diff env/lib/python3.9/site-packages/bleach/_vendor/html5lib/_inputstream.py @ 0:4f3585e2f14b draft default tip

"planemo upload commit 60cee0fc7c0cda8592644e1aad72851dec82c959"

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/env/lib/python3.9/site-packages/bleach/_vendor/html5lib/_inputstream.py	Mon Mar 22 18:12:50 2021 +0000
@@ -0,0 +1,918 @@
+from __future__ import absolute_import, division, unicode_literals
+
+from six import text_type
+from six.moves import http_client, urllib
+
+import codecs
+import re
+from io import BytesIO, StringIO
+
+import webencodings
+
+from .constants import EOF, spaceCharacters, asciiLetters, asciiUppercase
+from .constants import _ReparseException
+from . import _utils
+
+# Non-unicode versions of constants for use in the pre-parser
+spaceCharactersBytes = frozenset([item.encode("ascii") for item in spaceCharacters])
+asciiLettersBytes = frozenset([item.encode("ascii") for item in asciiLetters])
+asciiUppercaseBytes = frozenset([item.encode("ascii") for item in asciiUppercase])
+spacesAngleBrackets = spaceCharactersBytes | frozenset([b">", b"<"])
+
+
+invalid_unicode_no_surrogate = "[\u0001-\u0008\u000B\u000E-\u001F\u007F-\u009F\uFDD0-\uFDEF\uFFFE\uFFFF\U0001FFFE\U0001FFFF\U0002FFFE\U0002FFFF\U0003FFFE\U0003FFFF\U0004FFFE\U0004FFFF\U0005FFFE\U0005FFFF\U0006FFFE\U0006FFFF\U0007FFFE\U0007FFFF\U0008FFFE\U0008FFFF\U0009FFFE\U0009FFFF\U000AFFFE\U000AFFFF\U000BFFFE\U000BFFFF\U000CFFFE\U000CFFFF\U000DFFFE\U000DFFFF\U000EFFFE\U000EFFFF\U000FFFFE\U000FFFFF\U0010FFFE\U0010FFFF]"  # noqa
+
+if _utils.supports_lone_surrogates:
+    # Use one extra step of indirection and create surrogates with
+    # eval. Not using this indirection would introduce an illegal
+    # unicode literal on platforms not supporting such lone
+    # surrogates.
+    assert invalid_unicode_no_surrogate[-1] == "]" and invalid_unicode_no_surrogate.count("]") == 1
+    invalid_unicode_re = re.compile(invalid_unicode_no_surrogate[:-1] +
+                                    eval('"\\uD800-\\uDFFF"') +  # pylint:disable=eval-used
+                                    "]")
+else:
+    invalid_unicode_re = re.compile(invalid_unicode_no_surrogate)
+
+non_bmp_invalid_codepoints = {0x1FFFE, 0x1FFFF, 0x2FFFE, 0x2FFFF, 0x3FFFE,
+                              0x3FFFF, 0x4FFFE, 0x4FFFF, 0x5FFFE, 0x5FFFF,
+                              0x6FFFE, 0x6FFFF, 0x7FFFE, 0x7FFFF, 0x8FFFE,
+                              0x8FFFF, 0x9FFFE, 0x9FFFF, 0xAFFFE, 0xAFFFF,
+                              0xBFFFE, 0xBFFFF, 0xCFFFE, 0xCFFFF, 0xDFFFE,
+                              0xDFFFF, 0xEFFFE, 0xEFFFF, 0xFFFFE, 0xFFFFF,
+                              0x10FFFE, 0x10FFFF}
+
+ascii_punctuation_re = re.compile("[\u0009-\u000D\u0020-\u002F\u003A-\u0040\u005C\u005B-\u0060\u007B-\u007E]")
+
+# Cache for charsUntil()
+charsUntilRegEx = {}
+
+
+class BufferedStream(object):
+    """Buffering for streams that do not have buffering of their own
+
+    The buffer is implemented as a list of chunks on the assumption that
+    joining many strings will be slow since it is O(n**2)
+    """
+
+    def __init__(self, stream):
+        self.stream = stream
+        self.buffer = []
+        self.position = [-1, 0]  # chunk number, offset
+
+    def tell(self):
+        pos = 0
+        for chunk in self.buffer[:self.position[0]]:
+            pos += len(chunk)
