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task.py
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168 lines (136 loc) · 4.54 KB
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# Copyright (C) 2002-2006 Stephen Kennedy <stevek@gnome.org>
# Copyright (C) 2012-2013 Kai Willadsen <kai.willadsen@gmail.com>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 2 of the License, or (at
# your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
"""Classes to implement scheduling for cooperative threads."""
import traceback
class SchedulerBase:
"""Base class with common functionality for schedulers
Derived classes must implement get_current_task.
"""
def __init__(self):
self.tasks = []
self.callbacks = []
def __repr__(self):
return "%s" % self.tasks
def connect(self, signal, action):
assert signal == "runnable"
if action not in self.callbacks:
self.callbacks.append(action)
def add_task(self, task, atfront=False):
"""Add a task to the scheduler's task list
The task may be a function, generator or scheduler, and is
deemed to have finished when it returns a false value or raises
StopIteration.
"""
self.remove_task(task)
if atfront:
self.tasks.insert(0, task)
else:
self.tasks.append(task)
for callback in self.callbacks:
callback(self)
def remove_task(self, task):
"""Remove a single task from the scheduler"""
try:
self.tasks.remove(task)
except ValueError:
pass
def remove_all_tasks(self):
"""Remove all tasks from the scheduler"""
self.tasks = []
def add_scheduler(self, sched):
"""Adds a subscheduler as a child task of this scheduler"""
sched.connect("runnable", lambda t: self.add_task(t))
def remove_scheduler(self, sched):
"""Remove a sub-scheduler from this scheduler"""
self.remove_task(sched)
try:
self.callbacks.remove(sched)
except ValueError:
pass
def get_current_task(self):
"""Overridden function returning the next task to run"""
raise NotImplementedError
def __call__(self):
"""Run an iteration of the current task"""
if len(self.tasks):
r = self.iteration()
if r:
return r
return self.tasks_pending()
def complete_tasks(self):
"""Run all of the scheduler's current tasks to completion"""
while self.tasks_pending():
self.iteration()
def tasks_pending(self):
return len(self.tasks) != 0
def iteration(self):
"""Perform one iteration of the current task"""
try:
task = self.get_current_task()
except StopIteration:
return 0
try:
if hasattr(task, "__iter__"):
ret = next(task)
else:
ret = task()
except StopIteration:
pass
except Exception:
traceback.print_exc()
else:
if ret:
return ret
self.tasks.remove(task)
return 0
class LifoScheduler(SchedulerBase):
"""Scheduler calling most recently added tasks first"""
def get_current_task(self):
try:
return self.tasks[-1]
except IndexError:
raise StopIteration
class FifoScheduler(SchedulerBase):
"""Scheduler calling tasks in the order they were added"""
def get_current_task(self):
try:
return self.tasks[0]
except IndexError:
raise StopIteration
if __name__ == "__main__":
import random
import time
m = LifoScheduler()
def timetask(t):
while time.time() - t < 1:
print("***")
time.sleep(0.1)
print("!!!")
def sayhello(x):
for i in range(random.randint(2, 8)):
print("hello", x)
time.sleep(0.1)
yield 1
print("end", x)
s = FifoScheduler()
m.add_task(s)
s.add_task(sayhello(10))
s.add_task(sayhello(20))
s.add_task(sayhello(30))
while s.tasks_pending():
s.iteration()
time.sleep(2)
print("***")