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# Copyright (c) 2011-2012 OpenStack Foundation
# All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
"""
Filter support
"""
from nova import loadables
from nova.openstack.common import log as logging
LOG = logging.getLogger(__name__)
class BaseFilter(object):
"""Base class for all filter classes."""
def _filter_one(self, obj, filter_properties):
"""Return True if it passes the filter, False otherwise.
Override this in a subclass.
"""
return True
def filter_all(self, filter_obj_list, filter_properties):
"""Yield objects that pass the filter.
Can be overriden in a subclass, if you need to base filtering
decisions on all objects. Otherwise, one can just override
_filter_one() to filter a single object.
"""
for obj in filter_obj_list:
if self._filter_one(obj, filter_properties):
yield obj
class BaseFilterHandler(loadables.BaseLoader):
"""Base class to handle loading filter classes.
This class should be subclassed where one needs to use filters.
"""
def get_filtered_objects(self, filter_classes, objs,
filter_properties):
list_objs = list(objs)
LOG.debug("Starting with %d host(s)", len(list_objs))
for filter_cls in filter_classes:
cls_name = filter_cls.__name__
objs = filter_cls().filter_all(list_objs,
filter_properties)
if objs is None:
LOG.debug("Filter %(cls_name)s says to stop filtering",
{'cls_name': cls_name})
return
list_objs = list(objs)
LOG.debug("Filter %(cls_name)s returned %(obj_len)d host(s)",
{'cls_name': cls_name, 'obj_len': len(list_objs)})
if len(list_objs) == 0:
break
return list_objs
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