369 lines
12 KiB
Python
369 lines
12 KiB
Python
"""A parser for HTML and XHTML."""
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# This file is based on sgmllib.py, but the API is slightly different.
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# XXX There should be a way to distinguish between PCDATA (parsed
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# character data -- the normal case), RCDATA (replaceable character
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# data -- only char and entity references and end tags are special)
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# and CDATA (character data -- only end tags are special).
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import markupbase
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import re
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# Regular expressions used for parsing
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interesting_normal = re.compile('[&<]')
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interesting_cdata = re.compile(r'<(/|\Z)')
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incomplete = re.compile('&[a-zA-Z#]')
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entityref = re.compile('&([a-zA-Z][-.a-zA-Z0-9]*)[^a-zA-Z0-9]')
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charref = re.compile('&#(?:[0-9]+|[xX][0-9a-fA-F]+)[^0-9a-fA-F]')
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starttagopen = re.compile('<[a-zA-Z]')
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piclose = re.compile('>')
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commentclose = re.compile(r'--\s*>')
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tagfind = re.compile('[a-zA-Z][-.a-zA-Z0-9:_]*')
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attrfind = re.compile(
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r'\s*([a-zA-Z_][-.:a-zA-Z_0-9]*)(\s*=\s*'
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r'(\'[^\']*\'|"[^"]*"|[-a-zA-Z0-9./,:;+*%?!&$\(\)_#=~@]*))?')
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locatestarttagend = re.compile(r"""
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<[a-zA-Z][-.a-zA-Z0-9:_]* # tag name
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(?:\s+ # whitespace before attribute name
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(?:[a-zA-Z_][-.:a-zA-Z0-9_]* # attribute name
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(?:\s*=\s* # value indicator
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(?:'[^']*' # LITA-enclosed value
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|\"[^\"]*\" # LIT-enclosed value
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|[^'\">\s]+ # bare value
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)
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)?
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)
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)*
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\s* # trailing whitespace
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""", re.VERBOSE)
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endendtag = re.compile('>')
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endtagfind = re.compile('</\s*([a-zA-Z][-.a-zA-Z0-9:_]*)\s*>')
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class HTMLParseError(Exception):
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"""Exception raised for all parse errors."""
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def __init__(self, msg, position=(None, None)):
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assert msg
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self.msg = msg
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self.lineno = position[0]
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self.offset = position[1]
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def __str__(self):
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result = self.msg
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if self.lineno is not None:
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result = result + ", at line %d" % self.lineno
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if self.offset is not None:
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result = result + ", column %d" % (self.offset + 1)
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return result
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class HTMLParser(markupbase.ParserBase):
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"""Find tags and other markup and call handler functions.
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Usage:
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p = HTMLParser()
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p.feed(data)
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...
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p.close()
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Start tags are handled by calling self.handle_starttag() or
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self.handle_startendtag(); end tags by self.handle_endtag(). The
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data between tags is passed from the parser to the derived class
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by calling self.handle_data() with the data as argument (the data
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may be split up in arbitrary chunks). Entity references are
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passed by calling self.handle_entityref() with the entity
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reference as the argument. Numeric character references are
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passed to self.handle_charref() with the string containing the
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reference as the argument.
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"""
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CDATA_CONTENT_ELEMENTS = ("script", "style")
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def __init__(self):
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"""Initialize and reset this instance."""
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self.reset()
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def reset(self):
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"""Reset this instance. Loses all unprocessed data."""
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self.rawdata = ''
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self.lasttag = '???'
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self.interesting = interesting_normal
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markupbase.ParserBase.reset(self)
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def feed(self, data):
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"""Feed data to the parser.
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Call this as often as you want, with as little or as much text
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as you want (may include '\n').
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"""
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self.rawdata = self.rawdata + data
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self.goahead(0)
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def close(self):
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"""Handle any buffered data."""
