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'''VOLTTRON platform™ greenlet coroutine helper classes/functions.
These utilities are meant to be used with the BaseAgent and greenlet to
provide synchronization between light threads (coroutines).
'''
import greenlet
[docs]class Timeout(Exception):
'''Raised in the greenlet when waiting on a channel times out.'''
[docs]def sleep(timeout, create_timer):
'''Yield execution for timeout seconds.'''
current = greenlet.getcurrent()
timer = create_timer(timeout, current.switch)
current.parent.switch()
[docs]class WaitQueue(object):
'''A holder for tasklets waiting on asynchronous data.'''
def __init__(self, create_timer):
'''create_timer will be used to create timeouts.'''
self.tasks = []
self._timer = create_timer
[docs] def wait(self, timeout=None):
'''Wait for data to become available and return it
If timeout is None, wait indefinitely. Otherwise, timeout if
the task hasn't been notified within timeout seconds.
'''
current = greenlet.getcurrent()
tasks = self.tasks
tasks.append(current)
if timeout:
timer = self._timer(timeout, current.throw, Timeout)
try:
return current.parent.switch()
finally:
if timeout:
timer.cancel()
tasks.remove(current)
[docs] def notify_all(self, data):
'''Notify all waiting tasks of the arrival of data.'''
self.notify(data, None)
[docs] def notify(self, data, n=1):
'''Notify n waiting tasks of the arrival of data.'''
if n is None or n < 0:
tasks, self.tasks = self.tasks, []
else:
tasks, self.tasks = self.tasks[:n], self.tasks[n:]
for task in list(tasks):
task.switch(data)
[docs] def kill_all(self):
'''Kill all the tasks in the queue.'''
tasks, self.tasks = self.tasks, []
for task in tasks:
task.throw()