/**
* @module LRUCache
*/
declare const TYPE: unique symbol;
export type PosInt = number & {
[TYPE]: 'Positive Integer';
};
export type Index = number & {
[TYPE]: 'LRUCache Index';
};
export type UintArray = Uint8Array | Uint16Array | Uint32Array;
export type NumberArray = UintArray | number[];
declare class ZeroArray extends Array<number> {
constructor(size: number);
}
export type { ZeroArray };
export type { Stack };
export type StackLike = Stack | Index[];
declare class Stack {
#private;
heap: NumberArray;
length: number;
static create(max: number): StackLike;
constructor(max: number, HeapCls: {
new (n: number): NumberArray;
});
push(n: Index): void;
pop(): Index;
}
/**
* Promise representing an in-progress {@link LRUCache#fetch} call
*/
export type BackgroundFetch<V> = Promise<V | undefined> & {
__returned: BackgroundFetch<V> | undefined;
__abortController: AbortController;
__staleWhileFetching: V | undefined;
};
export type DisposeTask<K, V> = [
value: V,
key: K,
reason: LRUCache.DisposeReason
];
export declare namespace LRUCache {
/**
* An integer greater than 0, reflecting the calculated size of items
*/
type Size = number;
/**
* Integer greater than 0, representing some number of milliseconds, or the
* time at which a TTL started counting from.
*/
type Milliseconds = number;
/**
* An integer greater than 0, reflecting a number of items
*/
type Count = number;
/**
* The reason why an item was removed from the cache, passed
* to the {@link Disposer} methods.
*
* - `evict`: The item was evicted because it is the least recently used,
* and the cache is full.
* - `set`: A new value was set, overwriting the old value being disposed.
* - `delete`: The item was explicitly deleted, either by calling
* {@link LRUCache#delete}, {@link LRUCache#clear}, or
* {@link LRUCache#set} with an undefined value.
* - `expire`: The item was removed due to exceeding its TTL.
* - `fetch`: A {@link OptionsBase#fetchMethod} operation returned
* `undefined` or was aborted, causing the item to be deleted.
*/
type DisposeReason = 'evict' | 'set' | 'delete' | 'expire' | 'fetch';
/**
* A method called upon item removal, passed as the
* {@link OptionsBase.dispose} and/or
* {@link OptionsBase.disposeAfter} options.
*/
type Disposer<K, V> = (value: V, key: K, reason: DisposeReason) => void;
/**
* A function that returns the effective calculated size
* of an entry in the cache.
*/
type SizeCalculator<K, V> = (value: V, key: K) => Size;
/**
* Options provided to the
* {@link OptionsBase.fetchMethod} function.
*/
interface FetcherOptions<K, V, FC = unknown> {
signal: AbortSignal;
options: FetcherFetchOptions<K, V, FC>;
/**
* Object provided in the {@link FetchOptions.context} option to
* {@link LRUCache#fetch}
*/
context: FC;
}
/**
* Occasionally, it may be useful to track the internal behavior of the
* cache, particularly for logging, debugging, or for behavior within the
* `fetchMethod`. To do this, you can pass a `status` object to the
* {@link LRUCache#fetch}, {@link LRUCache#get}, {@link LRUCache#set},
* {@link LRUCache#memo}, and {@link LRUCache#has} methods.
*
* The `status` option should be a plain JavaScript object. The following
* fields will be set on it appropriately, depending on the situation.
*/
interface Status<V> {
/**
* The status of a set() operation.
*
* - add: the item was not found in the cache, and was added
* - update: the item was in the cache, with the same value provided
* - replace: the item was in the cache, and replaced
* - miss: the item was not added to the cache for some reason
*/
set?: 'add' | 'update' | 'replace' | 'miss';
/**
* the ttl stored for the item, or undefined if ttls are not used.
*/
ttl?: Milliseconds;
/**
* the start time for the item, or undefined if ttls are not used.
*/
start?: Milliseconds;
/**
* The timestamp used for TTL calculation
*/
now?: Milliseconds;
/**
* the remaining ttl for the item, or undefined if ttls are not used.
*/
remainingTTL?: Milliseconds;
/**
* The calculated size for the item, if sizes are used.
*/
entrySize?: Size;
/**
* The total calculated size of the cache, if sizes are used.
*/
totalCalculatedSize?: Size;
/**
* A flag indicating that the item was not stored, due to exceeding the
* {@link OptionsBase.maxEntrySize}
*/
maxEntrySizeExceeded?: true;
/**
* The old value, specified in the case of `set:'update'` or
* `set:'replace'`
*/
oldValue?: V;
/**
* The results of a {@link LRUCache#has} operation
*
* - hit: the item was found in the cache
* - stale: the item was found in the cache, but is stale
* - miss: the item was not found in the cache
*/
has?: 'hit' | 'stale' | 'miss';
/**
* The status of a {@link LRUCache#fetch} operation.
* Note that this can change as the underlying fetch() moves through
* various states.
*
* - inflight: there is another fetch() for this key which is in process
* - get: there is no {@link OptionsBase.fetchMethod}, so
* {@link LRUCache#get} was called.
* - miss: the item is not in cache, and will be fetched.
* - hit: the item is in the cache, and was resolved immediately.
* - stale: the item is in the cache, but stale.
* - refresh: the item is in the cache, and not stale, but
* {@link FetchOptions.forceRefresh} was specified.
*/
fetch?: 'get' | 'inflight' | 'miss' | 'hit' | 'stale' | 'refresh';
/**
* The {@link OptionsBase.fetchMethod} was called
*/
fetchDispatched?: true;
/**
* The cached value was updated after a successful call to
* {@link OptionsBase.fetchMethod}
*/
fetchUpdated?: true;
/**
* The reason for a fetch() rejection. Either the error raised by the
* {@link OptionsBase.fetchMethod}, or the reason for an
* AbortSignal.
*/
fetchError?: Error;
/**
* The fetch received an abort signal
*/
fetchAborted?: true;
/**
* The abort signal received was ignored, and the fetch was allowed to
* continue.
