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# Copyright 2013 OpenStack Foundation
# Copyright 2013 IBM Corp.
#
# 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.
import functools
from keystone import exception
from keystone.i18n import _
def truncated(f):
"""Ensure list truncation is detected in Driver list entity methods.
This is designed to wrap Driver list_{entity} methods in order to
calculate if the resultant list has been truncated. Provided a limit dict
is found in the hints list, we increment the limit by one so as to ask the
wrapped function for one more entity than the limit, and then once the list
has been generated, we check to see if the original limit has been
exceeded, in which case we truncate back to that limit and set the
'truncated' boolean to 'true' in the hints limit dict.
"""
@functools.wraps(f)
def wrapper(self, hints, *args, **kwargs):
if not hasattr(hints, 'limit'):
raise exception.UnexpectedError(
_('Cannot truncate a driver call without hints list as '
'first parameter after self '))
if hints.limit is None:
return f(self, hints, *args, **kwargs)
# A limit is set, so ask for one more entry than we need
list_limit = hints.limit['limit']
hints.set_limit(list_limit + 1)
ref_list = f(self, hints, *args, **kwargs)
# If we got more than the original limit then trim back the list and
# mark it truncated. In both cases, make sure we set the limit back
# to its original value.
if len(ref_list) > list_limit:
hints.set_limit(list_limit, truncated=True)
return ref_list[:list_limit]
else:
hints.set_limit(list_limit)
return ref_list
return wrapper
class Hints(object):
"""Encapsulate driver hints for listing entities.
Hints are modifiers that affect the return of entities from a
list_<entities> operation. They are typically passed to a driver to give
direction as to what filtering, pagination or list limiting actions are
being requested.
It is optional for a driver to action some or all of the list hints,
but any filters that it does satisfy must be marked as such by calling
removing the filter from the list.
A Hint object contains filters, which is a list of dicts that can be
accessed publicly. Also it contains a dict called limit, which will
indicate the amount of data we want to limit our listing to.
If the filter is discovered to never match, then `cannot_match` can be set
to indicate that there will not be any matches and the backend work can be
short-circuited.
Each filter term consists of:
* ``name``: the name of the attribute being matched
* ``value``: the value against which it is being matched
* ``comparator``: the operation, which can be one of ``equals``,
``contains``, ``startswith`` or ``endswith``
* ``case_sensitive``: whether any comparison should take account of
case
* ``type``: will always be 'filter'
"""
def __init__(self):
self.limit = None
self.filters = list()
self.cannot_match = False
def add_filter(self, name, value, comparator='equals',
case_sensitive=False):
"""Adds a filter to the filters list, which is publicly accessible."""
self.filters.append({'name': name, 'value': value,
'comparator': comparator,
'case_sensitive': case_sensitive,
'type': 'filter'})
def get_exact_filter_by_name(self, name):
"""Return a filter key and value if exact filter exists for name."""
for entry in self.filters:
if (entry['type'] == 'filter' and entry['name'] == name and
entry['comparator'] == 'equals'):
return entry
def set_limit(self, limit, truncated=False):
"""Set a limit to indicate the list should be truncated."""
self.limit = {'limit': limit, 'type': 'limit', 'truncated': truncated}
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