"""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).
import re
import string
__all__ = ["SGMLParser"]
# 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]*)/([^/]*)/')
piopen = re.compile('<\?')
piclose = re.compile('>')
endtagopen = re.compile('</[<>a-zA-Z]')
endbracket = re.compile('[<>]')
special = re.compile('<![^<>]*>')
commentopen = re.compile('<!--')
commentclose = re.compile(r'--\s*>')
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./:;+*%?!&$\(\)_#=~\'"]*))?')
declname = re.compile(r'[a-zA-Z][-_.a-zA-Z0-9]*\s*')
declstringlit = re.compile(r'(\'[^\']*\'|"[^"]*")\s*')
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:
# Interface -- initialize and reset this instance
def __init__(self, verbose=0):
self.verbose = verbose
self.reset()
# Interface -- reset this instance. Loses all unprocessed data
def reset(self):
self.rawdata = ''
self.stack = []
self.lasttag = '???'
self.nomoretags = 0
self.literal = 0
# For derived classes only -- enter literal mode (CDATA) till EOF
def setnomoretags(self):
self.nomoretags = self.literal = 1
# For derived classes only -- enter literal mode (CDATA)
def setliteral(self, *args):
self.literal = 1
# Interface -- 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().)
def feed(self, data):
self.rawdata = self.rawdata + data
self.goahead(0)
# Interface -- handle the remaining data
def close(self):
self.goahead(1)
# 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(0)
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 endtagopen.match(rawdata, i):
k = self.parse_endtag(i)
if k < 0: break
i = k
self.literal = 0
continue
if commentopen.match(rawdata, i):
if self.literal:
self.handle_data(rawdata[i])
i = i+1
continue
k = self.parse_comment(i)
if k < 0: break
i = i+k
continue
if piopen.match(rawdata, i):
if self.literal:
self.handle_data(rawdata[i])
i = i+1
continue
k = self.parse_pi(i)
if k < 0: break
i = i+k
continue
match = special.match(rawdata, i)
if match:
if self.literal:
self.handle_data(rawdata[i])
i = i+1
continue
# 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] == '&':
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:
raise SGMLParseError('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
# Internal -- parse comment, return length or -1 if not terminated
def parse_comment(self, i):
rawdata = self.rawdata
if rawdata[i:i+4] != '<!--':
raise SGMLParseError('unexpected call to parse_comment()')
match = commentclose.search(rawdata, i+4)
if not match:
return -1
j = match.start(0)
self.handle_comment(rawdata[i+4: j])
j = match.end(0)
return j-i
# Internal -- parse declaration.
def parse_declaration(self, i):
rawdata = self.rawdata
j = i + 2
# in practice, this should look like: ((name|stringlit) S*)+ '>'
while 1:
c = rawdata[j:j+1]
if c == ">":
# end of declaration syntax
self.handle_decl(rawdata[i+2:j])
return j + 1
if c in "\"'":
m = declstringlit.match(rawdata, j)
if not m:
# incomplete or an error?
return -1
j = m.end()
elif c in "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ":
m = declname.match(rawdata, j)
if not m:
# incomplete or an error?
return -1
j = m.end()
elif i == len(rawdata):
# end of buffer between tokens
return -1
else:
raise SGMLParseError(
"unexpected char in declaration: %s" % `rawdata[i]`)
assert 0, "can't get here!"
# Internal -- parse processing instr, return length or -1 if not terminated
def parse_pi(self, i):
rawdata = self.rawdata
if rawdata[i:i+2] != '<?':
raise SGMLParseError('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
__starttag_text = None
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:
raise SGMLParseError('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
# Example -- handle character reference, no need to override
def handle_charref(self, name):
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': '\''}
# Example -- handle entity reference, no need to override
def handle_entityref(self, name):
table = self.entitydefs
if table.has_key(name):
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(`self.testdata`) >= 70:
self.flush()
def flush(self):
data = self.testdata
if data:
self.testdata = ""
print 'data:', `data`
def handle_comment(self, data):
self.flush()
r = `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 close(self):
SGMLParser.close(self)
self.flush()
def test(args = None):
import sys
if not args:
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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