437 lines
15 KiB
Python
437 lines
15 KiB
Python
"""A parser for HTML."""
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# This file is based on sgmllib.py, but the API is slightly different.
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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 re
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import string
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# Regular expressions used for parsing
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interesting_normal = re.compile('[&<]')
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interesting_cdata = re.compile(r'<(/|\Z)')
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incomplete = re.compile('&([a-zA-Z][-.a-zA-Z0-9]*|#[0-9]*)?')
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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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starttagopen = re.compile('<[a-zA-Z]')
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piopen = re.compile(r'<\?')
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piclose = re.compile('>')
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endtagopen = re.compile('</')
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declopen = re.compile('<!')
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special = re.compile('<![^<>]*>')
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commentopen = re.compile('<!--')
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commentclose = re.compile(r'--\s*>')
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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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locatestarttagend = re.compile(r"""
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<[a-zA-Z][-.a-zA-Z0-9:_]* # tag name
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(?:\s+ # whitespace before attribute name
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(?:[a-zA-Z_][-.:a-zA-Z0-9_]* # attribute name
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(?:\s*=\s* # value indicator
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(?:'[^']*' # LITA-enclosed value
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|\"[^\"]*\" # LIT-enclosed value
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|[^'\">\s]+ # bare value
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)
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)?
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)
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)*
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\s* # trailing whitespace
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""", re.VERBOSE)
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endstarttag = re.compile(r"\s*/?>")
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endendtag = re.compile('>')
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endtagfind = re.compile('</\s*([a-zA-Z][-.a-zA-Z0-9:_]*)\s*>')
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declname = re.compile(r'[a-zA-Z][-_.a-zA-Z0-9]*\s*')
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declstringlit = re.compile(r'(\'[^\']*\'|"[^"]*")\s*')
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class HTMLParseError(Exception):
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"""Exception raised for all parse errors."""
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def __init__(self, msg, position=(None, None)):
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assert msg
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self.msg = msg
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self.lineno = position[0]
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self.offset = position[1]
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def __str__(self):
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result = self.msg
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if self.lineno is not None:
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result = result + ", at line %d" % self.lineno
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if self.offset is not None:
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result = result + ", column %d" % (self.offset + 1)
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return result
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# HTML parser class -- find tags and call handler functions.
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# Usage:
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#
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# p = HTMLParser(); p.feed(data); ...; p.close()
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# Start tags are handled by calling self.handle_starttag() or
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# self.handle_startendtag(); end tags by self.handle_endtag(). The
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# data between tags is passed from the parser to the derived class by
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# calling self.handle_data() with the data as argument (the data may
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# be split up in arbitrary chunks). Entity references are passed by
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# calling self.handle_entityref() with the entity reference as the
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# argument. Numeric character references are passed to
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# self.handle_charref() with the string containing the reference as
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# the argument.
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class HTMLParser:
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CDATA_CONTENT_ELEMENTS = ("script", "style")
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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.lasttag = '???'
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self.lineno = 1
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self.offset = 0
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self.interesting = interesting_normal
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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 -- update line number and offset. This should be
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# called for each piece of data exactly once, in order -- in other
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# words the concatenation of all the input strings to this
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# function should be exactly the entire input.
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def updatepos(self, i, j):
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if i >= j:
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return j
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rawdata = self.rawdata
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nlines = string.count(rawdata, "\n", i, j)
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if nlines:
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self.lineno = self.lineno + nlines
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pos = string.rindex(rawdata, "\n", i, j) # Should not fail
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self.offset = j-(pos+1)
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else:
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self.offset = self.offset + j-i
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return j
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# Interface -- return current line number and offset.
