/**
 * Origin Private File System (OPFS) Storage Backend
 *
 * High-performance browser storage using the File System Access API.
 * OPFS provides file-like semantics for browser persistence. Performance is
 * browser- and workload-dependent and should be measured for the target app.
 *
 * Features:
 * - Auto-initializing (no manual init() required)
 * - High performance for large binary data
 *
 * Browser Support:
 * - Chrome 86+
 * - Safari 15.2+
 * - Firefox 111+
 * - Edge 86+
 *
 * Note: This module is designed for browser environments only.
 * It will not work in Node.js/Bun server environments.
 */
import type { StorageBackend } from './StorageBackend.js';
export declare class OPFSBackend implements StorageBackend {
    private static mutationLocks;
    readonly type = "opfs";
    readonly namespace: string;
    private root;
    private initialized;
    private initPromise;
    /**
     * Create an OPFS backend scoped to one directory in the origin root.
     * Keeping a namespace boundary is important: clear() must never remove
     * files owned by another application sharing this origin.
     */
    constructor(namespace?: string);
    /**
     * Initialize the OPFS backend (optional - auto-initializes on first operation)
     * @deprecated No longer required - operations auto-initialize
     */
    init(): Promise<void>;
    private doInit;
    /**
     * Ensure backend is initialized (lazy init on first use).
     * Safe to call concurrently — only runs initialization once.
     */
    private ensureInitialized;
    private isNotFoundError;
    private formatError;
    private normalizeStorageError;
    private validateAndSplitPath;
    private canonicalizePath;
    private withSameRealmMutationLock;
    private withMutationLock;
    /**
     * Get a file handle, creating parent directories as needed
     */
    private getFileHandle;
    /**
     * Get a directory handle, creating if needed
     */
    private getDirectoryHandle;
    read(key: string): Promise<ArrayBuffer | null>;
    write(key: string, data: ArrayBuffer | Uint8Array): Promise<void>;
    private getOrCreateFileHandle;
    private removeFileUnlocked;
    private cleanupCreatedEmptyFile;
    private dataToArrayBuffer;
    private doWrite;
    append(key: string, data: ArrayBuffer | Uint8Array): Promise<void>;
    private doAppend;
    delete(key: string): Promise<void>;
    exists(key: string): Promise<boolean>;
    list(prefix?: string): Promise<string[]>;
    mkdir(path: string): Promise<void>;
    /** Clear only this backend's namespace in OPFS. */
    clear(): Promise<void>;
    /**
     * Check if OPFS is available in the current environment
     */
    static isAvailable(): boolean;
}
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