diff options
Diffstat (limited to 'Lib/copy_reg.py')
| -rw-r--r-- | Lib/copy_reg.py | 201 |
1 files changed, 201 insertions, 0 deletions
diff --git a/Lib/copy_reg.py b/Lib/copy_reg.py new file mode 100644 index 0000000..db17150 --- /dev/null +++ b/Lib/copy_reg.py @@ -0,0 +1,201 @@ +"""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 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: + constructor(constructor_ob) + +def constructor(object): + if not hasattr(object, '__call__'): + 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 + 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: + if getattr(self, "__slots__", None): + raise TypeError("a class that defines __slots__ without " + "defining __getstate__ cannot be pickled") + 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 _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, basestring): + slots = (slots,) + for name in slots: + # special descriptors + if name in ("__dict__", "__weakref__"): + continue + # mangled names + elif name.startswith('__') and not name.endswith('__'): + names.append('_%s%s' % (c.__name__, 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: 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 +# 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. |