dirOpenDirHaiku

fn dirOpenDirHaiku(
    userdata: ?*anyopaque,
    dir: Dir,
    sub_path: []const u8,
    options: Dir.OpenOptions,
) Dir.OpenError!Dir {
    const t: *Threaded = @ptrCast(@alignCast(userdata));
    _ = t;

    var path_buffer: [posix.PATH_MAX]u8 = undefined;
    const sub_path_posix = try pathToPosix(sub_path, &path_buffer);

    _ = options;

    const syscall: Syscall = try .start();
    while (true) {
        const rc = posix.system._kern_open_dir(dir.handle, sub_path_posix);
        if (rc >= 0) {
            syscall.finish();
            return .{ .handle = rc };
        }
        switch (@as(posix.E, @fromBackingInt(@intCast(rc)))) {
            .INTR => {
                try syscall.checkCancel();
                continue;
            },
            else => |e| {
                syscall.finish();
                switch (e) {
                    .FAULT => |err| return errnoBug(err),
                    .INVAL => |err| return errnoBug(err),
                    .BADF => |err| return errnoBug(err), // File descriptor used after closed.
                    .ACCES => return error.AccessDenied,
                    .LOOP => return error.SymLinkLoop,
                    .MFILE => return error.ProcessFdQuotaExceeded,
                    .NAMETOOLONG => return error.NameTooLong,
                    .NFILE => return error.SystemFdQuotaExceeded,
                    .NODEV => return error.NoDevice,
                    .NOENT => return error.FileNotFound,
                    .NOMEM => return error.SystemResources,
                    .NOTDIR => return error.NotDir,
                    .PERM => return error.PermissionDenied,
                    .BUSY => |err| return errnoBug(err),
                    else => |err| return posix.unexpectedErrno(err),
                }
            },
        }
    }
}