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"""A simple object database. As long as the server is not running in
multiprocess mode that's good enough.
"""
import dbm
from pickle import dumps
from pickle import loads
from threading import Lock
class Database:
def __init__(self, filename):
self.filename = filename
self._fs = dbm.open(filename, "cf")
self._local = {}
self._lock = Lock()
def __getitem__(self, key):
with self._lock:
return self._load_key(key)
def _load_key(self, key):
if key in self._local:
return self._local[key]
rv = loads(self._fs[key])
self._local[key] = rv
return rv
def __setitem__(self, key, value):
self._local[key] = value
def __delitem__(self, key):
with self._lock:
self._local.pop(key, None)
if key in self._fs:
del self._fs[key]
def __del__(self):
self.close()
def __contains__(self, key):
with self._lock:
try:
self._load_key(key)
except KeyError:
pass
return key in self._local
def setdefault(self, key, factory):
with self._lock:
try:
rv = self._load_key(key)
except KeyError:
self._local[key] = rv = factory()
return rv
def sync(self):
with self._lock:
for key, value in self._local.items():
self._fs[key] = dumps(value, 2)
self._fs.sync()
def close(self):
try:
self.sync()
self._fs.close()
except Exception:
pass
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