*/
fetchAbortIgnored?: true;
/**
* The fetchMethod promise resolved successfully
*/
fetchResolved?: true;
/**
* The fetchMethod promise was rejected
*/
fetchRejected?: true;
/**
* The status of a {@link LRUCache#get} operation.
*
* - fetching: The item is currently being fetched. If a previous value
* is present and allowed, that will be returned.
* - stale: The item is in the cache, and is stale.
* - hit: the item is in the cache
* - miss: the item is not in the cache
*/
get?: 'stale' | 'hit' | 'miss';
/**
* A fetch or get operation returned a stale value.
*/
returnedStale?: true;
}
/**
* options which override the options set in the LRUCache constructor
* when calling {@link LRUCache#fetch}.
*
* This is the union of {@link GetOptions} and {@link SetOptions}, plus
* {@link OptionsBase.noDeleteOnFetchRejection},
* {@link OptionsBase.allowStaleOnFetchRejection},
* {@link FetchOptions.forceRefresh}, and
* {@link FetcherOptions.context}
*
* Any of these may be modified in the {@link OptionsBase.fetchMethod}
* function, but the {@link GetOptions} fields will of course have no
* effect, as the {@link LRUCache#get} call already happened by the time
* the fetchMethod is called.
*/
interface FetcherFetchOptions<K, V, FC = unknown> extends Pick<OptionsBase<K, V, FC>, 'allowStale' | 'updateAgeOnGet' | 'noDeleteOnStaleGet' | 'sizeCalculation' | 'ttl' | 'noDisposeOnSet' | 'noUpdateTTL' | 'noDeleteOnFetchRejection' | 'allowStaleOnFetchRejection' | 'ignoreFetchAbort' | 'allowStaleOnFetchAbort'> {
status?: Status<V>;
size?: Size;
}
/**
* Options that may be passed to the {@link LRUCache#fetch} method.
*/
interface FetchOptions<K, V, FC> extends FetcherFetchOptions<K, V, FC> {
/**
* Set to true to force a re-load of the existing data, even if it
* is not yet stale.
*/
forceRefresh?: boolean;
/**
* Context provided to the {@link OptionsBase.fetchMethod} as
* the {@link FetcherOptions.context} param.
*
* If the FC type is specified as unknown (the default),
* undefined or void, then this is optional. Otherwise, it will
* be required.
*/
context?: FC;
signal?: AbortSignal;
status?: Status<V>;
}
/**
* Options provided to {@link LRUCache#fetch} when the FC type is something
* other than `unknown`, `undefined`, or `void`
*/
interface FetchOptionsWithContext<K, V, FC> extends FetchOptions<K, V, FC> {
context: FC;
}
/**
* Options provided to {@link LRUCache#fetch} when the FC type is
* `undefined` or `void`
*/
interface FetchOptionsNoContext<K, V> extends FetchOptions<K, V, undefined> {
context?: undefined;
}
interface MemoOptions<K, V, FC = unknown> extends Pick<OptionsBase<K, V, FC>, 'allowStale' | 'updateAgeOnGet' | 'noDeleteOnStaleGet' | 'sizeCalculation' | 'ttl' | 'noDisposeOnSet' | 'noUpdateTTL' | 'noDeleteOnFetchRejection' | 'allowStaleOnFetchRejection' | 'ignoreFetchAbort' | 'allowStaleOnFetchAbort'> {
/**
* Set to true to force a re-load of the existing data, even if it
* is not yet stale.
*/
forceRefresh?: boolean;
/**
* Context provided to the {@link OptionsBase.memoMethod} as
* the {@link MemoizerOptions.context} param.
*
* If the FC type is specified as unknown (the default),
* undefined or void, then this is optional. Otherwise, it will
* be required.
*/
context?: FC;
status?: Status<V>;
}
/**
* Options provided to {@link LRUCache#memo} when the FC type is something
* other than `unknown`, `undefined`, or `void`
*/
interface MemoOptionsWithContext<K, V, FC> extends MemoOptions<K, V, FC> {
context: FC;
}
/**
* Options provided to {@link LRUCache#memo} when the FC type is
* `undefined` or `void`
*/
interface MemoOptionsNoContext<K, V> extends MemoOptions<K, V, undefined> {
context?: undefined;
}
/**
* Options provided to the
* {@link OptionsBase.memoMethod} function.
*/
interface MemoizerOptions<K, V, FC = unknown> {
options: MemoizerMemoOptions<K, V, FC>;
/**
* Object provided in the {@link MemoOptions.context} option to
* {@link LRUCache#memo}
*/
context: FC;
}
/**
* options which override the options set in the LRUCache constructor
* when calling {@link LRUCache#memo}.
*
* This is the union of {@link GetOptions} and {@link SetOptions}, plus
* {@link MemoOptions.forceRefresh}, and
* {@link MemoerOptions.context}
*
* Any of these may be modified in the {@link OptionsBase.memoMethod}
* function, but the {@link GetOptions} fields will of course have no
* effect, as the {@link LRUCache#get} call already happened by the time
* the memoMethod is called.
*/
interface MemoizerMemoOptions<K, V, FC = unknown> extends Pick<OptionsBase<K, V, FC>, 'allowStale' | 'updateAgeOnGet' | 'noDeleteOnStaleGet' | 'sizeCalculation' | 'ttl' | 'noDisposeOnSet' | 'noUpdateTTL'> {
status?: Status<V>;
size?: Size;
start?: Milliseconds;
}
/**
* Options that may be passed to the {@link LRUCache#has} method.
*/
interface HasOptions<K, V, FC> extends Pick<OptionsBase<K, V, FC>, 'updateAgeOnHas'> {
status?: Status<V>;
}
/**
* Options that may be passed to the {@link LRUCache#get} method.
*/
interface GetOptions<K, V, FC> extends Pick<OptionsBase<K, V, FC>, 'allowStale' | 'updateAgeOnGet' | 'noDeleteOnStaleGet'> {
status?: Status<V>;
}
/**
* Options that may be passed to the {@link LRUCache#peek} method.
