kopia lustrzana https://github.com/micropython/micropython
54 wiersze
1.7 KiB
Python
54 wiersze
1.7 KiB
Python
# MicroPython uasyncio module
|
|
# MIT license; Copyright (c) 2019-2020 Damien P. George
|
|
|
|
from . import core
|
|
|
|
# Lock class for primitive mutex capability
|
|
class Lock:
|
|
def __init__(self):
|
|
# The state can take the following values:
|
|
# - 0: unlocked
|
|
# - 1: locked
|
|
# - <Task>: unlocked but this task has been scheduled to acquire the lock next
|
|
self.state = 0
|
|
# Queue of Tasks waiting to acquire this Lock
|
|
self.waiting = core.TaskQueue()
|
|
|
|
def locked(self):
|
|
return self.state == 1
|
|
|
|
def release(self):
|
|
if self.state != 1:
|
|
raise RuntimeError("Lock not acquired")
|
|
if self.waiting.peek():
|
|
# Task(s) waiting on lock, schedule next Task
|
|
self.state = self.waiting.pop_head()
|
|
core._task_queue.push_head(self.state)
|
|
else:
|
|
# No Task waiting so unlock
|
|
self.state = 0
|
|
|
|
async def acquire(self):
|
|
if self.state != 0:
|
|
# Lock unavailable, put the calling Task on the waiting queue
|
|
self.waiting.push_head(core.cur_task)
|
|
# Set calling task's data to the lock's queue so it can be removed if needed
|
|
core.cur_task.data = self.waiting
|
|
try:
|
|
yield
|
|
except core.CancelledError as er:
|
|
if self.state == core.cur_task:
|
|
# Cancelled while pending on resume, schedule next waiting Task
|
|
self.state = 1
|
|
self.release()
|
|
raise er
|
|
# Lock available, set it as locked
|
|
self.state = 1
|
|
return True
|
|
|
|
async def __aenter__(self):
|
|
return await self.acquire()
|
|
|
|
async def __aexit__(self, exc_type, exc, tb):
|
|
return self.release()
|