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def getpos(self):
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return self.lineno, self.offset
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__starttag_text = None
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# Interface -- return full source of start tag: "<...>"
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def get_starttag_text(self):
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return self.__starttag_text
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def set_cdata_mode(self):
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self.interesting = interesting_cdata
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def clear_cdata_mode(self):
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self.interesting = interesting_normal
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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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match = self.interesting.search(rawdata, i) # < or &
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if match:
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j = match.start()
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else:
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j = n
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if i < j: self.handle_data(rawdata[i:j])
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i = self.updatepos(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): # < + letter
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k = self.parse_starttag(i)
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elif endtagopen.match(rawdata, i): # </
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k = self.parse_endtag(i)
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if k >= 0:
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self.clear_cdata_mode()
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elif commentopen.match(rawdata, i): # <!--
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k = self.parse_comment(i)
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elif piopen.match(rawdata, i): # <?
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k = self.parse_pi(i)
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elif declopen.match(rawdata, i): # <!
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k = self.parse_declaration(i)
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else:
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if i < n-1:
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raise HTMLParseError(
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"invalid '<' construct: %s" % `rawdata[i:i+2]`,
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self.getpos())
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k = -1
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if k < 0:
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if end:
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raise HTMLParseError("EOF in middle of construct",
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self.getpos())
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break
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i = self.updatepos(i, k)
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elif rawdata[i] == '&':
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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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k = match.end()
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if rawdata[k-1] != ';':
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k = k-1
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i = self.updatepos(i, k)
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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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k = match.end()
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if rawdata[k-1] != ';':
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k = k-1
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i = self.updatepos(i, k)
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continue
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if incomplete.match(rawdata, i):
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if end:
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raise HTMLParseError(
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"EOF in middle of entity or char ref",
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self.getpos())
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return -1 # incomplete
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raise HTMLParseError("'&' not part of entity or char ref",
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self.getpos())
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else:
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assert 0, "interesting.search() lied"
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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 = self.updatepos(i, n)
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self.rawdata = rawdata[i:]
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# Internal -- parse comment, return end 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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assert rawdata[i:i+4] == '<!--', 'unexpected call to parse_comment()'
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match = commentclose.search(rawdata, i+4)
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if not match:
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return -1
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j = match.start()
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self.handle_comment(rawdata[i+4: j])
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j = match.end()
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return j
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# Internal -- parse declaration.
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def parse_declaration(self, 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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rawdata = self.rawdata
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j = i + 2
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assert rawdata[i:j] == "<!", "unexpected call to parse_declaration"
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if rawdata[j:j+1] in ("-", ""):
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# Start of comment followed by buffer boundary,
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# or just a buffer boundary.
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return -1
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# in practice, this should look like: ((name|stringlit) S*)+ '>'
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n = len(rawdata)
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while j < n:
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c = rawdata[j]
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if c == ">":
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# end of declaration syntax
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self.handle_decl(rawdata[i+2:j])
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return j + 1
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if c in "\"'":
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m = declstringlit.match(rawdata, j)
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if not m:
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return -1 # incomplete
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j = m.end()
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elif c in "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ":
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m = declname.match(rawdata, j)
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if not m:
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return -1 # incomplete
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j = m.end()
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else:
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raise HTMLParseError(
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"unexpected char in declaration: %s" % `rawdata[j]`,
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self.getpos())
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return -1 # incomplete
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# Internal -- parse processing instr, return end 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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assert rawdata[i:i+2] == '<?', '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()
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self.handle_pi(rawdata[i+2: j])
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j = match.end()
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return j
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# Internal -- handle starttag, return end 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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endpos = self.check_for_whole_start_tag(i)
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if endpos < 0:
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return endpos
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rawdata = self.rawdata
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self.__starttag_text = rawdata[i:endpos]
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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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match = tagfind.match(rawdata, i+1)
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assert match, 'unexpected call to parse_starttag()'
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k = match.end()
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self.lasttag = tag = string.lower(rawdata[i+1:k])
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while k < endpos:
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m = attrfind.match(rawdata, k)
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if not m:
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break
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attrname, rest, attrvalue = m.group(1, 2, 3)
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if not rest:
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attrvalue = None
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elif 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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attrvalue = self.unescape(attrvalue)
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attrs.append((string.lower(attrname), attrvalue))
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k = m.end()
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end = string.strip(rawdata[k:endpos])
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if end not in (">", "/>"):
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lineno, offset = self.getpos()
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if "\n" in self.__starttag_text:
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lineno = lineno + string.count(self.__starttag_text, "\n")
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offset = len(self.__starttag_text) \
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- string.rfind(self.__starttag_text, "\n")
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else:
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offset = offset + len(self.__starttag_text)
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raise HTMLParseError("junk characters in start tag: %s"
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% `rawdata[k:endpos][:20]`,
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(lineno, offset))
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if end[-2:] == '/>':
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# XHTML-style empty tag: <span attr="value" />
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self.handle_startendtag(tag, attrs)
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else:
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self.handle_starttag(tag, attrs)
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if tag in self.CDATA_CONTENT_ELEMENTS:
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self.set_cdata_mode()
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return endpos
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# Internal -- check to see if we have a complete starttag; return end
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# or -1 if incomplete.
