circuitpython/extmod/uasyncio/event.py

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# MicroPython uasyncio module
# MIT license; Copyright (c) 2019-2020 Damien P. George
from . import core
# Event class for primitive events that can be waited on, set, and cleared
class Event:
def __init__(self):
self.state = False # False=unset; True=set
self.waiting = core.TaskQueue() # Queue of Tasks waiting on completion of this event
def is_set(self):
return self.state
def set(self):
# Event becomes set, schedule any tasks waiting on it
# Note: This must not be called from anything except the thread running
# the asyncio loop (i.e. neither hard or soft IRQ, or a different thread).
while self.waiting.peek():
core._task_queue.push_head(self.waiting.pop_head())
self.state = True
def clear(self):
self.state = False
async def wait(self):
if not self.state:
# Event not set, put the calling task on the event's waiting queue
self.waiting.push_head(core.cur_task)
# Set calling task's data to the event's queue so it can be removed if needed
core.cur_task.data = self.waiting
yield
return True