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"""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). RCDATA is
# not supported at all.
import markupbase
import re
__all__ = ["SGMLParser", "SGMLParseError"]
# 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]*)/([^/]*)/')
piclose = re.compile('>')
endbracket = re.compile('[<>]')
tagfind = re.compile('[a-zA-Z][-_.a-zA-Z0-9]*')
attrfind = re.compile(
r'\s*([a-zA-Z_][-:.a-zA-Z_0-9]*)(\s*=\s*'
r'(\'[^\']*\'|"[^"]*"|[-a-zA-Z0-9./,:;+*%?!&$\(\)_#=~\'"@]*))?')
class SGMLParseError(RuntimeError):
"""Exception raised for all parse errors."""
pass
# 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 arbitrary
# chunks). Entity references are passed by calling
# self.handle_entityref() with the entity reference as argument.
class SGMLParser(markupbase.ParserBase):
def __init__(self, verbose=0):
"""Initialize and reset this instance."""
self.verbose = verbose
self.reset()
def reset(self):
"""Reset this instance. Loses all unprocessed data."""
self.__starttag_text = None
self.rawdata = ''
self.stack = []
self.lasttag = '???'
self.nomoretags = 0
self.literal = 0
markupbase.ParserBase.reset(self)
def setnomoretags(self):
"""Enter literal mode (CDATA) till EOF.
Intended for derived classes only.
"""
self.nomoretags = self.literal = 1
def setliteral(self, *args):
"""Enter literal mode (CDATA).
Intended for derived classes only.
"""
self.literal = 1
def feed(self, data):
"""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().)
"""
self.rawdata = self.rawdata + data
self.goahead(0)
def close(self):
"""Handle the remaining data."""
self.goahead(1)
def error(self, message):
raise SGMLParseError(message)
# 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()
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 rawdata.startswith("</", i):
k = self.parse_endtag(i)
if k < 0: break
i = k
self.literal = 0
continue
if self.literal:
if n > (i + 1):
self.handle_data("<")
i = i+1
else:
# incomplete
break
continue
if rawdata.startswith("<!--", i):
# Strictly speaking, a comment is --.*--
# within a declaration tag <!...>.
# This should be removed,
# and comments handled only in parse_declaration.
k = self.parse_comment(i)
if k < 0: break
i = k
continue
if rawdata.startswith("<?", i):
k = self.parse_pi(i)
if k < 0: break
i = i+k
continue
if rawdata.startswith("<!", i):
# This is some sort of declaration; in "HTML as
# deployed," this should only be the document type
# declaration ("<!DOCTYPE html...>").
k = self.parse_declaration(i)
if k < 0: break
i = k
continue
elif rawdata[i] == '&':
if self.literal:
self.handle_data(rawdata[i])
i = i+1
continue
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:
self.error('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
# Extensions for the DOCTYPE scanner:
_decl_otherchars = '='
# Internal -- parse processing instr, return length or -1 if not terminated
def parse_pi(self, i):
rawdata = self.rawdata
if rawdata[i:i+2] != '<?':
self.error('unexpected call to parse_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
def get_starttag_text(self):
return self.__starttag_text
# Internal -- handle starttag, return length or -1 if not terminated
def parse_starttag(self, i):
self.__starttag_text = None
start_pos = 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)
self.__starttag_text = '<%s/' % tag
tag = tag.lower()
k = match.end(0)
self.finish_shorttag(tag, data)
self.__starttag_text = rawdata[start_pos:match.end(1) + 1]
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:
self.error('unexpected call to parse_starttag')
k = match.end(0)
tag = rawdata[i+1:k].lower()
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((attrname.lower(), attrvalue))
k = match.end(0)
if rawdata[j] == '>':
j = j+1
self.__starttag_text = rawdata[start_pos:j]
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 = rawdata[i+2:j].strip().lower()
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
def handle_charref(self, name):
"""Handle character reference, no need to override."""
try:
n = int(name)
except ValueError:
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': '\''}
def handle_entityref(self, name):
"""Handle entity references.
There should be no need to override this method; it can be
tailored by setting up the self.entitydefs mapping appropriately.
"""
table = self.entitydefs
if name in table:
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 declaration, could be overridden
def handle_decl(self, decl):
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(repr(self.testdata)) >= 70:
self.flush()
def flush(self):
data = self.testdata
if data:
self.testdata = ""
print 'data:', repr(data)
def handle_comment(self, data):
self.flush()
r = repr(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 unknown_decl(self, data):
self.flush()
print '*** unknown decl: [' + data + ']'
def close(self):
SGMLParser.close(self)
self.flush()
def test(args = None):
import sys
if args is None:
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()
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