+# -*- coding: utf-8 -*-
+
+# Copyright (c) 2009 Evan Fosmark
+# Copyright (c) 2014 Jack Kaliko <kaliko@azylum.org>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+#
+
+# https://github.com/dmfrey/FileLock
+"""
+Plain file lock to une in context:
+ >>> with FileLock('/path/to/file/to/write'):
+ >>> # a lock file is maintain within the scope of this context:
+ >>> # /path/to/file/to/write.lock
+ >>> ... # process file writing
+"""
+
+import errno
+import os
+import time
+
+class FileLockException(Exception):
+ """FileLock Exception"""
+ pass
+
+class FileLock:
+ """ A plain file lock whit context-manager"""
+
+ def __init__(self, file_name, timeout=10, delay=.05):
+ """
+ Setup file lock.
+ Setup timeout and the delay.
+ """
+ self.filedsc = None
+ self.is_locked = False
+ dirname = os.path.dirname(file_name)
+ self.lockfile = os.path.join(dirname, '{0}.lock'.format(file_name))
+ self.file_name = file_name
+ self.timeout = timeout
+ self.delay = delay
+
+ def acquire(self):
+ """Acquire the lock, if possible.
+ """
+ start_time = time.time()
+ while True:
+ try:
+ self.filedsc = os.open(self.lockfile,
+ os.O_CREAT|os.O_EXCL|os.O_RDWR)
+ break
+ except OSError as err:
+ if err.errno != errno.EEXIST:
+ raise
+ if (time.time() - start_time) >= self.timeout:
+ raise FileLockException('Timeout occured.')
+ time.sleep(self.delay)
+ self.is_locked = True
+
+ def release(self):
+ """Release the lock.
+ """
+ if self.is_locked:
+ os.close(self.filedsc)
+ os.unlink(self.lockfile)
+ self.is_locked = False
+
+ def __enter__(self):
+ """start of the with statement.
+ """
+ if not self.is_locked:
+ self.acquire()
+ return self
+
+ def __exit__(self, type, value, traceback):
+ """end of the with statement
+ """
+ if self.is_locked:
+ self.release()
+
+ def __del__(self):
+ """Cleanup
+ """
+ self.release()
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