1 #!/usr/bin/env python

     2 """ Python Character Mapping Codec for ROT13.

     3 

     4     See http://ucsub.colorado.edu/~kominek/rot13/ for details.

     5 

     6     Written by Marc-Andre Lemburg (mal@lemburg.com).

     7 

     8 """#"

     9 

    10 import codecs

    11 

    12 ### Codec APIs

    13 

    14 class Codec(codecs.Codec):

    15 

    16     def encode(self,input,errors='strict'):

    17         return codecs.charmap_encode(input,errors,encoding_map)

    18 

    19     def decode(self,input,errors='strict'):

    20         return codecs.charmap_decode(input,errors,decoding_map)

    21 

    22 class IncrementalEncoder(codecs.IncrementalEncoder):

    23     def encode(self, input, final=False):

    24         return codecs.charmap_encode(input,self.errors,encoding_map)[0]

    25 

    26 class IncrementalDecoder(codecs.IncrementalDecoder):

    27     def decode(self, input, final=False):

    28         return codecs.charmap_decode(input,self.errors,decoding_map)[0]

    29 

    30 class StreamWriter(Codec,codecs.StreamWriter):

    31     pass

    32 

    33 class StreamReader(Codec,codecs.StreamReader):

    34     pass

    35 

    36 ### encodings module API

    37 

    38 def getregentry():

    39     return codecs.CodecInfo(

    40         name='rot-13',

    41         encode=Codec().encode,

    42         decode=Codec().decode,

    43         incrementalencoder=IncrementalEncoder,

    44         incrementaldecoder=IncrementalDecoder,

    45         streamwriter=StreamWriter,

    46         streamreader=StreamReader,

    47     )

    48 

    49 ### Decoding Map

    50 

    51 decoding_map = codecs.make_identity_dict(range(256))

    52 decoding_map.update({

    53    0x0041: 0x004e,

    54    0x0042: 0x004f,

    55    0x0043: 0x0050,

    56    0x0044: 0x0051,

    57    0x0045: 0x0052,

    58    0x0046: 0x0053,

    59    0x0047: 0x0054,

    60    0x0048: 0x0055,

    61    0x0049: 0x0056,

    62    0x004a: 0x0057,

    63    0x004b: 0x0058,

    64    0x004c: 0x0059,

    65    0x004d: 0x005a,

    66    0x004e: 0x0041,

    67    0x004f: 0x0042,

    68    0x0050: 0x0043,

    69    0x0051: 0x0044,

    70    0x0052: 0x0045,

    71    0x0053: 0x0046,

    72    0x0054: 0x0047,

    73    0x0055: 0x0048,

    74    0x0056: 0x0049,

    75    0x0057: 0x004a,

    76    0x0058: 0x004b,

    77    0x0059: 0x004c,

    78    0x005a: 0x004d,

    79    0x0061: 0x006e,

    80    0x0062: 0x006f,

    81    0x0063: 0x0070,

    82    0x0064: 0x0071,

    83    0x0065: 0x0072,

    84    0x0066: 0x0073,

    85    0x0067: 0x0074,

    86    0x0068: 0x0075,

    87    0x0069: 0x0076,

    88    0x006a: 0x0077,

    89    0x006b: 0x0078,

    90    0x006c: 0x0079,

    91    0x006d: 0x007a,

    92    0x006e: 0x0061,

    93    0x006f: 0x0062,

    94    0x0070: 0x0063,

    95    0x0071: 0x0064,

    96    0x0072: 0x0065,

    97    0x0073: 0x0066,

    98    0x0074: 0x0067,

    99    0x0075: 0x0068,

   100    0x0076: 0x0069,

   101    0x0077: 0x006a,

   102    0x0078: 0x006b,

   103    0x0079: 0x006c,

   104    0x007a: 0x006d,

   105 })

   106 

   107 ### Encoding Map

   108 

   109 encoding_map = codecs.make_encoding_map(decoding_map)

   110 

   111 ### Filter API

   112 

   113 def rot13(infile, outfile):

   114     outfile.write(infile.read().encode('rot-13'))

   115 

   116 if __name__ == '__main__':

   117     import sys

   118     rot13(sys.stdin, sys.stdout)