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# >>sys.stderr, This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at https://mozilla.org/MPL/2.0/.
'''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 as 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 as 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 as 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("{0} exists but stat() failed: {1}"
.format(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("{0} has been locked for more than "
"{1} seconds (PID {2})".format(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("{0}\n".format(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 given item as next item in the iteration.
'''
def __init__(self, iterable):
self.it = iter(iterable)
self.pushed_back = []
def __iter__(self):
return self
def __bool__(self):
if self.pushed_back:
return True
try:
self.pushed_back.insert(0, next(self.it))
except StopIteration:
return False
else:
return True
def __next__(self):
if self.pushed_back:
return self.pushed_back.pop()
return next(self.it)
def pushback(self, item):
self.pushed_back.append(item)
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