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d4b920c8bd
this clarifies that they are part of an internal API (albeit shared between pickle.py, copy_reg.py and cPickle.c). I'd like to do the same for copy_reg.dispatch_table, but worry that it might be used by existing code. This risk doesn't exist for the extension registry.
131 lines
4.3 KiB
Python
131 lines
4.3 KiB
Python
"""Helper to provide extensibility for pickle/cPickle.
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This is only useful to add pickle support for extension types defined in
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C, not for instances of user-defined classes.
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"""
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from types import ClassType as _ClassType
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__all__ = ["pickle", "constructor",
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"add_extension", "remove_extension", "clear_extension_cache"]
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dispatch_table = {}
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def pickle(ob_type, pickle_function, constructor_ob=None):
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if type(ob_type) is _ClassType:
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raise TypeError("copy_reg is not intended for use with classes")
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if not callable(pickle_function):
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raise TypeError("reduction functions must be callable")
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dispatch_table[ob_type] = pickle_function
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if constructor_ob is not None:
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constructor(constructor_ob)
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def constructor(object):
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if not callable(object):
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raise TypeError("constructors must be callable")
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# Example: provide pickling support for complex numbers.
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def pickle_complex(c):
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return complex, (c.real, c.imag)
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pickle(type(1j), pickle_complex, complex)
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# Support for picking new-style objects
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def _reconstructor(cls, base, state):
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obj = base.__new__(cls, state)
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base.__init__(obj, state)
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return obj
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_HEAPTYPE = 1<<9
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def _reduce(self):
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for base in self.__class__.__mro__:
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if hasattr(base, '__flags__') and not base.__flags__ & _HEAPTYPE:
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break
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else:
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base = object # not really reachable
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if base is object:
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state = None
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else:
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if base is self.__class__:
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raise TypeError, "can't pickle %s objects" % base.__name__
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state = base(self)
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args = (self.__class__, base, state)
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try:
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getstate = self.__getstate__
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except AttributeError:
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try:
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dict = self.__dict__
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except AttributeError:
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dict = None
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else:
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dict = getstate()
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if dict:
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return _reconstructor, args, dict
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else:
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return _reconstructor, args
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# A registry of extension codes. This is an ad-hoc compression
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# mechanism. Whenever a global reference to <module>, <name> is about
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# to be pickled, the (<module>, <name>) tuple is looked up here to see
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# if it is a registered extension code for it. Extension codes are
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# universal, so that the meaning of a pickle does not depend on
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# context. (There are also some codes reserved for local use that
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# don't have this restriction.) Codes are positive ints; 0 is
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# reserved.
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_extension_registry = {} # key -> code
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_inverted_registry = {} # code -> key
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_extension_cache = {} # code -> object
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# Don't ever rebind those names: cPickle grabs a reference to them when
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# it's initialized, and won't see a rebinding.
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def add_extension(module, name, code):
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"""Register an extension code."""
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code = int(code)
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if not 1 <= code < 0x7fffffff:
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raise ValueError, "code out of range"
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key = (module, name)
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if (_extension_registry.get(key) == code and
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_inverted_registry.get(code) == key):
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return # Redundant registrations are benign
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if key in _extension_registry:
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raise ValueError("key %s is already registered with code %s" %
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(key, _extension_registry[key]))
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if code in _inverted_registry:
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raise ValueError("code %s is already in use for key %s" %
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(code, _inverted_registry[code]))
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_extension_registry[key] = code
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_inverted_registry[code] = key
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def remove_extension(module, name, code):
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"""Unregister an extension code. For testing only."""
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key = (module, name)
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if (_extension_registry.get(key) != code or
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_inverted_registry.get(code) != key):
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raise ValueError("key %s is not registered with code %s" %
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(key, code))
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del _extension_registry[key]
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del _inverted_registry[code]
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if code in _extension_cache:
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del _extension_cache[code]
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def clear_extension_cache():
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_extension_cache.clear()
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# Standard extension code assignments
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# Reserved ranges
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# First Last Count Purpose
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# 1 127 127 Reserved for Python standard library
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# 128 191 64 Reserved for Zope 3
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# 192 239 48 Reserved for 3rd parties
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# 240 255 16 Reserved for private use (will never be assigned)
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# 256 Inf Inf Reserved for future assignment
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# Extension codes are assigned by the Python Software Foundation.
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