| """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 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) |
| |
| def constructor(object): |
| if not callable(object): |
| raise TypeError("constructors must be callable") |
| |
| # Example: provide pickling support for complex numbers. |
| |
| try: |
| complex |
| except NameError: |
| pass |
| else: |
| |
| 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) |
| else: |
| 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 |
| cls = self.__class__ |
| for base in cls.__mro__: |
| if hasattr(base, '__flags__') and not base.__flags__ & _HEAPTYPE: |
| break |
| else: |
| base = object # not really reachable |
| if base is object: |
| state = None |
| else: |
| if base is cls: |
| raise TypeError(f"cannot pickle {cls.__name__!r} object") |
| state = base(self) |
| args = (cls, base, state) |
| try: |
| getstate = self.__getstate__ |
| except AttributeError: |
| if getattr(self, "__slots__", None): |
| raise TypeError(f"cannot pickle {cls.__name__!r} object: " |
| f"a class that defines __slots__ without " |
| f"defining __getstate__ cannot be pickled " |
| f"with protocol {proto}") from None |
| try: |
| dict = self.__dict__ |
| except AttributeError: |
| dict = None |
| else: |
| dict = getstate() |
| if dict: |
| return _reconstructor, args, dict |
| else: |
| return _reconstructor, args |
| |
| # Helper for __reduce_ex__ protocol 2 |
| |
| def __newobj__(cls, *args): |
| return cls.__new__(cls, *args) |
| |
| def __newobj_ex__(cls, args, kwargs): |
| """Used by pickle protocol 4, instead of __newobj__ to allow classes with |
| keyword-only arguments to be pickled correctly. |
| """ |
| return cls.__new__(cls, *args, **kwargs) |
| |
| 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 |
| defined.) |
| """ |
| |
| # 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 |
| pass |
| else: |
| # 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__"): |
| continue |
| # mangled names |
| elif name.startswith('__') and not name.endswith('__'): |
| stripped = c.__name__.lstrip('_') |
| if stripped: |
| names.append('_%s%s' % (stripped, name)) |
| else: |
| names.append(name) |
| else: |
| names.append(name) |
| |
| # Cache the outcome in the class if at all possible |
| try: |
| cls.__slotnames__ = names |
| except: |
| 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(): |
| _extension_cache.clear() |
| |
| # 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. |