import codecs
import re
import types
from gettext import gettext
_ = gettext
from constants import EOF, spaceCharacters, asciiLetters, asciiUppercase
from constants import encodings
from utils import MethodDispatcher
class HTMLInputStream(object):
"""Provides a unicode stream of characters to the HTMLTokenizer.
This class takes care of character encoding and removing or replacing
incorrect byte-sequences and also provides column and line tracking.
"""
def __init__(self, source, encoding=None, parseMeta=True, chardet=True):
"""Initialises the HTMLInputStream.
HTMLInputStream(source, [encoding]) -> Normalized stream from source
for use by the HTML5Lib.
source can be either a file-object, local filename or a string.
The optional encoding parameter must be a string that indicates
the encoding. If specified, that encoding will be used,
regardless of any BOM or later declaration (such as in a meta
element)
parseMeta - Look for a <meta> element containing encoding information
"""
# List of where new lines occur
self.newLines = [0]
self.charEncoding = encoding
# Raw Stream - for unicode objects this will encode to utf-8 and set
# self.charEncoding as appropriate
self.rawStream = self.openStream(source)
# Encoding Information
#Number of bytes to use when looking for a meta element with
#encoding information
self.numBytesMeta = 512
#Number of bytes to use when using detecting encoding using chardet
self.numBytesChardet = 100
#Encoding to use if no other information can be found
self.defaultEncoding = "windows-1252"
#Detect encoding iff no explicit "transport level" encoding is supplied
if self.charEncoding is None or not isValidEncoding(self.charEncoding):
self.charEncoding = self.detectEncoding(parseMeta, chardet)
self.dataStream = codecs.getreader(self.charEncoding)(self.rawStream,
'replace')
self.queue = []
self.errors = []
self.line = self.col = 0
self.lineLengths = []
#Flag to indicate we may have a CR LF broken across a data chunk
self._lastChunkEndsWithCR = False
def openStream(self, source):
"""Produces a file object from source.
source can be either a file object, local filename or a string.
"""
# Already a file object
if hasattr(source, 'read'):
stream = source
else:
# Otherwise treat source as a string and convert to a file object
if isinstance(source, unicode):
source = source.encode('utf-8')
self.charEncoding = "utf-8"
import cStringIO
stream = cStringIO.StringIO(str(source))
return stream
def detectEncoding(self, parseMeta=True, chardet=True):
#First look for a BOM
#This will also read past the BOM if present
encoding = self.detectBOM()
#If there is no BOM need to look for meta elements with encoding
#information
if encoding is None and parseMeta:
encoding = self.detectEncodingMeta()
#Guess with chardet, if avaliable
if encoding is None and chardet:
try:
from chardet.universaldetector import UniversalDetector
buffers = []
detector = UniversalDetector()
while not detector.done:
buffer = self.rawStream.read(self.numBytesChardet)
if not buffer:
break
buffers.append(buffer)
detector.feed(buffer)
detector.close()
encoding = detector.result['encoding']
self.seek("".join(buffers), 0)
except ImportError:
pass
# If all else fails use the default encoding
if encoding is None:
encoding = self.defaultEncoding
#Substitute for equivalent encodings:
encodingSub = {"iso-8859-1":"windows-1252"}