+        pos += self.position[1]
+        return pos
+
+    def seek(self, pos):
+        assert pos <= self._bufferedBytes()
+        offset = pos
+        i = 0
+        while len(self.buffer[i]) < offset:
+            offset -= len(self.buffer[i])
+            i += 1
+        self.position = [i, offset]
+
+    def read(self, bytes):
+        if not self.buffer:
+            return self._readStream(bytes)
+        elif (self.position[0] == len(self.buffer) and
+              self.position[1] == len(self.buffer[-1])):
+            return self._readStream(bytes)
+        else:
+            return self._readFromBuffer(bytes)
+
+    def _bufferedBytes(self):
+        return sum([len(item) for item in self.buffer])
+
+    def _readStream(self, bytes):
+        data = self.stream.read(bytes)
+        self.buffer.append(data)
+        self.position[0] += 1
+        self.position[1] = len(data)
+        return data
+
+    def _readFromBuffer(self, bytes):
+        remainingBytes = bytes
+        rv = []
+        bufferIndex = self.position[0]
+        bufferOffset = self.position[1]
+        while bufferIndex < len(self.buffer) and remainingBytes != 0:
+            assert remainingBytes > 0
+            bufferedData = self.buffer[bufferIndex]
+
+            if remainingBytes <= len(bufferedData) - bufferOffset:
+                bytesToRead = remainingBytes
+                self.position = [bufferIndex, bufferOffset + bytesToRead]
+            else:
+                bytesToRead = len(bufferedData) - bufferOffset
+                self.position = [bufferIndex, len(bufferedData)]
+                bufferIndex += 1
+            rv.append(bufferedData[bufferOffset:bufferOffset + bytesToRead])
+            remainingBytes -= bytesToRead
+
+            bufferOffset = 0
+
+        if remainingBytes:
+            rv.append(self._readStream(remainingBytes))
+
+        return b"".join(rv)
+
+
+def HTMLInputStream(source, **kwargs):
+    # Work around Python bug #20007: read(0) closes the connection.
+    # http://bugs.python.org/issue20007
+    if (isinstance(source, http_client.HTTPResponse) or
+        # Also check for addinfourl wrapping HTTPResponse
+        (isinstance(source, urllib.response.addbase) and
+         isinstance(source.fp, http_client.HTTPResponse))):
+        isUnicode = False
+    elif hasattr(source, "read"):
+        isUnicode = isinstance(source.read(0), text_type)
+    else:
+        isUnicode = isinstance(source, text_type)
+
+    if isUnicode:
+        encodings = [x for x in kwargs if x.endswith("_encoding")]
+        if encodings:
+            raise TypeError("Cannot set an encoding with a unicode input, set %r" % encodings)
+
+        return HTMLUnicodeInputStream(source, **kwargs)
+    else:
+        return HTMLBinaryInputStream(source, **kwargs)
+
+
+class HTMLUnicodeInputStream(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.
+
+    """
+
+    _defaultChunkSize = 10240
+
+    def __init__(self, source):
+        """Initialises the HTMLInputStream.
+
+        HTMLInputStream(source, [encoding]) -> Normalized stream from source
+        for use by 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)
+
+        """
+
+        if not _utils.supports_lone_surrogates:
+            # Such platforms will have already checked for such
+            # surrogate errors, so no need to do this checking.
