// Format the sparse map.
			formatSPD := func(sp sparseDatas, sa sparseArray) sparseDatas {
				for i := 0; len(sp) > 0 && i < sa.MaxEntries(); i++ {
					f.formatNumeric(sa.Entry(i).Offset(), sp[0].Offset)
					f.formatNumeric(sa.Entry(i).Length(), sp[0].Length)
					sp = sp[1:]
				}
				if len(sp) > 0 {
					sa.IsExtended()[0] = 1
				}
				return sp
			}

	closed      bool
	compressors map[uint16]Compressor
	comment     string

	// testHookCloseSizeOffset if non-nil is called with the size
	// of offset of the central directory at Close.
	testHookCloseSizeOffset func(size, offset uint64)
}

type header struct {
	*FileHeader
	offset uint64
	raw    bool
}

// NewWriter returns a new [Writer] writing a zip file to w.
func NewWriter(w io.Writer) *Writer {