FuseSharp

FuseSharp is a FUSE binding for macOS (macFUSE) written in modern C#. It provides a clean API designed specifically to enable the development of userspace filesystems in .NET applications.

Note: This fork is a complete rewrite of the original FuseSharp for .NET 10. It binds directly against macFUSE's FUSE 2.x compatibility library (/usr/local/lib/libfuse.2.dylib) using LibraryImport and [UnmanagedCallersOnly] function pointers. The original native Adaptor shim, the Mono.Posix dependency, and the delegate-based marshaling layer have been removed entirely - no native components need to be built or shipped alongside the managed assembly, and both osx-arm64 and osx-x64 are supported.

Requirements

• macOS with macFUSE installed
• .NET 10 or later

Usage

Derive from FuseFileSystemBase and override the operations your filesystem supports. Only overridden callbacks are registered with FUSE; everything else is reported to the kernel as not implemented.

using FuseSharp;
using FuseSharp.Native;

sealed class MyFileSystem : FuseFileSystemBase
{
    public override bool SupportsMultiThreading => true;

    public override int GetAttr(ReadOnlySpan<byte> path, ref Stat stat, FuseFileInfoRef fiRef)
    {
        if (!path.SequenceEqual(RootPath))
            return -LibC.ENOENT;

        stat.st_mode = (ushort)(LibC.S_IFDIR | 0x1ED); // drwxr-xr-x
        stat.st_nlink = 2;
        return 0;
    }

    public override int ReadDir(ReadOnlySpan<byte> path, ulong offset, DirectoryContent content, ref FuseFileInfo fi)
    {
        content.AddEntry(".");
        content.AddEntry("..");
        return 0;
    }
}

Mount and unmount:

if (!Fuse.CheckDependencies())
    throw new InvalidOperationException("macFUSE is not installed.");

IFuseMount mount = Fuse.Mount("/path/to/mountpoint", new MyFileSystem(), new MountOptions()
{
    Options = "default_permissions,volname=MyVolume"
});

// ... the filesystem is served on a background thread ...

bool unmounted = await mount.UnmountAsync(force: true);

Project overview

Component	Purpose
FuseFileSystemBase	The abstract base class filesystem implementations derive from. Callbacks receive UTF-8 paths as spans and return 0 or a negated Darwin errno.
Fuse	Static entry point: CheckDependencies, Mount, LazyUnmount.
IFuseMount	A handle to a mounted filesystem with UnmountAsync.
Native/LibFuse	LibraryImport bindings for libfuse.2.dylib (fuse_mount, fuse_new, fuse_loop_mt, ...).
Native/LibC	Darwin libSystem bindings and POSIX constants (errno values, open flags, xattr, ...).
Native/FuseOperations	A blittable mirror of macFUSE's struct fuse_operations (FUSE API 26), layout-verified against the installed headers.

Mount options

The MountOptions.Options string is passed to FUSE verbatim (comma-separated). Commonly useful options (see the macFUSE mount options wiki):

Option	Description
volname=NAME	The volume name shown in Finder.
fsname=NAME	The file system name reported by mount.
default_permissions	Let the kernel enforce permissions based on GetAttr results.
allow_other / allow_root	Allow other users (requires the allow_other macFUSE tunable).
ro	Mount read-only.
noappledouble	Do not create AppleDouble (._) companion files.
iosize=N	I/O size in bytes (512 bytes - 32 MB, power of 2).
debug	Print FUSE debugging output.

License

See LICENSE. Based on FuseSharp by Códice Software / PlasticSCM.