Python port of ShadowsocksR
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#!/usr/bin/python
# -*- coding: utf-8 -*-
from __future__ import absolute_import, division, print_function, \
with_statement
import collections
import logging
import time
# this LRUCache is optimized for concurrency, not QPS
# n: concurrency, keys stored in the cache
# m: visits not timed out, proportional to QPS * timeout
# get & set is O(1), not O(n). thus we can support very large n
# TODO: if timeout or QPS is too large, then this cache is not very efficient,
# as sweep() causes long pause
class LRUCache(collections.MutableMapping):
"""This class is not thread safe"""
def __init__(self, timeout=60, close_callback=None, *args, **kwargs):
self.timeout = timeout
self.close_callback = close_callback
self._store = {}
self._time_to_keys = collections.defaultdict(list)
self._keys_to_last_time = {}
self._last_visits = collections.deque()
self.update(dict(*args, **kwargs)) # use the free update to set keys
def __getitem__(self, key):
# O(1)
t = time.time()
self._keys_to_last_time[key] = t
self._time_to_keys[t].append(key)
self._last_visits.append(t)
return self._store[key]
def __setitem__(self, key, value):
# O(1)
t = time.time()
self._keys_to_last_time[key] = t
self._store[key] = value
self._time_to_keys[t].append(key)
self._last_visits.append(t)
def __delitem__(self, key):
# O(1)
del self._store[key]
del self._keys_to_last_time[key]
def __iter__(self):
return iter(self._store)
def __len__(self):
return len(self._store)
def sweep(self):
# O(m)
now = time.time()
c = 0
while len(self._last_visits) > 0:
least = self._last_visits[0]
if now - least <= self.timeout:
break
if self.close_callback is not None:
for key in self._time_to_keys[least]:
if self._store.__contains__(key):
if now - self._keys_to_last_time[key] > self.timeout:
value = self._store[key]
self.close_callback(value)
for key in self._time_to_keys[least]:
self._last_visits.popleft()
if self._store.__contains__(key):
if now - self._keys_to_last_time[key] > self.timeout:
del self._store[key]
del self._keys_to_last_time[key]
c += 1
del self._time_to_keys[least]
if c:
logging.debug('%d keys swept' % c)
def test():
c = LRUCache(timeout=0.3)
c['a'] = 1
assert c['a'] == 1
time.sleep(0.5)
c.sweep()
assert 'a' not in c
c['a'] = 2
c['b'] = 3
time.sleep(0.2)
c.sweep()
assert c['a'] == 2
assert c['b'] == 3
time.sleep(0.2)
c.sweep()
c['b']
time.sleep(0.2)
c.sweep()
assert 'a' not in c
assert c['b'] == 3
time.sleep(0.5)
c.sweep()
assert 'a' not in c
assert 'b' not in c
if __name__ == '__main__':
test()