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"""A parser for SGML, using the derived class as a static DTD.""" |
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|
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# XXX This only supports those SGML features used by HTML. |
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|
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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). RCDATA is |
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# not supported at all. |
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|
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import _markupbase |
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import re |
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|
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__all__ = ["SGMLParser", "SGMLParseError"] |
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|
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# Regular expressions used for parsing |
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|
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interesting = re.compile('[&<]') |
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incomplete = re.compile('&([a-zA-Z][a-zA-Z0-9]*|#[0-9]*)?|' |
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'<([a-zA-Z][^<>]*|' |
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'/([a-zA-Z][^<>]*)?|' |
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'![^<>]*)?') |
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|
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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]+)[^0-9]') |
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|
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starttagopen = re.compile('<[>a-zA-Z]') |
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shorttagopen = re.compile('<[a-zA-Z][-.a-zA-Z0-9]*/') |
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shorttag = re.compile('<([a-zA-Z][-.a-zA-Z0-9]*)/([^/]*)/') |
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piclose = re.compile('>') |
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endbracket = re.compile('[<>]') |
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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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|
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|
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class SGMLParseError(RuntimeError): |
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"""Exception raised for all parse errors.""" |
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pass |
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|
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|
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# SGML parser base class -- find tags and call handler functions. |
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# Usage: p = SGMLParser(); p.feed(data); ...; p.close(). |
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# The dtd is defined by deriving a class which defines methods |
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# with special names to handle tags: start_foo and end_foo to handle |
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# <foo> and </foo>, respectively, or do_foo to handle <foo> by itself. |
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# (Tags are converted to lower case for this purpose.) The data |
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# between tags is passed to the parser by calling self.handle_data() |
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# with some data as argument (the data may be split up in arbitrary |
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# chunks). Entity references are passed by calling |
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# self.handle_entityref() with the entity reference as argument. |
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|
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class SGMLParser(_markupbase.ParserBase): |
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# Definition of entities -- derived classes may override |
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entity_or_charref = re.compile('&(?:' |
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'([a-zA-Z][-.a-zA-Z0-9]*)|#([0-9]+)' |
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')(;?)') |
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|
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def __init__(self, verbose=0): |
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"""Initialize and reset this instance.""" |
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self.verbose = verbose |
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self.reset() |
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|
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def reset(self): |
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"""Reset this instance. Loses all unprocessed data.""" |
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self.__starttag_text = None |
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self.rawdata = '' |
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self.stack = [] |
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self.lasttag = '???' |
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self.nomoretags = 0 |
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self.literal = 0 |
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_markupbase.ParserBase.reset(self) |
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|
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def setnomoretags(self): |
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"""Enter literal mode (CDATA) till EOF. |
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|
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Intended for derived classes only. |
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""" |
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self.nomoretags = self.literal = 1 |
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|
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def setliteral(self, *args): |
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"""Enter literal mode (CDATA). |
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|
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Intended for derived classes only. |
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""" |
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self.literal = 1 |
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|
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def feed(self, data): |
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"""Feed some data to the parser. |
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|
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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'). (This just saves the text, |
