99 lines
2.7 KiB
Python
99 lines
2.7 KiB
Python
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import time
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from collections.abc import MutableMapping
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from functools import lru_cache
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class DirCache(MutableMapping):
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"""
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Caching of directory listings, in a structure like::
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{"path0": [
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{"name": "path0/file0",
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"size": 123,
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"type": "file",
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...
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},
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{"name": "path0/file1",
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},
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...
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],
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"path1": [...]
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}
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Parameters to this class control listing expiry or indeed turn
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caching off
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"""
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def __init__(
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self,
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use_listings_cache=True,
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listings_expiry_time=None,
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max_paths=None,
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**kwargs,
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):
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"""
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Parameters
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----------
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use_listings_cache: bool
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If False, this cache never returns items, but always reports KeyError,
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and setting items has no effect
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listings_expiry_time: int or float (optional)
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Time in seconds that a listing is considered valid. If None,
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listings do not expire.
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max_paths: int (optional)
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The number of most recent listings that are considered valid; 'recent'
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refers to when the entry was set.
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"""
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self._cache = {}
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self._times = {}
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if max_paths:
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self._q = lru_cache(max_paths + 1)(lambda key: self._cache.pop(key, None))
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self.use_listings_cache = use_listings_cache
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self.listings_expiry_time = listings_expiry_time
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self.max_paths = max_paths
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def __getitem__(self, item):
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if self.listings_expiry_time is not None:
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if self._times.get(item, 0) - time.time() < -self.listings_expiry_time:
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del self._cache[item]
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if self.max_paths:
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self._q(item)
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return self._cache[item] # maybe raises KeyError
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def clear(self):
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self._cache.clear()
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def __len__(self):
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return len(self._cache)
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def __contains__(self, item):
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try:
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self[item]
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return True
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except KeyError:
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return False
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def __setitem__(self, key, value):
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if not self.use_listings_cache:
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return
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if self.max_paths:
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self._q(key)
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self._cache[key] = value
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if self.listings_expiry_time is not None:
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self._times[key] = time.time()
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def __delitem__(self, key):
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del self._cache[key]
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def __iter__(self):
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entries = list(self._cache)
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return (k for k in entries if k in self)
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def __reduce__(self):
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return (
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DirCache,
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(self.use_listings_cache, self.listings_expiry_time, self.max_paths),
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)
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