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140 lines
4.3 KiB
Python
140 lines
4.3 KiB
Python
#!/usr/bin/python3
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# -*- coding: utf-8 -*-
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# key-mapper - GUI for device specific keyboard mappings
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# Copyright (C) 2021 sezanzeb <proxima@sezanzeb.de>
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#
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# This file is part of key-mapper.
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#
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# key-mapper 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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# key-mapper 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 key-mapper. If not, see <https://www.gnu.org/licenses/>.
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"""Named bidirectional non-blocking pipes.
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>>> p1 = Pipe('foo')
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>>> p2 = Pipe('foo')
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>>> p1.send(1)
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>>> p2.poll()
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>>> p2.recv()
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>>> p2.send(2)
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>>> p1.poll()
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>>> p1.recv()
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Beware that pipes read any available messages,
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even those written by themselves.
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"""
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import os
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import time
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import json
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from keymapper.logger import logger
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from keymapper.paths import mkdir, chown
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class Pipe:
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"""Pipe object."""
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def __init__(self, path):
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"""Create a pipe, or open it if it already exists."""
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self._path = path
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self._unread = []
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self._created_at = time.time()
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paths = (f"{path}r", f"{path}w")
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mkdir(os.path.dirname(path))
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if not os.path.exists(paths[0]):
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logger.spam('Creating new pipe for "%s"', path)
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# The fd the link points to is closed, or none ever existed
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# If there is a link, remove it.
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if os.path.islink(paths[0]):
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os.remove(paths[0])
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if os.path.islink(paths[1]):
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os.remove(paths[1])
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self._fds = os.pipe()
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fds_dir = f"/proc/{os.getpid()}/fd/"
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chown(f"{fds_dir}{self._fds[0]}")
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chown(f"{fds_dir}{self._fds[1]}")
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# to make it accessible by path constants, create symlinks
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os.symlink(f"{fds_dir}{self._fds[0]}", paths[0])
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os.symlink(f"{fds_dir}{self._fds[1]}", paths[1])
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else:
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logger.spam('Using existing pipe for "%s"', path)
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# thanks to os.O_NONBLOCK, readline will return b'' when there
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# is nothing to read
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self._fds = (
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os.open(paths[0], os.O_RDONLY | os.O_NONBLOCK),
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os.open(paths[1], os.O_WRONLY | os.O_NONBLOCK),
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)
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self._handles = (open(self._fds[0], "r"), open(self._fds[1], "w"))
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def recv(self):
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"""Read an object from the pipe or None if nothing available.
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Doesn't transmit pickles, to avoid injection attacks on the
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privileged helper. Only messages that can be converted to json
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are allowed.
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"""
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if len(self._unread) > 0:
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return self._unread.pop(0)
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line = self._handles[0].readline()
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if len(line) == 0:
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return None
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parsed = json.loads(line)
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if parsed[0] < self._created_at and os.environ.get("UNITTEST"):
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# important to avoid race conditions between multiple unittests,
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# for example old terminate messages reaching a new instance of
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# the helper.
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logger.spam("Ignoring old message %s", parsed)
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return None
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return parsed[1]
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def send(self, message):
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"""Write an object to the pipe."""
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dump = json.dumps((time.time(), message))
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# there aren't any newlines supposed to be,
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# but if there are it breaks readline().
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self._handles[1].write(dump.replace("\n", ""))
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self._handles[1].write("\n")
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self._handles[1].flush()
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def poll(self):
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"""Check if there is anything that can be read."""
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if len(self._unread) > 0:
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return True
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# using select.select apparently won't mark the pipe as ready
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# anymore when there are multiple lines to read but only a single
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# line is retreived. Using read instead.
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msg = self.recv()
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if msg is not None:
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self._unread.append(msg)
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return len(self._unread) > 0
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def fileno(self):
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"""Compatibility to select.select"""
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return self._handles[0].fileno()
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