+            self.reportCharacterErrors = None
+        elif len("\U0010FFFF") == 1:
+            self.reportCharacterErrors = self.characterErrorsUCS4
+        else:
+            self.reportCharacterErrors = self.characterErrorsUCS2
+
+        # List of where new lines occur
+        self.newLines = [0]
+
+        self.charEncoding = (lookupEncoding("utf-8"), "certain")
+        self.dataStream = self.openStream(source)
+
+        self.reset()
+
+    def reset(self):
+        self.chunk = ""
+        self.chunkSize = 0
+        self.chunkOffset = 0
+        self.errors = []
+
+        # number of (complete) lines in previous chunks
+        self.prevNumLines = 0
+        # number of columns in the last line of the previous chunk
+        self.prevNumCols = 0
+
+        # Deal with CR LF and surrogates split over chunk boundaries
+        self._bufferedCharacter = None
+
+    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:
+            stream = StringIO(source)
+
+        return stream
+
+    def _position(self, offset):
+        chunk = self.chunk
+        nLines = chunk.count('\n', 0, offset)
+        positionLine = self.prevNumLines + nLines
+        lastLinePos = chunk.rfind('\n', 0, offset)
+        if lastLinePos == -1:
+            positionColumn = self.prevNumCols + offset
+        else:
+            positionColumn = offset - (lastLinePos + 1)
+        return (positionLine, positionColumn)
+
+    def position(self):
+        """Returns (line, col) of the current position in the stream."""
+        line, col = self._position(self.chunkOffset)
+        return (line + 1, col)
+
+    def char(self):
+        """ Read one character from the stream or queue if available. Return
+            EOF when EOF is reached.
+        """
+        # Read a new chunk from the input stream if necessary
+        if self.chunkOffset >= self.chunkSize:
+            if not self.readChunk():
+                return EOF
+
+        chunkOffset = self.chunkOffset
+        char = self.chunk[chunkOffset]
+        self.chunkOffset = chunkOffset + 1
+
+        return char
+
+    def readChunk(self, chunkSize=None):
+        if chunkSize is None:
+            chunkSize = self._defaultChunkSize
+
+        self.prevNumLines, self.prevNumCols = self._position(self.chunkSize)
+
+        self.chunk = ""
+        self.chunkSize = 0
+        self.chunkOffset = 0
+
+        data = self.dataStream.read(chunkSize)
+
+        # Deal with CR LF and surrogates broken across chunks
+        if self._bufferedCharacter:
+            data = self._bufferedCharacter + data
+            self._bufferedCharacter = None
+        elif not data:
+            # We have no more data, bye-bye stream
+            return False
+
+        if len(data) > 1:
+            lastv = ord(data[-1])
+            if lastv == 0x0D or 0xD800 <= lastv <= 0xDBFF:
+                self._bufferedCharacter = data[-1]
+                data = data[:-1]
+
+        if self.reportCharacterErrors:
+            self.reportCharacterErrors(data)
+
+        # Replace invalid characters
+        data = data.replace("\r\n", "\n")
+        data = data.replace("\r", "\n")
+
+        self.chunk = data
+        self.chunkSize = len(data)
+
+        return True
+
+    def characterErrorsUCS4(self, data):
+        for _ in range(len(invalid_unicode_re.findall(data))):
+            self.errors.append("invalid-codepoint")
+
+    def characterErrorsUCS2(self, data):
+        # Someone picked the wrong compile option
+        # You lose
+        skip = False
+        for match in invalid_unicode_re.finditer(data):
+            if skip:
+                continue
+            codepoint = ord(match.group())
+            pos = match.start()
+            # Pretty sure there should be endianness issues here
+            if _utils.isSurrogatePair(data[pos:pos + 2]):
+                # We have a surrogate pair!
+                char_val = _utils.surrogatePairToCodepoint(data[pos:pos + 2])
+                if char_val in non_bmp_invalid_codepoints:
+                    self.errors.append("invalid-codepoint")
+                skip = True
+            elif (codepoint >= 0xD800 and codepoint <= 0xDFFF and
+                  pos == len(data) - 1):
+                self.errors.append("invalid-codepoint")
+            else:
+                skip = False
+                self.errors.append("invalid-codepoint")
+
+    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' must be
+        a container that supports the 'in' method and iteration over its
+        characters.
