/usr/share/pyshared/ClusterShell/Engine/Select.py is in clustershell 1.6-4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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# Copyright CEA/DAM/DIF (2009, 2010, 2011)
# Contributors:
# Henri DOREAU <henri.doreau@gmail.com>
# Aurelien DEGREMONT <aurelien.degremont@cea.fr>
# Stephane THIELL <stephane.thiell@cea.fr>
#
# This file is part of the ClusterShell library.
#
# This software is governed by the CeCILL-C license under French law and
# abiding by the rules of distribution of free software. You can use,
# modify and/ or redistribute the software under the terms of the CeCILL-C
# license as circulated by CEA, CNRS and INRIA at the following URL
# "http://www.cecill.info".
#
# As a counterpart to the access to the source code and rights to copy,
# modify and redistribute granted by the license, users are provided only
# with a limited warranty and the software's author, the holder of the
# economic rights, and the successive licensors have only limited
# liability.
#
# In this respect, the user's attention is drawn to the risks associated
# with loading, using, modifying and/or developing or reproducing the
# software by the user in light of its specific status of free software,
# that may mean that it is complicated to manipulate, and that also
# therefore means that it is reserved for developers and experienced
# professionals having in-depth computer knowledge. Users are therefore
# encouraged to load and test the software's suitability as regards their
# requirements in conditions enabling the security of their systems and/or
# data to be ensured and, more generally, to use and operate it in the
# same conditions as regards security.
#
# The fact that you are presently reading this means that you have had
# knowledge of the CeCILL-C license and that you accept its terms.
"""
A select() based ClusterShell Engine.
The select() system call is available on almost every UNIX-like systems.
"""
import errno
import select
import sys
import time
from ClusterShell.Engine.Engine import Engine
from ClusterShell.Engine.Engine import EngineTimeoutException
from ClusterShell.Worker.EngineClient import EngineClientEOF
class EngineSelect(Engine):
"""
Select Engine
ClusterShell engine using the select.select mechanism
"""
identifier = "select"
def __init__(self, info):
"""
Initialize Engine.
"""
Engine.__init__(self, info)
self._fds_r = []
self._fds_w = []
def _register_specific(self, fd, event):
"""
Engine-specific fd registering. Called by Engine register.
"""
if event & (Engine.E_READ | Engine.E_ERROR):
self._fds_r.append(fd)
elif event & Engine.E_WRITE:
self._fds_w.append(fd)
def _unregister_specific(self, fd, ev_is_set):
"""
Engine-specific fd unregistering. Called by Engine unregister.
"""
if ev_is_set or True:
if fd in self._fds_r:
self._fds_r.remove(fd)
if fd in self._fds_w:
self._fds_w.remove(fd)
def _modify_specific(self, fd, event, setvalue):
"""
Engine-specific modifications after a interesting event change
for a file descriptor. Called automatically by Engine
register/unregister and set_events(). For the select() engine,
it appends/remove the fd to/from the concerned fd_sets.
"""
self._debug("MODSPEC fd=%d event=%x setvalue=%d" % (fd, event,
setvalue))
if setvalue:
self._register_specific(fd, event)
else:
self._unregister_specific(fd, True)
def runloop(self, timeout):
"""
Select engine run(): start clients and properly get replies
"""
if timeout == 0:
timeout = -1
start_time = time.time()
# run main event loop...
while self.evlooprefcnt > 0:
self._debug("LOOP evlooprefcnt=%d (reg_clifds=%s) (timers=%d)" %
(self.evlooprefcnt, self.reg_clifds.keys(), len(self.timerq)))
try:
timeo = self.timerq.nextfire_delay()
if timeout > 0 and timeo >= timeout:
# task timeout may invalidate clients timeout
self.timerq.clear()
timeo = timeout
elif timeo == -1:
timeo = timeout
self._current_loopcnt += 1
if timeo >= 0:
r_ready, w_ready, x_ready = \
select.select(self._fds_r, self._fds_w, [], timeo)
else:
# no timeout specified, do not supply the timeout argument
r_ready, w_ready, x_ready = \
select.select(self._fds_r, self._fds_w, [])
except select.error, (ex_errno, ex_strerror):
# might get interrupted by a signal
if ex_errno == errno.EINTR:
continue
elif ex_errno in [errno.EINVAL, errno.EBADF, errno.ENOMEM]:
print >> sys.stderr, "EngineSelect: %s" % ex_strerror
else:
raise
# iterate over fd on which events occured
for fd in set(r_ready) | set(w_ready):
# get client instance
client, fdev = self._fd2client(fd)
if client is None:
continue
# process this client
client._current_client = client
# check for possible unblocking read on this fd
if fd in r_ready:
assert fdev & (Engine.E_READ | Engine.E_ERROR)
assert client._events & fdev
self.modify(client, 0, fdev)
try:
if fdev & Engine.E_READ:
client._handle_read()
else:
client._handle_error()
except EngineClientEOF:
self._debug("EngineClientEOF %s" % client)
# if the EOF occurs on E_READ...
if fdev & Engine.E_READ:
# and if the client is also waiting for E_ERROR
if client._events & Engine.E_ERROR:
# just clear the event for E_READ
self.modify(client, 0, fdev)
else:
# otherwise we can remove the client
self.remove(client)
else:
# same thing in the other order...
if client._events & Engine.E_READ:
self.modify(client, 0, fdev)
else:
self.remove(client)
# check for writing
if fd in w_ready:
self._debug("W_READY fd=%d %s (r%s,e%s,w%s)" % (fd,
client.__class__.__name__, client.reader_fileno(),
client.error_fileno(), client.writer_fileno()))
assert fdev == Engine.E_WRITE
assert client._events & fdev
self.modify(client, 0, fdev)
client._handle_write()
# post processing
self._current_client = None
# apply any changes occured during processing
if client.registered:
self.set_events(client, client._new_events)
# check for task runloop timeout
if timeout > 0 and time.time() >= start_time + timeout:
raise EngineTimeoutException()
# process clients timeout
self.fire_timers()
self._debug("LOOP EXIT evlooprefcnt=%d (reg_clifds=%s) (timers=%d)" % \
(self.evlooprefcnt, self.reg_clifds, len(self.timerq)))
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