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121 lines
3.4 KiB
Python
121 lines
3.4 KiB
Python
# This Source Code Form is subject to the terms of the Mozilla Public
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# License, v. 2.0. If a copy of the MPL was not distributed with this
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# file, You can obtain one at http://mozilla.org/MPL/2.0/.
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'''Utility methods to be used by python build infrastructure.
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'''
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import os
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import errno
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import sys
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import time
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import stat
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class LockFile(object):
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'''LockFile is used by the lockFile method to hold the lock.
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This object should not be used directly, but only through
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the lockFile method below.
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'''
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def __init__(self, lockfile):
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self.lockfile = lockfile
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def __del__(self):
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while True:
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try:
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os.remove(self.lockfile)
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break
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except OSError, e:
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if e.errno == errno.EACCES:
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# another process probably has the file open, we'll retry.
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# just a short sleep since we want to drop the lock ASAP
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# (but we need to let some other process close the file first)
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time.sleep(0.1)
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else:
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# re-raise unknown errors
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raise
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def lockFile(lockfile, max_wait = 600):
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'''Create and hold a lockfile of the given name, with the given timeout.
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To release the lock, delete the returned object.
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'''
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while True:
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try:
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fd = os.open(lockfile, os.O_EXCL | os.O_RDWR | os.O_CREAT)
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# we created the lockfile, so we're the owner
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break
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except OSError, e:
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if e.errno == errno.EEXIST or \
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(sys.platform == "win32" and e.errno == errno.EACCES):
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pass
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else:
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# should not occur
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raise
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try:
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# the lock file exists, try to stat it to get its age
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# and read its contents to report the owner PID
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f = open(lockfile, "r")
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s = os.stat(lockfile)
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except EnvironmentError, e:
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if e.errno == errno.ENOENT or e.errno == errno.EACCES:
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# we didn't create the lockfile, so it did exist, but it's
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# gone now. Just try again
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continue
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sys.exit("%s exists but stat() failed: %s" %
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(lockfile, e.strerror))
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# we didn't create the lockfile and it's still there, check
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# its age
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now = int(time.time())
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if now - s[stat.ST_MTIME] > max_wait:
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pid = f.readline().rstrip()
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sys.exit("%s has been locked for more than " \
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"%d seconds (PID %s)" % (lockfile, max_wait,
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pid))
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# it's not been locked too long, wait a while and retry
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f.close()
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time.sleep(1)
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# if we get here. we have the lockfile. Convert the os.open file
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# descriptor into a Python file object and record our PID in it
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f = os.fdopen(fd, "w")
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f.write("%d\n" % os.getpid())
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f.close()
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return LockFile(lockfile)
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class pushback_iter(object):
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'''Utility iterator that can deal with pushed back elements.
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This behaves like a regular iterable, just that you can call
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iter.pushback(item)
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to get the givem item as next item in the iteration.
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'''
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def __init__(self, iterable):
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self.it = iter(iterable)
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self.pushed_back = []
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def __iter__(self):
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return self
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def __nonzero__(self):
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if self.pushed_back:
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return True
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try:
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self.pushed_back.insert(0, self.it.next())
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except StopIteration:
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return False
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else:
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return True
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def next(self):
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if self.pushed_back:
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return self.pushed_back.pop()
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return self.it.next()
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def pushback(self, item):
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self.pushed_back.append(item)
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