This file is indexed.

/usr/lib/python3/dist-packages/html5lib/inputstream.py is in python3-html5lib 0.999-3.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
from __future__ import absolute_import, division, unicode_literals
from six import text_type
from six.moves import http_client

import codecs
import re

from .constants import EOF, spaceCharacters, asciiLetters, asciiUppercase
from .constants import encodings, ReparseException
from . import utils

from io import StringIO

try:
    from io import BytesIO
except ImportError:
    BytesIO = StringIO

try:
    from io import BufferedIOBase
except ImportError:
    class BufferedIOBase(object):
        pass

# 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_re = re.compile("[\u0001-\u0008\u000B\u000E-\u001F\u007F-\u009F\uD800-\uDFFF\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]")

non_bmp_invalid_codepoints = set([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\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, encoding=None, parseMeta=True, chardet=True):
    if isinstance(source, http_client.HTTPResponse):
        # Work around Python bug #20007: read(0) closes the connection.
        # http://bugs.python.org/issue20007
        isUnicode = False
    elif hasattr(source, "read"):
        isUnicode = isinstance(source.read(0), text_type)
    else:
        isUnicode = isinstance(source, text_type)

    if isUnicode:
        if encoding is not None:
            raise TypeError("Cannot explicitly set an encoding with a unicode string")

        return HTMLUnicodeInputStream(source)
    else:
        return HTMLBinaryInputStream(source, encoding, parseMeta, chardet)


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)

        parseMeta - Look for a <meta> element containing encoding information

        """

        # Craziness
        if len("\U0010FFFF") == 1:
            self.reportCharacterErrors = self.characterErrorsUCS4
            self.replaceCharactersRegexp = re.compile("[\uD800-\uDFFF]")
        else:
            self.reportCharacterErrors = self.characterErrorsUCS2
            self.replaceCharactersRegexp = re.compile("([\uD800-\uDBFF](?![\uDC00-\uDFFF])|(?<![\uD800-\uDBFF])[\uDC00-\uDFFF])")

        # List of where new lines occur
        self.newLines = [0]

        self.charEncoding = ("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]

        self.reportCharacterErrors(data)

        # Replace invalid characters
        # Note U+0000 is dealt with in the tokenizer
        data = self.replaceCharactersRegexp.sub("\ufffd", data)

        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 i 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 None:
            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, encoding=None, parseMeta=True, chardet=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)

        parseMeta - Look for a <meta> element containing encoding information

        """
        # 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)

        self.charEncoding = (codecName(encoding), "certain")

        # 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[0] is None):
            self.charEncoding = self.detectEncoding(parseMeta, chardet)

        # Call superclass
        self.reset()

    def reset(self):
        self.dataStream = codecs.getreader(self.charEncoding[0])(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:
            stream = BufferedStream(stream)

        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()
        confidence = "certain"
        # If there is no BOM need to look for meta elements with encoding
        # information
        if encoding is None and parseMeta:
            encoding = self.detectEncodingMeta()
            confidence = "tentative"
        # Guess with chardet, if avaliable
        if encoding is None and chardet:
            confidence = "tentative"
            try:
                try:
                    from charade.universaldetector import UniversalDetector
                except ImportError:
                    from chardet.universaldetector import UniversalDetector
                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 = detector.result['encoding']
                self.rawStream.seek(0)
            except ImportError:
                pass
        # If all else fails use the default encoding
        if encoding is None:
            confidence = "tentative"
            encoding = self.defaultEncoding

        # Substitute for equivalent encodings:
        encodingSub = {"iso-8859-1": "windows-1252"}

        if encoding.lower() in encodingSub:
            encoding = encodingSub[encoding.lower()]

        return encoding, confidence

    def changeEncoding(self, newEncoding):
        assert self.charEncoding[1] != "certain"
        newEncoding = codecName(newEncoding)
        if newEncoding in ("utf-16", "utf-16-be", "utf-16-le"):
            newEncoding = "utf-8"
        if newEncoding is None:
            return
        elif newEncoding == self.charEncoding[0]:
            self.charEncoding = (self.charEncoding[0], "certain")
        else:
            self.rawStream.seek(0)
            self.reset()
            self.charEncoding = (newEncoding, "certain")
            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-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)
        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
        self.rawStream.seek(encoding and seek or 0)

        return encoding

    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 in ("utf-16", "utf-16-be", "utf-16-le"):
            encoding = "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):
        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"""
        p = self.position
        data = self[p:p + len(bytes)]
        rv = data.startswith(bytes)
        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"""
        newPosition = self[self.position:].find(bytes)
        if newPosition > -1:
            # XXX: This is ugly, but I can't see a nicer way to fix this.
            if self._position == -1:
                self._position = 0
            self._position += (newPosition + len(bytes) - 1)
            return True
        else:
            raise StopIteration


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 = (
            (b"<!--", self.handleComment),
            (b"<meta", self.handleMeta),
            (b"</", self.handlePossibleEndTag),
            (b"<!", self.handleOther),
            (b"<?", self.handleOther),
            (b"<", self.handlePossibleStartTag))
        for byte in self.data:
            keepParsing = True
            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 = codecName(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 = codecName(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 codecName(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:
        canonicalName = ascii_punctuation_re.sub("", encoding).lower()
        return encodings.get(canonicalName, None)
    else:
        return None