+        """
+
+        # Use a cache of regexps to find the required characters
+        try:
+            chars = charsUntilRegEx[(characters, opposite)]
+        except KeyError:
+            if __debug__:
+                for c in characters:
+                    assert(ord(c) < 128)
+            regex = "".join(["\\x%02x" % ord(c) for c in characters])
+            if not opposite:
+                regex = "^%s" % regex
+            chars = charsUntilRegEx[(characters, opposite)] = re.compile("[%s]+" % regex)
+
+        rv = []
+
+        while True:
+            # Find the longest matching prefix
+            m = chars.match(self.chunk, self.chunkOffset)
+            if m is None:
+                # If nothing matched, and it wasn't because we ran out of chunk,
+                # then stop
+                if self.chunkOffset != self.chunkSize:
+                    break
+            else:
+                end = m.end()
+                # If not the whole chunk matched, return everything
+                # up to the part that didn't match
+                if end != self.chunkSize:
+                    rv.append(self.chunk[self.chunkOffset:end])
+                    self.chunkOffset = end
+                    break
+            # If the whole remainder of the chunk matched,
+            # use it all and read the next chunk
+            rv.append(self.chunk[self.chunkOffset:])
+            if not self.readChunk():
+                # Reached EOF
+                break
+
+        r = "".join(rv)
+        return r
+
+    def unget(self, char):
+        # Only one character is allowed to be ungotten at once - it must
+        # be consumed again before any further call to unget
+        if char is not EOF:
+            if self.chunkOffset == 0:
+                # unget is called quite rarely, so it's a good idea to do
+                # more work here if it saves a bit of work in the frequently
+                # called char and charsUntil.
+                # So, just prepend the ungotten character onto the current
+                # chunk:
+                self.chunk = char + self.chunk
+                self.chunkSize += 1
+            else:
+                self.chunkOffset -= 1
+                assert self.chunk[self.chunkOffset] == char
+
+
+class HTMLBinaryInputStream(HTMLUnicodeInputStream):
+    """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, override_encoding=None, transport_encoding=None,
+                 same_origin_parent_encoding=None, likely_encoding=None,
+                 default_encoding="windows-1252", useChardet=True):
+        """Initialises the HTMLInputStream.
+
+        HTMLInputStream(source, [encoding]) -> Normalized stream from source
+        for use by 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)
+
+        """
+        # Raw Stream - for unicode objects this will encode to utf-8 and set
+        #              self.charEncoding as appropriate
+        self.rawStream = self.openStream(source)
+
+        HTMLUnicodeInputStream.__init__(self, self.rawStream)
+
+        # Encoding Information
+        # Number of bytes to use when looking for a meta element with
+        # encoding information
+        self.numBytesMeta = 1024
+        # Number of bytes to use when using detecting encoding using chardet
+        self.numBytesChardet = 100
+        # Things from args
+        self.override_encoding = override_encoding
+        self.transport_encoding = transport_encoding
+        self.same_origin_parent_encoding = same_origin_parent_encoding
+        self.likely_encoding = likely_encoding
+        self.default_encoding = default_encoding
+
+        # Determine encoding
+        self.charEncoding = self.determineEncoding(useChardet)
+        assert self.charEncoding[0] is not None
+
+        # Call superclass
+        self.reset()
+
+    def reset(self):
+        self.dataStream = self.charEncoding[0].codec_info.streamreader(self.rawStream, 'replace')
+        HTMLUnicodeInputStream.reset(self)
+
+    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:
+            stream = BytesIO(source)
+
+        try:
+            stream.seek(stream.tell())
+        except Exception:
+            stream = BufferedStream(stream)
+
+        return stream
+
+    def determineEncoding(self, chardet=True):
+        # BOMs take precedence over everything
+        # This will also read past the BOM if present
+        charEncoding = self.detectBOM(), "certain"
+        if charEncoding[0] is not None:
+            return charEncoding
+
+        # If we've been overridden, we've been overridden
+        charEncoding = lookupEncoding(self.override_encoding), "certain"
+        if charEncoding[0] is not None:
+            return charEncoding
+
+        # Now check the transport layer
+        charEncoding = lookupEncoding(self.transport_encoding), "certain"
+        if charEncoding[0] is not None:
+            return charEncoding
+
