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# -*- test-case-name: twisted._threads.test.test_memory -*-
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.
"""
Implementation of an in-memory worker that defers execution.
"""
from __future__ import absolute_import, division, print_function
from zope.interface import implementer
from . import IWorker
from ._convenience import Quit
NoMoreWork = object()
@implementer(IWorker)
class MemoryWorker(object):
"""
An L{IWorker} that queues work for later performance.
@ivar _quit: a flag indicating
@type _quit: L{Quit}
"""
def __init__(self, pending=list):
"""
Create a L{MemoryWorker}.
"""
self._quit = Quit()
self._pending = pending()
def do(self, work):
"""
Queue some work for to perform later; see L{createMemoryWorker}.
@param work: The work to perform.
"""
self._quit.check()
self._pending.append(work)
def quit(self):
"""
Quit this worker.
"""
self._quit.set()
self._pending.append(NoMoreWork)
def createMemoryWorker():
"""
Create an L{IWorker} that does nothing but defer work, to be performed
later.
@return: a worker that will enqueue work to perform later, and a callable
that will perform one element of that work.
@rtype: 2-L{tuple} of (L{IWorker}, L{callable})
"""
def perform():
if not worker._pending:
return False
if worker._pending[0] is NoMoreWork:
return False
worker._pending.pop(0)()
return True
worker = MemoryWorker()
return (worker, perform)
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