Add browser support via ZenFS

[Copilot]

Implements browser runtime support using ZenFS as suggested in issue #3. Enables filesystem operations in browsers with configurable storage backends (in-memory default, IndexedDB for persistence).

Changes

Infrastructure

• Added @zenfs/core dependency for browser filesystem abstraction
• Created src/utils/browser-fs.ts with initialization and configuration API
• Implemented race condition protection for concurrent initialization

Runtime-aware operations

• stat module: Updated stat, lstat, access to use ZenFS in browsers
• io module: Modified readFile, writeFile with runtime detection
• ops module: Added browser support for mkdir, rmdir, rm, unlink, readdir, rename, cp
• hash: Uses Web Crypto API in browsers (sha256/sha1/sha384/sha512 only)
• cwd/chdir: Returns "/" in browser, throws error on chdir attempt

Browser limitations

Operations not supported: chmod, chown, link, open, readlink, realpath, truncate, which, FsWatcher

Usage

// Zero-config in-memory filesystem
import { readFile, writeFile } from "@cross/fs/io";
await writeFile("/data/test.txt", "Hello browser!");

// Persistent storage via IndexedDB
import { configureBrowserFS } from "@cross/fs";
const { IndexedDB } = await import("@zenfs/dom");

await configureBrowserFS({
  mounts: { '/storage': { backend: IndexedDB } }
});

All existing Node.js/Deno/Bun functionality preserved. Operations automatically adapt to runtime environment.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• dl.deno.land
  • Triggering command: /usr/bin/curl curl -s REDACTED (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

Check if #3 is possible to implement

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[Hexagon]

@copilot would it be possible to implement this without the added dependency on zenfs?

[Copilot]

@copilot would it be possible to implement this without the added dependency on zenfs?

It's technically possible but would require significant custom implementation. Here are the options:

Without ZenFS, we'd need to:

1. Implement our own filesystem abstraction (path resolution, directory trees, metadata)
2. Use browser APIs directly (File System Access API, IndexedDB, etc.) - each with limitations:
   • File System Access API: requires user permission prompts, limited browser support
   • IndexedDB: complex to map to filesystem semantics
   • LocalStorage: size limits, synchronous only

Why ZenFS was chosen:

• Provides Node.js-compatible fs API out of the box
• Handles path resolution, directory hierarchies automatically
• Supports multiple backends (in-memory, IndexedDB, etc.)
• Well-maintained and battle-tested
• ~50KB gzipped, loaded only in browsers (dynamic import)

Alternative approach:
We could implement basic in-memory operations without dependencies, but would lose:

• Persistent storage options (IndexedDB backend)
• Complex path operations
• Directory tree management
• Multiple mount points

Would you prefer a minimal implementation without dependencies (limited features) or keep ZenFS for full functionality? I can implement either approach based on your preference.