Package cssutils :: Module codec |
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# Source Code for Module cssutils.codec

      1  #!/usr/bin/env python
      2
      3  """
      4  Python codec for CSS.
      5  """
      6
      7  __docformat__ = 'restructuredtext'
      8  __author__ = '$LastChangedBy: doerwalter $'
      9  __date__ = '$LastChangedDate: 2007-11-05 14:52:02 +0100 (Mo, 05 Nov 2007) $'
     10  __version__ = '$LastChangedRevision: 645 $'
     11
     12
     13  import codecs, marshal
     14
     15
     16  # We're using bits to store all possible candidate encodings (or variants, i.e.
     17  # we have two bits for the variants of UTF-16 and two for the
     18  # variants of UTF-32).
     19  #
     20  # Prefixes for various CSS encodings
     21  # UTF-8-SIG   xEF  xBB  xBF
     22  # UTF-16 (LE) xFF  xFE ~x00|~x00
     23  # UTF-16 (BE) xFE  xFF
     24  # UTF-16-LE    @   x00   @   x00
     25  # UTF-16-BE   x00   @
     26  # UTF-32 (LE) xFF  xFE  x00  x00
     27  # UTF-32 (BE) x00  x00  xFE  xFF
     28  # UTF-32-LE    @   x00  x00  x00
     29  # UTF-32-BE   x00  x00  x00   @
     30  # CHARSET      @    c    h    a  ...
     31
     32
     33
     34 -def _detectencoding_str(input, final=False):
     35      """
     36      Detect the encoding of the byte string ``input``, which contains the
     37      beginning of a CSS file. To detect the encoding the first few bytes are
     38      used (or if ``input`` is ASCII compatible and starts with a charset rule
     39      the encoding name from the rule.
     40
     41      If the encoding can't be detected yet, ``None`` is returned. ``final``
     42      specifies whether more data is available in later calls or not. If ``final``
     43      is true, ``_detectencoding_str()`` will never return ``None``.
     44      """
     45
     46      # A bit for every candidate
     47      CANDIDATE_UTF_8_SIG    =   1
     48      CANDIDATE_UTF_16_AS_LE =   2
     49      CANDIDATE_UTF_16_AS_BE =   4
     50      CANDIDATE_UTF_16_LE    =   8
     51      CANDIDATE_UTF_16_BE    =  16
     52      CANDIDATE_UTF_32_AS_LE =  32
     53      CANDIDATE_UTF_32_AS_BE =  64
     54      CANDIDATE_UTF_32_LE    = 128
     55      CANDIDATE_UTF_32_BE    = 256
     56      CANDIDATE_CHARSET      = 512
     57
     58      candidates = 1023 # all candidates
     59
     60      li = len(input)
     61      if li>=1:
     62          # Check first byte
     63          c = input[0]
     64          if c != "\xef":
     65              candidates &= ~CANDIDATE_UTF_8_SIG
     66          if c != "\xff":
     67              candidates &= ~(CANDIDATE_UTF_32_AS_LE|CANDIDATE_UTF_16_AS_LE)
     68          if c != "\xfe":
     69              candidates &= ~CANDIDATE_UTF_16_AS_BE
     70          if c != "@":
     71              candidates &= ~(CANDIDATE_UTF_32_LE|CANDIDATE_UTF_16_LE|CANDIDATE_CHARSET)
     72          if c != "\x00":
     73              candidates &= ~(CANDIDATE_UTF_32_AS_BE|CANDIDATE_UTF_32_BE|CANDIDATE_UTF_16_BE)
     74          if li>=2:
     75              # Check second byte
     76              c = input[1]
     77              if c != "\xbb":
     78                  candidates &= ~CANDIDATE_UTF_8_SIG
     79              if c != "\xfe":
     80                  candidates &= ~(CANDIDATE_UTF_16_AS_LE|CANDIDATE_UTF_32_AS_LE)
     81              if c != "\xff":
     82                  candidates &= ~CANDIDATE_UTF_16_AS_BE
     83              if c != "\x00":
     84                  candidates &= ~(CANDIDATE_UTF_16_LE|CANDIDATE_UTF_32_AS_BE|CANDIDATE_UTF_32_LE|CANDIDATE_UTF_32_BE)
     85              if c != "@":
     86                  candidates &= ~CANDIDATE_UTF_16_BE
     87              if c != "c":
