export interface FifoMapProps {
    maxSize: number;
}
/**
 * FIFO Map Cache.
 */
export declare class FifoMap<KeyType, ValueType> {
    private _db;
    private _fifoKeys;
    private _maxSize;
    constructor(props: FifoMapProps);
    get size(): number;
    /**
     * Get item.
     * @param key key
     * @returns `cached value`, if input key matches.\
       `undefined`, if it does not exist.
     */
    get: (key: KeyType) => ValueType | undefined;
    /**
     * Put item. \
     * It also deletes item as FIFO only when cache is full.
     * @param key key
     * @param value value
     * @returns `old item`, if cache is full and delete an item done. \
     *  `undefined`, if cache is not full and only put done.
     */
    put: (key: KeyType, value: ValueType) => {
        key: KeyType;
        value: ValueType & ({} | null);
    } | undefined;
    /**
     * Delete item.
     * @param key key
     * @returns `deleted item`, if key exists and deleted.\
     *  `undefined`, if key does not exist.
     */
    delete: (key: KeyType) => {
        key: KeyType;
        value: ValueType & ({} | null);
    } | undefined;
    /**
     * Clear all.
     */
    clear: () => void;
}