sloppyphrasescorer.java

一套java版本的搜索引擎源码

package org.apache.lucene.search;

/**
 * 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 org.apache.lucene.index.TermPositions;

import java.io.IOException;

final class SloppyPhraseScorer extends PhraseScorer {
    private int slop;

    SloppyPhraseScorer(Weight weight, TermPositions[] tps, int[] positions, Similarity similarity,
                       int slop, byte[] norms) {
        super(weight, tps, positions, similarity, norms);
        this.slop = slop;
    }

    protected final float phraseFreq() throws IOException {
        pq.clear();
        int end = 0;
        for (PhrasePositions pp = first; pp != null; pp = pp.next) {
            pp.firstPosition();
            if (pp.position > end)
                end = pp.position;
            pq.put(pp);				  // build pq from list
        }

        float freq = 0.0f;
        boolean done = false;
        do {
            PhrasePositions pp = (PhrasePositions) pq.pop();
            int start = pp.position;
            int next = ((PhrasePositions) pq.top()).position;
            for (int pos = start; pos <= next; pos = pp.position) {
                start = pos;				  // advance pp to min window
                if (!pp.nextPosition()) {
                    done = true;				  // ran out of a term -- done
                    break;
                }
            }

            int matchLength = end - start;
            if (matchLength <= slop)
                freq += getSimilarity().sloppyFreq(matchLength); // score match

            if (pp.position > end)
                end = pp.position;
            pq.put(pp);				  // restore pq
        } while (!done);

        return freq;
    }
}