#coding:utf-8
# Copyright (c) 2019  PaddlePaddle Authors. 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.

import threading


def synchronized(func):
    func.__lock__ = threading.Lock()

    def synced_func(*args, **kwargs):
        with func.__lock__:
            return func(*args, **kwargs)

    return synced_func


def singleton(cls):
    _instance = {}

    @synchronized
    def _get_instance(*args, **kwargs):
        if cls not in _instance:
            _instance[cls] = cls(*args, **kwargs)
        return _instance[cls]

    return _get_instance