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all the processing is done by goahead().) |
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""" |
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|
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self.rawdata = self.rawdata + data |
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self.goahead(0) |
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|
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def close(self): |
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"""Handle the remaining data.""" |
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self.goahead(1) |
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|
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def error(self, message): |
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raise SGMLParseError(message) |
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|
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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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if self.nomoretags: |
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self.handle_data(rawdata[i:n]) |
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i = n |
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break |
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match = interesting.search(rawdata, i) |
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if match: j = match.start() |
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else: j = n |
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if i < j: |
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self.handle_data(rawdata[i:j]) |
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i = j |
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if i == n: break |
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if rawdata[i] == '<': |
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if starttagopen.match(rawdata, i): |
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if self.literal: |
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self.handle_data(rawdata[i]) |
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i = i+1 |
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continue |
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k = self.parse_starttag(i) |
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if k < 0: break |
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i = k |
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continue |
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if rawdata.startswith("</", i): |
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k = self.parse_endtag(i) |
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if k < 0: break |
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i = k |
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self.literal = 0 |
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continue |
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if self.literal: |
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if n > (i + 1): |
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self.handle_data("<") |
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i = i+1 |
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else: |
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# incomplete |
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break |
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continue |
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if rawdata.startswith("<!--", i): |
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# Strictly speaking, a comment is --.*-- |
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# within a declaration tag <!...>. |
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# This should be removed, |
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# and comments handled only in parse_declaration. |
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k = self.parse_comment(i) |
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if k < 0: break |
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i = k |
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continue |
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if rawdata.startswith("<?", i): |
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k = self.parse_pi(i) |
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if k < 0: break |
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i = i+k |
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continue |
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if rawdata.startswith("<!", i): |
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# This is some sort of declaration; in "HTML as |
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# deployed," this should only be the document type |
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# declaration ("<!DOCTYPE html...>"). |
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k = self.parse_declaration(i) |
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if k < 0: break |
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i = k |
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continue |
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elif rawdata[i] == '&': |
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if self.literal: |
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self.handle_data(rawdata[i]) |
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i = i+1 |
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continue |
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match = charref.match(rawdata, i) |
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if match: |
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name = match.group(1) |
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self.handle_charref(name) |
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i = match.end(0) |
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if rawdata[i-1] != ';': i = i-1 |
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continue |
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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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i = match.end(0) |
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if rawdata[i-1] != ';': i = i-1 |
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continue |
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else: |
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self.error('neither < nor & ??') |
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# We get here only if incomplete matches but |
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# nothing else |
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match = incomplete.match(rawdata, i) |
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if not match: |
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self.handle_data(rawdata[i]) |