     88                  candidates &= ~CANDIDATE_CHARSET
     89              if li>=3:
     90                  # Check third byte
     91                  c = input[2]
     92                  if c != "\xbf":
     93                      candidates &= ~CANDIDATE_UTF_8_SIG
     94                  if c != "c":
     95                      candidates &= ~CANDIDATE_UTF_16_LE
     96                  if c != "\x00":
     97                      candidates &= ~(CANDIDATE_UTF_32_AS_LE|CANDIDATE_UTF_32_LE|CANDIDATE_UTF_32_BE)
     98                  if c != "\xfe":
     99                      candidates &= ~CANDIDATE_UTF_32_AS_BE
    100                  if c != "h":
    101                      candidates &= ~CANDIDATE_CHARSET
    102                  if li>=4:
    103                      # Check fourth byte
    104                      c = input[3]
    105                      if input[2:4] == "\x00\x00":
    106                          candidates &= ~CANDIDATE_UTF_16_AS_LE
    107                      if c != "\x00":
    108                          candidates &= ~(CANDIDATE_UTF_16_LE|CANDIDATE_UTF_32_AS_LE|CANDIDATE_UTF_32_LE)
    109                      if c != "\xff":
    110                          candidates &= ~CANDIDATE_UTF_32_AS_BE
    111                      if c != "@":
    112                          candidates &= ~CANDIDATE_UTF_32_BE
    113                      if c != "a":
    114                          candidates &= ~CANDIDATE_CHARSET
    115      if candidates == 0:
    116          return "utf-8"
    117      if not (candidates & (candidates-1)): # only one candidate remaining
    118          if candidates == CANDIDATE_UTF_8_SIG and li >= 3:
    119              return "utf-8-sig"
    120          elif candidates == CANDIDATE_UTF_16_AS_LE and li >= 2:
    121              return "utf-16"
    122          elif candidates == CANDIDATE_UTF_16_AS_BE and li >= 2:
    123              return "utf-16"
    124          elif candidates == CANDIDATE_UTF_16_LE and li >= 4:
    125              return "utf-16-le"
    126          elif candidates == CANDIDATE_UTF_16_BE and li >= 2:
    127              return "utf-16-be"
    128          elif candidates == CANDIDATE_UTF_32_AS_LE and li >= 4:
    129              return "utf-32"
    130          elif candidates == CANDIDATE_UTF_32_AS_BE and li >= 4:
    131              return "utf-32"
    132          elif candidates == CANDIDATE_UTF_32_LE and li >= 4:
    133              return "utf-32-le"
    134          elif candidates == CANDIDATE_UTF_32_BE and li >= 4:
    135              return "utf-32-be"
    136          elif candidates == CANDIDATE_CHARSET and li >= 4:
    137              prefix = '@charset "'
    138              if input.startswith(prefix):
    139                  pos = input.find('"', len(prefix))
    140                  if pos >= 0:
    141                      return input[len(prefix):pos]
    142      # if this is the last call, and we haven't determined an encoding yet,
    143      # we default to UTF-8
    144      if final:
    145          return "utf-8"
    146      return None # dont' know yet
    147
    148
    149 -def _detectencoding_unicode(input, final=False):
    150      """
    151      Detect the encoding of the unicode string ``input``, which contains the
    152      beginning of a CSS file. The encoding is detected from the charset rule
    153      at the beginning of ``input``. If there is no charset rule, ``"utf-8"``
    154      will be returned.
    155
    156      If the encoding can't be detected yet, ``None`` is returned. ``final``
    157      specifies whether more data will be available in later calls or not. If
    158      ``final`` is true, ``_detectencoding_unicode()`` will never return ``None``.
