Home | History | Annotate | Download | only in encodings 
      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 (at] 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     )
    103