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self.goahead(1)
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def error(self, message):
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raise HTMLParseError(message, self.getpos())
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__starttag_text = None
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def get_starttag_text(self):
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"""Return full source of start tag: '<...>'."""
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return self.__starttag_text
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def set_cdata_mode(self):
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self.interesting = interesting_cdata
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def clear_cdata_mode(self):
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self.interesting = interesting_normal
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# Internal -- handle data as far as reasonable. May leave state
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# and data to be processed by a subsequent call. If 'end' is
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# true, force handling all data as if followed by EOF marker.
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def goahead(self, end):
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rawdata = self.rawdata
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i = 0
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n = len(rawdata)
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while i < n:
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match = self.interesting.search(rawdata, i) # < or &
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if match:
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j = match.start()
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else:
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j = n
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if i < j: self.handle_data(rawdata[i:j])
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i = self.updatepos(i, j)
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if i == n: break
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startswith = rawdata.startswith
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if startswith('<', i):
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if starttagopen.match(rawdata, i): # < + letter
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k = self.parse_starttag(i)
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elif startswith("</", i):
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k = self.parse_endtag(i)
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elif startswith("<!--", i):
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k = self.parse_comment(i)
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elif startswith("<?", i):
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k = self.parse_pi(i)
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elif startswith("<!", i):
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k = self.parse_declaration(i)
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elif (i + 1) < n:
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self.handle_data("<")
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k = i + 1
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else:
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break
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if k < 0:
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if end:
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self.error("EOF in middle of construct")
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break
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i = self.updatepos(i, k)
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elif startswith("&#", i):
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match = charref.match(rawdata, i)
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if match:
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name = match.group()[2:-1]
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self.handle_charref(name)
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k = match.end()
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if not startswith(';', k-1):
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k = k - 1
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i = self.updatepos(i, k)
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continue
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else:
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break
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elif startswith('&', i):
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match = entityref.match(rawdata, i)
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if match:
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name = match.group(1)
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self.handle_entityref(name)
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k = match.end()
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if not startswith(';', k-1):
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k = k - 1
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i = self.updatepos(i, k)
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continue
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match = incomplete.match(rawdata, i)
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if match:
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# match.group() will contain at least 2 chars
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if end and match.group() == rawdata[i:]:
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self.error("EOF in middle of entity or char ref")
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# incomplete
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break
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elif (i + 1) < n:
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# not the end of the buffer, and can't be confused
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# with some other construct
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self.handle_data("&")
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i = self.updatepos(i, i + 1)
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else:
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break
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else:
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assert 0, "interesting.search() lied"
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# end while
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if end and i < n:
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self.handle_data(rawdata[i:n])
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i = self.updatepos(i, n)
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self.rawdata = rawdata[i:]
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# Internal -- parse processing instr, return end or -1 if not terminated
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def parse_pi(self, i):
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rawdata = self.rawdata
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assert rawdata[i:i+2] == '<?', 'unexpected call to parse_pi()'
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match = piclose.search(rawdata, i+2) # >
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if not match:
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return -1
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j = match.start()
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self.handle_pi(rawdata[i+2: j])
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j = match.end()
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return j
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# Internal -- handle starttag, return end or -1 if not terminated
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def parse_starttag(self, i):
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self.__starttag_text = None
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endpos = self.check_for_whole_start_tag(i)
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if endpos < 0:
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return endpos
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rawdata = self.rawdata
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self.__starttag_text = rawdata[i:endpos]
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# Now parse the data between i+1 and j into a tag and attrs
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attrs = []
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match = tagfind.match(rawdata, i+1)
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assert match, 'unexpected call to parse_starttag()'
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k = match.end()
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self.lasttag = tag = rawdata[i+1:k].lower()
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while k < endpos:
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m = attrfind.match(rawdata, k)
