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|
"Thread-safe in-memory cache backend."
import time
try:
import cPickle as pickle
except ImportError:
import pickle
from django.core.cache.backends.base import BaseCache
from django.utils.synch import RWLock
# Global in-memory store of cache data. Keyed by name, to provide
# multiple named local memory caches.
_caches = {}
_expire_info = {}
_locks = {}
class LocMemCache(BaseCache):
def __init__(self, name, params):
BaseCache.__init__(self, params)
global _caches, _expire_info, _locks
self._cache = _caches.setdefault(name, {})
self._expire_info = _expire_info.setdefault(name, {})
self._lock = _locks.setdefault(name, RWLock())
def add(self, key, value, timeout=None, version=None):
key = self.make_key(key, version=version)
self.validate_key(key)
self._lock.writer_enters()
try:
exp = self._expire_info.get(key)
if exp is None or exp <= time.time():
try:
self._set(key, pickle.dumps(value), timeout)
return True
except pickle.PickleError:
pass
return False
finally:
self._lock.writer_leaves()
def get(self, key, default=None, version=None):
key = self.make_key(key, version=version)
self.validate_key(key)
self._lock.reader_enters()
try:
exp = self._expire_info.get(key)
if exp is None:
return default
elif exp > time.time():
try:
return pickle.loads(self._cache[key])
except pickle.PickleError:
return default
finally:
self._lock.reader_leaves()
self._lock.writer_enters()
try:
try:
del self._cache[key]
del self._expire_info[key]
except KeyError:
pass
return default
finally:
self._lock.writer_leaves()
def _set(self, key, value, timeout=None):
if len(self._cache) >= self._max_entries:
self._cull()
if timeout is None:
timeout = self.default_timeout
self._cache[key] = value
self._expire_info[key] = time.time() + timeout
def set(self, key, value, timeout=None, version=None):
key = self.make_key(key, version=version)
self.validate_key(key)
self._lock.writer_enters()
# Python 2.4 doesn't allow combined try-except-finally blocks.
try:
try:
self._set(key, pickle.dumps(value), timeout)
except pickle.PickleError:
pass
finally:
self._lock.writer_leaves()
def has_key(self, key, version=None):
key = self.make_key(key, version=version)
self.validate_key(key)
self._lock.reader_enters()
try:
exp = self._expire_info.get(key)
if exp is None:
return False
elif exp > time.time():
return True
finally:
self._lock.reader_leaves()
self._lock.writer_enters()
try:
try:
del self._cache[key]
del self._expire_info[key]
except KeyError:
pass
return False
finally:
self._lock.writer_leaves()
def _cull(self):
if self._cull_frequency == 0:
self.clear()
else:
doomed = [k for (i, k) in enumerate(self._cache) if i % self._cull_frequency == 0]
for k in doomed:
self._delete(k)
def _delete(self, key):
try:
del self._cache[key]
except KeyError:
pass
try:
del self._expire_info[key]
except KeyError:
pass
def delete(self, key, version=None):
key = self.make_key(key, version=version)
self.validate_key(key)
self._lock.writer_enters()
try:
self._delete(key)
finally:
self._lock.writer_leaves()
def clear(self):
self._cache.clear()
self._expire_info.clear()
# For backwards compatibility
class CacheClass(LocMemCache):
pass
|
