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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,38 +1,116 @@ | ||
| from typing import Dict, Generic, TypeVar, TYPE_CHECKING | ||
| import sys | ||
| from threading import Lock | ||
| from typing import Dict, Generic, List, Optional, TypeVar, Union, overload | ||
|
|
||
| CacheKey = TypeVar("CacheKey") | ||
| CacheValue = TypeVar("CacheValue") | ||
| DefaultValue = TypeVar("DefaultValue") | ||
|
|
||
| if sys.version_info < (3, 9): | ||
| from typing_extensions import OrderedDict | ||
| else: | ||
| from collections import OrderedDict | ||
|
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||
|
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| class LRUCache(OrderedDict[CacheKey, CacheValue]): | ||
| class LRUCache(Generic[CacheKey, CacheValue]): | ||
| """ | ||
| A dictionary-like container that stores a given maximum items. | ||
| If an additional item is added when the LRUCache is full, the least | ||
| recently used key is discarded to make room for the new item. | ||
| The implementation is similar to functools.lru_cache, which uses a linked | ||
| list to keep track of the most recently used items. | ||
| Each entry is stored as [PREV, NEXT, KEY, VALUE] where PREV is a reference | ||
| to the previous entry, and NEXT is a reference to the next value. | ||
| """ | ||
|
|
||
| def __init__(self, cache_size: int) -> None: | ||
| self.cache_size = cache_size | ||
| def __init__(self, maxsize: int) -> None: | ||
| self.maxsize = maxsize | ||
| self.cache: Dict[CacheKey, List[object]] = {} | ||
| self.full = False | ||
| self.root: List[object] = [] | ||
| self._lock = Lock() | ||
| super().__init__() | ||
|
|
||
| def __setitem__(self, key: CacheKey, value: CacheValue) -> None: | ||
| """Store a new views, potentially discarding an old value.""" | ||
| if key not in self: | ||
| if len(self) >= self.cache_size: | ||
| self.popitem(last=False) | ||
| super().__setitem__(key, value) | ||
| def __len__(self) -> int: | ||
| return len(self.cache) | ||
|
|
||
| def set(self, key: CacheKey, value: CacheValue) -> None: | ||
| """Set a value. | ||
| Args: | ||
| key (CacheKey): Key. | ||
| value (CacheValue): Value. | ||
| """ | ||
| with self._lock: | ||
| link = self.cache.get(key) | ||
| if link is None: | ||
| root = self.root | ||
| if not root: | ||
| self.root[:] = [self.root, self.root, key, value] | ||
| else: | ||
| self.root = [root[0], root, key, value] | ||
| root[0][1] = self.root # type: ignore[index] | ||
| root[0] = self.root | ||
| self.cache[key] = self.root | ||
|
|
||
| if self.full or len(self.cache) > self.maxsize: | ||
| self.full = True | ||
| root = self.root | ||
| last = root[0] | ||
| last[0][1] = root # type: ignore[index] | ||
| root[0] = last[0] # type: ignore[index] | ||
| del self.cache[last[2]] # type: ignore[index] | ||
|
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| __setitem__ = set | ||
|
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||
| @overload | ||
| def get(self, key: CacheKey) -> Optional[CacheValue]: | ||
| ... | ||
|
|
||
| @overload | ||
| def get( | ||
| self, key: CacheKey, default: DefaultValue | ||
| ) -> Union[CacheValue, DefaultValue]: | ||
| ... | ||
|
|
||
| def get( | ||
| self, key: CacheKey, default: Optional[DefaultValue] = None | ||
| ) -> Union[CacheValue, Optional[DefaultValue]]: | ||
| """Get a value from the cache, or return a default if the key is not present. | ||
| Args: | ||
| key (CacheKey): Key | ||
| default (Optional[DefaultValue], optional): Default to return if key is not present. Defaults to None. | ||
| Returns: | ||
| Union[CacheValue, Optional[DefaultValue]]: Either the value or a default. | ||
| """ | ||
| link = self.cache.get(key) | ||
| if link is None: | ||
| return default | ||
| if link is not self.root: | ||
| with self._lock: | ||
| link[0][1] = link[1] # type: ignore[index] | ||
| link[1][0] = link[0] # type: ignore[index] | ||
| root = self.root | ||
| link[0] = root[0] | ||
| link[1] = root | ||
| root[0][1] = link # type: ignore[index] | ||
| root[0] = link | ||
| self.root = link | ||
| return link[3] # type: ignore[return-value] | ||
|
|
||
| def __getitem__(self, key: CacheKey) -> CacheValue: | ||
| """Gets the item, but also makes it most recent.""" | ||
| value: CacheValue = super().__getitem__(key) | ||
| super().__delitem__(key) | ||
| super().__setitem__(key, value) | ||
| return value | ||
| link = self.cache[key] | ||
| if link is not self.root: | ||
| with self._lock: | ||
| link[0][1] = link[1] # type: ignore[index] | ||
| link[1][0] = link[0] # type: ignore[index] | ||
| root = self.root | ||
| link[0] = root[0] | ||
| link[1] = root | ||
| root[0][1] = link # type: ignore[index] | ||
| root[0] = link | ||
| self.root = link | ||
| return link[3] # type: ignore[return-value] | ||
|
|
||
| def __contains__(self, key: CacheKey) -> bool: | ||
| return key in self.cache |
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