156 lines
5.2 KiB
Python
156 lines
5.2 KiB
Python
# -*- 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()
|