*/
interface PeekOptions<K, V, FC> extends Pick<OptionsBase<K, V, FC>, 'allowStale'> {
}
/**
* Options that may be passed to the {@link LRUCache#set} method.
*/
interface SetOptions<K, V, FC> extends Pick<OptionsBase<K, V, FC>, 'sizeCalculation' | 'ttl' | 'noDisposeOnSet' | 'noUpdateTTL'> {
/**
* If size tracking is enabled, then setting an explicit size
* in the {@link LRUCache#set} call will prevent calling the
* {@link OptionsBase.sizeCalculation} function.
*/
size?: Size;
/**
* If TTL tracking is enabled, then setting an explicit start
* time in the {@link LRUCache#set} call will override the
* default time from `performance.now()` or `Date.now()`.
*
* Note that it must be a valid value for whichever time-tracking
* method is in use.
*/
start?: Milliseconds;
status?: Status<V>;
}
/**
* The type signature for the {@link OptionsBase.fetchMethod} option.
*/
type Fetcher<K, V, FC = unknown> = (key: K, staleValue: V | undefined, options: FetcherOptions<K, V, FC>) => Promise<V | undefined | void> | V | undefined | void;
/**
* the type signature for the {@link OptionsBase.memoMethod} option.
*/
type Memoizer<K, V, FC = unknown> = (key: K, staleValue: V | undefined, options: MemoizerOptions<K, V, FC>) => V;
/**
* Options which may be passed to the {@link LRUCache} constructor.
*
* Most of these may be overridden in the various options that use
* them.
*
* Despite all being technically optional, the constructor requires that
* a cache is at minimum limited by one or more of {@link OptionsBase.max},
* {@link OptionsBase.ttl}, or {@link OptionsBase.maxSize}.
*
* If {@link OptionsBase.ttl} is used alone, then it is strongly advised
* (and in fact required by the type definitions here) that the cache
* also set {@link OptionsBase.ttlAutopurge}, to prevent potentially
* unbounded storage.
*
* All options are also available on the {@link LRUCache} instance, making
* it safe to pass an LRUCache instance as the options argumemnt to
* make another empty cache of the same type.
*
* Some options are marked as read-only, because changing them after
* instantiation is not safe. Changing any of the other options will of
* course only have an effect on subsequent method calls.
*/
interface OptionsBase<K, V, FC> {
/**
* The maximum number of items to store in the cache before evicting
* old entries. This is read-only on the {@link LRUCache} instance,
* and may not be overridden.
*
* If set, then storage space will be pre-allocated at construction
* time, and the cache will perform significantly faster.
*
* Note that significantly fewer items may be stored, if
* {@link OptionsBase.maxSize} and/or {@link OptionsBase.ttl} are also
* set.
*
* **It is strongly recommended to set a `max` to prevent unbounded growth
* of the cache.**
*/
max?: Count;
/**
* Max time in milliseconds for items to live in cache before they are
* considered stale. Note that stale items are NOT preemptively removed by
* default, and MAY live in the cache, contributing to its LRU max, long
* after they have expired, unless {@link OptionsBase.ttlAutopurge} is
* set.
*
* If set to `0` (the default value), then that means "do not track
* TTL", not "expire immediately".
*
* Also, as this cache is optimized for LRU/MRU operations, some of
* the staleness/TTL checks will reduce performance, as they will incur
* overhead by deleting items.
*
* This is not primarily a TTL cache, and does not make strong TTL
* guarantees. There is no pre-emptive pruning of expired items, but you
* _may_ set a TTL on the cache, and it will treat expired items as missing
* when they are fetched, and delete them.
*
* Optional, but must be a non-negative integer in ms if specified.
*
* This may be overridden by passing an options object to `cache.set()`.
*
* At least one of `max`, `maxSize`, or `TTL` is required. This must be a
* positive integer if set.
*
* Even if ttl tracking is enabled, **it is strongly recommended to set a
* `max` to prevent unbounded growth of the cache.**
*
* If ttl tracking is enabled, and `max` and `maxSize` are not set,
* and `ttlAutopurge` is not set, then a warning will be emitted
* cautioning about the potential for unbounded memory consumption.
* (The TypeScript definitions will also discourage this.)
*/
ttl?: Milliseconds;
/**
* Minimum amount of time in ms in which to check for staleness.
* Defaults to 1, which means that the current time is checked
* at most once per millisecond.
*
* Set to 0 to check the current time every time staleness is tested.
* (This reduces performance, and is theoretically unnecessary.)
*
* Setting this to a higher value will improve performance somewhat
* while using ttl tracking, albeit at the expense of keeping stale
* items around a bit longer than their TTLs would indicate.
*
* @default 1
*/
ttlResolution?: Milliseconds;
/**
* Preemptively remove stale items from the cache.
*
* Note that this may *significantly* degrade performance, especially if
* the cache is storing a large number of items. It is almost always best
* to just leave the stale items in the cache, and let them fall out as new
* items are added.
*
* Note that this means that {@link OptionsBase.allowStale} is a bit
* pointless, as stale items will be deleted almost as soon as they
* expire.
*
* Use with caution!
*/
ttlAutopurge?: boolean;
/**
* When using time-expiring entries with `ttl`, setting this to `true` will
* make each item's age reset to 0 whenever it is retrieved from cache with
* {@link LRUCache#get}, causing it to not expire. (It can still fall out
* of cache based on recency of use, of course.)
*
* Has no effect if {@link OptionsBase.ttl} is not set.
*
* This may be overridden by passing an options object to `cache.get()`.
*/
updateAgeOnGet?: boolean;
/**
* When using time-expiring entries with `ttl`, setting this to `true` will
* make each item's age reset to 0 whenever its presence in the cache is
* checked with {@link LRUCache#has}, causing it to not expire. (It can
* still fall out of cache based on recency of use, of course.)
*
* Has no effect if {@link OptionsBase.ttl} is not set.
*/
updateAgeOnHas?: boolean;
/**
* Allow {@link LRUCache#get} and {@link LRUCache#fetch} calls to return
* stale data, if available.
