| #!/usr/bin/env python3 |
| # |
| # Copyright (c) 2019, The OpenThread Authors. |
| # All rights reserved. |
| # |
| # Redistribution and use in source and binary forms, with or without |
| # modification, are permitted provided that the following conditions are met: |
| # 1. Redistributions of source code must retain the above copyright |
| # notice, this list of conditions and the following disclaimer. |
| # 2. Redistributions in binary form must reproduce the above copyright |
| # notice, this list of conditions and the following disclaimer in the |
| # documentation and/or other materials provided with the distribution. |
| # 3. Neither the name of the copyright holder nor the |
| # names of its contributors may be used to endorse or promote products |
| # derived from this software without specific prior written permission. |
| # |
| # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" |
| # AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| # ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE |
| # LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
| # CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
| # SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
| # INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
| # CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| # ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
| # POSSIBILITY OF SUCH DAMAGE. |
| # |
| |
| from functools import wraps |
| |
| |
| def cached(f): |
| """ |
| Decorator to convert a function to cache its return value when it's called by the first time. |
| |
| :param f: The function to decorate. |
| :return: The caching function. |
| """ |
| cache_key = '_once_' + f.__name__ |
| |
| @wraps(f) |
| def once_f(self): |
| try: |
| v = object.__getattribute__(self, cache_key) # can not use getattr, will trigger __getattr__ wrongly |
| except AttributeError: |
| v = f(self) |
| setattr(self, cache_key, v) |
| return v |
| |
| return once_f |
| |
| |
| def cached_property(f): |
| """ |
| Decorator for declaring a property that caches its value. |
| |
| :param f: The property getter function. |
| |
| :return: The caching property. |
| """ |
| return property(cached(f)) |