hdr  Header     // Shallow copy of Header that is safe for mutations
	blk  block      // Buffer to use as temporary local storage

	// err is a persistent error.
	// It is only the responsibility of every exported method of Writer to
	// ensure that this error is sticky.
	err error
}

// NewWriter creates a new Writer writing to w.
func NewWriter(w io.Writer) *Writer {
	return &Writer{w: w, curr: &regFileWriter{w, 0}}
}

// It walks the directory tree starting at the root of the filesystem
// adding each file to the zip using deflate while maintaining the directory structure.
func (w *Writer) AddFS(fsys fs.FS) error {
	return fs.WalkDir(fsys, ".", func(name string, d fs.DirEntry, err error) error {
		if err != nil {
			return err
		}
		if d.IsDir() {
			return nil
		}
		info, err := d.Info()
		if err != nil {
			return err
		}