64 lines
1.7 KiB
Python
64 lines
1.7 KiB
Python
import collections
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import itertools
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import time
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class Cache:
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def __init__(self, maxage=None, maxlen=None, shrink_delay=None):
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self.maxage = maxage
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self.maxlen = maxlen
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self.shrink_delay = shrink_delay
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self.last_shrink = time.time()
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self._dict = {}
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self._recency = {}
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def __getitem__(self, key):
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self._shrink()
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value = self._dict[key]
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self._maintain(key)
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return value
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def __setitem__(self, key, value):
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self._shrink()
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self._dict[key] = value
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self._maintain(key)
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def _maintain(self, key):
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self._recency[key] = time.time()
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def _shrink(self):
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if self.shrink_delay is not None:
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if time.time() - self.last_shrink > self.shrink_delay:
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return
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now = time.time()
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self.last_shrink = now
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if self.maxlen is None:
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pop_count = 0
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else:
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pop_count = len(self._dict) - self.maxlen
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pop_count = max(0, pop_count)
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keys = sorted(self._recency.keys(), key=self._recency.get)
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for key in itertools.islice(keys, 0, pop_count):
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self.remove(key)
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if self.maxage is not None:
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for key in itertools.islice(keys, pop_count, None):
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last_used = self._recency[key]
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age = now - last_used
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if age > self.maxage:
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self.remove(key)
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def get(self, key, fallback=None):
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try:
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return self[key]
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except KeyError:
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return fallback
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def remove(self, key):
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try:
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self._dict.pop(key)
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self._recency.pop(key)
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except KeyError:
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return
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