*
* By default, if you set `ttl`, stale items will only be deleted from the
* cache when you `get(key)`. That is, it's not preemptively pruning items,
* unless {@link OptionsBase.ttlAutopurge} is set.
*
* If you set `allowStale:true`, it'll return the stale value *as well as*
* deleting it. If you don't set this, then it'll return `undefined` when
* you try to get a stale entry.
*
* Note that when a stale entry is fetched, _even if it is returned due to
* `allowStale` being set_, it is removed from the cache immediately. You
* can suppress this behavior by setting
* {@link OptionsBase.noDeleteOnStaleGet}, either in the constructor, or in
* the options provided to {@link LRUCache#get}.
*
* This may be overridden by passing an options object to `cache.get()`.
* The `cache.has()` method will always return `false` for stale items.
*
* Only relevant if a ttl is set.
*/
allowStale?: boolean;
/**
* Function that is called on items when they are dropped from the
* cache, as `dispose(value, key, reason)`.
*
* This can be handy if you want to close file descriptors or do
* other cleanup tasks when items are no longer stored in the cache.
*
* **NOTE**: It is called _before_ the item has been fully removed
* from the cache, so if you want to put it right back in, you need
* to wait until the next tick. If you try to add it back in during
* the `dispose()` function call, it will break things in subtle and
* weird ways.
*
* Unlike several other options, this may _not_ be overridden by
* passing an option to `set()`, for performance reasons.
*
* The `reason` will be one of the following strings, corresponding
* to the reason for the item's deletion:
*
* - `evict` Item was evicted to make space for a new addition
* - `set` Item was overwritten by a new value
* - `expire` Item expired its TTL
* - `fetch` Item was deleted due to a failed or aborted fetch, or a
* fetchMethod returning `undefined.
* - `delete` Item was removed by explicit `cache.delete(key)`,
* `cache.clear()`, or `cache.set(key, undefined)`.
*/
dispose?: Disposer<K, V>;
/**
* The same as {@link OptionsBase.dispose}, but called *after* the entry
* is completely removed and the cache is once again in a clean state.
*
* It is safe to add an item right back into the cache at this point.
* However, note that it is *very* easy to inadvertently create infinite
* recursion this way.
*/
disposeAfter?: Disposer<K, V>;
/**
* Set to true to suppress calling the
* {@link OptionsBase.dispose} function if the entry key is
* still accessible within the cache.
*
* This may be overridden by passing an options object to
* {@link LRUCache#set}.
*
* Only relevant if `dispose` or `disposeAfter` are set.
*/
noDisposeOnSet?: boolean;
/**
* Boolean flag to tell the cache to not update the TTL when setting a new
* value for an existing key (ie, when updating a value rather than
* inserting a new value). Note that the TTL value is _always_ set (if
* provided) when adding a new entry into the cache.
*
* Has no effect if a {@link OptionsBase.ttl} is not set.
*
* May be passed as an option to {@link LRUCache#set}.
*/
noUpdateTTL?: boolean;
/**
* Set to a positive integer to track the sizes of items added to the
* cache, and automatically evict items in order to stay below this size.
* Note that this may result in fewer than `max` items being stored.
*
* Attempting to add an item to the cache whose calculated size is greater
* that this amount will be a no-op. The item will not be cached, and no
* other items will be evicted.
*
* Optional, must be a positive integer if provided.
*
* Sets `maxEntrySize` to the same value, unless a different value is
* provided for `maxEntrySize`.
*
* At least one of `max`, `maxSize`, or `TTL` is required. This must be a
* positive integer if set.
*
* Even if size tracking is enabled, **it is strongly recommended to set a
* `max` to prevent unbounded growth of the cache.**
*
* Note also that size tracking can negatively impact performance,
* though for most cases, only minimally.
*/
maxSize?: Size;
/**
* The maximum allowed size for any single item in the cache.
*
* If a larger item is passed to {@link LRUCache#set} or returned by a
* {@link OptionsBase.fetchMethod} or {@link OptionsBase.memoMethod}, then
* it will not be stored in the cache.
*
* Attempting to add an item whose calculated size is greater than
* this amount will not cache the item or evict any old items, but
* WILL delete an existing value if one is already present.
*
* Optional, must be a positive integer if provided. Defaults to
* the value of `maxSize` if provided.
*/
maxEntrySize?: Size;
/**
* A function that returns a number indicating the item's size.
*
* Requires {@link OptionsBase.maxSize} to be set.
*
* If not provided, and {@link OptionsBase.maxSize} or
* {@link OptionsBase.maxEntrySize} are set, then all
* {@link LRUCache#set} calls **must** provide an explicit
* {@link SetOptions.size} or sizeCalculation param.
*/
sizeCalculation?: SizeCalculator<K, V>;
/**
* Method that provides the implementation for {@link LRUCache#fetch}
*
* ```ts
* fetchMethod(key, staleValue, { signal, options, context })
* ```
*
* If `fetchMethod` is not provided, then `cache.fetch(key)` is equivalent
* to `Promise.resolve(cache.get(key))`.
*
* If at any time, `signal.aborted` is set to `true`, or if the
* `signal.onabort` method is called, or if it emits an `'abort'` event
* which you can listen to with `addEventListener`, then that means that
* the fetch should be abandoned. This may be passed along to async
* functions aware of AbortController/AbortSignal behavior.
*
* The `fetchMethod` should **only** return `undefined` or a Promise
* resolving to `undefined` if the AbortController signaled an `abort`
* event. In all other cases, it should return or resolve to a value
* suitable for adding to the cache.
*
* The `options` object is a union of the options that may be provided to
* `set()` and `get()`. If they are modified, then that will result in
* modifying the settings to `cache.set()` when the value is resolved, and
* in the case of
* {@link OptionsBase.noDeleteOnFetchRejection} and
* {@link OptionsBase.allowStaleOnFetchRejection}, the handling of
* `fetchMethod` failures.
