| | 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] |
| |
|
| | 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), |
| | ) |
| |
|
