"""A parser for HTML."""

# This file is based on sgmllib.py, but the API is slightly different.

# 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

# Regular expressions used for parsing

interesting_normal = re.compile('[&<]')

interesting_cdata = re.compile(r'<(/|\Z)')

incomplete = re.compile('&([a-zA-Z][-.a-zA-Z0-9]*|#[0-9]*)?')

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]')

piopen = re.compile(r'<\?')

piclose = re.compile('>')

endtagopen = re.compile('</')

declopen = 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./:;+*%?!&$\(\)_#=~]*))?')

locatestarttagend = re.compile(r"""

<[a-zA-Z][-.a-zA-Z0-9:_]* # tag name

(?:\s+ # whitespace before attribute name

(?:[a-zA-Z_][-.:a-zA-Z0-9_]* # attribute name

(?:\s*=\s* # value indicator

(?:'[^']*' # LITA-enclosed value

|\"[^\"]*\" # LIT-enclosed value

|[^'\">\s]+ # bare value

)

)?

)

)*

\s* # trailing whitespace

""", re.VERBOSE)

endstarttag = re.compile(r"\s*/?>")

endendtag = re.compile('>')

endtagfind = re.compile('</\s*([a-zA-Z][-.a-zA-Z0-9:_]*)\s*>')

declname = re.compile(r'[a-zA-Z][-_.a-zA-Z0-9]*\s*')

declstringlit = re.compile(r'(\'[^\']*\'|"[^"]*")\s*')

class HTMLParseError(Exception):

"""Exception raised for all parse errors."""

def __init__(self, msg, position=(None, None)):

assert msg

self.msg = msg

self.lineno = position[0]

self.offset = position[1]

def __str__(self):

result = self.msg

if self.lineno is not None:

result = result + ", at line %d" % self.lineno

if self.offset is not None:

result = result + ", column %d" % (self.offset + 1)

return result

# HTML parser class -- find tags and call handler functions.

# Usage:

#

# p = HTMLParser(); p.feed(data); ...; p.close()

# Start tags are handled by calling self.handle_starttag() or

# self.handle_startendtag(); end tags by self.handle_endtag(). The

# data between tags is passed from the parser to the derived class by

# calling self.handle_data() with the 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 the

# argument. Numeric character references are passed to

# self.handle_charref() with the string containing the reference as

# the argument.

class HTMLParser:

CDATA_CONTENT_ELEMENTS = ("script", "style")

# 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.lasttag = '???'

self.lineno = 1

self.offset = 0

self.interesting = interesting_normal

# 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 -- update line number and offset. This should be

# called for each piece of data exactly once, in order -- in other

# words the concatenation of all the input strings to this

# function should be exactly the entire input.

def updatepos(self, i, j):

if i >= j:

return j

rawdata = self.rawdata

nlines = string.count(rawdata, "\n", i, j)

if nlines:

self.lineno = self.lineno + nlines

pos = string.rindex(rawdata, "\n", i, j) # Should not fail

self.offset = j-(pos+1)

else:

self.offset = self.offset + j-i

return j

# Interface -- return current line number and offset.

def getpos(self):

return self.lineno, self.offset

__starttag_text = None

# Interface -- return full source of start tag: "<...>"

def get_starttag_text(self):

return self.__starttag_text

def set_cdata_mode(self):

self.interesting = interesting_cdata

def clear_cdata_mode(self):

self.interesting = interesting_normal

# 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:

match = self.interesting.search(rawdata, i) # < or &

if match:

j = match.start()

else:

j = n

if i < j: self.handle_data(rawdata[i:j])

i = self.updatepos(i, j)

if i == n: break

if rawdata[i] == '<':

if starttagopen.match(rawdata, i): # < + letter

k = self.parse_starttag(i)

elif endtagopen.match(rawdata, i): # </

k = self.parse_endtag(i)

if k >= 0:

self.clear_cdata_mode()

elif commentopen.match(rawdata, i): # <!--

k = self.parse_comment(i)

elif piopen.match(rawdata, i): # <?

k = self.parse_pi(i)

elif declopen.match(rawdata, i): # <!

k = self.parse_declaration(i)

else:

if i < n-1:

raise HTMLParseError(

"invalid '<' construct: %s" % `rawdata[i:i+2]`,

self.getpos())

k = -1

if k < 0:

if end:

raise HTMLParseError("EOF in middle of construct",

self.getpos())

break

i = self.updatepos(i, k)

elif rawdata[i] == '&':

match = charref.match(rawdata, i)

if match:

name = match.group(1)

self.handle_charref(name)

k = match.end()

if rawdata[k-1] != ';':

k = k-1

i = self.updatepos(i, k)

continue

match = entityref.match(rawdata, i)

if match:

name = match.group(1)

self.handle_entityref(name)

k = match.end()

if rawdata[k-1] != ';':

k = k-1

i = self.updatepos(i, k)

continue

if incomplete.match(rawdata, i):

if end:

raise HTMLParseError(

"EOF in middle of entity or char ref",

self.getpos())

return -1 # incomplete

raise HTMLParseError("'&' not part of entity or char ref",

self.getpos())

else:

assert 0, "interesting.search() lied"

# end while

if end and i < n:

self.handle_data(rawdata[i:n])

i = self.updatepos(i, n)

self.rawdata = rawdata[i:]

# Internal -- parse comment, return end or -1 if not terminated

def parse_comment(self, i):

rawdata = self.rawdata

assert rawdata[i:i+4] == '<!--', 'unexpected call to parse_comment()'

match = commentclose.search(rawdata, i+4)

if not match:

return -1

j = match.start()

self.handle_comment(rawdata[i+4: j])

j = match.end()

return j

# Internal -- parse declaration.

def parse_declaration(self, i):