+        # Look for meta elements with encoding information
+        charEncoding = self.detectEncodingMeta(), "tentative"
+        if charEncoding[0] is not None:
+            return charEncoding
+
+        # Parent document encoding
+        charEncoding = lookupEncoding(self.same_origin_parent_encoding), "tentative"
+        if charEncoding[0] is not None and not charEncoding[0].name.startswith("utf-16"):
+            return charEncoding
+
+        # "likely" encoding
+        charEncoding = lookupEncoding(self.likely_encoding), "tentative"
+        if charEncoding[0] is not None:
+            return charEncoding
+
+        # Guess with chardet, if available
+        if chardet:
+            try:
+                from chardet.universaldetector import UniversalDetector
+            except ImportError:
+                pass
+            else:
+                buffers = []
+                detector = UniversalDetector()
+                while not detector.done:
+                    buffer = self.rawStream.read(self.numBytesChardet)
+                    assert isinstance(buffer, bytes)
+                    if not buffer:
+                        break
+                    buffers.append(buffer)
+                    detector.feed(buffer)
+                detector.close()
+                encoding = lookupEncoding(detector.result['encoding'])
+                self.rawStream.seek(0)
+                if encoding is not None:
+                    return encoding, "tentative"
+
+        # Try the default encoding
+        charEncoding = lookupEncoding(self.default_encoding), "tentative"
+        if charEncoding[0] is not None:
+            return charEncoding
+
+        # Fallback to html5lib's default if even that hasn't worked
+        return lookupEncoding("windows-1252"), "tentative"
+
+    def changeEncoding(self, newEncoding):
+        assert self.charEncoding[1] != "certain"
+        newEncoding = lookupEncoding(newEncoding)
+        if newEncoding is None:
+            return
+        if newEncoding.name in ("utf-16be", "utf-16le"):
+            newEncoding = lookupEncoding("utf-8")
+            assert newEncoding is not None
+        elif newEncoding == self.charEncoding[0]:
+            self.charEncoding = (self.charEncoding[0], "certain")
+        else:
+            self.rawStream.seek(0)
+            self.charEncoding = (newEncoding, "certain")
+            self.reset()
+            raise _ReparseException("Encoding changed from %s to %s" % (self.charEncoding[0], newEncoding))
+
+    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-16le', codecs.BOM_UTF16_BE: 'utf-16be',
+            codecs.BOM_UTF32_LE: 'utf-32le', codecs.BOM_UTF32_BE: 'utf-32be'
+        }
+
+        # Go to beginning of file and read in 4 bytes
+        string = self.rawStream.read(4)
+        assert isinstance(string, bytes)
+
+        # 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
+        if encoding:
+            self.rawStream.seek(seek)
+            return lookupEncoding(encoding)
+        else:
+            self.rawStream.seek(0)
+            return None
+
+    def detectEncodingMeta(self):
+        """Report the encoding declared by the meta element
+        """
+        buffer = self.rawStream.read(self.numBytesMeta)
+        assert isinstance(buffer, bytes)
+        parser = EncodingParser(buffer)
+        self.rawStream.seek(0)
+        encoding = parser.getEncoding()
+
+        if encoding is not None and encoding.name in ("utf-16be", "utf-16le"):
+            encoding = lookupEncoding("utf-8")
+
+        return encoding
+
+
+class EncodingBytes(bytes):
+    """String-like object with an associated position and various extra methods
+    If the position is ever greater than the string length then an exception is
+    raised"""
+    def __new__(self, value):
+        assert isinstance(value, bytes)
+        return bytes.__new__(self, value.lower())
+
+    def __init__(self, value):
+        # pylint:disable=unused-argument
+        self._position = -1
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        p = self._position = self._position + 1
+        if p >= len(self):
+            raise StopIteration
+        elif p < 0:
+            raise TypeError
+        return self[p:p + 1]
+
+    def next(self):
+        # Py2 compat
+        return self.__next__()
+
+    def previous(self):
+        p = self._position
+        if p >= len(self):
+            raise StopIteration
+        elif p < 0:
+            raise TypeError
+        self._position = p = p - 1
+        return self[p:p + 1]
+
+    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:self.position + 1]
+
+    currentByte = property(getCurrentByte)
+
+    def skip(self, chars=spaceCharactersBytes):
+        """Skip past a list of characters"""
+        p = self.position               # use property for the error-checking
+        while p < len(self):
+            c = self[p:p + 1]
+            if c not in chars:
