src/Lucene.Net.Analysis.Common/Analysis/Sinks/TokenRangeSinkFilter.cs

using Lucene.Net.Util;
using System;

namespace Lucene.Net.Analysis.Sinks
{
    /*
     * 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.
     */

    /// <summary>
    /// Counts the tokens as they go by and saves to the internal list those between the range of lower and upper, exclusive of upper
    /// </summary>
    public class TokenRangeSinkFilter : TeeSinkTokenFilter.SinkFilter
    {
        private readonly int lower;
        private readonly int upper;
        private int count;

        public TokenRangeSinkFilter(int lower, int upper)
        {
            if (lower < 1)
            {
                throw new ArgumentOutOfRangeException("lower must be greater than zero");
            }
            if (lower > upper)
            {
                throw new ArgumentOutOfRangeException("lower must not be greater than upper");
            }
            this.lower = lower;
            this.upper = upper;
        }

        public override bool Accept(AttributeSource source)
        {
            try
            {
                if (count >= lower && count < upper)
                {
                    return true;
                }
                return false;
            }
            finally
            {
                count++;
            }
        }

        public override void Reset()
        {
            count = 0;
        }
    }
}