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