FilteredDocIdSetIterator.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;

namespace Lucene.Net.Search
{
    
    /// <summary> Abstract decorator class of a DocIdSetIterator
    /// implementation that provides on-demand filter/validation
    /// mechanism on an underlying DocIdSetIterator.  See <see cref="FilteredDocIdSet" />
    ///.
    /// </summary>
    public abstract class FilteredDocIdSetIterator:DocIdSetIterator
    {
        protected internal DocIdSetIterator internalInnerIter;
        private int doc;
        
        /// <summary> Constructor.</summary>
        /// <param name="innerIter">Underlying DocIdSetIterator.
        /// </param>
        protected FilteredDocIdSetIterator(DocIdSetIterator innerIter)
        {
            if (innerIter == null)
            {
                throw new System.ArgumentException("null iterator");
            }
            internalInnerIter = innerIter;
            doc = - 1;
        }
        
        /// <summary> Validation method to determine whether a docid should be in the result set.</summary>
        /// <param name="doc">docid to be tested
        /// </param>
        /// <returns> true if input docid should be in the result set, false otherwise.
        /// </returns>
        /// <seealso cref="FilteredDocIdSetIterator(DocIdSetIterator)">
        /// </seealso>
        public abstract /*protected internal*/ bool Match(int doc);
        
        public override int DocID()
        {
            return doc;
        }
        
        public override int NextDoc()
        {
            while ((doc = internalInnerIter.NextDoc()) != NO_MORE_DOCS)
            {
                if (Match(doc))
                {
                    return doc;
                }
            }
            return doc;
        }
        
        public override int Advance(int target)
        {
            doc = internalInnerIter.Advance(target);
            if (doc != NO_MORE_DOCS)
            {
                if (Match(doc))
                {
                    return doc;
                }
                else
                {
                    while ((doc = internalInnerIter.NextDoc()) != NO_MORE_DOCS)
                    {
                        if (Match(doc))
                        {
                            return doc;
                        }
                    }
                    return doc;
                }
            }
            return doc;
        }
    }
}