mirror of
https://github.com/avatao-content/baseimage-tutorial-framework
synced 2024-11-15 04:17:16 +00:00
46 lines
1.2 KiB
Python
46 lines
1.2 KiB
Python
from os import remove
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from contextlib import contextmanager
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from fcntl import flock, LOCK_EX, LOCK_UN
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class RefCounter:
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def __init__(self, lockpath):
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self.lockpath = lockpath
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self._lockfile = open(self.lockpath, 'a+')
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with self.locked():
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counter = self._read_counter()
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self._write_counter(counter+1)
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@contextmanager
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def locked(self):
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flock(self._lockfile, LOCK_EX)
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yield
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flock(self._lockfile, LOCK_UN)
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def _read_counter(self):
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self._lockfile.seek(0)
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try:
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counter = int(self._lockfile.read())
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except ValueError:
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counter = 0
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return counter
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def _write_counter(self, counter):
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self._lockfile.seek(0)
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self._lockfile.truncate()
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self._lockfile.write(str(counter))
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self._lockfile.flush()
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def teardown_instance(self):
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with self.locked():
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counter = self._read_counter()
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if counter <= 1:
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remove(self.lockpath)
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self.deallocate()
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else:
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self._write_counter(counter-1)
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self._lockfile.close()
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def deallocate(self):
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pass
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