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#
# This file is part of pysnmp software.
#
# Copyright (c) 2005-2020, Ilya Etingof <etingof@gmail.com>
# License: https://www.pysnmp.com/pysnmp/license.html
#
# Limited-size dictionary-like class to use for caches
#
"""
This module defines a limited-size dictionary-like class to use for caches.
Classes:
Cache: Limited-size dictionary-like class to use for caches.
Usage:
This module is used to create a cache instance with a limited size.
"""
class Cache:
"""Limited-size dictionary-like class to use for caches."""
def __init__(self, maxSize=256):
"""Create cache instance."""
self.__maxSize = maxSize
self.__size = 0
self.__chopSize = maxSize // 10
self.__chopSize = self.__chopSize and self.__chopSize or 1
self.__cache = {}
self.__usage = {}
def __contains__(self, k):
"""Check if key is in cache."""
return k in self.__cache
def __getitem__(self, k):
"""Get cache entry."""
self.__usage[k] += 1
return self.__cache[k]
def __len__(self):
"""Return number of entries in cache."""
return self.__size
def __setitem__(self, k, v):
"""Set cache entry."""
if self.__size >= self.__maxSize:
usageKeys = sorted(self.__usage, key=lambda x, d=self.__usage: d[x])
for _k in usageKeys[: self.__chopSize]:
del self.__cache[_k]
del self.__usage[_k]
self.__size -= self.__chopSize
if k not in self.__cache:
self.__size += 1
self.__usage[k] = 0
self.__cache[k] = v
def __delitem__(self, k):
"""Delete cache entry."""
del self.__cache[k]
del self.__usage[k]
self.__size -= 1
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