*
* For example, a DNS cache may update the TTL based on the value returned
* from a remote DNS server by changing `options.ttl` in the `fetchMethod`.
*/
fetchMethod?: Fetcher<K, V, FC>;
/**
* Method that provides the implementation for {@link LRUCache#memo}
*/
memoMethod?: Memoizer<K, V, FC>;
/**
* Set to true to suppress the deletion of stale data when a
* {@link OptionsBase.fetchMethod} returns a rejected promise.
*/
noDeleteOnFetchRejection?: boolean;
/**
* Do not delete stale items when they are retrieved with
* {@link LRUCache#get}.
*
* Note that the `get` return value will still be `undefined`
* unless {@link OptionsBase.allowStale} is true.
*
* When using time-expiring entries with `ttl`, by default stale
* items will be removed from the cache when the key is accessed
* with `cache.get()`.
*
* Setting this option will cause stale items to remain in the cache, until
* they are explicitly deleted with `cache.delete(key)`, or retrieved with
* `noDeleteOnStaleGet` set to `false`.
*
* This may be overridden by passing an options object to `cache.get()`.
*
* Only relevant if a ttl is used.
*/
noDeleteOnStaleGet?: boolean;
/**
* Set to true to allow returning stale data when a
* {@link OptionsBase.fetchMethod} throws an error or returns a rejected
* promise.
*
* This differs from using {@link OptionsBase.allowStale} in that stale
* data will ONLY be returned in the case that the {@link LRUCache#fetch}
* fails, not any other times.
*
* If a `fetchMethod` fails, and there is no stale value available, the
* `fetch()` will resolve to `undefined`. Ie, all `fetchMethod` errors are
* suppressed.
*
* Implies `noDeleteOnFetchRejection`.
*
* This may be set in calls to `fetch()`, or defaulted on the constructor,
* or overridden by modifying the options object in the `fetchMethod`.
*/
allowStaleOnFetchRejection?: boolean;
/**
* Set to true to return a stale value from the cache when the
* `AbortSignal` passed to the {@link OptionsBase.fetchMethod} dispatches
* an `'abort'` event, whether user-triggered, or due to internal cache
* behavior.
*
* Unless {@link OptionsBase.ignoreFetchAbort} is also set, the underlying
* {@link OptionsBase.fetchMethod} will still be considered canceled, and
* any value it returns will be ignored and not cached.
*
* Caveat: since fetches are aborted when a new value is explicitly
* set in the cache, this can lead to fetch returning a stale value,
* since that was the fallback value _at the moment the `fetch()` was
* initiated_, even though the new updated value is now present in
* the cache.
*
* For example:
*
* ```ts
* const cache = new LRUCache<string, any>({
* ttl: 100,
* fetchMethod: async (url, oldValue, { signal }) => {
* const res = await fetch(url, { signal })
* return await res.json()
* }
* })
* cache.set('https://example.com/', { some: 'data' })
* // 100ms go by...
* const result = cache.fetch('https://example.com/')
* cache.set('https://example.com/', { other: 'thing' })
* console.log(await result) // { some: 'data' }
* console.log(cache.get('https://example.com/')) // { other: 'thing' }
* ```
*/
allowStaleOnFetchAbort?: boolean;
/**
* Set to true to ignore the `abort` event emitted by the `AbortSignal`
* object passed to {@link OptionsBase.fetchMethod}, and still cache the
* resulting resolution value, as long as it is not `undefined`.
*
* When used on its own, this means aborted {@link LRUCache#fetch} calls
* are not immediately resolved or rejected when they are aborted, and
* instead take the full time to await.
*
* When used with {@link OptionsBase.allowStaleOnFetchAbort}, aborted
* {@link LRUCache#fetch} calls will resolve immediately to their stale
* cached value or `undefined`, and will continue to process and eventually
* update the cache when they resolve, as long as the resulting value is
* not `undefined`, thus supporting a "return stale on timeout while
* refreshing" mechanism by passing `AbortSignal.timeout(n)` as the signal.
*
* For example:
*
* ```ts
* const c = new LRUCache({
* ttl: 100,
* ignoreFetchAbort: true,
* allowStaleOnFetchAbort: true,
* fetchMethod: async (key, oldValue, { signal }) => {
* // note: do NOT pass the signal to fetch()!
* // let's say this fetch can take a long time.
* const res = await fetch(`https://slow-backend-server/${key}`)
* return await res.json()
* },
* })
*
* // this will return the stale value after 100ms, while still
* // updating in the background for next time.
* const val = await c.fetch('key', { signal: AbortSignal.timeout(100) })
* ```
*
* **Note**: regardless of this setting, an `abort` event _is still
* emitted on the `AbortSignal` object_, so may result in invalid results
* when passed to other underlying APIs that use AbortSignals.
*
* This may be overridden in the {@link OptionsBase.fetchMethod} or the
* call to {@link LRUCache#fetch}.
*/
ignoreFetchAbort?: boolean;
}
interface OptionsMaxLimit<K, V, FC> extends OptionsBase<K, V, FC> {
max: Count;
}
interface OptionsTTLLimit<K, V, FC> extends OptionsBase<K, V, FC> {
ttl: Milliseconds;
ttlAutopurge: boolean;
}
interface OptionsSizeLimit<K, V, FC> extends OptionsBase<K, V, FC> {
maxSize: Size;
}
/**
* The valid safe options for the {@link LRUCache} constructor
*/
type Options<K, V, FC> = OptionsMaxLimit<K, V, FC> | OptionsSizeLimit<K, V, FC> | OptionsTTLLimit<K, V, FC>;
/**
* Entry objects used by {@link LRUCache#load} and {@link LRUCache#dump},
* and returned by {@link LRUCache#info}.
*/
interface Entry<V> {
value: V;
ttl?: Milliseconds;
size?: Size;
start?: Milliseconds;
}
}
/**
* Default export, the thing you're using this module to get.
*
* The `K` and `V` types define the key and value types, respectively. The
* optional `FC` type defines the type of the `context` object passed to
* `cache.fetch()` and `cache.memo()`.
