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