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use deque instead of heapq

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clowwindy 2014-10-31 15:49:24 +08:00
parent da11d02706
commit ac94104ac0
1 changed files with 14 additions and 7 deletions
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21
shadowsocks/lru_cache.py
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@ -3,10 +3,17 @@
import collections import collections
import logging import logging
import heapq
import time 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): class LRUCache(collections.MutableMapping):
"""This class is not thread safe""" """This class is not thread safe"""
@ -16,24 +23,24 @@ class LRUCache(collections.MutableMapping):
self._store = {} self._store = {}
self._time_to_keys = collections.defaultdict(list) self._time_to_keys = collections.defaultdict(list)
self._keys_to_last_time = {} self._keys_to_last_time = {}
self._last_visits = [] self._last_visits = collections.deque()
self.update(dict(*args, **kwargs)) # use the free update to set keys self.update(dict(*args, **kwargs)) # use the free update to set keys
def __getitem__(self, key): def __getitem__(self, key):
# O(logm) # O(1)
t = time.time() t = time.time()
self._keys_to_last_time[key] = t self._keys_to_last_time[key] = t
self._time_to_keys[t].append(key) self._time_to_keys[t].append(key)
heapq.heappush(self._last_visits, t) self._last_visits.append(t)
return self._store[key] return self._store[key]
def __setitem__(self, key, value): def __setitem__(self, key, value):
# O(logm) # O(1)
t = time.time() t = time.time()
self._keys_to_last_time[key] = t self._keys_to_last_time[key] = t
self._store[key] = value self._store[key] = value
self._time_to_keys[t].append(key) self._time_to_keys[t].append(key)
heapq.heappush(self._last_visits, t) self._last_visits.append(t)
def __delitem__(self, key): def __delitem__(self, key):
# O(1) # O(1)
@ -61,7 +68,7 @@ class LRUCache(collections.MutableMapping):
value = self._store[key] value = self._store[key]
self.close_callback(value) self.close_callback(value)
for key in self._time_to_keys[least]: for key in self._time_to_keys[least]:
heapq.heappop(self._last_visits) self._last_visits.popleft()
if self._store.__contains__(key): if self._store.__contains__(key):
if now - self._keys_to_last_time[key] > self.timeout: if now - self._keys_to_last_time[key] > self.timeout:
del self._store[key] del self._store[key]