*
* Keys and values **must not** be `null` or `undefined`.
*
* All properties from the options object (with the exception of `max`,
* `maxSize`, `fetchMethod`, `memoMethod`, `dispose` and `disposeAfter`) are
* added as normal public members. (The listed options are read-only getters.)
*
* Changing any of these will alter the defaults for subsequent method calls.
*/
export declare class LRUCache<K extends {}, V extends {}, FC = unknown> implements Map<K, V> {
#private;
/**
* {@link LRUCache.OptionsBase.ttl}
*/
ttl: LRUCache.Milliseconds;
/**
* {@link LRUCache.OptionsBase.ttlResolution}
*/
ttlResolution: LRUCache.Milliseconds;
/**
* {@link LRUCache.OptionsBase.ttlAutopurge}
*/
ttlAutopurge: boolean;
/**
* {@link LRUCache.OptionsBase.updateAgeOnGet}
*/
updateAgeOnGet: boolean;
/**
* {@link LRUCache.OptionsBase.updateAgeOnHas}
*/
updateAgeOnHas: boolean;
/**
* {@link LRUCache.OptionsBase.allowStale}
*/
allowStale: boolean;
/**
* {@link LRUCache.OptionsBase.noDisposeOnSet}
*/
noDisposeOnSet: boolean;
/**
* {@link LRUCache.OptionsBase.noUpdateTTL}
*/
noUpdateTTL: boolean;
/**
* {@link LRUCache.OptionsBase.maxEntrySize}
*/
maxEntrySize: LRUCache.Size;
/**
* {@link LRUCache.OptionsBase.sizeCalculation}
*/
sizeCalculation?: LRUCache.SizeCalculator<K, V>;
/**
* {@link LRUCache.OptionsBase.noDeleteOnFetchRejection}
*/
noDeleteOnFetchRejection: boolean;
/**
* {@link LRUCache.OptionsBase.noDeleteOnStaleGet}
*/
noDeleteOnStaleGet: boolean;
/**
* {@link LRUCache.OptionsBase.allowStaleOnFetchAbort}
*/
allowStaleOnFetchAbort: boolean;
/**
* {@link LRUCache.OptionsBase.allowStaleOnFetchRejection}
*/
allowStaleOnFetchRejection: boolean;
/**
* {@link LRUCache.OptionsBase.ignoreFetchAbort}
*/
ignoreFetchAbort: boolean;
/**
* Do not call this method unless you need to inspect the
* inner workings of the cache. If anything returned by this
* object is modified in any way, strange breakage may occur.
*
* These fields are private for a reason!
*
* @internal
*/
static unsafeExposeInternals<K extends {}, V extends {}, FC extends unknown = unknown>(c: LRUCache<K, V, FC>): {
starts: ZeroArray | undefined;
ttls: ZeroArray | undefined;
sizes: ZeroArray | undefined;
keyMap: Map<K, number>;
keyList: (K | undefined)[];
valList: (V | BackgroundFetch<V> | undefined)[];
next: NumberArray;
prev: NumberArray;
readonly head: Index;
readonly tail: Index;
free: StackLike;
isBackgroundFetch: (p: any) => boolean;
backgroundFetch: (k: K, index: number | undefined, options: LRUCache.FetchOptions<K, V, FC>, context: any) => BackgroundFetch<V>;
moveToTail: (index: number) => void;
indexes: (options?: {
allowStale: boolean;
}) => Generator<Index, void, unknown>;
rindexes: (options?: {
allowStale: boolean;
}) => Generator<Index, void, unknown>;
isStale: (index: number | undefined) => boolean;
};
/**
* {@link LRUCache.OptionsBase.max} (read-only)
*/
get max(): LRUCache.Count;
/**
* {@link LRUCache.OptionsBase.maxSize} (read-only)
*/
get maxSize(): LRUCache.Count;
/**
* The total computed size of items in the cache (read-only)
*/
get calculatedSize(): LRUCache.Size;
/**
* The number of items stored in the cache (read-only)
*/
get size(): LRUCache.Count;
/**
* {@link LRUCache.OptionsBase.fetchMethod} (read-only)
*/
get fetchMethod(): LRUCache.Fetcher<K, V, FC> | undefined;
get memoMethod(): LRUCache.Memoizer<K, V, FC> | undefined;
/**
* {@link LRUCache.OptionsBase.dispose} (read-only)
*/
get dispose(): LRUCache.Disposer<K, V> | undefined;
/**
* {@link LRUCache.OptionsBase.disposeAfter} (read-only)
*/
get disposeAfter(): LRUCache.Disposer<K, V> | undefined;
constructor(options: LRUCache.Options<K, V, FC> | LRUCache<K, V, FC>);
/**
* Return the number of ms left in the item's TTL. If item is not in cache,
* returns `0`. Returns `Infinity` if item is in cache without a defined TTL.
*/
getRemainingTTL(key: K): number;
/**
* Return a generator yielding `[key, value]` pairs,
* in order from most recently used to least recently used.
*/
entries(): Generator<[K, V], void, unknown>;
/**
* Inverse order version of {@link LRUCache.entries}
*
* Return a generator yielding `[key, value]` pairs,
* in order from least recently used to most recently used.
*/
rentries(): Generator<(K | V | BackgroundFetch<V> | undefined)[], void, unknown>;
/**
* Return a generator yielding the keys in the cache,
* in order from most recently used to least recently used.
*/
keys(): Generator<K, void, unknown>;
/**
* Inverse order version of {@link LRUCache.keys}
*
* Return a generator yielding the keys in the cache,
* in order from least recently used to most recently used.
*/
rkeys(): Generator<K, void, unknown>;
/**
* Return a generator yielding the values in the cache,
* in order from most recently used to least recently used.
*/
values(): Generator<V, void, unknown>;
/**
* Inverse order version of {@link LRUCache.values}
*
* Return a generator yielding the values in the cache,
* in order from least recently used to most recently used.
