final int bytesPerChunk;
    private final byte[] decodabet;
    private final boolean[] validPadding;
    private final boolean ignoreCase;

    Alphabet(String name, char[] chars) {
      this(name, chars, decodabetFor(chars), /* ignoreCase= */ false);
    }

    private Alphabet(String name, char[] chars, byte[] decodabet, boolean ignoreCase) {
      this.name = checkNotNull(name);
      this.chars = checkNotNull(chars);