if encoding.lower() in encodingSub:
encoding = encodingSub[encoding.lower()]
return encoding
def detectBOM(self):
"""Attempts to detect at BOM at the start of the stream. If
an encoding can be determined from the BOM return the name of the
encoding otherwise return None"""
bomDict = {
codecs.BOM_UTF8: 'utf-8',
codecs.BOM_UTF16_LE: 'utf-16-le', codecs.BOM_UTF16_BE: 'utf-16-be',
codecs.BOM_UTF32_LE: 'utf-32-le', codecs.BOM_UTF32_BE: 'utf-32-be'
}
# Go to beginning of file and read in 4 bytes
string = self.rawStream.read(4)
# Try detecting the BOM using bytes from the string
encoding = bomDict.get(string[:3]) # UTF-8
seek = 3
if not encoding:
# Need to detect UTF-32 before UTF-16
encoding = bomDict.get(string) # UTF-32
seek = 4
if not encoding:
encoding = bomDict.get(string[:2]) # UTF-16
seek = 2
# Set the read position past the BOM if one was found, otherwise
# set it to the start of the stream
self.seek(string, encoding and seek or 0)
return encoding
def seek(self, buffer, n):
"""Unget buffer[n:]"""
if hasattr(self.rawStream, 'unget'):
self.rawStream.unget(buffer[n:])
return
if hasattr(self.rawStream, 'seek'):
try:
self.rawStream.seek(n)
return
except IOError:
pass
class BufferedStream:
def __init__(self, data, stream):
self.data = data
self.stream = stream
def read(self, chars=-1):
if chars == -1 or chars > len(self.data):
result = self.data
self.data = ''
if chars == -1:
return result + self.stream.read()
else:
return result + self.stream.read(chars-len(result))
elif not self.data:
return self.stream.read(chars)
else:
result = self.data[:chars]
self.data = self.data[chars:]
return result
def unget(self, data):
if self.data:
self.data += data
else:
self.data = data
self.rawStream = BufferedStream(buffer[n:], self.rawStream)
def detectEncodingMeta(self):
"""Report the encoding declared by the meta element
"""
buffer = self.rawStream.read(self.numBytesMeta)
parser = EncodingParser(buffer)
self.seek(buffer, 0)
return parser.getEncoding()
def position(self):
"""Returns (line, col) of the current position in the stream."""
line, col = self.line, self.col
return (line + 1, col)
def char(self):
""" Read one character from the stream or queue if available. Return
EOF when EOF is reached.
"""
if not self.queue:
self.readChunk()
#If we still don't have a character we have reached EOF
if not self.queue:
return EOF
char = self.queue.pop(0)
# update position in stream
if char == '\n':
self.lineLengths.append(self.col)
self.line += 1
self.col = 0
else:
self.col += 1
return char
def readChunk(self, chunkSize=10240):
data = self.dataStream.read(chunkSize)
if not data:
return
#Replace null characters
for i in xrange(data.count(u"\u0000")):
self.errors.append(_('null character found in input stream, '
'replaced with U+FFFD'))
data = data.replace(u"\u0000", u"\ufffd")
#Check for CR LF broken across chunks
if (self._lastChunkEndsWithCR and data[0] == "\n"):
data = data[1:]
self._lastChunkEndsWithCR = data[-1] == "\r"
data = data.replace("\r\n", "\n")
data = data.replace("\r", "\n")
data = unicode(data)
self.queue.extend([char for char in data])
def charsUntil(self, characters, opposite = False):
""" Returns a string of characters from the stream up to but not
including any character in characters or EOF. characters can be
any container that supports the in method being called on it.
