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KeywordRepeatFilter.cs
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KeywordRepeatFilter.cs
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using Lucene.Net.Analysis.TokenAttributes;
namespace Lucene.Net.Analysis.Miscellaneous
{
/*
* 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>
/// This TokenFilter emits each incoming token twice once as keyword and once non-keyword, in other words once with
/// <see cref="KeywordAttribute.IsKeyword"/> set to <c>true</c> and once set to <c>false</c>.
/// This is useful if used with a stem filter that respects the <see cref="KeywordAttribute"/> to index the stemmed and the
/// un-stemmed version of a term into the same field.
/// </summary>
public sealed class KeywordRepeatFilter : TokenFilter
{
private readonly IKeywordAttribute keywordAttribute;
private readonly IPositionIncrementAttribute posIncAttr;
private State state;
/// <summary>
/// Construct a token stream filtering the given input.
/// </summary>
public KeywordRepeatFilter(TokenStream input)
: base(input)
{
keywordAttribute = AddAttribute<IKeywordAttribute>();
posIncAttr = AddAttribute<IPositionIncrementAttribute>();
}
public override bool IncrementToken()
{
if (state != null)
{
RestoreState(state);
posIncAttr.PositionIncrement = 0;
keywordAttribute.IsKeyword = false;
state = null;
return true;
}
if (m_input.IncrementToken())
{
state = CaptureState();
keywordAttribute.IsKeyword = true;
return true;
}
return false;
}
public override void Reset()
{
base.Reset();
state = null;
}
}
}