import { Undefinable } from '@thermopylae/core.declarations';
import { CacheBackend } from '../contracts/cache-backend';
import { CacheEntry } from '../contracts/commons';
/**
 * Backend which has a pool of reusable {@link CacheEntry}. Pool can have a fixed or dynamic size.
 * If pool has a fixed size, trying to insert keys above that size will result in an error. <br/>
 * Each time *key* is inserted, a free {@link CacheEntry} is taken from pool to hold the *value*.
 * When *key* is deleted/expires/cleared, it's according {@link CacheEntry} is returned to pool and can be used by another *key*.
 *
 * @template Key	Type of the *key*.
 * @template Value	Type of the *value*.
 * @template Entry	Type of the cache entry. <br/>
 * 					Defaults to {@link CacheEntry}.
 */
declare class EntryPoolCacheBackend<Key, Value, Entry extends CacheEntry<Key, Value> = CacheEntry<Key, Value>> implements CacheBackend<Key, Value> {
    private readonly store;
    private readonly entryPool;
    /**
     * @param capacity	Backend capacity. <br/>
     * 					When given, cache will not grow above *capacity* (i.e. will have a fixed size). <br/>
     * 					If you omit this argument, backend will have a dynamic size.
     */
    constructor(capacity?: number);
    /**
     * @inheritDoc
     */
    get(key: Key): Undefinable<Entry>;
    /**
     * @inheritDoc
     */
    has(key: Key): boolean;
    /**
     * @inheritDoc
     */
    set(key: Key, value: Value): Entry;
    /**
     * @inheritDoc
     */
    del(entry: Entry): void;
    /**
     * @inheritDoc
     */
    clear(): void;
    /**
     * @inheritDoc
     */
    get size(): number;
    /**
     * @inheritDoc
     */
    [Symbol.iterator](): IterableIterator<[Key, Entry]>;
    /**
     * @inheritDoc
     */
    keys(): IterableIterator<Key>;
    /**
     * @inheritDoc
     */
    values(): IterableIterator<Entry>;
}
export { EntryPoolCacheBackend };