m_lib/hash/zshelve.py

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