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# Copyright 2007 Google Inc.
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software Foundation,
# Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
"""Package level factory implementation for cache implementations.
We use a factory instead of relying on the __init__.py module to
register cache implementations at import time. This is much more
reliable.
"""
__author__ = "springer@google.com (Matthew Springer)"
import logging
from nss_cache.caches import files
_cache_implementations = {}
def RegisterImplementation(cache_name, map_name, cache):
"""Register a Cache implementation with the CacheFactory.
Child modules are expected to call this method in the file-level scope
so that the CacheFactory is aware of them.
Args:
cache_name: (string) The name of the NSS backend.
map_name: (string) The name of the map handled by this Cache.
cache: A class type that is a subclass of Cache.
Returns: Nothing
"""
global _cache_implementations
if cache_name not in _cache_implementations:
logging.info("Registering [%s] cache for [%s].", cache_name, map_name)
_cache_implementations[cache_name] = {}
_cache_implementations[cache_name][map_name] = cache
def Create(conf, map_name, automount_mountpoint=None):
"""Cache creation factory method.
Args:
conf: a dictionary of configuration key/value pairs, including one
required attribute 'name'
map_name: a string identifying the map name to handle
automount_mountpoint: A string containing the automount mountpoint, used only
by automount maps.
Returns:
an instance of a Cache
Raises:
RuntimeError: problem instantiating the requested cache
"""
global _cache_implementations
if not _cache_implementations:
raise RuntimeError("no cache implementations exist")
cache_name = conf["name"]
if cache_name not in _cache_implementations:
raise RuntimeError("cache not implemented: %r" % (cache_name,))
if map_name not in _cache_implementations[cache_name]:
raise RuntimeError("map %r not supported by cache %r" % (map_name, cache_name))
return _cache_implementations[cache_name][map_name](
conf, map_name, automount_mountpoint=automount_mountpoint
)
files.RegisterAllImplementations(RegisterImplementation)
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