org.apache.lucene.search.highlight.SimpleSpanFragmenter.java Source code

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Here is the source code for org.apache.lucene.search.highlight.SimpleSpanFragmenter.java

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/*
 * 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.
 */
package org.apache.lucene.search.highlight;

import java.util.List;

import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;
import org.apache.lucene.analysis.tokenattributes.PositionIncrementAttribute;
import org.apache.lucene.search.spans.Spans;

/**
 * {@link Fragmenter} implementation which breaks text up into same-size
 * fragments but does not split up {@link Spans}. This is a simple sample class.
 */
public class SimpleSpanFragmenter implements Fragmenter {
    private static final int DEFAULT_FRAGMENT_SIZE = 100;
    private int fragmentSize;
    private int currentNumFrags;
    private int position = -1;
    private QueryScorer queryScorer;
    private int waitForPos = -1;
    private int textSize;
    private CharTermAttribute termAtt;
    private PositionIncrementAttribute posIncAtt;
    private OffsetAttribute offsetAtt;

    /**
     * @param queryScorer QueryScorer that was used to score hits
     */
    public SimpleSpanFragmenter(QueryScorer queryScorer) {
        this(queryScorer, DEFAULT_FRAGMENT_SIZE);
    }

    /**
     * @param queryScorer QueryScorer that was used to score hits
     * @param fragmentSize size in chars of each fragment
     */
    public SimpleSpanFragmenter(QueryScorer queryScorer, int fragmentSize) {
        this.fragmentSize = fragmentSize;
        this.queryScorer = queryScorer;
    }

    /* (non-Javadoc)
     * @see org.apache.lucene.search.highlight.Fragmenter#isNewFragment()
     */
    @Override
    public boolean isNewFragment() {
        position += posIncAtt.getPositionIncrement();

        if (waitForPos <= position) {
            waitForPos = -1;
        } else if (waitForPos != -1) {
            return false;
        }

        WeightedSpanTerm wSpanTerm = queryScorer.getWeightedSpanTerm(termAtt.toString());

        if (wSpanTerm != null) {
            List<PositionSpan> positionSpans = wSpanTerm.getPositionSpans();

            for (PositionSpan positionSpan : positionSpans) {
                if (positionSpan.start == position) {
                    waitForPos = positionSpan.end + 1;
                    break;
                }
            }
        }

        boolean isNewFrag = offsetAtt.endOffset() >= (fragmentSize * currentNumFrags)
                && (textSize - offsetAtt.endOffset()) >= (fragmentSize >>> 1);

        if (isNewFrag) {
            currentNumFrags++;
        }

        return isNewFrag;
    }

    /* (non-Javadoc)
     * @see org.apache.lucene.search.highlight.Fragmenter#start(java.lang.String, org.apache.lucene.analysis.TokenStream)
     */
    @Override
    public void start(String originalText, TokenStream tokenStream) {
        position = -1;
        currentNumFrags = 1;
        textSize = originalText.length();
        termAtt = tokenStream.addAttribute(CharTermAttribute.class);
        posIncAtt = tokenStream.addAttribute(PositionIncrementAttribute.class);
        offsetAtt = tokenStream.addAttribute(OffsetAttribute.class);
    }
}