/*
* 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 Lucene.Net.Analysis.Tokenattributes;
namespace Lucene.Net.Analysis
{
/// Transforms the token stream as per the Porter stemming algorithm.
/// Note: the input to the stemming filter must already be in lower case,
/// so you will need to use LowerCaseFilter or LowerCaseTokenizer farther
/// down the Tokenizer chain in order for this to work properly!
///
/// To use this filter with other analyzers, you'll want to write an
/// Analyzer class that sets up the TokenStream chain as you want it.
/// To use this with LowerCaseTokenizer, for example, you'd write an
/// analyzer like this:
///
///
/// class MyAnalyzer extends Analyzer {
/// public final TokenStream tokenStream(String fieldName, Reader reader) {
/// return new PorterStemFilter(new LowerCaseTokenizer(reader));
/// }
/// }
///
///
public sealed class PorterStemFilter:TokenFilter
{
private readonly PorterStemmer stemmer;
private readonly ITermAttribute termAtt;
public PorterStemFilter(TokenStream in_Renamed):base(in_Renamed)
{
stemmer = new PorterStemmer();
termAtt = AddAttribute();
}
public override bool IncrementToken()
{
if (!input.IncrementToken())
return false;
if (stemmer.Stem(termAtt.TermBuffer(), 0, termAtt.TermLength()))
termAtt.SetTermBuffer(stemmer.ResultBuffer, 0, stemmer.ResultLength);
return true;
}
}
}