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331 lines
8.8 KiB
Python
331 lines
8.8 KiB
Python
# A parser for SGML, using the derived class as static DTD.
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# XXX This only supports those SGML features used by HTML.
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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 regex
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import string
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# Regular expressions used for parsing
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incomplete = regex.compile(
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'<!-?\|</[a-zA-Z][a-zA-Z0-9]*[ \t\n]*\|</?\|' +
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'&#[a-zA-Z0-9]*\|&[a-zA-Z][a-zA-Z0-9]*\|&')
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entityref = regex.compile('&[a-zA-Z][a-zA-Z0-9]*[;.]')
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charref = regex.compile('&#[a-zA-Z0-9]+;')
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starttagopen = regex.compile('<[a-zA-Z]')
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endtag = regex.compile('</[a-zA-Z][a-zA-Z0-9]*[ \t\n]*>')
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special = regex.compile('<![^<>]*>')
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commentopen = regex.compile('<!--')
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commentclose = regex.compile('--[ \t\n]*>')
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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 arbutrary
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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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class SGMLParser:
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# Interface -- initialize and reset this instance
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def __init__(self):
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self.reset()
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# Interface -- reset this instance. Loses all unprocessed data
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def reset(self):
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self.rawdata = ''
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self.stack = []
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self.nomoretags = 0
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self.literal = 0
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# For derived classes only -- enter literal mode (CDATA) till EOF
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def setnomoretags(self):
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self.nomoretags = self.literal = 1
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# For derived classes only -- enter literal mode (CDATA)
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def setliteral(self, *args):
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self.literal = 1
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# Interface -- feed some data to the parser. Call this as
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# often as you want, with as little or as much text as you
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# want (may include '\n'). (This just saves the text, all the
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# processing is done by goahead().)
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def feed(self, data):
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self.rawdata = self.rawdata + data
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self.goahead(0)
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# Interface -- handle the remaining data
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def close(self):
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self.goahead(1)
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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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j = incomplete.search(rawdata, i)
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if j < 0: j = n
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if i < j: 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) >= 0:
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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 = i + k
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continue
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k = endtag.match(rawdata, i)
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if k >= 0:
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j = i+k
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self.parse_endtag(rawdata[i:j])
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i = j
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self.literal = 0
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continue
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if commentopen.match(rawdata, i) >= 0:
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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_comment(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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k = special.match(rawdata, i)
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if k >= 0:
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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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i = i+k
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continue
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elif rawdata[i] == '&':
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k = charref.match(rawdata, i)
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if k >= 0:
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j = i+k
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self.handle_charref(rawdata[i+2:j-1])
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i = j
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continue
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k = entityref.match(rawdata, i)
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if k >= 0:
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j = i+k
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self.handle_entityref(rawdata[i+1:j-1])
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i = j
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continue
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else:
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raise RuntimeError, 'neither < nor & ??'
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# We get here only if incomplete matches but
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# nothing else
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k = incomplete.match(rawdata, i)
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if k < 0: raise RuntimeError, 'no incomplete match ??'
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j = i+k
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if j == n: 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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# Internal -- parse comment, return length or -1 if not terminated
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def parse_comment(self, i):
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rawdata = self.rawdata
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if rawdata[i:i+4] <> '<!--':
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raise RuntimeError, 'unexpected call to handle_comment'
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j = commentclose.search(rawdata, i+4)
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if j < 0:
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return -1
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self.handle_comment(rawdata[i+4: j])
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j = j+commentclose.match(rawdata, j)
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return j-i
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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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rawdata = self.rawdata
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try:
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j = string.index(rawdata, '>', i)
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except string.index_error:
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return -1
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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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tagfind = regex.compile('[a-zA-Z][a-zA-Z0-9]*')
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# XXX Should also support value-less attributes (e.g. ISMAP)
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# XXX Should use regex.group()
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attrfind = regex.compile(
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'[ \t\n]+\([a-zA-Z][a-zA-Z0-9]*\)' +
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'\([ \t\n]*=[ \t\n]*' +
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'\(\'[^\']*\';\|"[^"]*"\|[-a-zA-Z0-9./:+*%?!()_#]+\)\)?')