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if not m:
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break
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attrname, rest, attrvalue = m.group(1, 2, 3)
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if not rest:
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attrvalue = None
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elif attrvalue[:1] == '\'' == attrvalue[-1:] or \
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attrvalue[:1] == '"' == attrvalue[-1:]:
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attrvalue = attrvalue[1:-1]
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attrvalue = self.unescape(attrvalue)
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attrs.append((attrname.lower(), attrvalue))
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k = m.end()
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end = rawdata[k:endpos].strip()
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if end not in (">", "/>"):
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lineno, offset = self.getpos()
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if "\n" in self.__starttag_text:
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lineno = lineno + self.__starttag_text.count("\n")
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offset = len(self.__starttag_text) \
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- self.__starttag_text.rfind("\n")
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else:
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offset = offset + len(self.__starttag_text)
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self.error("junk characters in start tag: %r"
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% (rawdata[k:endpos][:20],))
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if end.endswith('/>'):
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# XHTML-style empty tag: <span attr="value" />
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self.handle_startendtag(tag, attrs)
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else:
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self.handle_starttag(tag, attrs)
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if tag in self.CDATA_CONTENT_ELEMENTS:
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self.set_cdata_mode()
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return endpos
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# Internal -- check to see if we have a complete starttag; return end
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# or -1 if incomplete.
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def check_for_whole_start_tag(self, i):
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rawdata = self.rawdata
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m = locatestarttagend.match(rawdata, i)
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if m:
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j = m.end()
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next = rawdata[j:j+1]
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if next == ">":
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return j + 1
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if next == "/":
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if rawdata.startswith("/>", j):
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return j + 2
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if rawdata.startswith("/", j):
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# buffer boundary
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return -1
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# else bogus input
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self.updatepos(i, j + 1)
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self.error("malformed empty start tag")
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if next == "":
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# end of input
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return -1
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if next in ("abcdefghijklmnopqrstuvwxyz=/"
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"ABCDEFGHIJKLMNOPQRSTUVWXYZ"):
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# end of input in or before attribute value, or we have the
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# '/' from a '/>' ending
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return -1
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self.updatepos(i, j)
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self.error("malformed start tag")
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raise AssertionError("we should not get here!")
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# Internal -- parse endtag, return end or -1 if incomplete
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def parse_endtag(self, i):
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rawdata = self.rawdata
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assert rawdata[i:i+2] == "</", "unexpected call to parse_endtag"
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match = endendtag.search(rawdata, i+1) # >
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if not match:
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return -1
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j = match.end()
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match = endtagfind.match(rawdata, i) # </ + tag + >
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if not match:
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self.error("bad end tag: %r" % (rawdata[i:j],))
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tag = match.group(1)
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self.handle_endtag(tag.lower())
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self.clear_cdata_mode()
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return j
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# Overridable -- finish processing of start+end tag: <tag.../>
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def handle_startendtag(self, tag, attrs):
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self.handle_starttag(tag, attrs)
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self.handle_endtag(tag)
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# Overridable -- handle start tag
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def handle_starttag(self, tag, attrs):
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pass
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# Overridable -- handle end tag
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def handle_endtag(self, tag):
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pass
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# Overridable -- handle character reference
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def handle_charref(self, name):
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pass
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# Overridable -- handle entity reference
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def handle_entityref(self, name):
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pass
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# Overridable -- handle data
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def handle_data(self, data):
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pass
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# Overridable -- handle comment
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def handle_comment(self, data):
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pass
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# Overridable -- handle declaration
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def handle_decl(self, decl):
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pass
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# Overridable -- handle processing instruction
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def handle_pi(self, data):
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pass
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def unknown_decl(self, data):
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self.error("unknown declaration: %r" % (data,))
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# Internal -- helper to remove special character quoting
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def unescape(self, s):
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if '&' not in s:
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return s
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s = s.replace("<", "<")
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s = s.replace(">", ">")
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s = s.replace("'", "'")
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s = s.replace(""", '"')
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s = s.replace("&", "&") # Must be last
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return s
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