+                self._position = p
+                return c
+            p += 1
+        self._position = p
+        return None
+
+    def skipUntil(self, chars):
+        p = self.position
+        while p < len(self):
+            c = self[p:p + 1]
+            if c in chars:
+                self._position = p
+                return c
+            p += 1
+        self._position = p
+        return None
+
+    def matchBytes(self, bytes):
+        """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"""
+        rv = self.startswith(bytes, self.position)
+        if rv:
+            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"""
+        try:
+            self._position = self.index(bytes, self.position) + len(bytes) - 1
+        except ValueError:
+            raise StopIteration
+        return True
+
+
+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):
+        if b"<meta" not in self.data:
+            return None
+
+        methodDispatch = (
+            (b"<!--", self.handleComment),
+            (b"<meta", self.handleMeta),
+            (b"</", self.handlePossibleEndTag),
+            (b"<!", self.handleOther),
+            (b"<?", self.handleOther),
+            (b"<", self.handlePossibleStartTag))
+        for _ in self.data:
+            keepParsing = True
+            try:
+                self.data.jumpTo(b"<")
+            except StopIteration:
+                break
+            for key, method in methodDispatch:
+                if self.data.matchBytes(key):
+                    try:
+                        keepParsing = method()
+                        break
+                    except StopIteration:
+                        keepParsing = False
+                        break
+            if not keepParsing:
+                break
+
+        return self.encoding
+
+    def handleComment(self):
+        """Skip over comments"""
+        return self.data.jumpTo(b"-->")
+
+    def handleMeta(self):
+        if self.data.currentByte not in spaceCharactersBytes:
+            # 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
+        hasPragma = False
+        pendingEncoding = None
+        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] == b"http-equiv":
+                    hasPragma = attr[1] == b"content-type"
+                    if hasPragma and pendingEncoding is not None:
+                        self.encoding = pendingEncoding
+                        return False
+                elif attr[0] == b"charset":
+                    tentativeEncoding = attr[1]
+                    codec = lookupEncoding(tentativeEncoding)
+                    if codec is not None:
+                        self.encoding = codec
+                        return False
+                elif attr[0] == b"content":
+                    contentParser = ContentAttrParser(EncodingBytes(attr[1]))
+                    tentativeEncoding = contentParser.parse()
+                    if tentativeEncoding is not None:
+                        codec = lookupEncoding(tentativeEncoding)
+                        if codec is not None:
+                            if hasPragma:
+                                self.encoding = codec
+                                return False
+                            else:
+                                pendingEncoding = codec
+
+    def handlePossibleStartTag(self):
+        return self.handlePossibleTag(False)
+
+    def handlePossibleEndTag(self):
+        next(self.data)
+        return self.handlePossibleTag(True)
+
+    def handlePossibleTag(self, endTag):
+        data = self.data
+        if data.currentByte not in asciiLettersBytes:
+            # 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:
+                data.previous()
+                self.handleOther()
+            return True
+
+        c = data.skipUntil(spacesAngleBrackets)
+        if c == b"<":
+            # return to the first step in the overall "two step" algorithm
+            # reprocessing the < byte
+            data.previous()
+        else:
+            # Read all attributes
+            attr = self.getAttribute()
+            while attr is not None:
+                attr = self.getAttribute()
+        return True
+
+    def handleOther(self):
+        return self.data.jumpTo(b">")
+
+    def getAttribute(self):
+        """Return a name,value pair for the next attribute in the stream,
+        if one is found, or None"""
+        data = self.data
+        # Step 1 (skip chars)
+        c = data.skip(spaceCharactersBytes | frozenset([b"/"]))
+        assert c is None or len(c) == 1
+        # Step 2
+        if c in (b">", None):
+            return None
+        # Step 3
+        attrName = []
+        attrValue = []
+        # Step 4 attribute name
+        while True:
+            if c == b"=" and attrName:
+                break
+            elif c in spaceCharactersBytes:
+                # Step 6!
