PhrasePositions.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
{
    
    /// <summary> Position of a term in a document that takes into account the term offset within the phrase. </summary>
    sealed class PhrasePositions
    {
        internal int doc; // current doc
        internal int position; // position in doc
        internal int count; // remaining pos in this doc
        internal int offset; // position in phrase
        internal TermPositions tp; // stream of positions
        internal PhrasePositions next; // used to make lists
        internal bool repeats; // there's other pp for same term (e.g. query="1st word 2nd word"~1) 
        
        internal PhrasePositions(TermPositions t, int o)
        {
            tp = t;
            offset = o;
        }
        
        internal bool Next()
        {
            // increments to next doc
            if (!tp.Next())
            {
                tp.Close(); // close stream
                doc = System.Int32.MaxValue; // sentinel value
                return false;
            }
            doc = tp.Doc;
            position = 0;
            return true;
        }
        
        internal bool SkipTo(int target)
        {
            if (!tp.SkipTo(target))
            {
                tp.Close(); // close stream
                doc = System.Int32.MaxValue; // sentinel value
                return false;
            }
            doc = tp.Doc;
            position = 0;
            return true;
        }
        
        
        internal void  FirstPosition()
        {
            count = tp.Freq; // read first pos
            NextPosition();
        }
        
        /// <summary> Go to next location of this term current document, and set 
        /// <c>position</c> as <c>location - offset</c>, so that a 
        /// matching exact phrase is easily identified when all PhrasePositions 
        /// have exactly the same <c>position</c>.
        /// </summary>
        internal bool NextPosition()
        {
            if (count-- > 0)
            {
                // read subsequent pos's
                position = tp.NextPosition() - offset;
                return true;
            }
            else
                return false;
        }
    }
}