m_lib/hash/zshelve.py

   1 """Compressed shelves.
   2 Author: Oleg Broytman <phd@phd.pp.ru>
   3 Copyright (C) 2001-2003 PhiloSoft Design
   4 License: Python"""
   5
   6
   7 from shelve import DbfilenameShelf
   8 from zlib import compress, decompress
   9
  10 try:
  11    from cPickle import dumps, loads
  12 except ImportError:
  13    from Pickle import dumps, loads
  14
  15
  16 class CompressedShelf(DbfilenameShelf):
  17     """Shelf implementation using zlib for compressing data."""
  18
  19     compress_level = 6 # default compression
  20
  21     def __getitem__(self, key):
  22         return loads(decompress(self.dict[key]))
  23
  24     def __setitem__(self, key, value):
  25         self.dict[key] = compress(dumps(value), self.compress_level)
  26
  27
  28 class CompressedKeysShelf(CompressedShelf):
  29     """CompressedShelf implementation that also compresses keys."""
  30
  31     def keys(self):
  32         _keys = []
  33         for key in self.dict.keys():
  34             _keys.append(decompress(key))
  35         return _keys
  36
  37     def has_key(self, key):
  38         return self.dict.has_key(compress(key, self.compress_level))
  39
  40     def __getitem__(self, key):
  41         return CompressedShelf.__getitem__(self, compress(key, self.compress_level))
  42
  43     def __setitem__(self, key, value):
  44         CompressedShelf.__setitem__(self, compress(key, self.compress_level), value)
  45
  46     def __delitem__(self, key):
  47         del self.dict[compress(key, self.compress_level)]