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123 lines
3.8 KiB
Python
123 lines
3.8 KiB
Python
# -*- coding: utf-8 -*-
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# input-remapper - GUI for device specific keyboard mappings
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# Copyright (C) 2023 sezanzeb <proxima@sezanzeb.de>
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#
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# This file is part of input-remapper.
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#
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# input-remapper is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# input-remapper is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with input-remapper. If not, see <https://www.gnu.org/licenses/>.
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"""Share a dictionary across processes."""
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import atexit
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import multiprocessing
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import select
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from typing import Optional, Any
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from inputremapper.logger import logger
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class SharedDict:
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"""Share a dictionary across processes."""
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# because unittests terminate all child processes in cleanup I can't use
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# multiprocessing.Manager
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def __init__(self):
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"""Create a shared dictionary."""
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super().__init__()
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# To avoid blocking forever if something goes wrong. The maximum
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# observed time communication takes was 0.001 for me on a slow pc
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self._timeout = 0.02
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self.pipe = multiprocessing.Pipe()
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self.process = None
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atexit.register(self._stop)
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def start(self):
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"""Ensure the process to manage the dictionary is running."""
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if self.process is not None and self.process.is_alive():
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logger.debug("SharedDict process already running")
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return
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# if the manager has already been running in the past but stopped
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# for some reason, the dictionary contents are lost.
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logger.debug("Starting SharedDict process")
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self.process = multiprocessing.Process(target=self.manage)
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self.process.start()
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def manage(self):
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"""Manage the dictionary, handle read and write requests."""
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logger.debug("SharedDict process started")
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shared_dict = {}
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while True:
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message = self.pipe[0].recv()
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logger.debug("SharedDict got %s", message)
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if message[0] == "stop":
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return
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if message[0] == "set":
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shared_dict[message[1]] = message[2]
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if message[0] == "clear":
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shared_dict.clear()
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if message[0] == "get":
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self.pipe[0].send(shared_dict.get(message[1]))
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if message[0] == "ping":
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self.pipe[0].send("pong")
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def _stop(self):
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"""Stop the managing process."""
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self.pipe[1].send(("stop",))
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def _clear(self):
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"""Clears the memory."""
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self.pipe[1].send(("clear",))
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def get(self, key: str):
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"""Get a value from the dictionary.
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If it doesn't exist, returns None.
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"""
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return self[key]
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def is_alive(self, timeout: Optional[int] = None):
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"""Check if the manager process is running."""
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self.pipe[1].send(("ping",))
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select.select([self.pipe[1]], [], [], timeout or self._timeout)
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if self.pipe[1].poll():
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return self.pipe[1].recv() == "pong"
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return False
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def __setitem__(self, key: str, value: Any):
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self.pipe[1].send(("set", key, value))
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def __getitem__(self, key: str):
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self.pipe[1].send(("get", key))
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select.select([self.pipe[1]], [], [], self._timeout)
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if self.pipe[1].poll():
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return self.pipe[1].recv()
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logger.error("select.select timed out")
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return None
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def __del__(self):
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self._stop()
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