    159      """
    160      prefix = u'@charset "'
    161      if input.startswith(prefix):
    162          pos = input.find(u'"', len(prefix))
    163          if pos >= 0:
    164              return input[len(prefix):pos]
    165      elif final or not prefix.startswith(input):
    166          # if this is the last call, and we haven't determined an encoding yet,
    167          # (or the string definitely doesn't start with prefix) we default to UTF-8
    168          return "utf-8"
    169      return None # don't know yet
    170
    171
    172 -def _fixencoding(input, encoding, final=False):
    173      """
    174      Replace the name of the encoding in the charset rule at the beginning of
    175      ``input`` with ``encoding``. If ``input`` doesn't starts with a charset
    176      rule, ``input`` will be returned unmodified.
    177
    178      If the encoding can't be found yet, ``None`` is returned. ``final``
    179      specifies whether more data will be available in later calls or not.
    180      If ``final`` is true, ``_fixencoding()`` will never return ``None``.
    181      """
    182      prefix = u'@charset "'
    183      if len(input) > len(prefix):
    184          if input.startswith(prefix):
    185              pos = input.find(u'"', len(prefix))
    186              if pos >= 0:
    187                  if encoding.replace("_", "-").lower() == "utf-8-sig":
    188                      encoding = u"utf-8"
    189                  return prefix + encoding + input[pos:]
    190              # we haven't seen the end of the encoding name yet => fall through
    191          else:
    192              return input # doesn't start with prefix, so nothing to fix
    193      elif not prefix.startswith(input) or final:
    194          # can't turn out to be a @charset rule later (or there is no "later")
    195          return input
    196      if final:
    197          return input
    198      return None # don't know yet
    199
    200
    201 -def decode(input, errors="strict", encoding=None):
    202      if encoding is None:
    203          encoding = _detectencoding_str(input, True)
    204      if encoding == "css":
    205          raise ValueError("css not allowed as encoding name")
    206      (input, consumed) = codecs.getdecoder(encoding)(input, errors)
    207      return (_fixencoding(input, unicode(encoding), True), consumed)
    208
    209
    210 -def encode(input, errors="strict", encoding=None):
    211      consumed = len(input)
    212      if encoding is None:
    213          encoding = _detectencoding_unicode(input, True)
    214          if encoding.replace("_", "-").lower() == "utf-8-sig":
    215              input = _fixencoding(input, u"utf-8", True)
    216      else:
    217          input = _fixencoding(input, unicode(encoding), True)
    218      if encoding == "css":
    219          raise ValueError("css not allowed as encoding name")
    220      encoder = codecs.getencoder(encoding)
    221      return (encoder(input, errors)[0], consumed)
    222
    223
    224 -def _bytes2int(bytes):
    225      # Helper: convert an 8 bit string into an ``int``.
    226      i = 0
    227      for byte in bytes:
    228          i = (i<<8) + ord(byte)
    229      return i
    230
    231
    232 -def _int2bytes(i):
    233      # Helper: convert an ``int`` into an 8-bit string.
    234      v = []
    235      while i:
    236          v.insert(0, chr(i&0xff))
    237          i >>= 8
    238      return "".join(v)
    239
    240
    241  if hasattr(codecs, "IncrementalDecoder"):
    242 -    class IncrementalDecoder(codecs.IncrementalDecoder):
    243 -        def __init__(self, errors="strict", encoding=None):
    244              self.decoder = None
    245              self.encoding = encoding
    246              codecs.IncrementalDecoder.__init__(self, errors)
    247              # Store ``errors`` somewhere else,
    248              # because we have to hide it in a property
    249              self._errors = errors
    250              self.buffer = ""
    251              self.headerfixed = False
    252
    253 -        def iterdecode(self, input):
    254              for part in input:
    255                  result = self.decode(part, False)
    256                  if result:
    257                      yield result
    258              result = self.decode("", True)
    259              if result:
    260                  yield result
    261
    262 -        def decode(self, input, final=False):
    263              # We're doing basically the same as a ``BufferedIncrementalDecoder``,
    264              # but since the buffer is only relevant until the encoding has been
    265              # detected (in which case the buffer of the underlying codec might
    266              # kick in), we're implementing buffering ourselves to avoid some
    267              # overhead.
