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# BSD LICENSE
#
# Copyright(c) 2010-2014 Intel Corporation. All rights reserved.
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# * Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# * Redistributions in binary form must reproduce the above copyright
# notice, this list of conditions and the following disclaimer in
# the documentation and/or other materials provided with the
# distribution.
# * Neither the name of Intel Corporation nor the names of its
# contributors may be used to endorse or promote products derived
# from this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
"""
Wrapper class for serializer module
"""
import os
import pickle
class Singleton(type):
_instances = {}
def __call__(self, *args, **kwargs):
if self not in self._instances:
self._instances[self] = \
super(Singleton, self).__call__(*args, **kwargs)
return self._instances[self]
class Serializer(object):
"""
Two-levels cache implementation for storing/retrieving any kind of object
using using a key-value model. It uses the pickle module to store objects
into a file.
This class implements the Singleton pattern. Everytime its constructor
is called it will return a reference to the same instance.
"""
__metaclass__ = Singleton
def __init__(self):
self.volatile_cache = {}
self.filename = 'serializer.cache'
def save(self, object_name, object_to_save):
"""
Saves an object into the volatile dictionary cache - which
resides in memory.
"""
self.volatile_cache[object_name] = object_to_save
def load(self, object_name):
"""
Loads and returns an object from the volatile cache.
"""
return self.volatile_cache.get(object_name, None)
def set_serialized_filename(self, filename):
"""
Sets the name of the non-volatile cache file to be used in the future
"""
self.filename = filename
def save_to_file(self):
"""
Saves the volatile cache to a file (non-volatile) using the pickle
module. Returns True in case everything went OK, False otherwise.
"""
try:
serialized_file = open(self.filename, 'w')
pickle.dump(self.volatile_cache, serialized_file)
serialized_file.close()
return True
except:
return False
def load_from_file(self):
"""
Reads from a pickle-like file using pickle module and populates the
volatile cache. Returns True in case everything went OK, False
otherwise.
"""
try:
serialized_file = open(self.filename, 'r')
self.volatile_cache = pickle.load(serialized_file)
serialized_file.close()
return True
except:
self.volatile_cache.clear()
return False
def discard_cache(self):
"""
Discards both volatile and non-volatile cache.
"""
self.volatile_cache.clear()
if os.path.exists(self.filename):
os.remove(self.filename)
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