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from threading import RLock
from typing import Optional
from reactivex import abc
class SerialDisposable(abc.DisposableBase):
"""Represents a disposable resource whose underlying disposable
resource can be replaced by another disposable resource, causing
automatic disposal of the previous underlying disposable resource.
"""
def __init__(self) -> None:
self.current: Optional[abc.DisposableBase] = None
self.is_disposed = False
self.lock = RLock()
super().__init__()
def get_disposable(self) -> Optional[abc.DisposableBase]:
return self.current
def set_disposable(self, value: abc.DisposableBase) -> None:
"""If the SerialDisposable has already been disposed, assignment
to this property causes immediate disposal of the given
disposable object. Assigning this property disposes the previous
disposable object."""
old: Optional[abc.DisposableBase] = None
with self.lock:
should_dispose = self.is_disposed
if not should_dispose:
old = self.current
self.current = value
if old is not None:
old.dispose()
if should_dispose:
value.dispose()
disposable = property(get_disposable, set_disposable)
def dispose(self) -> None:
"""Disposes the underlying disposable as well as all future
replacements."""
old: Optional[abc.DisposableBase] = None
with self.lock:
if not self.is_disposed:
self.is_disposed = True
old = self.current
self.current = None
if old is not None:
old.dispose()
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