root / lib / utils / wrapper.py @ dbb4f850
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# Copyright (C) 2006, 2007, 2010, 2011, 2012 Google Inc.
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful, but
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# WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301, USA.
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"""Utility functions wrapping other functions.
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"""
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import sys |
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import time |
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import socket |
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import errno |
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import tempfile |
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import fcntl |
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import os |
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import select |
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import logging |
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def TestDelay(duration): |
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"""Sleep for a fixed amount of time.
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@type duration: float
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@param duration: the sleep duration
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@rtype: boolean
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@return: False for negative value, True otherwise
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"""
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if duration < 0: |
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return False, "Invalid sleep duration" |
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time.sleep(duration) |
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return True, None |
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def CloseFdNoError(fd, retries=5): |
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"""Close a file descriptor ignoring errors.
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@type fd: int
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@param fd: the file descriptor
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@type retries: int
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@param retries: how many retries to make, in case we get any
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other error than EBADF
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"""
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try:
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os.close(fd) |
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except OSError, err: |
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if err.errno != errno.EBADF:
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if retries > 0: |
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CloseFdNoError(fd, retries - 1)
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# else either it's closed already or we're out of retries, so we
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# ignore this and go on
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def SetCloseOnExecFlag(fd, enable): |
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"""Sets or unsets the close-on-exec flag on a file descriptor.
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@type fd: int
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@param fd: File descriptor
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@type enable: bool
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@param enable: Whether to set or unset it.
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"""
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flags = fcntl.fcntl(fd, fcntl.F_GETFD) |
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if enable:
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flags |= fcntl.FD_CLOEXEC |
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else:
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flags &= ~fcntl.FD_CLOEXEC |
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fcntl.fcntl(fd, fcntl.F_SETFD, flags) |
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def SetNonblockFlag(fd, enable): |
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"""Sets or unsets the O_NONBLOCK flag on on a file descriptor.
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@type fd: int
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@param fd: File descriptor
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@type enable: bool
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@param enable: Whether to set or unset it
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"""
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flags = fcntl.fcntl(fd, fcntl.F_GETFL) |
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if enable:
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flags |= os.O_NONBLOCK |
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else:
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flags &= ~os.O_NONBLOCK |
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fcntl.fcntl(fd, fcntl.F_SETFL, flags) |
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def RetryOnSignal(fn, *args, **kwargs): |
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"""Calls a function again if it failed due to EINTR.
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"""
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while True: |
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try:
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return fn(*args, **kwargs)
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except EnvironmentError, err: |
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if err.errno != errno.EINTR:
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raise
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except (socket.error, select.error), err:
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# In python 2.6 and above select.error is an IOError, so it's handled
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# above, in 2.5 and below it's not, and it's handled here.
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if not (err.args and err.args[0] == errno.EINTR): |
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raise
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def IgnoreProcessNotFound(fn, *args, **kwargs): |
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"""Ignores ESRCH when calling a process-related function.
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ESRCH is raised when a process is not found.
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@rtype: bool
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@return: Whether process was found
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"""
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try:
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fn(*args, **kwargs) |
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except EnvironmentError, err: |
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# Ignore ESRCH
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if err.errno == errno.ESRCH:
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return False |
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raise
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return True |
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def IgnoreSignals(fn, *args, **kwargs): |
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"""Tries to call a function ignoring failures due to EINTR.
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"""
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try:
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return fn(*args, **kwargs)
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except EnvironmentError, err: |
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if err.errno == errno.EINTR:
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return None |
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else:
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raise
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except (select.error, socket.error), err:
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# In python 2.6 and above select.error is an IOError, so it's handled
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# above, in 2.5 and below it's not, and it's handled here.
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if err.args and err.args[0] == errno.EINTR: |
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return None |
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else:
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raise
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def GetClosedTempfile(*args, **kwargs): |
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"""Creates a temporary file and returns its path.
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"""
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(fd, path) = tempfile.mkstemp(*args, **kwargs) |
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CloseFdNoError(fd) |
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return path
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def IsExecutable(filename): |
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"""Checks whether a file exists and is executable.
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@type filename: string
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@param filename: Filename
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@rtype: bool
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"""
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return os.path.isfile(filename) and os.access(filename, os.X_OK) |
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def ResetTempfileModule(_time=time.time): |
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"""Resets the random name generator of the tempfile module.
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This function should be called after C{os.fork} in the child process to
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ensure it creates a newly seeded random generator. Otherwise it would
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generate the same random parts as the parent process. If several processes
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race for the creation of a temporary file, this could lead to one not getting
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a temporary name.
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"""
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# pylint: disable=W0212
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if ((sys.hexversion >= 0x020703F0 and sys.hexversion < 0x03000000) or |
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sys.hexversion >= 0x030203F0):
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# Python 2.7 automatically resets the RNG on pid changes (i.e. forking)
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return
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try:
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lock = tempfile._once_lock |
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lock.acquire() |
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try:
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# Re-seed random name generator
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if tempfile._name_sequence:
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tempfile._name_sequence.rng.seed(hash(_time()) ^ os.getpid())
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finally:
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lock.release() |
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except AttributeError: |
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logging.critical("The tempfile module misses at least one of the"
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" '_once_lock' and '_name_sequence' attributes")
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