/// <summary>
 /// See <see cref="BaseEncoding.GetDecodeCountWithoutArgumentsValidation(char[], int, int)"/>.
 /// </summary>
 /// <exception cref="FormatException">input sequence is not a valid base sequence</exception>
 protected override int GetDecodeCountWithoutArgumentsValidation(char[] chars, int offset, int length)
 {
     return(b.DecodeSize(length));
 }