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Python Source  |  2003-07-18  |  1.9 KB  |  73 lines
  1. """Helper to provide extensibility for pickle/cPickle.
  2.  
  3. This is only useful to add pickle support for extension types defined in
  4. C, not for instances of user-defined classes.
  5. """
  6.  
  7. from types import ClassType as _ClassType
  8.  
  9. __all__ = ["pickle","constructor"]
  10.  
  11. dispatch_table = {}
  12. safe_constructors = {}
  13.  
  14. def pickle(ob_type, pickle_function, constructor_ob=None):
  15.     if type(ob_type) is _ClassType:
  16.         raise TypeError("copy_reg is not intended for use with classes")
  17.  
  18.     if not callable(pickle_function):
  19.         raise TypeError("reduction functions must be callable")
  20.     dispatch_table[ob_type] = pickle_function
  21.  
  22.     if constructor_ob is not None:
  23.         constructor(constructor_ob)
  24.  
  25. def constructor(object):
  26.     if not callable(object):
  27.         raise TypeError("constructors must be callable")
  28.     safe_constructors[object] = 1
  29.  
  30. # Example: provide pickling support for complex numbers.
  31.  
  32. def pickle_complex(c):
  33.     return complex, (c.real, c.imag)
  34.  
  35. pickle(type(1j), pickle_complex, complex)
  36.  
  37. # Support for picking new-style objects
  38.  
  39. def _reconstructor(cls, base, state):
  40.     obj = base.__new__(cls, state)
  41.     base.__init__(obj, state)
  42.     return obj
  43. _reconstructor.__safe_for_unpickling__ = 1
  44.  
  45. _HEAPTYPE = 1<<9
  46.  
  47. def _reduce(self):
  48.     for base in self.__class__.__mro__:
  49.         if hasattr(base, '__flags__') and not base.__flags__ & _HEAPTYPE:
  50.             break
  51.     else:
  52.         base = object # not really reachable
  53.     if base is object:
  54.         state = None
  55.     else:
  56.         if base is self.__class__:
  57.             raise TypeError, "can't pickle %s objects" % base.__name__
  58.         state = base(self)
  59.     args = (self.__class__, base, state)
  60.     try:
  61.         getstate = self.__getstate__
  62.     except AttributeError:
  63.         try:
  64.             dict = self.__dict__
  65.         except AttributeError:
  66.             dict = None
  67.     else:
  68.         dict = getstate()
  69.     if dict:
  70.         return _reconstructor, args, dict
  71.     else:
  72.         return _reconstructor, args
  73.