s := blk.toGNU().sparse()
	spd := make(sparseDatas, 0, s.maxEntries())
	for {
		for i := 0; i < s.maxEntries(); i++ {
			// This termination condition is identical to GNU and BSD tar.
			if s.entry(i).offset()[0] == 0x00 {
				break // Don't return, need to process extended headers (even if empty)
			}
			offset := p.parseNumeric(s.entry(i).offset())
			length := p.parseNumeric(s.entry(i).length())
			if p.err != nil {

    assertThat(converter.convert("0")).isEqualTo(0);
    assertThat(converter.convert("-1")).isEqualTo(-1);
    assertThat(converter.convert("0xff")).isEqualTo(255);
    assertThat(converter.convert("0xFF")).isEqualTo(255);
    assertThat(converter.convert("-0xFF")).isEqualTo(-255);
    assertThat(converter.convert("#0000FF")).isEqualTo(255);
    assertThat(converter.convert("0666")).isEqualTo(438);
  }

		tw := NewWriter(new(bytes.Buffer))
		hdr := &Header{Name: "dir/", Typeflag: TypeDir}
		if err := tw.WriteHeader(hdr); err != nil {
			t.Fatalf("WriteHeader() = %v, want nil", err)
		}
		if _, err := tw.Write([]byte{0x00}); err != ErrWriteTooLong {
			t.Fatalf("Write() = %v, want %v", err, ErrWriteTooLong)
		}
	})

	t.Run("NegativeSize", func(t *testing.T) {
		tw := NewWriter(new(bytes.Buffer))

010D          ; valid                                  # 1.1  LATIN SMALL LETTER C WITH CARON
010E          ; mapped                 ; 010F          # 1.1  LATIN CAPITAL LETTER D WITH CARON
010F          ; valid                                  # 1.1  LATIN SMALL LETTER D WITH CARON
0110          ; mapped                 ; 0111          # 1.1  LATIN CAPITAL LETTER D WITH STROKE