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i = i+1 |
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continue |
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j = match.end(0) |
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if j == n: |
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break # Really incomplete |
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self.handle_data(rawdata[i:j]) |
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i = j |
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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 = n |
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self.rawdata = rawdata[i:] |
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# XXX if end: check for empty stack |
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|
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# Extensions for the DOCTYPE scanner: |
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_decl_otherchars = '=' |
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|
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# Internal -- parse processing instr, return length 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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if rawdata[i:i+2] != '<?': |
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self.error('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(0) |
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self.handle_pi(rawdata[i+2: j]) |
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j = match.end(0) |
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return j-i |
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|
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def get_starttag_text(self): |
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return self.__starttag_text |
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|
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# Internal -- handle starttag, return length 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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start_pos = i |
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rawdata = self.rawdata |
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if shorttagopen.match(rawdata, i): |
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# SGML shorthand: <tag/data/ == <tag>data</tag> |
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# XXX Can data contain &... (entity or char refs)? |
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# XXX Can data contain < or > (tag characters)? |
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# XXX Can there be whitespace before the first /? |
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match = shorttag.match(rawdata, i) |
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if not match: |
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return -1 |
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tag, data = match.group(1, 2) |
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self.__starttag_text = '<%s/' % tag |
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tag = tag.lower() |
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k = match.end(0) |
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self.finish_shorttag(tag, data) |
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self.__starttag_text = rawdata[start_pos:match.end(1) + 1] |
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return k |
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# XXX The following should skip matching quotes (' or ") |
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# As a shortcut way to exit, this isn't so bad, but shouldn't |
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# be used to locate the actual end of the start tag since the |
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# < or > characters may be embedded in an attribute value. |
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match = endbracket.search(rawdata, i+1) |
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if not match: |
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return -1 |
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j = match.start(0) |
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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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if rawdata[i:i+2] == '<>': |
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# SGML shorthand: <> == <last open tag seen> |
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k = j |
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tag = self.lasttag |
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else: |
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match = tagfind.match(rawdata, i+1) |
267 |
if not match: |
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self.error('unexpected call to parse_starttag') |
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k = match.end(0) |
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tag = rawdata[i+1:k].lower() |
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self.lasttag = tag |
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while k < j: |
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match = attrfind.match(rawdata, k) |
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if not match: break |
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attrname, rest, attrvalue = match.group(1, 2, 3) |
276 |
if not rest: |
277 |
attrvalue = attrname |
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else: |
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if (attrvalue[:1] == "'" == attrvalue[-1:] or |
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attrvalue[:1] == '"' == attrvalue[-1:]): |
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# strip quotes |
282 |
attrvalue = attrvalue[1:-1] |
283 |
attrvalue = self.entity_or_charref.sub( |
284 |
self._convert_ref, attrvalue) |
285 |
attrs.append((attrname.lower(), attrvalue)) |
286 |
k = match.end(0) |
287 |
if rawdata[j] == '>': |
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j = j+1 |
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self.__starttag_text = rawdata[start_pos:j] |
290 |
self.finish_starttag(tag, attrs) |
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return j |
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|
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# Internal -- convert entity or character reference |
294 |
def _convert_ref(self, match): |
295 |
if match.group(2): |
296 |
return self.convert_charref(match.group(2)) or \ |
297 |
'&#%s%s' % match.groups()[1:] |
298 |
elif match.group(3): |
299 |
return self.convert_entityref(match.group(1)) or \ |
300 |
'&%s;' % match.group(1) |
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else: |
302 |
return '&%s' % match.group(1) |
303 |
|
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# Internal -- parse endtag |
