawdata.find('>', i+9) if gtpos == -1: return -1 self.handle_decl(rawdata[i+2:gtpos]) return gtpos+1 else: return self.parse_bogus_comment(i) # Internal -- parse bogus comment, return length or -1 if not terminated # see http://www.w3.org/TR/html5/tokenization.html#bogus-comment-state def parse_bogus_comment(self, i, report=1): rawdata = self.rawdata if rawdata[i:i+2] not in ('<!', '</'): self.error('unexpected call to parse_comment()') pos = rawdata.find('>', i+2) if pos == -1: return -1 if report: self.handle_comment(rawdata[i+2:pos]) return pos + 1 # Internal -- parse processing instr, return end or -1 if not terminated def parse_pi(self, i): rawdata = self.rawdata assert rawdata[i:i+2] == '<?', 'unexpected call to parse_pi()' match = piclose.search(rawdata, i+2) # > if not match: return -1 j = match.start() self.handle_pi(rawdata[i+2: j]) j = match.end() return j # Internal -- handle starttag, return end or -1 if not terminated def parse_starttag(self, i): self.__starttag_text = None endpos = self.check_for_whole_start_tag(i) if endpos < 0: return endpos rawdata = self.rawdata self.__starttag_text = rawdata[i:endpos] # Now parse the data between i+1 and j into a tag and attrs attrs = [] match = tagfind.match(rawdata, i+1) assert match, 'unexpected call to parse_starttag()' k = match.end() self.lasttag = tag = match.group(1).lower() while k < endpos: if self.strict: m = attrfind.match(rawdata, k) else: m = attrfind_tolerant.match(rawdata, k) if not m: break attrname, rest, attrvalue = m.group(1, 2, 3) if not rest: attrvalue = None elif attrvalue[:1] == '\'' == attrvalue[-1:] or \ attrvalue[:1] == '"' == attrvalue[-1:]: attrvalue = attrvalue[1:-1] if attrvalue: attrvalue = self.unescape(attrvalue) attrs.append((attrname.lower(), attrvalue)) k = m.end() end = rawdata[k:endpos].strip() if end not in (">", "/>"): lineno, offset = self.getpos() if "\n" in self.__starttag_text: lineno = lineno + self.__starttag_text.count("\n") offset = len(self.__starttag_text) \ - self.__starttag_text.rfind("\n") else: offset = offset + len(self.__starttag_text) if self.strict: self.error("junk characters in start tag: %r" % (rawdata[k:endpos][:20],)) self.handle_data(rawdata[i:endpos]) return endpos if end.endswith('/>'): # XHTML-style empty tag: <span attr="value" /> self.handle_startendtag(tag, attrs) else: self.handle_starttag(tag, attrs) if tag in self.CDATA_CONTENT_ELEMENTS: self.set_cdata_mode(tag) return endpos # Internal -- check to see if we have a complete starttag; return end # or -1 if incomplete. def check_for_whole_start_tag(self, i): rawdata = self.rawdata if self.strict: m = locatestarttagend.match(rawdata, i) else: m = locatestarttagend_tolerant.match(rawdata, i) if m: j = m.end() next = rawdata[j:j+1] if next == ">": return j + 1 if next == "/": if rawdata.startswith("/>", j): return j + 2 if rawdata.startswith("/", j): # buffer boundary return -1 # else bogus input if self.strict: self.updatepos(i, j + 1) self.error("malformed empty start tag") if j > i: return j else: return i + 1 if next == "": # end of input return -1 if next in ("abcdefghijklmnopqrstuvwxyz=/" "ABCDEFGHIJKLMNOPQRSTUVWXYZ"): # end of input in or before attribute value, or we have the # '/' from a '/>' ending return -1 if self.strict: self.updatepos(i, j) self.error("malformed start tag") if j > i: return j else: return i + 1 raise AssertionError("we should not get here!") # Internal -- parse endtag, return end or -1 if incomplete def parse_endtag(self, i): rawdata = self.rawdata assert rawdata[i:i+2] == "</", "unexpected call to parse_endtag" match = endendtag.search(rawdata, i+1) # > if not match: return -1 gtpos = match.end() match = endtagfind.match(rawdata, i) # </ + tag + > if not match: if self.cdata_elem is not None: self.handle_data(rawdata[i:gtpos]) return gtpos if self.strict: self.error("bad end tag: %r" % (rawdata[i:gtpos],)) # find the name: w3.org/TR/html5/tokenization.html#tag-name-state namematch = tagfind_tolerant.match(rawdata, i+2) if not namematch: # w3.org/TR/html5/tokenization.html#end-tag-open-state if rawdata[i:i+3] == '</>': return i+3 else: return self.parse_bogus_comment(i) tagname = namematch.group().lower() # consume and ignore other stuff between the name and the > # Note: this is not 100% correct, since we might have things like # </tag attr=">">, but looking for > after tha name should cover # most of the cases and is much simpler gtpos = rawdata.find('>', namematch.end()) self.handle_endtag(tagname) return gtpos+1 elem = match.group(1).lower() # script or style if self.cdata_elem is not None: if elem != self.cdata_elem: self.handle_data(rawdata[i:gtpos]) return gtpos self.handle_endtag(elem.lower()) self.clear_cdata_mode() return gtpos # Overridable -- finish processing of start+end tag: <tag.../> def handle_startendtag(self, tag, attrs): self.handle_starttag(tag, attrs) self.handle_endtag(tag) # Overridable -- handle start tag def handle_starttag(self, tag, attrs): pass # Overridable -- handle end tag def handle_endtag(self, tag): pass # Overridable -- handle character reference def handle_charref(self, name): pass # Overridable -- handle entity reference def handle_entityref(self, name): pass # Overridable -- handle data def handle_data(self, data): pass # Overridable -- handle comment def handle_comment(self, data): pass # Overridable -- handle declaration def handle_decl(self, decl): pass # Overridable -- handle processing instruction def handle_pi(self, data): pass def unknown_decl(self, data): if self.strict: self.error("unknown declaration: %r" % (data,)) # Internal -- helper to remove special character quoting entitydefs = None def unescape(self, s): if '&' not in s: return s def replaceEntities(s): s = s.groups()[0] try: if s[0] == "#": s = s[1:] if s[0] in ['x','X']: c = int(s[1:], 16) else: c = int(s) return chr(c) except ValueError: return '&#'+ s +';' else: # Cannot use name2codepoint directly, because HTMLParser # supports apos, which is not part of HTML 4 import html.entities if HTMLParser.entitydefs is None: entitydefs = HTMLParser.entitydefs = {'apos':"'"} for k, v in html.entities.name2codepoint.items(): entitydefs[k] = chr(v) try: return self.entitydefs[s] except KeyError: return '&'+s+';' return re.sub(r"&(#?[xX]?(?:[0-9a-fA-F]+|\w{1,8}));", replaceEntities, s, flags=re.ASCII)