# A parser for SGML, using the derived class as 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 regex
import string
# Regular expressions used for parsing
incomplete = regex.compile( \
'<!-?\|</[a-zA-Z][a-zA-Z0-9]*[ \t\n]*\|</?\|' + \
'&#[a-zA-Z0-9]*\|&[a-zA-Z][a-zA-Z0-9]*\|&')
entityref = regex.compile('&[a-zA-Z][a-zA-Z0-9]*[;.]')
charref = regex.compile('&#[a-zA-Z0-9]+;')
starttagopen = regex.compile('<[a-zA-Z]')
endtag = regex.compile('</[a-zA-Z][a-zA-Z0-9]*[ \t\n]*>')
commentopen = regex.compile('<!--')
# 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 arbutrary
# 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):
self.reset()
# Interface -- reset this instance. Loses all unprocessed data
def reset(self):
self.rawdata = ''
self.stack = []
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 process() or close().)
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
j = incomplete.search(rawdata, i)
if j < 0: 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) >= 0:
if self.literal:
self.handle_data(rawdata[i])
i = i+1
continue
k = self.parse_starttag(i)
if k < 0: break
i = i + k
continue
k = endtag.match(rawdata, i)
if k >= 0:
j = i+k
self.parse_endtag(rawdata[i:j])
i = j
self.literal = 0
continue
if commentopen.match(rawdata, i) >= 0:
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
elif rawdata[i] == '&':
k = charref.match(rawdata, i)
if k >= 0:
j = i+k
self.handle_charref(rawdata[i+2:j-1])
i = j
continue
k = entityref.match(rawdata, i)
if k >= 0:
j = i+k
self.handle_entityref(rawdata[i+1:j-1])
i = j
continue
else:
raise RuntimeError, 'neither < nor & ??'
# We get here only if incomplete matches but
# nothing else
k = incomplete.match(rawdata, i)
if k < 0: raise RuntimeError, 'no incomplete match ??'
j = i+k
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 ternimated
def parse_comment(self, i):
rawdata = self.rawdata
if rawdata[i:i+4] <> '<!--':
raise RuntimeError, 'unexpected call to handle_comment'
try:
j = string.index(rawdata, '--', i+4)
except string.index_error:
return -1
self.handle_comment(rawdata[i+4: j])
j = j+2
n = len(rawdata)
while j < n and rawdata[j] in ' \t\n': j = j+1
if j == n: return -1 # Wait for final '>'
if rawdata[j] == '>':
j = j+1
else:
print '*** comment not terminated with >'
print repr(rawdata[j-5:j]), '*!*', repr(rawdata[j:j+5])
return j-i
# Internal -- handle starttag, return length or -1 if not terminated
def parse_starttag(self, i):
rawdata = self.rawdata
try:
j = string.index(rawdata, '>', i)
except string.index_error:
return -1
# Now parse the data between i+1 and j into a tag and attrs
attrs = []
tagfind = regex.compile('[a-zA-Z][a-zA-Z0-9]*')
attrfind = regex.compile( \
'[ \t\n]+\([a-zA-Z][a-zA-Z0-9]*\)' + \
'\([ \t\n]*=[ \t\n]*' + \
'\(\'[^\']*\';\|"[^"]*"\|[-a-zA-Z0-9./:+*%?!()_#]+\)\)?')
k = tagfind.match(rawdata, i+1)
if k < 0:
raise RuntimeError, 'unexpected call to parse_starttag'
k = i+1+k
tag = string.lower(rawdata[i+1:k])
while k < j:
l = attrfind.match(rawdata, k)
if l < 0: break
regs = attrfind.regs
a1, b1 = regs[1]
a2, b2 = regs[2]
a3, b3 = regs[3]
attrname = rawdata[a1:b1]
if '=' in rawdata[k:k+l]:
attrvalue = rawdata[a3:b3]
if attrvalue[:1] == '\'' == attrvalue[-1:] or \
attrvalue[:1] == '"' == attrvalue[-1:]:
attrvalue = attrvalue[1:-1]
else:
attrvalue = ''
attrs.append(string.lower(attrname), attrvalue)
k = k + l
j = j+1
try:
method = getattr(self, 'start_' + tag)
except AttributeError:
try:
method = getattr(self, 'do_' + tag)
except AttributeError:
self.unknown_starttag(tag, attrs)
return j-i
method(attrs)
return j-i
self.stack.append(tag)
method(attrs)
return j-i
# Internal -- parse endtag
def parse_endtag(self, data):
if data[:2] <> '</' or data[-1:] <> '>':
raise RuntimeError, 'unexpected call to parse_endtag'
tag = string.lower(string.strip(data[2:-1]))
try:
method = getattr(self, 'end_' + tag)
except AttributeError:
self.unknown_endtag(tag)
return
if self.stack and self.stack[-1] == tag:
del self.stack[-1]
else:
print '*** Unbalanced </' + tag + '>'
print '*** Stack:', self.stack
found = None
for i in range(len(self.stack)):
if self.stack[i] == tag: found = i
if found <> None:
del self.stack[found:]
method()
# Example -- handle character reference, no need to override
def handle_charref(self, name):
try:
n = string.atoi(name)
except string.atoi_error:
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.__class__.entitydefs
name = string.lower(name)
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
# 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 TestSGML(SGMLParser):
def handle_data(self, data):
r = repr(data)
if len(r) > 72:
r = r[:35] + '...' + r[-35:]
print 'data:', r
def handle_comment(self, data):
r = repr(data)
if len(r) > 68:
r = r[:32] + '...' + r[-32:]
print 'comment:', r
def unknown_starttag(self, tag, attrs):
print 'start tag: <' + tag,
for name, value in attrs:
print name + '=' + '"' + value + '"',
print '>'
def unknown_endtag(self, tag):
print 'end tag: </' + tag + '>'
def unknown_entityref(self, ref):
print '*** unknown entity ref: &' + ref + ';'
def unknown_charref(self, ref):
print '*** unknown char ref: &#' + ref + ';'
def test():
file = 'test.html'
f = open(file, 'r')
x = TestSGML()
while 1:
line = f.readline()
if not line:
x.close()
break
x.feed(line)
#test()
|