# -*- coding: utf-8 -*-
# Copyright (C) 2013 Sebastian Wiesner <[email protected]>
# This library is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by the
# Free Software Foundation; either version 2.1 of the License, or (at your
# option) any later version.
# This library is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
# for more details.
# You should have received a copy of the GNU Lesser General Public License
# along with this library; if not, write to the Free Software Foundation,
# Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
"""
pyudev._os.poll
===============
Operating system interface for pyudev.
.. moduleauthor:: Sebastian Wiesner <[email protected]>
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
from __future__ import unicode_literals
import select
from pyudev._util import eintr_retry_call
class Poll(object):
"""A poll object.
This object essentially provides a more convenient interface around
:class:`select.poll`.
"""
_EVENT_TO_MASK = {'r': select.POLLIN,
'w': select.POLLOUT}
@staticmethod
def _has_event(events, event):
return events & event != 0
@classmethod
def for_events(cls, *events):
"""Listen for ``events``.
``events`` is a list of ``(fd, event)`` pairs, where ``fd`` is a file
descriptor or file object and ``event`` either ``'r'`` or ``'w'``. If
``r``, listen for whether that is ready to be read. If ``w``, listen
for whether the channel is ready to be written to.
"""
notifier = eintr_retry_call(select.poll)
for fd, event in events:
mask = cls._EVENT_TO_MASK.get(event)
if not mask:
raise ValueError('Unknown event type: {0!r}'.format(event))
notifier.register(fd, mask)
return cls(notifier)
def __init__(self, notifier):
"""Create a poll object for the given ``notifier``.
``notifier`` is the :class:`select.poll` object wrapped by the new poll
object.
"""
self._notifier = notifier
def poll(self, timeout=None):
"""Poll for events.
``timeout`` is an integer specifying how long to wait for events (in
milliseconds). If omitted, ``None`` or negative, wait until an event
occurs.
Return a list of all events that occurred before ``timeout``, where
each event is a pair ``(fd, event)``. ``fd`` is the integral file
descriptor, and ``event`` a string indicating the event type. If
``'r'``, there is data to read from ``fd``. If ``'w'``, ``fd`` is
writable without blocking now. If ``'h'``, the file descriptor was
hung up (i.e. the remote side of a pipe was closed).
"""
# Return a list to allow clients to determine whether there are any
# events at all with a simple truthiness test.
return list(self._parse_events(eintr_retry_call(self._notifier.poll, timeout)))
def _parse_events(self, events):
"""Parse ``events``.
``events`` is a list of events as returned by
:meth:`select.poll.poll()`.
Yield all parsed events.
"""
for fd, event_mask in events:
if self._has_event(event_mask, select.POLLNVAL):
raise IOError('File descriptor not open: {0!r}'.format(fd))
elif self._has_event(event_mask, select.POLLERR):
raise IOError('Error while polling fd: {0!r}'.format(fd))
if self._has_event(event_mask, select.POLLIN):
yield fd, 'r'
if self._has_event(event_mask, select.POLLOUT):
yield fd, 'w'
if self._has_event(event_mask, select.POLLHUP):
yield fd, 'h'