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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.Collections.Generic;
using Version = Lucene.Net.Util.Version;
namespace Lucene.Net.Analysis
{
/// <summary> Filters <see cref="LetterTokenizer" /> with <see cref="LowerCaseFilter" /> and
/// <see cref="StopFilter" />.
///
/// <a name="version"/>
/// <p/>
/// You must specify the required <see cref="Version" /> compatibility when creating
/// StopAnalyzer:
/// <list type="bullet">
/// <item>As of 2.9, position increments are preserved</item>
/// </list>
/// </summary>
public sealed class StopAnalyzer:Analyzer
{
private readonly ISet<string> stopWords;
private readonly bool enablePositionIncrements;
/// <summary>An unmodifiable set containing some common English words that are not usually useful
/// for searching.
/// </summary>
public static ISet<string> ENGLISH_STOP_WORDS_SET;
/// <summary> Builds an analyzer which removes words in ENGLISH_STOP_WORDS.</summary>
public StopAnalyzer(Version matchVersion)
{
stopWords = ENGLISH_STOP_WORDS_SET;
enablePositionIncrements = StopFilter.GetEnablePositionIncrementsVersionDefault(matchVersion);
}
/// <summary>Builds an analyzer with the stop words from the given set.</summary>
public StopAnalyzer(Version matchVersion, ISet<string> stopWords)
{
this.stopWords = stopWords;
enablePositionIncrements = StopFilter.GetEnablePositionIncrementsVersionDefault(matchVersion);
}
/// <summary> Builds an analyzer with the stop words from the given file.
///
/// </summary>
/// <seealso cref="WordlistLoader.GetWordSet(System.IO.FileInfo)">
/// </seealso>
/// <param name="matchVersion">See <a href="#version">above</a>
/// </param>
/// <param name="stopwordsFile">File to load stop words from
/// </param>
public StopAnalyzer(Version matchVersion, System.IO.FileInfo stopwordsFile)
{
stopWords = WordlistLoader.GetWordSet(stopwordsFile);
enablePositionIncrements = StopFilter.GetEnablePositionIncrementsVersionDefault(matchVersion);
}
/// <summary>Builds an analyzer with the stop words from the given reader. </summary>
/// <seealso cref="WordlistLoader.GetWordSet(System.IO.TextReader)">
/// </seealso>
/// <param name="matchVersion">See <a href="#Version">above</a>
/// </param>
/// <param name="stopwords">Reader to load stop words from
/// </param>
public StopAnalyzer(Version matchVersion, System.IO.TextReader stopwords)
{
stopWords = WordlistLoader.GetWordSet(stopwords);
enablePositionIncrements = StopFilter.GetEnablePositionIncrementsVersionDefault(matchVersion);
}
/// <summary>Filters LowerCaseTokenizer with StopFilter. </summary>
public override TokenStream TokenStream(System.String fieldName, System.IO.TextReader reader)
{
return new StopFilter(enablePositionIncrements, new LowerCaseTokenizer(reader), stopWords);
}
/// <summary>Filters LowerCaseTokenizer with StopFilter. </summary>
private class SavedStreams
{
public SavedStreams(StopAnalyzer enclosingInstance)
{
InitBlock(enclosingInstance);
}
private void InitBlock(StopAnalyzer enclosingInstance)
{
this.enclosingInstance = enclosingInstance;
}
private StopAnalyzer enclosingInstance;
public StopAnalyzer Enclosing_Instance
{
get
{
return enclosingInstance;
}
}
internal Tokenizer source;
internal TokenStream result;
}
public override TokenStream ReusableTokenStream(System.String fieldName, System.IO.TextReader reader)
{
var streams = (SavedStreams) PreviousTokenStream;
if (streams == null)
{
streams = new SavedStreams(this) {source = new LowerCaseTokenizer(reader)};
streams.result = new StopFilter(enablePositionIncrements, streams.source, stopWords);
PreviousTokenStream = streams;
}
else
streams.source.Reset(reader);
return streams.result;
}
static StopAnalyzer()
{
{
var stopWords = new System.String[]{"a", "an", "and", "are", "as", "at", "be", "but", "by", "for", "if", "in", "into", "is", "it", "no", "not", "of", "on", "or", "such", "that", "the", "their", "then", "there", "these", "they", "this", "to", "was", "will", "with"};
var stopSet = new CharArraySet(stopWords.Length, false);
stopSet.AddAll(stopWords);
ENGLISH_STOP_WORDS_SET = CharArraySet.UnmodifiableSet(stopSet);
}
}
}
}
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