/// <reference types="node" />
import I = require('./interfaces');
/**
 * Constructs a new PersistentStorage instead
 * @param opts
 * @param {boolean=false} opts.useCompression
 * @param {string=} opts.keyPrefix
 * @param opts.storageBackend
 * @constructor
 */
declare class PersistentStorage {
    private config;
    private store;
    private cache;
    constructor(opts: I.Config);
    static generateSalt(lengthBytes: number): string;
    static generateIV(lengthBytes: number): Buffer;
    readonly length: number;
    /**
     * Sets a value in the persistent storage
     * @param {string} key - Key to associate this value with
     * @param {*} value - Value to store, if undefined will delete the given key
     */
    setItem(key: string, value: any): void;
    /**
     * Gets a value from the persistant storage, uses in memory cache if possible
     * @param {string} key - Key to retrieve
     * @returns {*}
     */
    getItem(key: string): any;
    /**
     * Gets the nth key in the store, note that the order of keys is not guaranteed but
     * will be consistent so long as the key set stays the same.
     * @param {number} n
     * @returns {string}
     */
    key(n: number): string;
    /**
     * Gets an array of the keys in the store
     * @returns {string[]}
     */
    keys(): string[];
    /**
     * Removes an item from the store
     * @param {string} key
     */
    removeItem(key: string): void;
    /**
     * Clears all items from the store
     */
    clear(): void;
    /**
     * Clears all items from the cache
     */
    purgeCache(): void;
}
export = PersistentStorage;