SpawnDev.AsyncFileSystem

Cross-platform async file system for .NET. Same API on desktop (native filesystem) and browser (OPFS — Origin Private File System).

Features

• Unified IAsyncFS interface — one API for both platforms
• Browser: OPFS via FileSystemDirectoryHandle (persistent, survives page reloads)
• Desktop: Native filesystem via System.IO
• Full file operations: Read, Write, Append, Delete, Directory management
• Stream support: GetReadStream, GetWriteStream for large files
• JSON serialization: ReadJSON<T>, WriteJSON built-in
• File system change events: FileSystemChanged event
• Path utilities: Cross-platform path manipulation via IOPath

Quick Start

Browser (Blazor WASM) — OPFS

using SpawnDev.AsyncFileSystem;
using SpawnDev.AsyncFileSystem.BrowserWASM;

// Get the OPFS root directory
var fs = new AsyncFSFileSystemDirectoryHandle();

// Write and read files — persists across page reloads
await fs.Write("data/config.json", """{"setting": true}""");
var config = await fs.ReadText("data/config.json");

// Binary data
await fs.Write("data/model.bin", modelBytes);
var bytes = await fs.ReadBytes("data/model.bin");

Desktop (.NET) — Native Filesystem

using SpawnDev.AsyncFileSystem;
using SpawnDev.AsyncFileSystem.Native;

var fs = new AsyncFSNative("/path/to/data");

await fs.Write("cache/piece_0", pieceData);
var data = await fs.ReadBytes("cache/piece_0");

API Reference

IAsyncFS

Method	Description
Write(path, byte[])	Write binary data
Write(path, string)	Write text
Write(path, Stream)	Write from stream
ReadBytes(path)	Read as byte array
ReadText(path)	Read as string
ReadStream(path)	Get read stream
Append(path, data)	Append to file
ReadJSON<T>(path)	Deserialize JSON file
WriteJSON(path, obj)	Serialize to JSON file
FileExists(path)	Check if file exists
DirectoryExists(path)	Check if directory exists
Exists(path)	Check if path exists
CreateDirectory(path)	Create directory
Remove(path, recursive)	Delete file or directory
GetFiles(path)	List files in directory
GetDirectories(path)	List subdirectories
GetEntries(path)	List all entries
GetInfo(path)	Get file/directory info
GetReadStream(path)	Get read-only stream
GetWriteStream(path)	Get writable stream

Use Cases

• Torrent piece storage — SpawnDev.WebTorrent uses this for persistent piece caching in the browser
• ML model caching — Cache downloaded model weights in OPFS so they load instantly on return visits
• Application data — Config files, user data, cached assets
• Offline-first apps — Store data locally in the browser, sync when online

Credits

Built by Todd Tanner (@LostBeard) and the SpawnDev team.

License

MIT