305 |
def parse_endtag(self, i): |
306 |
rawdata = self.rawdata |
307 |
match = endbracket.search(rawdata, i+1) |
308 |
if not match: |
309 |
return -1 |
310 |
j = match.start(0) |
311 |
tag = rawdata[i+2:j].strip().lower() |
312 |
if rawdata[j] == '>': |
313 |
j = j+1 |
314 |
self.finish_endtag(tag) |
315 |
return j |
316 |
|
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# Internal -- finish parsing of <tag/data/ (same as <tag>data</tag>) |
318 |
def finish_shorttag(self, tag, data): |
319 |
self.finish_starttag(tag, []) |
320 |
self.handle_data(data) |
321 |
self.finish_endtag(tag) |
322 |
|
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# Internal -- finish processing of start tag |
324 |
# Return -1 for unknown tag, 0 for open-only tag, 1 for balanced tag |
325 |
def finish_starttag(self, tag, attrs): |
326 |
try: |
327 |
method = getattr(self, 'start_' + tag) |
328 |
except AttributeError: |
329 |
try: |
330 |
method = getattr(self, 'do_' + tag) |
331 |
except AttributeError: |
332 |
self.unknown_starttag(tag, attrs) |
333 |
return -1 |
334 |
else: |
335 |
self.handle_starttag(tag, method, attrs) |
336 |
return 0 |
337 |
else: |
338 |
self.stack.append(tag) |
339 |
self.handle_starttag(tag, method, attrs) |
340 |
return 1 |
341 |
|
342 |
# Internal -- finish processing of end tag |
343 |
def finish_endtag(self, tag): |
344 |
if not tag: |
345 |
found = len(self.stack) - 1 |
346 |
if found < 0: |
347 |
self.unknown_endtag(tag) |
348 |
return |
349 |
else: |
350 |
if tag not in self.stack: |
351 |
try: |
352 |
method = getattr(self, 'end_' + tag) |
353 |
except AttributeError: |
354 |
self.unknown_endtag(tag) |
355 |
else: |
356 |
self.report_unbalanced(tag) |
357 |
return |
358 |
found = len(self.stack) |
359 |
for i in range(found): |
360 |
if self.stack[i] == tag: found = i |
361 |
while len(self.stack) > found: |
362 |
tag = self.stack[-1] |
363 |
try: |
364 |
method = getattr(self, 'end_' + tag) |
365 |
except AttributeError: |
366 |
method = None |
367 |
if method: |
368 |
self.handle_endtag(tag, method) |
369 |
else: |
370 |
self.unknown_endtag(tag) |
371 |
del self.stack[-1] |
372 |
|
373 |
# Overridable -- handle start tag |
374 |
def handle_starttag(self, tag, method, attrs): |
375 |
method(attrs) |
376 |
|
377 |
# Overridable -- handle end tag |
378 |
def handle_endtag(self, tag, method): |
379 |
method() |
380 |
|
381 |
# Example -- report an unbalanced </...> tag. |
382 |
def report_unbalanced(self, tag): |
383 |
if self.verbose: |
384 |
print('*** Unbalanced </' + tag + '>') |
385 |
print('*** Stack:', self.stack) |
386 |
|
387 |
def convert_charref(self, name): |
388 |
"""Convert character reference, may be overridden.""" |
389 |
try: |
390 |
n = int(name) |
391 |
except ValueError: |
392 |
return |
393 |
if not 0 <= n <= 127: |
394 |
return |
395 |
return self.convert_codepoint(n) |
396 |
|
397 |
def convert_codepoint(self, codepoint): |
398 |
return chr(codepoint) |
399 |
|
400 |
def handle_charref(self, name): |
401 |
"""Handle character reference, no need to override.""" |
402 |
replacement = self.convert_charref(name) |
403 |
if replacement is None: |
404 |
self.unknown_charref(name) |
405 |
else: |
406 |
self.handle_data(replacement) |
407 |
|
408 |
# Definition of entities -- derived classes may override |
409 |
entitydefs = \ |
410 |
{'lt': '<', 'gt': '>', 'amp': '&', 'quot': '"', 'apos': '\''} |
411 |
|
412 |
def convert_entityref(self, name): |
413 |
"""Convert entity references. |
414 |
|
415 |
As an alternative to overriding this method; one can tailor the |
416 |
results by setting up the self.entitydefs mapping appropriately. |
417 |
""" |
418 |
table = self.entitydefs |
419 |
if name in table: |
420 |
return table[name] |
421 |
else: |
422 |
return |
423 |
|
424 |
def handle_entityref(self, name): |
425 |
"""Handle entity references, no need to override.""" |
426 |
replacement = self.convert_entityref(name) |
427 |
if replacement is None: |
428 |
self.unknown_entityref(name) |
429 |
else: |
430 |
self.handle_data(replacement) |
431 |
|
432 |
# Example -- handle data, should be overridden |
433 |
def handle_data(self, data): |
434 |
pass |
435 |
|
436 |
# Example -- handle comment, could be overridden |
437 |
def handle_comment(self, data): |
438 |
pass |
439 |
|
440 |
# Example -- handle declaration, could be overridden |
441 |
def handle_decl(self, decl): |
442 |
pass |
443 |
|
444 |
# Example -- handle processing instruction, could be overridden |
445 |
def handle_pi(self, data): |
446 |
pass |
447 |
|
448 |
# To be overridden -- handlers for unknown objects |
449 |
def unknown_starttag(self, tag, attrs): pass |
450 |
def unknown_endtag(self, tag): pass |
451 |
def unknown_charref(self, ref): pass |
452 |
def unknown_entityref(self, ref): pass |
453 |
|
454 |
|
455 |
class TestSGMLParser(SGMLParser): |
456 |
|
457 |
def __init__(self, verbose=0): |
458 |
self.testdata = "" |
459 |
SGMLParser.__init__(self, verbose) |
460 |
|
461 |
def handle_data(self, data): |
462 |
self.testdata = self.testdata + data |
463 |
if len(repr(self.testdata)) >= 70: |
464 |
self.flush() |
465 |
|
466 |
def flush(self): |
467 |
data = self.testdata |
468 |
if data: |
469 |
self.testdata = "" |
470 |
print('data:', repr(data)) |
471 |
|
472 |
def handle_comment(self, data): |
473 |
self.flush() |
474 |
r = repr(data) |
475 |
if len(r) > 68: |
476 |
r = r[:32] + '...' + r[-32:] |
477 |
print('comment:', r) |
478 |
|
479 |
def unknown_starttag(self, tag, attrs): |
480 |
self.flush() |
481 |
if not attrs: |
482 |
print('start tag: <' + tag + '>') |
483 |
else: |
484 |
print('start tag: <' + tag, end=' ') |
485 |
for name, value in attrs: |
486 |
print(name + '=' + '"' + value + '"', end=' ') |
487 |
print('>') |
488 |
|
489 |
def unknown_endtag(self, tag): |
490 |
self.flush() |
491 |
print('end tag: </' + tag + '>') |
492 |
|
493 |
def unknown_entityref(self, ref): |
494 |
self.flush() |
495 |
print('*** unknown entity ref: &' + ref + ';') |
496 |
|
497 |
def unknown_charref(self, ref): |
498 |
self.flush() |
499 |
print('*** unknown char ref: &#' + ref + ';') |
500 |
|
501 |
def unknown_decl(self, data): |
502 |
self.flush() |
503 |
print('*** unknown decl: [' + data + ']') |
504 |
|
505 |
def close(self): |
506 |
SGMLParser.close(self) |
507 |
self.flush() |
508 |
|
509 |
|
510 |
def test(args = None): |
511 |
import sys |
512 |
|
513 |
if args is None: |
514 |
args = sys.argv[1:] |
515 |
|
516 |
if args and args[0] == '-s': |
517 |
args = args[1:] |
518 |
klass = SGMLParser |
519 |
else: |
520 |
klass = TestSGMLParser |
521 |
|
522 |
if args: |
523 |
file = args[0] |
524 |
else: |
525 |
file = 'test.html' |
526 |
|
527 |
if file == '-': |
528 |
f = sys.stdin |
529 |
else: |
530 |
try: |
531 |
f = open(file, 'r') |
532 |
except IOError as msg: |
533 |
print(file, ":", msg) |
534 |
sys.exit(1) |
535 |
|
536 |
data = f.read() |
537 |
if f is not sys.stdin: |
538 |
f.close() |
539 |
|
540 |
x = klass() |
541 |
for c in data: |
542 |
x.feed(c) |
543 |
x.close() |
544 |
|
545 |
|
546 |
if __name__ == '__main__': |
547 |
test() |