WinFsp.Native

Zero-alloc, AOT-ready WinFsp binding for modern .NET — build user-mode file systems on Windows with native performance.

Why WinFsp.Native?

	WinFsp.Native	Official WinFsp.Net
Native AOT	Full support (IsAotCompatible)	Not compatible (reflection-based)
Target	.NET 8+	.NET Standard 2.0 / .NET Framework 3.5
Hot-path alloc	Zero managed heap allocation	Allocates per callback
P/Invoke	[LibraryImport] source generator	[DllImport] with marshaling
Async I/O	ValueTask<T> + STATUS_PENDING	Synchronous only
API style	IFileSystem interface + FileSystemHost	Inheritance-based FileSystemBase
Dependencies	Zero NuGet dependencies	Microsoft.Win32.Registry + System.IO.FileSystem.AccessControl

Quick Start

dotnet add package WinFsp.Native

using WinFsp.Native;

class MyFs : IFileSystem
{
    public bool SynchronousIo => true;

    public int GetVolumeInfo(out ulong totalSize, out ulong freeSize, out string volumeLabel)
    {
        totalSize = 1024 * 1024;
        freeSize = 512 * 1024;
        volumeLabel = "MyDrive";
        return NtStatus.Success;
    }

    // Implement other IFileSystem methods...
}

// Mount
var host = new FileSystemHost(new MyFs());
host.Mount("Z:");

Two API Levels

High-Level: IFileSystem + FileSystemHost

Implement the IFileSystem interface with familiar .NET types (string, Memory<byte>, ValueTask<T>). The FileSystemHost handles all WinFsp plumbing — mounting, callback dispatch, async STATUS_PENDING, buffer management, and cancellation.

using WinFsp.Native;

// One using gets you everything: IFileSystem, FileSystemHost, NtStatus,
// FspFileInfo, CleanupFlags, CreateOptions, result types, etc.

Low-Level: WinFspFileSystem

Direct function pointer access to all 64 WinFsp callback slots. Full control, zero abstraction overhead.

using WinFsp.Native;
using WinFsp.Native.Interop; // FspVolumeParams, FspFileSystemInterface, etc.

var fs = new WinFspFileSystem();
fs.VolumeParams.SectorSize = 4096;
fs.Interface.Read = &OnRead;
fs.Mount("Z:");

Prerequisites

• Windows 10/11
• WinFsp 2.x installed (with Developer files for building)
• .NET 8.0+ SDK

Project Structure

src/WinFsp.Native/           # The binding library
tests/WinFsp.Native.Tests/   # Integration tests (mounts real WinFsp FS)
examples/HelloFs/             # Minimal read-only file system example

Building

dotnet build
dotnet test
dotnet pack

License

MIT — see LICENSE.

Runtime dependency: WinFsp (GPLv3 with FLOSS exception). WinFsp must be installed on the target machine. This binding library does not redistribute WinFsp binaries.