| """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"] |
| |
| dispatch_table = {} |
| |
| 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 |
| |
| 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. |
| |
| def pickle_complex(c): |
| return complex, (c.real, c.imag) |
| |
| pickle(type(1j), pickle_complex, complex) |
| |
| # Support for picking new-style objects |
| |
| def _reconstructor(cls, base, state): |
| obj = base.__new__(cls, state) |
| base.__init__(obj, state) |
| return obj |
| |
| _HEAPTYPE = 1<<9 |
| |
| def _reduce(self): |
| for base in self.__class__.__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 self.__class__: |
| raise TypeError, "can't pickle %s objects" % base.__name__ |
| state = base(self) |
| args = (self.__class__, base, state) |
| try: |
| getstate = self.__getstate__ |
| except AttributeError: |
| try: |
| dict = self.__dict__ |
| except AttributeError: |
| dict = None |
| else: |
| dict = getstate() |
| if dict: |
| return _reconstructor, args, dict |
| else: |
| return _reconstructor, args |
| |
| # 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: 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.""" |
| 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 3 |
| # 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. |