/**
   * Returns a {@code ByteSink} that writes base-encoded bytes to the specified {@code CharSink}.
   */
  @J2ktIncompatible
  @GwtIncompatible // ByteSink,CharSink
  public final ByteSink encodingSink(CharSink encodedSink) {
    checkNotNull(encodedSink);
    return new ByteSink() {
      @Override
      public OutputStream openStream() throws IOException {
        return encodingStream(encodedSink.openStream());