    268              if self.decoder is None:
    269                  input = self.buffer + input
    270                  self.encoding = _detectencoding_str(input, final)
    271                  if self.encoding is None:
    272                      self.buffer = input # retry the complete input on the next call
    273                      return u"" # no encoding determined yet, so no output
    274                  if self.encoding == "css":
    275                      raise ValueError("css not allowed as encoding name")
    276                  self.buffer = "" # drop buffer, as the decoder might keep its own
    277                  decoder = codecs.getincrementaldecoder(self.encoding)
    278                  self.decoder = decoder(self._errors)
    279              if self.headerfixed:
    280                  return self.decoder.decode(input, final)
    281              # If we haven't fixed the header yet,
    282              # the content of ``self.buffer`` is a ``unicode`` object
    283              output = self.buffer + self.decoder.decode(input, final)
    284              encoding = self.encoding
    285              if encoding.replace("_", "-").lower() == "utf-8-sig":
    286                  encoding = "utf-8"
    287              newoutput = _fixencoding(output, unicode(encoding), final)
    288              if newoutput is None:
    289                  # retry fixing the @charset rule (but keep the decoded stuff)
    290                  self.buffer = output
    291                  return u""
    292              self.headerfixed = True
    293              return newoutput
    294
    295 -        def reset(self):
    296              codecs.IncrementalDecoder.reset(self)
    297              self.decoder = None
    298              self.buffer = ""
    299              self.headerfixed = False
    300
    301 -        def _geterrors(self):
    302              return self._errors
    303
    304 -        def _seterrors(self, errors):
    305              # Setting ``errors`` must be done on the real decoder too
    306              if self.decoder is not None:
    307                  self.decoder.errors = errors
    308              self._errors = errors
    309          errors = property(_geterrors, _seterrors)
    310
    311 -        def getstate(self):
    312              if self.decoder is not None:
    313                  state = (self.encoding, self.buffer, self.headerfixed, True, self.decoder.getstate())
    314              else:
    315                  state = (self.encoding, self.buffer, self.headerfixed, False, None)
    316              return ("", _bytes2int(marshal.dumps(state)))
    317
    318 -        def setstate(self, state):
    319              state = _int2bytes(marshal.loads(state[1])) # ignore buffered input
    320              self.encoding = state[0]
    321              self.buffer = state[1]
    322              self.headerfixed = state[2]
    323              if state[3] is not None:
    324                  self.decoder = codecs.getincrementaldecoder(self.encoding)(self._errors)
    325                  self.decoder.setstate(state[4])
    326              else:
    327                  self.decoder = None
    328
    329
    330  if hasattr(codecs, "IncrementalEncoder"):
    331 -    class IncrementalEncoder(codecs.IncrementalEncoder):
    332 -        def __init__(self, errors="strict", encoding=None):
    333              self.encoder = None
    334              self.encoding = encoding
    335              codecs.IncrementalEncoder.__init__(self, errors)
    336              # Store ``errors`` somewhere else,
    337              # because we have to hide it in a property
    338              self._errors = errors
    339              self.buffer = u""
    340
    341 -        def iterencode(self, input):
    342              for part in input:
    343                  result = self.encode(part, False)
    344                  if result:
    345                      yield result
    346              result = self.encode(u"", True)
    347              if result:
    348                  yield result
    349
    350 -        def encode(self, input, final=False):
    351              if self.encoder is None:
    352                  input = self.buffer + input
    353                  if self.encoding is not None:
    354                      # Replace encoding in the @charset rule with the specified one
    355                      encoding = self.encoding
    356                      if encoding.replace("_", "-").lower() == "utf-8-sig":
    357                          encoding = "utf-8"
    358                      newinput = _fixencoding(input, unicode(encoding), final)
    359                      if newinput is None: # @charset rule incomplete => Retry next time
    360                          self.buffer = input
    361                          return ""
    362                      input = newinput
    363                  else:
    364                      # Use encoding from the @charset declaration
