Exitf("resize output file failed: %v", err)
	}

	low, high := uint32(filesize), uint32(filesize>>32)
	fmap, err := syscall.CreateFileMapping(syscall.Handle(out.f.Fd()), nil, syscall.PAGE_READWRITE, high, low, nil)
	if err != nil {
		return err
	}
	defer syscall.CloseHandle(fmap)

	ptr, err := syscall.MapViewOfFile(fmap, syscall.FILE_MAP_READ|syscall.FILE_MAP_WRITE, 0, 0, uintptr(filesize))
	if err != nil {
		return err
	}