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bazarr/libs/dogpile/cache/backends/memory.py

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3.5 KiB

"""
Memory Backends
---------------
Provides simple dictionary-based backends.
The two backends are :class:`.MemoryBackend` and :class:`.MemoryPickleBackend`;
the latter applies a serialization step to cached values while the former
places the value as given into the dictionary.
"""
from ..api import CacheBackend, NO_VALUE
from ...util.compat import pickle
class MemoryBackend(CacheBackend):
"""A backend that uses a plain dictionary.
There is no size management, and values which
are placed into the dictionary will remain
until explicitly removed. Note that
Dogpile's expiration of items is based on
timestamps and does not remove them from
the cache.
E.g.::
from dogpile.cache import make_region
region = make_region().configure(
'dogpile.cache.memory'
)
To use a Python dictionary of your choosing,
it can be passed in with the ``cache_dict``
argument::
my_dictionary = {}
region = make_region().configure(
'dogpile.cache.memory',
arguments={
"cache_dict":my_dictionary
}
)
"""
pickle_values = False
def __init__(self, arguments):
self._cache = arguments.pop("cache_dict", {})
def get(self, key):
value = self._cache.get(key, NO_VALUE)
if value is not NO_VALUE and self.pickle_values:
value = pickle.loads(value)
return value
def get_multi(self, keys):
ret = [
self._cache.get(key, NO_VALUE)
for key in keys]
if self.pickle_values:
ret = [
pickle.loads(value)
if value is not NO_VALUE else value
for value in ret
]
return ret
def set(self, key, value):
if self.pickle_values:
value = pickle.dumps(value, pickle.HIGHEST_PROTOCOL)
self._cache[key] = value
def set_multi(self, mapping):
pickle_values = self.pickle_values
for key, value in mapping.items():
if pickle_values:
value = pickle.dumps(value, pickle.HIGHEST_PROTOCOL)
self._cache[key] = value
def delete(self, key):
self._cache.pop(key, None)
def delete_multi(self, keys):
for key in keys:
self._cache.pop(key, None)
class MemoryPickleBackend(MemoryBackend):
"""A backend that uses a plain dictionary, but serializes objects on
:meth:`.MemoryBackend.set` and deserializes :meth:`.MemoryBackend.get`.
E.g.::
from dogpile.cache import make_region
region = make_region().configure(
'dogpile.cache.memory_pickle'
)
The usage of pickle to serialize cached values allows an object
as placed in the cache to be a copy of the original given object, so
that any subsequent changes to the given object aren't reflected
in the cached value, thus making the backend behave the same way
as other backends which make use of serialization.
The serialization is performed via pickle, and incurs the same
performance hit in doing so as that of other backends; in this way
the :class:`.MemoryPickleBackend` performance is somewhere in between
that of the pure :class:`.MemoryBackend` and the remote server oriented
backends such as that of Memcached or Redis.
Pickle behavior here is the same as that of the Redis backend, using
either ``cPickle`` or ``pickle`` and specifying ``HIGHEST_PROTOCOL``
upon serialize.
.. versionadded:: 0.5.3
"""
pickle_values = True