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