gecko/config/utils.py

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# ***** BEGIN LICENSE BLOCK *****
# Version: MPL 1.1/GPL 2.0/LGPL 2.1
#
# The contents of this file are subject to the Mozilla Public License Version
# 1.1 (the "License"); you may not use this file except in compliance with
# the License. You may obtain a copy of the License at
# http://www.mozilla.org/MPL/
#
# Software distributed under the License is distributed on an "AS IS" basis,
# WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
# for the specific language governing rights and limitations under the
# License.
#
# The Original Code is Mozilla build system.
#
# The Initial Developer of the Original Code is
# Mozilla Foundation.
# Portions created by the Initial Developer are Copyright (C) 2008
# the Initial Developer. All Rights Reserved.
#
# Contributor(s):
# Axel Hecht <axel@pike.org>
#
# Alternatively, the contents of this file may be used under the terms of
# either the GNU General Public License Version 2 or later (the "GPL"), or
# the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
# in which case the provisions of the GPL or the LGPL are applicable instead
# of those above. If you wish to allow use of your version of this file only
# under the terms of either the GPL or the LGPL, and not to allow others to
# use your version of this file under the terms of the MPL, indicate your
# decision by deleting the provisions above and replace them with the notice
# and other provisions required by the GPL or the LGPL. If you do not delete
# the provisions above, a recipient may use your version of this file under
# the terms of any one of the MPL, the GPL or the LGPL.
#
# ***** END LICENSE BLOCK *****
'''Utility methods to be used by python build infrastructure.
'''
import os
import errno
import sys
import time
import stat
class LockFile(object):
'''LockFile is used by the lockFile method to hold the lock.
This object should not be used directly, but only through
the lockFile method below.
'''
def __init__(self, lockfile):
self.lockfile = lockfile
def __del__(self):
while True:
try:
os.remove(self.lockfile)
break
except OSError, e:
if e.errno == errno.EACCES:
# another process probably has the file open, we'll retry.
# just a short sleep since we want to drop the lock ASAP
# (but we need to let some other process close the file first)
time.sleep(0.1)
else:
# re-raise unknown errors
raise
def lockFile(lockfile, max_wait = 600):
'''Create and hold a lockfile of the given name, with the given timeout.
To release the lock, delete the returned object.
'''
while True:
try:
fd = os.open(lockfile, os.O_EXCL | os.O_RDWR | os.O_CREAT)
# we created the lockfile, so we're the owner
break
except OSError, e:
if e.errno == errno.EEXIST or \
(sys.platform == "win32" and e.errno == errno.EACCES):
pass
else:
# should not occur
raise
try:
# the lock file exists, try to stat it to get its age
# and read its contents to report the owner PID
f = open(lockfile, "r")
s = os.stat(lockfile)
except EnvironmentError, e:
if e.errno == errno.ENOENT or e.errno == errno.EACCES:
# we didn't create the lockfile, so it did exist, but it's
# gone now. Just try again
continue
sys.exit("%s exists but stat() failed: %s" %
(lockfile, e.strerror))
# we didn't create the lockfile and it's still there, check
# its age
now = int(time.time())
if now - s[stat.ST_MTIME] > max_wait:
pid = f.readline().rstrip()
sys.exit("%s has been locked for more than " \
"%d seconds (PID %s)" % (lockfile, max_wait,
pid))
# it's not been locked too long, wait a while and retry
f.close()
time.sleep(1)
# if we get here. we have the lockfile. Convert the os.open file
# descriptor into a Python file object and record our PID in it
f = os.fdopen(fd, "w")
f.write("%d\n" % os.getpid())
f.close()
return LockFile(lockfile)
class pushback_iter(object):
'''Utility iterator that can deal with pushed back elements.
This behaves like a regular iterable, just that you can call
iter.pushback(item)
to get the givem item as next item in the iteration.
'''
def __init__(self, iterable):
self.it = iter(iterable)
self.pushed_back = []
def __iter__(self):
return self
def __nonzero__(self):
if self.pushed_back:
return True
try:
self.pushed_back.insert(0, self.it.next())
except StopIteration:
return False
else:
return True
def next(self):
if self.pushed_back:
return self.pushed_back.pop()
return self.it.next()
def pushback(self, item):
self.pushed_back.append(item)