1#!/usr/bin/env python3
2# coding=utf-8
3
4#
5# Copyright (c) 2020-2023 Huawei Device Co., Ltd.
6# Licensed under the Apache License, Version 2.0 (the "License");
7# you may not use this file except in compliance with the License.
8# You may obtain a copy of the License at
9#
10#     http://www.apache.org/licenses/LICENSE-2.0
11#
12# Unless required by applicable law or agreed to in writing, software
13# distributed under the License is distributed on an "AS IS" BASIS,
14# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15# See the License for the specific language governing permissions and
16# limitations under the License.
17#
18
19from threading import RLock
20
21__all__ = ["SingleType"]
22
23
24class SingleType(type):
25    _lock = RLock()
26
27    def __call__(cls, *args, **kwargs):
28        with SingleType._lock:
29            if not hasattr(cls, "_instance"):
30                cls._instance = super(SingleType, cls).__call__(*args, **kwargs)
31        return getattr(cls, "_instance")
32