96 lines
3.0 KiB
Python
96 lines
3.0 KiB
Python
import asyncio
|
|
from contextlib import suppress
|
|
|
|
|
|
class AsyncLink:
|
|
"""Facilitate two-way connection between asyncio and a worker thread."""
|
|
|
|
def __init__(self):
|
|
"""Initialize; must be called from async context."""
|
|
self.loop = asyncio.get_running_loop()
|
|
self.queue = asyncio.Queue(maxsize=1)
|
|
|
|
async def __call__(self, command) -> asyncio.Future:
|
|
"""Run command in worker thread; awaitable.
|
|
|
|
Args:
|
|
command: Command to run in worker thread.
|
|
"""
|
|
fut = self.loop.create_future()
|
|
await self.queue.put((command, fut))
|
|
return await fut
|
|
|
|
@property
|
|
def to_sync(self):
|
|
"""Yield SyncRequests from async caller when called from worker thread."""
|
|
while (req := self._await(self._get())) is not None:
|
|
yield SyncRequest(self, req)
|
|
|
|
async def _get(self):
|
|
"""Retrieve an item from the queue; handle cancellation."""
|
|
with suppress(asyncio.CancelledError):
|
|
ret = await self.queue.get()
|
|
self.queue.task_done()
|
|
return ret
|
|
|
|
def _await(self, coro):
|
|
"""Run coroutine in main thread and return result; called from worker."""
|
|
return asyncio.run_coroutine_threadsafe(coro, self.loop).result()
|
|
|
|
async def stop(self):
|
|
"""Stop worker and clean up."""
|
|
while not self.queue.empty():
|
|
command, future = self.queue.get_nowait()
|
|
if not future.done():
|
|
future.set_exception(Exception("AsyncLink stopped"))
|
|
self.queue.task_done()
|
|
await self.queue.put(None)
|
|
|
|
|
|
async def set_result(fut: asyncio.Future, value=None, exception=None):
|
|
"""Set result or exception on an asyncio.Future object.
|
|
|
|
Args:
|
|
fut (asyncio.Future): Future to set result or exception on.
|
|
value: Result to set on the future.
|
|
exception: Exception to set on the future.
|
|
"""
|
|
with suppress(asyncio.InvalidStateError):
|
|
if exception is None:
|
|
fut.set_result(value)
|
|
else:
|
|
fut.set_exception(exception)
|
|
|
|
|
|
class SyncRequest:
|
|
"""Handle values from sync thread in main asyncio event loop."""
|
|
|
|
def __init__(self, alink: AsyncLink, req):
|
|
"""Initialize SyncRequest with AsyncLink and request."""
|
|
self.alink = alink
|
|
self.command, self.future = req
|
|
self.done = False
|
|
|
|
def __enter__(self):
|
|
"""Provide command to with-block and handle exceptions."""
|
|
return self.command
|
|
|
|
def __exit__(self, exc_type, exc, traceback):
|
|
"""Set result or exception on exit; suppress exceptions in with-block."""
|
|
if exc:
|
|
self.set_exception(exc)
|
|
return True
|
|
if not self.done:
|
|
self.set_result(None)
|
|
return None
|
|
|
|
def set_result(self, value):
|
|
"""Set result value; mark as done."""
|
|
self.done = True
|
|
self.alink._await(set_result(self.future, value))
|
|
|
|
def set_exception(self, exc):
|
|
"""Set exception; mark as done."""
|
|
self.done = True
|
|
self.alink._await(set_result(self.future, exception=exc))
|