*/
rvalues(): Generator<V | BackgroundFetch<V> | undefined, void, unknown>;
/**
* Iterating over the cache itself yields the same results as
* {@link LRUCache.entries}
*/
[Symbol.iterator](): Generator<[K, V], void, unknown>;
/**
* A String value that is used in the creation of the default string
* description of an object. Called by the built-in method
* `Object.prototype.toString`.
*/
[Symbol.toStringTag]: string;
/**
* Find a value for which the supplied fn method returns a truthy value,
* similar to `Array.find()`. fn is called as `fn(value, key, cache)`.
*/
find(fn: (v: V, k: K, self: LRUCache<K, V, FC>) => boolean, getOptions?: LRUCache.GetOptions<K, V, FC>): V | undefined;
/**
* Call the supplied function on each item in the cache, in order from most
* recently used to least recently used.
*
* `fn` is called as `fn(value, key, cache)`.
*
* If `thisp` is provided, function will be called in the `this`-context of
* the provided object, or the cache if no `thisp` object is provided.
*
* Does not update age or recenty of use, or iterate over stale values.
*/
forEach(fn: (v: V, k: K, self: LRUCache<K, V, FC>) => any, thisp?: any): void;
/**
* The same as {@link LRUCache.forEach} but items are iterated over in
* reverse order. (ie, less recently used items are iterated over first.)
*/
rforEach(fn: (v: V, k: K, self: LRUCache<K, V, FC>) => any, thisp?: any): void;
/**
* Delete any stale entries. Returns true if anything was removed,
* false otherwise.
*/
purgeStale(): boolean;
/**
* Get the extended info about a given entry, to get its value, size, and
* TTL info simultaneously. Returns `undefined` if the key is not present.
*
* Unlike {@link LRUCache#dump}, which is designed to be portable and survive
* serialization, the `start` value is always the current timestamp, and the
* `ttl` is a calculated remaining time to live (negative if expired).
*
* Always returns stale values, if their info is found in the cache, so be
* sure to check for expirations (ie, a negative {@link LRUCache.Entry#ttl})
* if relevant.
*/
info(key: K): LRUCache.Entry<V> | undefined;
/**
* Return an array of [key, {@link LRUCache.Entry}] tuples which can be
* passed to {@link LRLUCache#load}.
*
* The `start` fields are calculated relative to a portable `Date.now()`
* timestamp, even if `performance.now()` is available.
*
* Stale entries are always included in the `dump`, even if
* {@link LRUCache.OptionsBase.allowStale} is false.
*
* Note: this returns an actual array, not a generator, so it can be more
* easily passed around.
*/
dump(): [K, LRUCache.Entry<V>][];
/**
* Reset the cache and load in the items in entries in the order listed.
*
* The shape of the resulting cache may be different if the same options are
* not used in both caches.
*
* The `start` fields are assumed to be calculated relative to a portable
* `Date.now()` timestamp, even if `performance.now()` is available.
*/
load(arr: [K, LRUCache.Entry<V>][]): void;
/**
* Add a value to the cache.
*
* Note: if `undefined` is specified as a value, this is an alias for
* {@link LRUCache#delete}
*
* Fields on the {@link LRUCache.SetOptions} options param will override
* their corresponding values in the constructor options for the scope
* of this single `set()` operation.
*
* If `start` is provided, then that will set the effective start
* time for the TTL calculation. Note that this must be a previous
* value of `performance.now()` if supported, or a previous value of
* `Date.now()` if not.
*
* Options object may also include `size`, which will prevent
* calling the `sizeCalculation` function and just use the specified
* number if it is a positive integer, and `noDisposeOnSet` which
* will prevent calling a `dispose` function in the case of
* overwrites.
*
* If the `size` (or return value of `sizeCalculation`) for a given
* entry is greater than `maxEntrySize`, then the item will not be
* added to the cache.
*
* Will update the recency of the entry.
*
* If the value is `undefined`, then this is an alias for
* `cache.delete(key)`. `undefined` is never stored in the cache.
*/
set(k: K, v: V | BackgroundFetch<V> | undefined, setOptions?: LRUCache.SetOptions<K, V, FC>): this;
/**
* Evict the least recently used item, returning its value or
* `undefined` if cache is empty.
*/
pop(): V | undefined;
/**
* Check if a key is in the cache, without updating the recency of use.
* Will return false if the item is stale, even though it is technically
* in the cache.
*
* Check if a key is in the cache, without updating the recency of
* use. Age is updated if {@link LRUCache.OptionsBase.updateAgeOnHas} is set
* to `true` in either the options or the constructor.
*
* Will return `false` if the item is stale, even though it is technically in
* the cache. The difference can be determined (if it matters) by using a
* `status` argument, and inspecting the `has` field.
*
* Will not update item age unless
* {@link LRUCache.OptionsBase.updateAgeOnHas} is set.
*/
has(k: K, hasOptions?: LRUCache.HasOptions<K, V, FC>): boolean;
/**
* Like {@link LRUCache#get} but doesn't update recency or delete stale
* items.
*
* Returns `undefined` if the item is stale, unless
* {@link LRUCache.OptionsBase.allowStale} is set.
*/
peek(k: K, peekOptions?: LRUCache.PeekOptions<K, V, FC>): V | undefined;
/**
* Make an asynchronous cached fetch using the
* {@link LRUCache.OptionsBase.fetchMethod} function.
*
* If the value is in the cache and not stale, then the returned
* Promise resolves to the value.
*
* If not in the cache, or beyond its TTL staleness, then
* `fetchMethod(key, staleValue, { options, signal, context })` is
* called, and the value returned will be added to the cache once
* resolved.
*
* If called with `allowStale`, and an asynchronous fetch is
* currently in progress to reload a stale value, then the former
* stale value will be returned.
*
* If called with `forceRefresh`, then the cached item will be
* re-fetched, even if it is not stale. However, if `allowStale` is also
* set, then the old value will still be returned. This is useful
* in cases where you want to force a reload of a cached value. If
* a background fetch is already in progress, then `forceRefresh`
* has no effect.
*
* If multiple fetches for the same key are issued, then they will all be
* coalesced into a single call to fetchMethod.
