ExactPhraseScorer.cs

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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.
 */

using System;

using Lucene.Net.Index;

namespace Lucene.Net.Search
{
    
    sealed class ExactPhraseScorer:PhraseScorer
    {
        
        internal ExactPhraseScorer(Weight weight, TermPositions[] tps, int[] offsets, Similarity similarity, byte[] norms):base(weight, tps, offsets, similarity, norms)
        {
        }
        
        protected internal override float PhraseFreq()
        {
            // sort list with pq
            pq.Clear();
            for (PhrasePositions pp = first; pp != null; pp = pp.next)
            {
                pp.FirstPosition();
                pq.Add(pp); // build pq from list
            }
            PqToList(); // rebuild list from pq
            
            // for counting how many times the exact phrase is found in current document,
            // just count how many times all PhrasePosition's have exactly the same position.   
            int freq = 0;
            do 
            {
                // find position w/ all terms
                while (first.position < last.position)
                {
                    // scan forward in first
                    do 
                    {
                        if (!first.NextPosition())
                            return freq;
                    }
                    while (first.position < last.position);
                    FirstToLast();
                }
                freq++; // all equal: a match
            }
            while (last.NextPosition());
            
            return freq;
        }
    }
}