import type { NodesetImageStore } from "../dist/api/index.js";
export interface FileNodesetImageStoreOptions {
    /**
     * the directory; defaults to `NODE_OPCUA_NODESET_IMAGE_DIR`, then
     * `$XDG_CACHE_HOME/node-opcua/nodeset-images`, then `~/.cache/node-opcua/nodeset-images`
     */
    directory?: string;
    /** the size the store stays under, oldest images dropped first @default 256 MiB */
    maxBytes?: number;
}
/** the default directory: per user, never the shared temp root, since a server trusts what it reads here */
export declare function defaultNodesetImageDirectory(): string;
/**
 * the images in a directory of the user's, one file per key, written atomically; a corrupt or
 * foreign file is the loader's to detect and this store's to replace; the store stays under a
 * size by dropping the least recently written images
 */
export declare class FileNodesetImageStore implements NodesetImageStore {
    readonly directory: string;
    private readonly maxBytes;
    constructor(options?: FileNodesetImageStoreOptions);
    private fileOf;
    get(key: string): Promise<Uint8Array | undefined>;
    put(key: string, image: Uint8Array): Promise<void>;
    /** drop the oldest images until the directory fits, never the one just written */
    private evict;
    /** the keys the directory holds */
    keys(): Promise<string[]>;
}