name    string
		extra   []byte
		wanterr error
	}{
		{
			name:    strings.Repeat("x", 1<<16),
			extra:   []byte{},
			wanterr: errLongName,
		},
		{
			name:    "long_extra",
			extra:   bytes.Repeat([]byte{0xff}, 1<<16),
			wanterr: errLongExtra,
		},
	}

	// write a zip file
	buf := new(bytes.Buffer)
	w := NewWriter(buf)

	for _, test := range headerTests {