# This is some sort of declaration; in "HTML as

# deployed," this should only be the document type

# declaration ("<!DOCTYPE html...>").

rawdata = self.rawdata

j = i + 2

assert rawdata[i:j] == "<!", "unexpected call to parse_declaration"

if rawdata[j:j+1] in ("-", ""):

# Start of comment followed by buffer boundary,

# or just a buffer boundary.

return -1

# in practice, this should look like: ((name|stringlit) S*)+ '>'

n = len(rawdata)

while j < n:

c = rawdata[j]

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:

return -1 # incomplete

j = m.end()

elif c in "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ":

m = declname.match(rawdata, j)

if not m:

return -1 # incomplete

j = m.end()

else:

raise HTMLParseError(

"unexpected char in declaration: %s" % `rawdata[j]`,

self.getpos())

return -1 # incomplete

# Internal -- parse processing instr, return end or -1 if not terminated

def parse_pi(self, i):

rawdata = self.rawdata

assert rawdata[i:i+2] == '<?', 'unexpected call to parse_pi()'

match = piclose.search(rawdata, i+2) # >

if not match:

return -1

j = match.start()

self.handle_pi(rawdata[i+2: j])

j = match.end()

return j

# Internal -- handle starttag, return end or -1 if not terminated

def parse_starttag(self, i):

self.__starttag_text = None

endpos = self.check_for_whole_start_tag(i)

if endpos < 0:

return endpos

rawdata = self.rawdata

self.__starttag_text = rawdata[i:endpos]

# Now parse the data between i+1 and j into a tag and attrs

attrs = []

match = tagfind.match(rawdata, i+1)

assert match, 'unexpected call to parse_starttag()'

k = match.end()

self.lasttag = tag = string.lower(rawdata[i+1:k])

while k < endpos:

m = attrfind.match(rawdata, k)

if not m:

break

attrname, rest, attrvalue = m.group(1, 2, 3)

if not rest:

attrvalue = None

elif attrvalue[:1] == '\'' == attrvalue[-1:] or \

attrvalue[:1] == '"' == attrvalue[-1:]:

attrvalue = attrvalue[1:-1]

attrvalue = self.unescape(attrvalue)

attrs.append((string.lower(attrname), attrvalue))

k = m.end()

end = string.strip(rawdata[k:endpos])

if end not in (">", "/>"):

lineno, offset = self.getpos()

if "\n" in self.__starttag_text:

lineno = lineno + string.count(self.__starttag_text, "\n")

offset = len(self.__starttag_text) \

- string.rfind(self.__starttag_text, "\n")

else:

offset = offset + len(self.__starttag_text)

raise HTMLParseError("junk characters in start tag: %s"

% `rawdata[k:endpos][:20]`,

(lineno, offset))

if end[-2:] == '/>':

# XHTML-style empty tag: <span attr="value" />

self.handle_startendtag(tag, attrs)

else:

self.handle_starttag(tag, attrs)

if tag in self.CDATA_CONTENT_ELEMENTS:

self.set_cdata_mode()

return endpos

# Internal -- check to see if we have a complete starttag; return end

# or -1 if incomplete.

def check_for_whole_start_tag(self, i):

rawdata = self.rawdata

m = locatestarttagend.match(rawdata, i)

if m:

j = m.end()

next = rawdata[j:j+1]

if next == ">":

return j + 1

if next == "/":

s = rawdata[j:j+2]

if s == "/>":

return j + 2

if s == "/":

# buffer boundary

return -1

# else bogus input

self.updatepos(i, j + 1)

raise HTMLParseError("malformed empty start tag",

self.getpos())

if next == "":

# end of input

return -1

if next in ("abcdefghijklmnopqrstuvwxyz=/"

"ABCDEFGHIJKLMNOPQRSTUVWXYZ"):

# end of input in or before attribute value, or we have the

# '/' from a '/>' ending

return -1

self.updatepos(i, j)

raise HTMLParseError("malformed start tag", self.getpos())

raise AssertionError("we should not gt here!")

# Internal -- parse endtag, return end or -1 if incomplete

def parse_endtag(self, i):

rawdata = self.rawdata

assert rawdata[i:i+2] == "</", "unexpected call to parse_endtag"

match = endendtag.search(rawdata, i+1) # >

if not match:

return -1

j = match.end()

match = endtagfind.match(rawdata, i) # </ + tag + >

if not match:

raise HTMLParseError("bad end tag: %s" % `rawdata[i:j]`,

self.getpos())

tag = match.group(1)

self.handle_endtag(string.lower(tag))

return j

# Overridable -- finish processing of start+end tag: <tag.../>

def handle_startendtag(self, tag, attrs):

self.handle_starttag(tag, attrs)

self.handle_endtag(tag)

# Overridable -- handle start tag

def handle_starttag(self, tag, attrs):

pass

# Overridable -- handle end tag

def handle_endtag(self, tag):

pass

# Overridable -- handle character reference

def handle_charref(self, name):

pass

# Overridable -- handle entity reference

def handle_entityref(self, name):

pass

# Overridable -- handle data

def handle_data(self, data):

pass

# Overridable -- handle comment

def handle_comment(self, data):

pass

# Overridable -- handle declaration

def handle_decl(self, decl):

pass

# Overridable -- handle processing instruction

def handle_pi(self, data):

pass

# Internal -- helper to remove special character quoting

def unescape(self, s):

if '&' not in s:

return s

s = string.replace(s, "&lt;", "<")

s = string.replace(s, "&gt;", ">")

s = string.replace(s, "&apos;", "'")

s = string.replace(s, "&quot;", '"')

s = string.replace(s, "&amp;", "&") # Must be last

return s