    365                      self.encoding = _detectencoding_unicode(input, final)
    366                  if self.encoding is not None:
    367                      if self.encoding == "css":
    368                          raise ValueError("css not allowed as encoding name")
    369                      info = codecs.lookup(self.encoding)
    370                      encoding = self.encoding
    371                      if self.encoding.replace("_", "-").lower() == "utf-8-sig":
    372                          input = _fixencoding(input, u"utf-8", True)
    373                      self.encoder = info.incrementalencoder(self._errors)
    374                      self.buffer = u""
    375                  else:
    376                      self.buffer = input
    377                      return ""
    378              return self.encoder.encode(input, final)
    379
    380 -        def reset(self):
    381              codecs.IncrementalEncoder.reset(self)
    382              self.encoder = None
    383              self.buffer = u""
    384
    385 -        def _geterrors(self):
    386              return self._errors
    387
    388 -        def _seterrors(self, errors):
    389              # Setting ``errors ``must be done on the real encoder too
    390              if self.encoder is not None:
    391                  self.encoder.errors = errors
    392              self._errors = errors
    393          errors = property(_geterrors, _seterrors)
    394
    395 -        def getstate(self):
    396              if self.encoder is not None:
    397                  state = (self.encoding, self.buffer, True, self.encoder.getstate())
    398              else:
    399                  state = (self.encoding, self.buffer, False, None)
    400              return _bytes2int(marshal.dumps(state))
    401
    402 -        def setstate(self, state):
    403              state = _int2bytes(marshal.loads(state))
    404              self.encoding = state[0]
    405              self.buffer = state[1]
    406              if state[2] is not None:
    407                  self.encoder = codecs.getincrementalencoder(self.encoding)(self._errors)
    408                  self.encoder.setstate(state[4])
    409              else:
    410                  self.encoder = None
    411
    412
    413 -class StreamWriter(codecs.StreamWriter):
    414 -    def __init__(self, stream, errors="strict", encoding=None, header=False):
    415          codecs.StreamWriter.__init__(self, stream, errors)
    416          self.streamwriter = None
    417          self.encoding = encoding
    418          self._errors = errors
    419          self.buffer = u""
    420
    421 -    def encode(self, input, errors='strict'):
    422          li = len(input)
    423          if self.streamwriter is None:
    424              input = self.buffer + input
    425              li = len(input)
    426              if self.encoding is not None:
    427                  # Replace encoding in the @charset rule with the specified one
    428                  encoding = self.encoding
    429                  if encoding.replace("_", "-").lower() == "utf-8-sig":
    430                      encoding = "utf-8"
    431                  newinput = _fixencoding(input, unicode(encoding), False)
    432                  if newinput is None: # @charset rule incomplete => Retry next time
    433                      self.buffer = input
    434                      return ("", 0)
    435                  input = newinput
    436              else:
    437                  # Use encoding from the @charset declaration
    438                  self.encoding = _detectencoding_unicode(input, False)
    439              if self.encoding is not None:
    440                  if self.encoding == "css":
    441                      raise ValueError("css not allowed as encoding name")
    442                  self.streamwriter = codecs.getwriter(self.encoding)(self.stream, self._errors)
    443                  encoding = self.encoding
    444                  if self.encoding.replace("_", "-").lower() == "utf-8-sig":
    445                      input = _fixencoding(input, u"utf-8", True)
    446                  self.buffer = u""
    447              else:
    448                  self.buffer = input
    449                  return ("", 0)
    450          return (self.streamwriter.encode(input, errors)[0], li)
    451
    452 -    def _geterrors(self):
    453          return self._errors
    454
    455 -    def _seterrors(self, errors):
    456          # Setting ``errors`` must be done on the streamwriter too
    457          if self.streamwriter is not None:
    458              self.streamwriter.errors = errors
    459          self._errors = errors
    460      errors = property(_geterrors, _seterrors)
    461
    462
    463 -class StreamReader(codecs.StreamReader):
    464 -    def __init__(self, stream, errors="strict", encoding=None):
