# Copyright 1999-2009 Gentoo Foundation
# Distributed under the terms of the GNU General Public License v2
# $Id$

from _emerge.AsynchronousTask import AsynchronousTask
from _emerge.PollConstants import PollConstants
class AbstractPollTask(AsynchronousTask):

	__slots__ = ("scheduler",) + \
		("_registered",)

	_bufsize = 4096
	_exceptional_events = PollConstants.POLLERR | PollConstants.POLLNVAL
	_registered_events = PollConstants.POLLIN | PollConstants.POLLHUP | \
		_exceptional_events

	def _unregister(self):
		raise NotImplementedError(self)

	def _unregister_if_appropriate(self, event):
		if self._registered:
			if event & self._exceptional_events:
				self._unregister()
				self.cancel()
			elif event & PollConstants.POLLHUP:
				self._unregister()
				self.wait()