"""
#This method is currently 40-50% of our total runtime and badly needs
#optimizing
#Possible improvements:
# - use regexp to find characters that match the required character set
# (with regexp cache since we do the same searches many many times)
# - improve EOF handling for fewer if statements
if not self.queue:
self.readChunk()
#Break if we have reached EOF
if not self.queue or self.queue[0] == None:
return u""
i = 0
while (self.queue[i] in characters) == opposite:
i += 1
if i == len(self.queue):
self.readChunk()
#If the queue doesn't grow we have reached EOF
if i == len(self.queue) or self.queue[i] is EOF:
break
#XXX- wallpaper over bug in calculation below
#Otherwise change the stream position
if self.queue[i] == '\n':
self.lineLengths.append(self.col)
self.line += 1
self.col = 0
else:
self.col += 1
rv = u"".join(self.queue[:i])
self.queue = self.queue[i:]
#Calculate where we now are in the stream
#One possible optimisation would be to store all read characters and
#Calculate this on an as-needed basis (perhaps flushing the read data
#every time we read a new chunk) rather than once per call here and
#in .char()
#XXX Temporarily disable this because there is a bug
#lines = rv.split("\n")
#
#if lines:
# #Add number of lines passed onto positon
# oldCol = self.col
# self.line += len(lines)-1
# if len(lines) > 1:
# self.col = len(lines[-1])
# else:
# self.col += len(lines[0])
#
# if self.lineLengths and oldCol > 0:
# self.lineLengths[-1] += len(lines[0])
# lines = lines[1:-1]
# else:
# lines = lines[:-1]
#
# for line in lines:
# self.lineLengths.append(len(line))
#
return rv
def unget(self, chars):
if chars:
self.queue = list(chars) + self.queue
#Alter the current line, col position
for c in chars[::-1]:
if c == '\n':
self.line -= 1
self.col = self.lineLengths[self.line]
else:
self.col -= 1
class EncodingBytes(str):
"""String-like object with an assosiated position and various extra methods
If the position is ever greater than the string length then an exception is
raised"""
def __init__(self, value):
str.__init__(self, value)
self._position=-1
def __iter__(self):
return self
def next(self):
self._position += 1
rv = self[self.position]
return rv
def setPosition(self, position):
if self._position >= len(self):
raise StopIteration
self._position = position
def getPosition(self):
if self._position >= len(self):
raise StopIteration
if self._position >= 0:
return self._position
else:
return None
position = property(getPosition, setPosition)
def getCurrentByte(self):
return self[self.position]
currentByte = property(getCurrentByte)
def skip(self, chars=spaceCharacters):
"""Skip past a list of characters"""
while self.currentByte in chars:
self.position += 1
def matchBytes(self, bytes, lower=False):
"""Look for a sequence of bytes at the start of a string. If the bytes
are found return True and advance the position to the byte after the
match. Otherwise return False and leave the position alone"""
data = self[self.position:self.position+len(bytes)]
if lower:
data = data.lower()
rv = data.startswith(bytes)
if rv == True:
self.position += len(bytes)
return rv
def jumpTo(self, bytes):
"""Look for the next sequence of bytes matching a given sequence. If
a match is found advance the position to the last byte of the match"""
newPosition = self[self.position:].find(bytes)
if newPosition > -1:
self._position += (newPosition + len(bytes)-1)
return True
else:
raise StopIteration
def findNext(self, byteList):
"""Move the pointer so it points to the next byte in a set of possible
bytes"""
while (self.currentByte not in byteList):
self.position += 1
class EncodingParser(object):
"""Mini parser for detecting character encoding from meta elements"""
def __init__(self, data):
"""string - the data to work on for encoding detection"""
self.data = EncodingBytes(data)
self.encoding = None
def getEncoding(self):
methodDispatch = (
("<!--",self.handleComment),
("<meta",self.handleMeta),
("</",self.handlePossibleEndTag),
("<!",self.handleOther),
("<?",self.handleOther),
("<",self.handlePossibleStartTag))
for byte in self.data:
keepParsing = True
for key, method in methodDispatch:
if self.data.matchBytes(key, lower=True):
try:
keepParsing = method()
break
except StopIteration:
keepParsing=False
break
if not keepParsing:
break
if self.encoding is not None:
self.encoding = self.encoding.strip()
return self.encoding
def handleComment(self):
"""Skip over comments"""
return self.data.jumpTo("-->")
def handleMeta(self):
