features/pep-3151 / Lib /

The default branch has multiple heads

"""Helper to provide extensibility for pickle.

This is only useful to add pickle support for extension types defined in
C, not for instances of user-defined classes.

__all__ = ["pickle", "constructor",
           "add_extension", "remove_extension", "clear_extension_cache"]

dispatch_table = {}

def pickle(ob_type, pickle_function, constructor_ob=None):
    if not hasattr(pickle_function, '__call__'):
        raise TypeError("reduction functions must be callable")
    dispatch_table[ob_type] = pickle_function

    # The constructor_ob function is a vestige of safe for unpickling.
    # There is no reason for the caller to pass it anymore.
    if constructor_ob is not None:

def constructor(object):
    if not hasattr(object, '__call__'):
        raise TypeError("constructors must be callable")

# Example: provide pickling support for complex numbers.

except NameError:

    def pickle_complex(c):
        return complex, (c.real, c.imag)

    pickle(complex, pickle_complex, complex)

# Support for pickling new-style objects

def _reconstructor(cls, base, state):
    if base is object:
        obj = object.__new__(cls)
        obj = base.__new__(cls, state)
        if base.__init__ != object.__init__:
            base.__init__(obj, state)
    return obj

_HEAPTYPE = 1<<9

# Python code for object.__reduce_ex__ for protocols 0 and 1

def _reduce_ex(self, proto):
    assert proto < 2
    for base in self.__class__.__mro__:
        if hasattr(base, '__flags__') and not base.__flags__ & _HEAPTYPE:
        base = object # not really reachable
    if base is object:
        state = None
        if base is self.__class__:
            raise TypeError("can't pickle %s objects" % base.__name__)
        state = base(self)
    args = (self.__class__, base, state)
        getstate = self.__getstate__
    except AttributeError:
        if getattr(self, "__slots__", None):
            raise TypeError("a class that defines __slots__ without "
                            "defining __getstate__ cannot be pickled")
            dict = self.__dict__
        except AttributeError:
            dict = None
        dict = getstate()
    if dict:
        return _reconstructor, args, dict
        return _reconstructor, args

# Helper for __reduce_ex__ protocol 2

def __newobj__(cls, *args):
    return cls.__new__(cls, *args)

def _slotnames(cls):
    """Return a list of slot names for a given class.

    This needs to find slots defined by the class and its bases, so we
    can't simply return the __slots__ attribute.  We must walk down
    the Method Resolution Order and concatenate the __slots__ of each
    class found there.  (This assumes classes don't modify their
    __slots__ attribute to misrepresent their slots after the class is

    # Get the value from a cache in the class if possible
    names = cls.__dict__.get("__slotnames__")
    if names is not None:
        return names

    # Not cached -- calculate the value
    names = []
    if not hasattr(cls, "__slots__"):
        # This class has no slots
        # Slots found -- gather slot names from all base classes
        for c in cls.__mro__:
            if "__slots__" in c.__dict__:
                slots = c.__dict__['__slots__']
                # if class has a single slot, it can be given as a string
                if isinstance(slots, str):
                    slots = (slots,)
                for name in slots:
                    # special descriptors
                    if name in ("__dict__", "__weakref__"):
                    # mangled names
                    elif name.startswith('__') and not name.endswith('__'):
                        names.append('_%s%s' % (c.__name__, name))

    # Cache the outcome in the class if at all possible
        cls.__slotnames__ = names
        pass # But don't die if we can't

    return names

# A registry of extension codes.  This is an ad-hoc compression
# mechanism.  Whenever a global reference to <module>, <name> is about
# to be pickled, the (<module>, <name>) tuple is looked up here to see
# if it is a registered extension code for it.  Extension codes are
# universal, so that the meaning of a pickle does not depend on
# context.  (There are also some codes reserved for local use that
# don't have this restriction.)  Codes are positive ints; 0 is
# reserved.

_extension_registry = {}                # key -> code
_inverted_registry = {}                 # code -> key
_extension_cache = {}                   # code -> object
# Don't ever rebind those names:  pickling grabs a reference to them when
# it's initialized, and won't see a rebinding.

def add_extension(module, name, code):
    """Register an extension code."""
    code = int(code)
    if not 1 <= code <= 0x7fffffff:
        raise ValueError("code out of range")
    key = (module, name)
    if (_extension_registry.get(key) == code and
        _inverted_registry.get(code) == key):
        return # Redundant registrations are benign
    if key in _extension_registry:
        raise ValueError("key %s is already registered with code %s" %
                         (key, _extension_registry[key]))
    if code in _inverted_registry:
        raise ValueError("code %s is already in use for key %s" %
                         (code, _inverted_registry[code]))
    _extension_registry[key] = code
    _inverted_registry[code] = key

def remove_extension(module, name, code):
    """Unregister an extension code.  For testing only."""
    key = (module, name)
    if (_extension_registry.get(key) != code or
        _inverted_registry.get(code) != key):
        raise ValueError("key %s is not registered with code %s" %
                         (key, code))
    del _extension_registry[key]
    del _inverted_registry[code]
    if code in _extension_cache:
        del _extension_cache[code]

def clear_extension_cache():

# Standard extension code assignments

# Reserved ranges

# First  Last Count  Purpose
#     1   127   127  Reserved for Python standard library
#   128   191    64  Reserved for Zope
#   192   239    48  Reserved for 3rd parties
#   240   255    16  Reserved for private use (will never be assigned)
#   256   Inf   Inf  Reserved for future assignment

# Extension codes are assigned by the Python Software Foundation.