, is about
# to be pickled, the (, ) 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.