@Override
  public int compareTo(byte[] value, int offset, int length) {
    return engine.compareTo(value, offset, length);
  }
Specifies the {@link Charset} to use to convert the row key to a String.
<p>
The row key needs to be converted to a String in order to be matched against the regular
expression. This method controls which charset is used to do this conversion.
<p>
If the row key is made of arbitrary bytes, the charset {@code ISO-8859-1} is recommended.
@param charset The charset to use.
hbase-client/src/main/java/org/apache/hadoop/hbase/filter/RegexStringComparator.java