edu.mit.ll.vizlinc.highlight.TokenStreamFromTermPositionVector.java Source code

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Here is the source code for edu.mit.ll.vizlinc.highlight.TokenStreamFromTermPositionVector.java

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package edu.mit.ll.vizlinc.highlight;

/**
 * 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.
 */
import java.io.IOException;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;

import org.apache.lucene.analysis.Token;
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.index.TermPositionVector;
import org.apache.lucene.index.TermVectorOffsetInfo;
import org.apache.lucene.util.CollectionUtil;

public final class TokenStreamFromTermPositionVector extends TokenStream {

    private final List<Token> positionedTokens = new ArrayList<Token>();

    private Iterator<Token> tokensAtCurrentPosition;

    private CharTermAttribute termAttribute;

    private PositionIncrementAttribute positionIncrementAttribute;

    private OffsetAttribute offsetAttribute;

    /**
     * Constructor.
     * 
     * @param termPositionVector TermPositionVector that contains the data for
     *        creating the TokenStream. Must have positions and offsets.
     */
    public TokenStreamFromTermPositionVector(final TermPositionVector termPositionVector) {
        termAttribute = addAttribute(CharTermAttribute.class);
        positionIncrementAttribute = addAttribute(PositionIncrementAttribute.class);
        offsetAttribute = addAttribute(OffsetAttribute.class);
        final String[] terms = termPositionVector.getTerms();
        for (int i = 0; i < terms.length; i++) {
            final TermVectorOffsetInfo[] offsets = termPositionVector.getOffsets(i);
            final int[] termPositions = termPositionVector.getTermPositions(i);
            for (int j = 0; j < termPositions.length; j++) {
                Token token;
                if (offsets != null) {
                    token = new Token(terms[i].toCharArray(), 0, terms[i].length(), offsets[j].getStartOffset(),
                            offsets[j].getEndOffset());
                } else {
                    token = new Token();
                    token.setEmpty().append(terms[i]);
                }
                // Yes - this is the position, not the increment! This is for
                // sorting. This value
                // will be corrected before use.
                token.setPositionIncrement(termPositions[j]);
                this.positionedTokens.add(token);
            }
        }
        CollectionUtil.mergeSort(this.positionedTokens, tokenComparator);
        int lastPosition = -1;
        for (final Token token : this.positionedTokens) {
            int thisPosition = token.getPositionIncrement();
            token.setPositionIncrement(thisPosition - lastPosition);
            lastPosition = thisPosition;
        }
        this.tokensAtCurrentPosition = this.positionedTokens.iterator();
    }

    private static final Comparator<Token> tokenComparator = new Comparator<Token>() {
        public int compare(final Token o1, final Token o2) {
            return o1.getPositionIncrement() - o2.getPositionIncrement();
        }
    };

    @Override
    public boolean incrementToken() throws IOException {
        if (this.tokensAtCurrentPosition.hasNext()) {
            final Token next = this.tokensAtCurrentPosition.next();
            clearAttributes();
            termAttribute.setEmpty().append(next);
            positionIncrementAttribute.setPositionIncrement(next.getPositionIncrement());
            offsetAttribute.setOffset(next.startOffset(), next.endOffset());
            return true;
        }
        return false;
    }

    @Override
    public void reset() throws IOException {
        this.tokensAtCurrentPosition = this.positionedTokens.iterator();
    }
}