    465          codecs.StreamReader.__init__(self, stream, errors)
    466          self.streamreader = None
    467          self.encoding = encoding
    468          self._errors = errors
    469
    470 -    def decode(self, input, errors='strict'):
    471          if self.streamreader is None:
    472              self.encoding = _detectencoding_str(input, False)
    473              if self.encoding is None:
    474                  return (u"", 0) # no encoding determined yet, so no output
    475              if self.encoding == "css":
    476                  raise ValueError("css not allowed as encoding name")
    477              streamreader = codecs.getreader(self.encoding)
    478              streamreader = streamreader(self.stream, self._errors)
    479              (output, consumed) = streamreader.decode(input, errors)
    480              encoding = self.encoding
    481              if encoding.replace("_", "-").lower() == "utf-8-sig":
    482                  encoding = "utf-8"
    483              newoutput = _fixencoding(output, unicode(encoding), False)
    484              if newoutput is not None:
    485                  self.streamreader = streamreader
    486                  return (newoutput, consumed)
    487              return (u"", 0) # we will create a new streamreader on the next call
    488          return self.streamreader.decode(input, errors)
    489
    490 -    def _geterrors(self):
    491          return self._errors
    492
    493 -    def _seterrors(self, errors):
    494          # Setting ``errors`` must be done on the streamreader too
    495          if self.streamreader is not None:
    496              self.streamreader.errors = errors
    497          self._errors = errors
    498      errors = property(_geterrors, _seterrors)
    499
    500
    501  if hasattr(codecs, "CodecInfo"):
    502      # We're running on Python 2.5 or better
    503 -    def search_function(name):
    504          if name == "css":
    505              return codecs.CodecInfo(
    506                  name="css",
    507                  encode=encode,
    508                  decode=decode,
    509                  incrementalencoder=IncrementalEncoder,
    510                  incrementaldecoder=IncrementalDecoder,
    511                  streamwriter=StreamWriter,
    512                  streamreader=StreamReader,
    513              )
    514  else:
    515      # If we're running on Python 2.4, define the utf-8-sig codec here
    516 -    def utf8sig_encode(input, errors='strict'):
    517          return (codecs.BOM_UTF8 + codecs.utf_8_encode(input, errors)[0], len(input))
    518
    519 -    def utf8sig_decode(input, errors='strict'):
    520          prefix = 0
    521          if input[:3] == codecs.BOM_UTF8:
    522              input = input[3:]
    523              prefix = 3
    524          (output, consumed) = codecs.utf_8_decode(input, errors, True)
    525          return (output, consumed+prefix)
    526
    527 -    class UTF8SigStreamWriter(codecs.StreamWriter):
    528 -        def reset(self):
    529              codecs.StreamWriter.reset(self)
    530              try:
    531                  del self.encode
    532              except AttributeError:
    533                  pass
    534
    535 -        def encode(self, input, errors='strict'):
    536              self.encode = codecs.utf_8_encode
    537              return utf8sig_encode(input, errors)
    538
    539 -    class UTF8SigStreamReader(codecs.StreamReader):
    540 -        def reset(self):
    541              codecs.StreamReader.reset(self)
    542              try:
    543                  del self.decode
    544              except AttributeError:
    545                  pass
    546
    547 -        def decode(self, input, errors='strict'):
    548              if len(input) < 3 and codecs.BOM_UTF8.startswith(input):
    549                  # not enough data to decide if this is a BOM
    550                  # => try again on the next call
    551                  return (u"", 0)
    552              self.decode = codecs.utf_8_decode
    553              return utf8sig_decode(input, errors)
    554
    555 -    def search_function(name):
    556          import encodings
    557          name = encodings.normalize_encoding(name)
    558          if name == "css":
    559              return (encode, decode, StreamReader, StreamWriter)
    560          elif name == "utf_8_sig":
    561              return (utf8sig_encode, utf8sig_decode, UTF8SigStreamReader, UTF8SigStreamWriter)
    562
    563
    564  codecs.register(search_function)
    565
    566
    567  # Error handler for CSS escaping
    568
    569 -def cssescape(exc):
    570      if not isinstance(exc, UnicodeEncodeError):
    571          raise TypeError("don't know how to handle %r" % exc)
    572      return (u"".join(u"\\%06x" % ord(c) for c in exc.object[exc.start:exc.end]), exc.end)
    573
    574  codecs.register_error("cssescape", cssescape)
    575