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     )