if self.data.currentByte not in spaceCharacters:
#if we have <meta not followed by a space so just keep going
return True
#We have a valid meta element we want to search for attributes
while True:
#Try to find the next attribute after the current position
attr = self.getAttribute()
if attr is None:
return True
else:
if attr[0] == "charset":
tentativeEncoding = attr[1]
if isValidEncoding(tentativeEncoding):
self.encoding = tentativeEncoding
return False
elif attr[0] == "content":
contentParser = ContentAttrParser(EncodingBytes(attr[1]))
tentativeEncoding = contentParser.parse()
if isValidEncoding(tentativeEncoding):
self.encoding = tentativeEncoding
return False
def handlePossibleStartTag(self):
return self.handlePossibleTag(False)
def handlePossibleEndTag(self):
self.data.position+=1
return self.handlePossibleTag(True)
def handlePossibleTag(self, endTag):
if self.data.currentByte not in asciiLetters:
#If the next byte is not an ascii letter either ignore this
#fragment (possible start tag case) or treat it according to
#handleOther
if endTag:
self.data.position -= 1
self.handleOther()
return True
self.data.findNext(list(spaceCharacters) + ["<", ">"])
if self.data.currentByte == "<":
#return to the first step in the overall "two step" algorithm
#reprocessing the < byte
self.data.position -= 1
else:
#Read all attributes
attr = self.getAttribute()
while attr is not None:
attr = self.getAttribute()
return True
def handleOther(self):
return self.data.jumpTo(">")
def getAttribute(self):
"""Return a name,value pair for the next attribute in the stream,
if one is found, or None"""
self.data.skip(list(spaceCharacters)+["/"])
if self.data.currentByte == "<":
self.data.position -= 1
return None
elif self.data.currentByte == ">":
return None
attrName = []
attrValue = []
spaceFound = False
#Step 5 attribute name
while True:
if self.data.currentByte == "=" and attrName:
break
elif self.data.currentByte in spaceCharacters:
spaceFound=True
break
elif self.data.currentByte in ("/", "<", ">"):
return "".join(attrName), ""
elif self.data.currentByte in asciiUppercase:
attrName.extend(self.data.currentByte.lower())
else:
attrName.extend(self.data.currentByte)
#Step 6
self.data.position += 1
#Step 7
if spaceFound:
self.data.skip()
#Step 8
if self.data.currentByte != "=":
self.data.position -= 1
return "".join(attrName), ""
#XXX need to advance position in both spaces and value case
#Step 9
self.data.position += 1
#Step 10
self.data.skip()
#Step 11
if self.data.currentByte in ("'", '"'):
#11.1
quoteChar = self.data.currentByte
while True:
self.data.position+=1
#11.3
if self.data.currentByte == quoteChar:
self.data.position += 1
return "".join(attrName), "".join(attrValue)
#11.4
elif self.data.currentByte in asciiUppercase:
attrValue.extend(self.data.currentByte.lower())
#11.5
else:
attrValue.extend(self.data.currentByte)
elif self.data.currentByte in (">", '<'):
return "".join(attrName), ""
elif self.data.currentByte in asciiUppercase:
attrValue.extend(self.data.currentByte.lower())
else:
attrValue.extend(self.data.currentByte)
while True:
self.data.position +=1
if self.data.currentByte in (
list(spaceCharacters) + [">", '<']):
return "".join(attrName), "".join(attrValue)
elif self.data.currentByte in asciiUppercase:
attrValue.extend(self.data.currentByte.lower())
else:
attrValue.extend(self.data.currentByte)
class ContentAttrParser(object):
def __init__(self, data):
self.data = data
def parse(self):
try:
#Skip to the first ";"
self.data.jumpTo(";")
self.data.position += 1
self.data.skip()
#Check if the attr name is charset
#otherwise return
self.data.jumpTo("charset")
self.data.position += 1
self.data.skip()
if not self.data.currentByte == "=":
#If there is no = sign keep looking for attrs
return None
self.data.position += 1
self.data.skip()
#Look for an encoding between matching quote marks
if self.data.currentByte in ('"', "'"):
quoteMark = self.data.currentByte
self.data.position += 1
oldPosition = self.data.position
self.data.jumpTo(quoteMark)
return self.data[oldPosition:self.data.position]
else:
#Unquoted value
oldPosition = self.data.position
try:
self.data.findNext(spaceCharacters)
return self.data[oldPosition:self.data.position]
except StopIteration:
#Return the whole remaining value
return self.data[oldPosition:]
except StopIteration:
return None
def isValidEncoding(encoding):
"""Determine if a string is a supported encoding"""
return (encoding is not None and type(encoding) == types.StringType and
encoding.lower().strip() in encodings)