f4990130fb3bd409640d9f81570541d91bdaf0cb
"""Helper to provide extensibility for pickle/cPickle.
This is only useful to add pickle support for extension types defined in
C, not for instances of user-defined classes.
from types
import ClassType
as _ClassType
__all__
= ["pickle", "constructor",
"add_extension", "remove_extension", "clear_extension_cache"]
def pickle(ob_type
, pickle_function
, constructor_ob
=None):
if type(ob_type
) is _ClassType
:
raise TypeError("copy_reg is not intended for use with classes")
if not callable(pickle_function
):
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:
constructor(constructor_ob
)
raise TypeError("constructors must be callable")
# Example: provide pickling support for complex numbers.
return complex, (c
.real
, c
.imag
)
pickle(complex, pickle_complex
, complex)
# Support for pickling new-style objects
def _reconstructor(cls
, base
, state
):
obj
= object.__new
__(cls
)
obj
= base
.__new
__(cls
, state
)
base
.__init
__(obj
, state
)
# Python code for object.__reduce_ex__ for protocols 0 and 1
def _reduce_ex(self
, proto
):
for base
in self
.__class
__.__mro
__:
if hasattr(base
, '__flags__') and not base
.__flags
__ & _HEAPTYPE
:
base
= object # not really reachable
if base
is self
.__class
__:
raise TypeError, "can't pickle %s objects" % base
.__name
__
args
= (self
.__class
__, base
, state
)
getstate
= self
.__getstate
__
if getattr(self
, "__slots__", None):
raise TypeError("a class that defines __slots__ without "
"defining __getstate__ cannot be pickled")
return _reconstructor
, args
, dict
return _reconstructor
, args
# Helper for __reduce_ex__ protocol 2
def __newobj__(cls
, *args
):
return cls
.__new
__(cls
, *args
)
"""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__")
# Not cached -- calculate the value
if not hasattr(cls
, "__slots__"):
# This class has no slots
# Slots found -- gather slot names from all base classes
if "__slots__" in c
.__dict
__:
names
+= [name
for name
in c
.__dict
__["__slots__"]
if name
not in ("__dict__", "__weakref__")]
# Cache the outcome in the class if at all possible
cls
.__slotnames
__ = names
pass # But don't die if we can't
# 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
_extension_registry
= {} # key -> code
_inverted_registry
= {} # code -> key
_extension_cache
= {} # code -> object
# Don't ever rebind those names: cPickle 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."""
if not 1 <= code
<= 0x7fffffff:
raise ValueError, "code out of range"
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."""
if (_extension_registry
.get(key
) != code
or
_inverted_registry
.get(code
) != key
):
raise ValueError("key %s is not registered with code %s" %
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
# 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.