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"File-based cache backend"
import md5
import os, time
try:
import cPickle as pickle
except ImportError:
import pickle
from django.core.cache.backends.base import BaseCache
class CacheClass(BaseCache):
def __init__(self, dir, params):
BaseCache.__init__(self, params)
max_entries = params.get('max_entries', 300)
try:
self._max_entries = int(max_entries)
except (ValueError, TypeError):
self._max_entries = 300
cull_frequency = params.get('cull_frequency', 3)
try:
self._cull_frequency = int(cull_frequency)
except (ValueError, TypeError):
self._cull_frequency = 3
self._dir = dir
if not os.path.exists(self._dir):
self._createdir()
def add(self, key, value, timeout=None):
if self.has_key(key):
return None
self.set(key, value, timeout)
def get(self, key, default=None):
fname = self._key_to_file(key)
try:
f = open(fname, 'rb')
exp = pickle.load(f)
now = time.time()
if exp < now:
f.close()
self._delete(fname)
else:
return pickle.load(f)
except (IOError, OSError, EOFError, pickle.PickleError):
pass
return default
def set(self, key, value, timeout=None):
fname = self._key_to_file(key)
dirname = os.path.dirname(fname)
if timeout is None:
timeout = self.default_timeout
self._cull()
try:
if not os.path.exists(dirname):
os.makedirs(dirname)
f = open(fname, 'wb')
now = time.time()
pickle.dump(now + timeout, f, pickle.HIGHEST_PROTOCOL)
pickle.dump(value, f, pickle.HIGHEST_PROTOCOL)
except (IOError, OSError):
pass
def delete(self, key):
try:
self._delete(self._key_to_file(key))
except (IOError, OSError):
pass
def _delete(self, fname):
os.remove(fname)
try:
# Remove the 2 subdirs if they're empty
dirname = os.path.dirname(fname)
os.rmdir(dirname)
os.rmdir(os.path.dirname(dirname))
except (IOError, OSError):
pass
def has_key(self, key):
fname = self._key_to_file(key)
try:
f = open(fname, 'rb')
exp = pickle.load(f)
now = time.time()
if exp < now:
f.close()
self._delete(fname)
return False
else:
return True
except (IOError, OSError, EOFError, pickle.PickleError):
return False
def _cull(self):
if int(self._num_entries) < self._max_entries:
return
try:
filelist = os.listdir(self._dir)
except (IOError, OSError):
return
if self._cull_frequency == 0:
doomed = filelist
else:
doomed = [os.path.join(self._dir, k) for (i, k) in enumerate(filelist) if i % self._cull_frequency == 0]
for topdir in doomed:
try:
for root, _, files in os.walk(topdir):
for f in files:
self._delete(os.path.join(root, f))
except (IOError, OSError):
pass
def _createdir(self):
try:
os.makedirs(self._dir)
except OSError:
raise EnvironmentError, "Cache directory '%s' does not exist and could not be created'" % self._dir
def _key_to_file(self, key):
"""
Convert the filename into an md5 string. We'll turn the first couple
bits of the path into directory prefixes to be nice to filesystems
that have problems with large numbers of files in a directory.
Thus, a cache key of "foo" gets turnned into a file named
``{cache-dir}ac/bd/18db4cc2f85cedef654fccc4a4d8``.
"""
path = md5.new(key.encode('utf-8')).hexdigest()
path = os.path.join(path[:2], path[2:4], path[4:])
return os.path.join(self._dir, path)
def _get_num_entries(self):
count = 0
for _,_,files in os.walk(self._dir):
count += len(files)
return count
_num_entries = property(_get_num_entries)
|
