| # |
| # Copyright (C) 2018 Codethink Limited |
| # |
| # This program is free software; you can redistribute it and/or |
| # modify it under the terms of the GNU Lesser General Public |
| # License as published by the Free Software Foundation; either |
| # version 2 of the License, or (at your option) any later version. |
| # |
| # This library 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 |
| # Lesser General Public License for more details. |
| # |
| # You should have received a copy of the GNU Lesser General Public |
| # License along with this library. If not, see <http://www.gnu.org/licenses/>. |
| # |
| # Authors: |
| # Tristan Van Berkom <tristan.vanberkom@codethink.co.uk> |
| |
| |
| import hashlib |
| |
| import ujson |
| |
| |
| # Internal record of the size of a cache key |
| _CACHEKEY_SIZE = len(hashlib.sha256().hexdigest()) |
| |
| |
| # Hex digits |
| _HEX_DIGITS = "0123456789abcdef" |
| |
| |
| # is_key() |
| # |
| # Check if the passed in string *could be* a cache key. This basically checks |
| # that the length matches a sha256 hex digest, and that the string does not |
| # contain any non-hex characters and is fully lower case. |
| # |
| # Args: |
| # key (str): The string to check |
| # |
| # Returns: |
| # (bool): Whether or not `key` could be a cache key |
| # |
| def is_key(key): |
| if len(key) != _CACHEKEY_SIZE: |
| return False |
| return not any(ch not in _HEX_DIGITS for ch in key) |
| |
| |
| # generate_key() |
| # |
| # Generate an sha256 hex digest from the given value. The value |
| # can be a simple value or recursive dictionary with lists etc, |
| # anything simple enough to serialize. |
| # |
| # Args: |
| # value: A value to get a key for |
| # |
| # Returns: |
| # (str): An sha256 hex digest of the given value |
| # |
| def generate_key(value): |
| ustring = ujson.dumps(value, sort_keys=True, escape_forward_slashes=False).encode("utf-8") |
| return hashlib.sha256(ustring).hexdigest() |