TermToBytesRefAttribute.java

package com.antbrains.wordseg.luceneanalyzer;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * This attribute is requested by TermsHashPerField to index the contents. This attribute can be
 * used to customize the final byte[] encoding of terms.
 * <p>
 * Consumers of this attribute call {@link #getBytesRef()} up-front, and then invoke
 * {@link #fillBytesRef()} for each term. Example:
 * 
 * <pre class="prettyprint">
 *   final TermToBytesRefAttribute termAtt = tokenStream.getAttribute(TermToBytesRefAttribute.class);
 *   final BytesRef bytes = termAtt.getBytesRef();
 * 
 *   while (termAtt.incrementToken() {
 * 
 *     // you must call termAtt.fillBytesRef() before doing something with the bytes.
 *     // this encodes the term value (internally it might be a char[], etc) into the bytes.
 *     int hashCode = termAtt.fillBytesRef();
 * 
 *     if (isInteresting(bytes)) {
 *     
 *       // because the bytes are reused by the attribute (like CharTermAttribute's char[] buffer),
 *       // you should make a copy if you need persistent access to the bytes, otherwise they will
 *       // be rewritten across calls to incrementToken()
 * 
 *       doSomethingWith(new BytesRef(bytes));
 *     }
 *   }
 *   ...
 * </pre>
 * 
 * @lucene.experimental This is a very expert API, please use {@link CharTermAttributeImpl} and its
 *                      implementation of this method for UTF-8 terms.
 */
public interface TermToBytesRefAttribute extends Attribute {
  /**
   * Updates the bytes {@link #getBytesRef()} to contain this term's final encoding, and returns its
   * hashcode.
   * 
   * @return the hashcode as defined by {@link BytesRef#hashCode}:
   * 
   *         <pre>
   * int hash = 0;
   * for (int i = termBytes.offset; i < termBytes.offset + termBytes.length; i++) {
   *   hash = 31 * hash + termBytes.bytes[i];
   * }
   * </pre>
   * 
   *         Implement this for performance reasons, if your code can calculate the hash on-the-fly.
   *         If this is not the case, just return {@code termBytes.hashCode()}.
   */
  public int fillBytesRef();

  /**
   * Retrieve this attribute's BytesRef. The bytes are updated from the current term when the
   * consumer calls {@link #fillBytesRef()}.
   * 
   * @return this Attributes internal BytesRef.
   */
  public BytesRef getBytesRef();
}