# -*- coding: utf-8 -*-
import os
import re
import tempfile
from time import time
from .basecache import BaseCache
from .posixemulation import rename, _items
try:
import cPickle as pickle
except ImportError:
import pickle
try:
from hashlib import md5
except ImportError:
from md5 import new as md5
class MemCache(BaseCache):
"""Simple memory cache for single process environments. This class exists
mainly for the development server and is not 100% thread safe. It tries
to use as many atomic operations as possible and no locks for simplicity
but it could happen under heavy load that keys are added multiple times.
:param threshold: the maximum number of items the cache stores before
it starts deleting some.
:param default_timeout: the default timeout that is used if no timeout is
specified on :meth:`~BaseCache.set`.
"""
def __init__(self, threshold=500, default_timeout=300):
BaseCache.__init__(self, default_timeout)
self._cache = {}
self.clear = self._cache.clear
self._threshold = threshold
def _prune(self):
if len(self._cache) > self._threshold:
now = time()
for idx, (key, (expires, _)) in enumerate(self._cache.items()):
if expires <= now or idx % 3 == 0:
self._cache.pop(key, None)
def get(self, key):
now = time()
expires, value = self._cache.get(key, (0, None))
if expires > time():
return pickle.loads(value)
def set(self, key, value, timeout=None):
if timeout is None:
timeout = self.default_timeout
self._prune()
self._cache[key] = (time() + timeout, pickle.dumps(value,
pickle.HIGHEST_PROTOCOL))
def add(self, key, value, timeout=None):
if timeout is None:
timeout = self.default_timeout
if len(self._cache) > self._threshold:
self._prune()
item = (time() + timeout, pickle.dumps(value,
pickle.HIGHEST_PROTOCOL))
self._cache.setdefault(key, item)
def delete(self, key):
self._cache.pop(key, None)
