dirRealPathFileWindows

fn dirRealPathFileWindows(userdata: ?*anyopaque, dir: Dir, sub_path: []const u8, out_buffer: []u8) Dir.RealPathFileError!usize {
    const t: *Threaded = @ptrCast(@alignCast(userdata));
    _ = t;

    var path_name_w = try sliceToPrefixedFileW(dir.handle, sub_path, .{});

    const h_file = handle: {
        if (OpenFile(path_name_w.span(), .{
            .dir = dir.handle,
            .access_mask = .{
                .GENERIC = .{ .READ = true },
                .STANDARD = .{ .SYNCHRONIZE = true },
            },
            .creation = .OPEN,
            .filter = .any,
        })) |handle| {
            break :handle handle;
        } else |err| switch (err) {
            error.WouldBlock => unreachable,
            else => |e| return e,
        }
    };
    defer windows.CloseHandle(h_file);

    // We can re-use the path buffer for the WTF-16 representation since
    // we don't need the prefixed path anymore
    return realPathWindowsBuf(h_file, out_buffer, &path_name_w.data);
}