54 lines
1.7 KiB
Python
54 lines
1.7 KiB
Python
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# MicroPython uasyncio module
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# MIT license; Copyright (c) 2019-2020 Damien P. George
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from . import core
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# Lock class for primitive mutex capability
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class Lock:
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def __init__(self):
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# The state can take the following values:
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# - 0: unlocked
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# - 1: locked
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# - <Task>: unlocked but this task has been scheduled to acquire the lock next
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self.state = 0
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# Queue of Tasks waiting to acquire this Lock
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self.waiting = core.TaskQueue()
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def locked(self):
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return self.state == 1
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def release(self):
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if self.state != 1:
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raise RuntimeError
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if self.waiting.peek():
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# Task(s) waiting on lock, schedule next Task
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self.state = self.waiting.pop_head()
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core._task_queue.push_head(self.state)
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else:
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# No Task waiting so unlock
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self.state = 0
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async def acquire(self):
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if self.state != 0:
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# Lock unavailable, put the calling Task on the waiting queue
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self.waiting.push_head(core.cur_task)
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# Set calling task's data to the lock's queue so it can be removed if needed
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core.cur_task.data = self.waiting
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try:
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yield
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except core.CancelledError as er:
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if self.state == core.cur_task:
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# Cancelled while pending on resume, schedule next waiting Task
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self.state = 1
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self.release()
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raise er
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# Lock available, set it as locked
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self.state = 1
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return True
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async def __aenter__(self):
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return await self.acquire()
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async def __aexit__(self, exc_type, exc, tb):
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return self.release()
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