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k = tagfind.match(rawdata, i+1)
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if k < 0:
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raise RuntimeError, 'unexpected call to parse_starttag'
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k = i+1+k
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tag = string.lower(rawdata[i+1:k])
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while k < j:
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l = attrfind.match(rawdata, k)
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if l < 0: break
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regs = attrfind.regs
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a1, b1 = regs[1]
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a2, b2 = regs[2]
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a3, b3 = regs[3]
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attrname = rawdata[a1:b1]
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if '=' in rawdata[k:k+l]:
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attrvalue = rawdata[a3:b3]
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if 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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else:
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attrvalue = ''
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attrs.append((string.lower(attrname), attrvalue))
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k = k + l
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j = j+1
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try:
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method = getattr(self, 'start_' + tag)
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except AttributeError:
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try:
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method = getattr(self, 'do_' + tag)
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except AttributeError:
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self.unknown_starttag(tag, attrs)
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return j-i
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method(attrs)
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return j-i
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self.stack.append(tag)
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method(attrs)
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return j-i
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# Internal -- parse endtag
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def parse_endtag(self, data):
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if data[:2] <> '</' or data[-1:] <> '>':
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raise RuntimeError, 'unexpected call to parse_endtag'
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tag = string.lower(string.strip(data[2:-1]))
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try:
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method = getattr(self, 'end_' + tag)
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except AttributeError:
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self.unknown_endtag(tag)
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return
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if self.stack and self.stack[-1] == tag:
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del self.stack[-1]
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else:
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self.report_unbalanced(tag)
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# Now repair it
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found = None
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for i in range(len(self.stack)):
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if self.stack[i] == tag: found = i
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if found <> None:
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del self.stack[found:]
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method()
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# Example -- report an unbalanced </...> tag.
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def report_unbalanced(self, tag):
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print '*** Unbalanced </' + tag + '>'
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print '*** Stack:', self.stack
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# Example -- handle character reference, no need to override
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def handle_charref(self, name):
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try:
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n = string.atoi(name)
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except string.atoi_error:
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self.unknown_charref(name)
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return
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if not 0 <= n <= 255:
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self.unknown_charref(name)
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return
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self.handle_data(chr(n))
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# Definition of entities -- derived classes may override
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entitydefs = \
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{'lt': '<', 'gt': '>', 'amp': '&', 'quot': '"', 'apos': '\''}
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# Example -- handle entity reference, no need to override
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def handle_entityref(self, name):
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table = self.entitydefs
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name = string.lower(name)
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if table.has_key(name):
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self.handle_data(table[name])
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else:
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self.unknown_entityref(name)
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return
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# Example -- handle data, should be overridden
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def handle_data(self, data):
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pass
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# Example -- handle comment, could be overridden
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def handle_comment(self, data):
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pass
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# To be overridden -- handlers for unknown objects
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def unknown_starttag(self, tag, attrs): pass
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def unknown_endtag(self, tag): pass
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def unknown_charref(self, ref): pass
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def unknown_entityref(self, ref): pass
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class TestSGML(SGMLParser):
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def handle_data(self, data):
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r = repr(data)
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if len(r) > 72:
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r = r[:35] + '...' + r[-35:]
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print 'data:', r
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def handle_comment(self, data):
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r = repr(data)
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if len(r) > 68:
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r = r[:32] + '...' + r[-32:]
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print 'comment:', r
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def unknown_starttag(self, tag, attrs):
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print 'start tag: <' + tag,
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for name, value in attrs:
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print name + '=' + '"' + value + '"',
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print '>'
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def unknown_endtag(self, tag):
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print 'end tag: </' + tag + '>'
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def unknown_entityref(self, ref):
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print '*** unknown entity ref: &' + ref + ';'
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def unknown_charref(self, ref):
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print '*** unknown char ref: &#' + ref + ';'
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def test():
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file = 'test.html'
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f = open(file, 'r')
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x = TestSGML()
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while 1:
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line = f.readline()
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if not line:
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x.close()
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break
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x.feed(line)
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if __name__ == '__main__':
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test()
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