@J2ktIncompatible
@GwtIncompatible
@ElementTypesAreNonnullByDefault
final class CharSequenceReader extends Reader {

  @CheckForNull private CharSequence seq;
  private int pos;
  private int mark;

  /** Creates a new reader wrapping the given character sequence. */
  public CharSequenceReader(CharSequence seq) {
    this.seq = checkNotNull(seq);
  }

  private void checkOpen() throws IOException {

@J2ktIncompatible
@GwtIncompatible
@ElementTypesAreNonnullByDefault
final class CharSequenceReader extends Reader {

  @CheckForNull private CharSequence seq;
  private int pos;
  private int mark;

  /** Creates a new reader wrapping the given character sequence. */
  public CharSequenceReader(CharSequence seq) {
    this.seq = checkNotNull(seq);
  }

  private void checkOpen() throws IOException {

            + "0123456789\r\n"
            + "!@#$%^&*()-=_+\t[]{};':\",./<>?\\| ");
  }

  public void testMarkAndReset() throws IOException {
    String string = "abcdefghijklmnopqrstuvwxyz";
    CharSequenceReader reader = new CharSequenceReader(string);
    assertTrue(reader.markSupported());

    assertEquals(string, readFully(reader));
    assertFullyRead(reader);

    // reset and read again
    reader.reset();

    protected CharSequenceCharSource(CharSequence seq) {
      this.seq = checkNotNull(seq);
    }

    @Override
    public Reader openStream() {
      return new CharSequenceReader(seq);
    }

    @Override
    public String read() {
      return seq.toString();
    }

    @Override
    public boolean isEmpty() {
      return seq.length() == 0;
    }