| Current File : //usr/lib/python3/dist-packages/pip/_vendor/urllib3/packages/backports/weakref_finalize.py |
# -*- coding: utf-8 -*-
"""
backports.weakref_finalize
~~~~~~~~~~~~~~~~~~
Backports the Python 3 ``weakref.finalize`` method.
"""
from __future__ import absolute_import
import itertools
import sys
from weakref import ref
__all__ = ["weakref_finalize"]
class weakref_finalize(object):
"""Class for finalization of weakrefable objects
finalize(obj, func, *args, **kwargs) returns a callable finalizer
object which will be called when obj is garbage collected. The
first time the finalizer is called it evaluates func(*arg, **kwargs)
and returns the result. After this the finalizer is dead, and
calling it just returns None.
When the program exits any remaining finalizers for which the
atexit attribute is true will be run in reverse order of creation.
By default atexit is true.
"""
# Finalizer objects don't have any state of their own. They are
# just used as keys to lookup _Info objects in the registry. This
# ensures that they cannot be part of a ref-cycle.
__slots__ = ()
_registry = {}
_shutdown = False
_index_iter = itertools.count()
_dirty = False
_registered_with_atexit = False
class _Info(object):
__slots__ = ("weakref", "func", "args", "kwargs", "atexit", "index")
def __init__(self, obj, func, *args, **kwargs):
if not self._registered_with_atexit:
# We may register the exit function more than once because
# of a thread race, but that is harmless
import atexit
atexit.register(self._exitfunc)
weakref_finalize._registered_with_atexit = True
info = self._Info()
info.weakref = ref(obj, self)
info.func = func
info.args = args
info.kwargs = kwargs or None
info.atexit = True
info.index = next(self._index_iter)
self._registry[self] = info
weakref_finalize._dirty = True
def __call__(self, _=None):
"""If alive then mark as dead and return func(*args, **kwargs);
otherwise return None"""
info = self._registry.pop(self, None)
if info and not self._shutdown:
return info.func(*info.args, **(info.kwargs or {}))
def detach(self):
"""If alive then mark as dead and return (obj, func, args, kwargs);
otherwise return None"""
info = self._registry.get(self)
obj = info and info.weakref()
if obj is not None and self._registry.pop(self, None):
return (obj, info.func, info.args, info.kwargs or {})
def peek(self):
"""If alive then return (obj, func, args, kwargs);
otherwise return None"""
info = self._registry.get(self)
obj = info and info.weakref()
if obj is not None:
return (obj, info.func, info.args, info.kwargs or {})
@property
def alive(self):
"""Whether finalizer is alive"""
return self in self._registry
@property
def atexit(self):
"""Whether finalizer should be called at exit"""
info = self._registry.get(self)
return bool(info) and info.atexit
@atexit.setter
def atexit(self, value):
info = self._registry.get(self)
if info:
info.atexit = bool(value)
def __repr__(self):
info = self._registry.get(self)
obj = info and info.weakref()
if obj is None:
return "<%s object at %#x; dead>" % (type(self).__name__, id(self))
else:
return "<%s object at %#x; for %r at %#x>" % (
type(self).__name__,
id(self),
type(obj).__name__,
id(obj),
)
@classmethod
def _select_for_exit(cls):
# Return live finalizers marked for exit, oldest first
L = [(f, i) for (f, i) in cls._registry.items() if i.atexit]
L.sort(key=lambda item: item[1].index)
return [f for (f, i) in L]
@classmethod
def _exitfunc(cls):
# At shutdown invoke finalizers for which atexit is true.
# This is called once all other non-daemonic threads have been
# joined.
reenable_gc = False
try:
if cls._registry:
import gc
if gc.isenabled():
reenable_gc = True
gc.disable()
pending = None
while True:
if pending is None or weakref_finalize._dirty:
pending = cls._select_for_exit()
weakref_finalize._dirty = False
if not pending:
break
f = pending.pop()
try:
# gc is disabled, so (assuming no daemonic
# threads) the following is the only line in
# this function which might trigger creation
# of a new finalizer
f()
except Exception:
sys.excepthook(*sys.exc_info())
assert f not in cls._registry
finally:
# prevent any more finalizers from executing during shutdown
weakref_finalize._shutdown = True
if reenable_gc:
gc.enable()