@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 {