+                c = data.skip()
+                break
+            elif c in (b"/", b">"):
+                return b"".join(attrName), b""
+            elif c in asciiUppercaseBytes:
+                attrName.append(c.lower())
+            elif c is None:
+                return None
+            else:
+                attrName.append(c)
+            # Step 5
+            c = next(data)
+        # Step 7
+        if c != b"=":
+            data.previous()
+            return b"".join(attrName), b""
+        # Step 8
+        next(data)
+        # Step 9
+        c = data.skip()
+        # Step 10
+        if c in (b"'", b'"'):
+            # 10.1
+            quoteChar = c
+            while True:
+                # 10.2
+                c = next(data)
+                # 10.3
+                if c == quoteChar:
+                    next(data)
+                    return b"".join(attrName), b"".join(attrValue)
+                # 10.4
+                elif c in asciiUppercaseBytes:
+                    attrValue.append(c.lower())
+                # 10.5
+                else:
+                    attrValue.append(c)
+        elif c == b">":
+            return b"".join(attrName), b""
+        elif c in asciiUppercaseBytes:
+            attrValue.append(c.lower())
+        elif c is None:
+            return None
+        else:
+            attrValue.append(c)
+        # Step 11
+        while True:
+            c = next(data)
+            if c in spacesAngleBrackets:
+                return b"".join(attrName), b"".join(attrValue)
+            elif c in asciiUppercaseBytes:
+                attrValue.append(c.lower())
+            elif c is None:
+                return None
+            else:
+                attrValue.append(c)
+
+
+class ContentAttrParser(object):
+    def __init__(self, data):
+        assert isinstance(data, bytes)
+        self.data = data
+
+    def parse(self):
+        try:
+            # Check if the attr name is charset
+            # otherwise return
+            self.data.jumpTo(b"charset")
+            self.data.position += 1
+            self.data.skip()
+            if not self.data.currentByte == b"=":
+                # 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 (b'"', b"'"):
+                quoteMark = self.data.currentByte
+                self.data.position += 1
+                oldPosition = self.data.position
+                if self.data.jumpTo(quoteMark):
+                    return self.data[oldPosition:self.data.position]
+                else:
+                    return None
+            else:
+                # Unquoted value
+                oldPosition = self.data.position
+                try:
+                    self.data.skipUntil(spaceCharactersBytes)
+                    return self.data[oldPosition:self.data.position]
+                except StopIteration:
+                    # Return the whole remaining value
+                    return self.data[oldPosition:]
+        except StopIteration:
+            return None
+
+
+def lookupEncoding(encoding):
+    """Return the python codec name corresponding to an encoding or None if the
+    string doesn't correspond to a valid encoding."""
+    if isinstance(encoding, bytes):
+        try:
+            encoding = encoding.decode("ascii")
+        except UnicodeDecodeError:
+            return None
+
+    if encoding is not None:
+        try:
+            return webencodings.lookup(encoding)
+        except AttributeError:
+            return None
+    else:
+        return None