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def check_for_whole_start_tag(self, i):
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rawdata = self.rawdata
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m = locatestarttagend.match(rawdata, i)
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if m:
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j = m.end()
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next = rawdata[j:j+1]
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if next == ">":
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return j + 1
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if next == "/":
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s = rawdata[j:j+2]
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if s == "/>":
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return j + 2
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if s == "/":
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# buffer boundary
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return -1
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# else bogus input
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self.updatepos(i, j + 1)
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raise HTMLParseError("malformed empty start tag",
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self.getpos())
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if next == "":
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# end of input
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return -1
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if next in ("abcdefghijklmnopqrstuvwxyz=/"
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"ABCDEFGHIJKLMNOPQRSTUVWXYZ"):
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# end of input in or before attribute value, or we have the
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# '/' from a '/>' ending
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return -1
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self.updatepos(i, j)
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raise HTMLParseError("malformed start tag", self.getpos())
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raise AssertionError("we should not gt here!")
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# Internal -- parse endtag, return end or -1 if incomplete
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def parse_endtag(self, i):
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rawdata = self.rawdata
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assert rawdata[i:i+2] == "</", "unexpected call to parse_endtag"
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match = endendtag.search(rawdata, i+1) # >
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if not match:
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return -1
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j = match.end()
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match = endtagfind.match(rawdata, i) # </ + tag + >
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if not match:
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raise HTMLParseError("bad end tag: %s" % `rawdata[i:j]`,
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self.getpos())
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tag = match.group(1)
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self.handle_endtag(string.lower(tag))
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return j
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# Overridable -- finish processing of start+end tag: <tag.../>
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def handle_startendtag(self, tag, attrs):
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self.handle_starttag(tag, attrs)
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self.handle_endtag(tag)
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# Overridable -- handle start tag
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def handle_starttag(self, tag, attrs):
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pass
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# Overridable -- handle end tag
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def handle_endtag(self, tag):
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pass
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# Overridable -- handle character reference
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def handle_charref(self, name):
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pass
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# Overridable -- handle entity reference
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def handle_entityref(self, name):
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pass
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# Overridable -- handle data
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def handle_data(self, data):
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pass
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# Overridable -- handle comment
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def handle_comment(self, data):
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pass
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# Overridable -- handle declaration
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def handle_decl(self, decl):
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pass
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# Overridable -- handle processing instruction
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def handle_pi(self, data):
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pass
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# Internal -- helper to remove special character quoting
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def unescape(self, s):
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if '&' not in s:
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return s
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s = string.replace(s, "<", "<")
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s = string.replace(s, ">", ">")
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s = string.replace(s, "'", "'")
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s = string.replace(s, """, '"')
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s = string.replace(s, "&", "&") # Must be last
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return s
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