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# Copyright 1999-2011 Gentoo Foundation
# Distributed under the terms of the GNU General Public License v2
import errno
import logging
import os
from portage.util import writemsg_level
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 isAlive(self):
return bool(self._registered)
def _read_buf(self, fd, event):
"""
| POLLIN | RETURN
| BIT | VALUE
| ---------------------------------------------------
| 1 | Read self._bufsize into a string of bytes,
| | handling EAGAIN and EIO. An empty string
| | of bytes indicates EOF.
| ---------------------------------------------------
| 0 | None
"""
# NOTE: array.fromfile() is no longer used here because it has
# bugs in all known versions of Python (including Python 2.7
# and Python 3.2).
buf = None
if event & PollConstants.POLLIN:
try:
buf = os.read(fd, self._bufsize)
except OSError as e:
# EIO happens with pty on Linux after the
# slave end of the pty has been closed.
if e.errno == errno.EIO:
# EOF: return empty string of bytes
buf = b''
elif e.errno == errno.EAGAIN:
# EAGAIN: return None
buf = None
else:
raise
return buf
def _unregister(self):
raise NotImplementedError(self)
def _log_poll_exception(self, event):
writemsg_level(
"!!! %s received strange poll event: %s\n" % \
(self.__class__.__name__, event,),
level=logging.ERROR, noiselevel=-1)
def _unregister_if_appropriate(self, event):
if self._registered:
if event & self._exceptional_events:
self._log_poll_exception(event)
self._unregister()
self.cancel()
elif event & PollConstants.POLLHUP:
self._unregister()
self.wait()
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