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parser.py
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"""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 re import warnings import _markupbase from html import unescape __all__ = ['HTMLParser'] # 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]') endtagopen = re.compile('</[a-zA-Z]') piclose = re.compile('>') commentclose = re.compile(r'--\s*>') # Note: # 1) if you change tagfind/attrfind remember to update locatestarttagend too; # 2) if you change tagfind/attrfind and/or locatestarttagend the parser will # explode, so don't do it. # 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(r'([a-zA-Z][^\t\n\r\f />\x00]*)(?:\s|/(?!>))*') attrfind_tolerant = re.compile( r'((?<=[\'"\s/])[^\s/>][^\s/=>]*)(\s*=+\s*' r'(\'[^\']*\'|"[^"]*"|(?![\'"])[^>\s]*))?(?:\s|/(?!>))*') locatestarttagend_tolerant = re.compile(r""" <[a-zA-Z][^\t\n\r\f />\x00]* # 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(r'</\s*([a-zA-Z][-.a-zA-Z0-9:_]*)\s*>') 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). If convert_charrefs is True the character references are converted automatically to the corresponding Unicode character (and self.handle_data() is no longer split in chunks), otherwise they are passed by calling self.handle_entityref() or self.handle_charref() with the string containing respectively the named or numeric reference as the argument. """ CDATA_CONTENT_ELEMENTS = ("script", "style") def __init__(self, *, convert_charrefs=True): """Initialize and reset this instance. If convert_charrefs is True (the default), all character references are automatically converted to the corresponding Unicode characters. """ self.convert_charrefs = convert_charrefs 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) __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: if self.convert_charrefs and not self.cdata_elem: j = rawdata.find('<', i) if j < 0: # if we can't find the next <, either we are at the end # or there's more text incoming. If the latter is True, # we can't pass the text to handle_data in case we have # a charref cut in half at end. Try to determine if # this is the case before proceeding by looking for an # & near the end and see if it's followed by a space or ;. amppos = rawdata.rfind('&', max(i, n-34)) if (amppos >= 0 and not re.compile(r'[\s;]').search(rawdata, amppos)): break # wait till we get all the text j = n else: match = self.interesting.search(rawdata, i) # < or & if match: j = match.start() else: if self.cdata_elem: break j = n if i < j: if self.convert_charrefs and not self.cdata_elem: self.handle_data(unescape(rawdata[i:j])) else: 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): k = self.parse_html_declaration(i) elif (i + 1) < n or end: self.handle_data("<") k = i + 1 else: break if k < 0: if not end: break if starttagopen.match(rawdata, i): # < + letter pass elif startswith("</", i): if i + 2 == n: self.handle_data("</") elif endtagopen.match(rawdata, i): # </ + letter pass else: # bogus comment self.handle_comment(rawdata[i+2:]) elif startswith("<!--", i): j = n for suffix in ("--!", "--", "-"): if rawdata.endswith(suffix, i+4): j -= len(suffix) break self.handle_comment(rawdata[i+4:j]) elif startswith("<![CDATA[", i): self.unknown_decl(rawdata[i+3:]) elif rawdata[i:i+9].lower() == '<!doctype': self.handle_decl(rawdata[i+2:]) elif startswith("<!", i): # bogus comment self.handle_comment(rawdata[i+2:]) elif startswith("<?", i): self.handle_pi(rawdata[i+2:]) else: raise AssertionError("we should not get here!") k = n 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[i:i+2]) i = self.updatepos(i, 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:]: k = match.end() 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: if self.convert_charrefs and not self.cdata_elem: self.handle_data(unescape(rawdata[i:n])) else: 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 assert rawdata[i:i+2] == '<!', ('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 assert rawdata[i:i+2] in ('<!', '</'), ('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_tolerant.match(rawdata, i+1) assert match, 'unexpected call to parse_starttag()' k = match.end() self.lasttag = tag = match.group(1).lower() while k < endpos: 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 = 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) 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 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 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 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 # 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(1).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): pass # Internal -- helper to remove special character quoting def unescape(self, s): warnings.warn('The unescape method is deprecated and will be removed ' 'in 3.5, use html.unescape() instead.', DeprecationWarning, stacklevel=2) return unescape(s)