Lib/encodings/zlib_codec.py

   1 """ Python 'zlib_codec' Codec - zlib compression encoding
   2
   3     Unlike most of the other codecs which target Unicode, this codec
   4     will return Python string objects for both encode and decode.
   5
   6     Written by Marc-Andre Lemburg (mal@lemburg.com).
   7
   8 """
   9 import codecs
  10 import zlib # this codec needs the optional zlib module !
  11
  12 ### Codec APIs
  13
  14 def zlib_encode(input,errors='strict'):
  15
  16     """ Encodes the object input and returns a tuple (output
  17         object, length consumed).
  18
  19         errors defines the error handling to apply. It defaults to
  20         'strict' handling which is the only currently supported
  21         error handling for this codec.
  22
  23     """
  24     assert errors == 'strict'
  25     output = zlib.compress(input)
  26     return (output, len(input))
  27
  28 def zlib_decode(input,errors='strict'):
  29
  30     """ Decodes the object input and returns a tuple (output
  31         object, length consumed).
  32
  33         input must be an object which provides the bf_getreadbuf
  34         buffer slot. Python strings, buffer objects and memory
  35         mapped files are examples of objects providing this slot.
  36
  37         errors defines the error handling to apply. It defaults to
  38         'strict' handling which is the only currently supported
  39         error handling for this codec.
  40
  41     """
  42     assert errors == 'strict'
  43     output = zlib.decompress(input)
  44     return (output, len(input))
  45
  46 class Codec(codecs.Codec):
  47
  48     def encode(self, input, errors='strict'):
  49         return zlib_encode(input, errors)
  50     def decode(self, input, errors='strict'):
  51         return zlib_decode(input, errors)
  52
  53 class IncrementalEncoder(codecs.IncrementalEncoder):
  54     def __init__(self, errors='strict'):
  55         assert errors == 'strict'
  56         self.errors = errors
  57         self.compressobj = zlib.compressobj()
  58
  59     def encode(self, input, final=False):
  60         if final:
  61             c = self.compressobj.compress(input)
  62             return c + self.compressobj.flush()
  63         else:
  64             return self.compressobj.compress(input)
  65
  66     def reset(self):
  67         self.compressobj = zlib.compressobj()
  68
  69 class IncrementalDecoder(codecs.IncrementalDecoder):
  70     def __init__(self, errors='strict'):
  71         assert errors == 'strict'
  72         self.errors = errors
  73         self.decompressobj = zlib.decompressobj()
  74
  75     def decode(self, input, final=False):
  76         if final:
  77             c = self.decompressobj.decompress(input)
  78             return c + self.decompressobj.flush()
  79         else:
  80             return self.decompressobj.decompress(input)
  81
  82     def reset(self):
  83         self.decompressobj = zlib.decompressobj()
  84
  85 class StreamWriter(Codec,codecs.StreamWriter):
  86     pass
  87
  88 class StreamReader(Codec,codecs.StreamReader):
  89     pass
  90
  91 ### encodings module API
  92
  93 def getregentry():
  94     return codecs.CodecInfo(
  95         name='zlib',
  96         encode=zlib_encode,
  97         decode=zlib_decode,
  98         incrementalencoder=IncrementalEncoder,
  99         incrementaldecoder=IncrementalDecoder,
 100         streamreader=StreamReader,
 101         streamwriter=StreamWriter,
 102     )