*
* Note that this means that handling options such as
* {@link LRUCache.OptionsBase.allowStaleOnFetchAbort},
* {@link LRUCache.FetchOptions.signal},
* and {@link LRUCache.OptionsBase.allowStaleOnFetchRejection} will be
* determined by the FIRST fetch() call for a given key.
*
* This is a known (fixable) shortcoming which will be addresed on when
* someone complains about it, as the fix would involve added complexity and
* may not be worth the costs for this edge case.
*
* If {@link LRUCache.OptionsBase.fetchMethod} is not specified, then this is
* effectively an alias for `Promise.resolve(cache.get(key))`.
*
* When the fetch method resolves to a value, if the fetch has not
* been aborted due to deletion, eviction, or being overwritten,
* then it is added to the cache using the options provided.
*
* If the key is evicted or deleted before the `fetchMethod`
* resolves, then the AbortSignal passed to the `fetchMethod` will
* receive an `abort` event, and the promise returned by `fetch()`
* will reject with the reason for the abort.
*
* If a `signal` is passed to the `fetch()` call, then aborting the
* signal will abort the fetch and cause the `fetch()` promise to
* reject with the reason provided.
*
* **Setting `context`**
*
* If an `FC` type is set to a type other than `unknown`, `void`, or
* `undefined` in the {@link LRUCache} constructor, then all
* calls to `cache.fetch()` _must_ provide a `context` option. If
* set to `undefined` or `void`, then calls to fetch _must not_
* provide a `context` option.
*
* The `context` param allows you to provide arbitrary data that
* might be relevant in the course of fetching the data. It is only
* relevant for the course of a single `fetch()` operation, and
* discarded afterwards.
*
* **Note: `fetch()` calls are inflight-unique**
*
* If you call `fetch()` multiple times with the same key value,
* then every call after the first will resolve on the same
* promise<sup>1</sup>,
* _even if they have different settings that would otherwise change
* the behavior of the fetch_, such as `noDeleteOnFetchRejection`
* or `ignoreFetchAbort`.
*
* In most cases, this is not a problem (in fact, only fetching
* something once is what you probably want, if you're caching in
* the first place). If you are changing the fetch() options
* dramatically between runs, there's a good chance that you might
* be trying to fit divergent semantics into a single object, and
* would be better off with multiple cache instances.
*
* **1**: Ie, they're not the "same Promise", but they resolve at
* the same time, because they're both waiting on the same
* underlying fetchMethod response.
*/
fetch(k: K, fetchOptions: unknown extends FC ? LRUCache.FetchOptions<K, V, FC> : FC extends undefined | void ? LRUCache.FetchOptionsNoContext<K, V> : LRUCache.FetchOptionsWithContext<K, V, FC>): Promise<undefined | V>;
fetch(k: unknown extends FC ? K : FC extends undefined | void ? K : never, fetchOptions?: unknown extends FC ? LRUCache.FetchOptions<K, V, FC> : FC extends undefined | void ? LRUCache.FetchOptionsNoContext<K, V> : never): Promise<undefined | V>;
/**
* In some cases, `cache.fetch()` may resolve to `undefined`, either because
* a {@link LRUCache.OptionsBase#fetchMethod} was not provided (turning
* `cache.fetch(k)` into just an async wrapper around `cache.get(k)`) or
* because `ignoreFetchAbort` was specified (either to the constructor or
* in the {@link LRUCache.FetchOptions}). Also, the
* {@link OptionsBase.fetchMethod} may return `undefined` or `void`, making
* the test even more complicated.
*
* Because inferring the cases where `undefined` might be returned are so
* cumbersome, but testing for `undefined` can also be annoying, this method
* can be used, which will reject if `this.fetch()` resolves to undefined.
*/
forceFetch(k: K, fetchOptions: unknown extends FC ? LRUCache.FetchOptions<K, V, FC> : FC extends undefined | void ? LRUCache.FetchOptionsNoContext<K, V> : LRUCache.FetchOptionsWithContext<K, V, FC>): Promise<V>;
forceFetch(k: unknown extends FC ? K : FC extends undefined | void ? K : never, fetchOptions?: unknown extends FC ? LRUCache.FetchOptions<K, V, FC> : FC extends undefined | void ? LRUCache.FetchOptionsNoContext<K, V> : never): Promise<V>;
/**
* If the key is found in the cache, then this is equivalent to
* {@link LRUCache#get}. If not, in the cache, then calculate the value using
* the {@link LRUCache.OptionsBase.memoMethod}, and add it to the cache.
*
* If an `FC` type is set to a type other than `unknown`, `void`, or
* `undefined` in the LRUCache constructor, then all calls to `cache.memo()`
* _must_ provide a `context` option. If set to `undefined` or `void`, then
* calls to memo _must not_ provide a `context` option.
*
* The `context` param allows you to provide arbitrary data that might be
* relevant in the course of fetching the data. It is only relevant for the
* course of a single `memo()` operation, and discarded afterwards.
*/
memo(k: K, memoOptions: unknown extends FC ? LRUCache.MemoOptions<K, V, FC> : FC extends undefined | void ? LRUCache.MemoOptionsNoContext<K, V> : LRUCache.MemoOptionsWithContext<K, V, FC>): V;
memo(k: unknown extends FC ? K : FC extends undefined | void ? K : never, memoOptions?: unknown extends FC ? LRUCache.MemoOptions<K, V, FC> : FC extends undefined | void ? LRUCache.MemoOptionsNoContext<K, V> : never): V;
/**
* Return a value from the cache. Will update the recency of the cache
* entry found.
*
* If the key is not found, get() will return `undefined`.
*/
get(k: K, getOptions?: LRUCache.GetOptions<K, V, FC>): V | undefined;
/**
* Deletes a key out of the cache.
*
* Returns true if the key was deleted, false otherwise.
*/
delete(k: K): boolean;
/**
* Clear the cache entirely, throwing away all values.
*/
clear(): void;
}
//# sourceMappingURL=index.d.ts.map