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# Copyright (C) 2017 Jan Jancar
#
# This file is a part of the Mailman PGP plugin.
#
# 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 3 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, see <http://www.gnu.org/licenses/>.
from public import public
from sqlalchemy import Integer, TypeDecorator
@public
class EnumFlag(TypeDecorator):
"""Simple bitwise flag from an `enum.Enum`, assumes it is unique."""
impl = Integer
def __init__(self, enum, *args, **kw):
super().__init__(*args, **kw)
self.enum = enum
def process_bind_param(self, value, dialect):
# value is a set/frozenset of Enums.
if value is None:
return None
if not isinstance(value, (set, frozenset)):
raise ValueError
int_value = 0
for enum in reversed(self.enum):
int_value = int_value << 1
if enum in value:
int_value += 1
return int_value
def process_result_value(self, value, dialect):
# value is an integer.
if value is None:
return None
if value == 0:
return frozenset()
result = set()
for enum in self.enum:
if value % 2 == 1:
result.add(enum)
value = value >> 1
return frozenset(result)
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