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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.Analysis
{
/// <summary> This class can be used if the Tokens of a TokenStream
/// are intended to be consumed more than once. It caches
/// all Tokens locally in a List.
///
/// CachingTokenFilter implements the optional method
/// {@link TokenStream#Reset()}, which repositions the
/// stream to the first Token.
///
/// </summary>
public class CachingTokenFilter : TokenFilter
{
private System.Collections.IList cache;
private System.Collections.IEnumerator iterator;
public CachingTokenFilter(TokenStream input) : base(input)
{
}
public override Token Next()
{
if (cache == null)
{
// fill cache lazily
cache = new System.Collections.ArrayList();
FillCache();
iterator = cache.GetEnumerator();
}
if (!iterator.MoveNext())
{
// the cache is exhausted, return null
return null;
}
return (Token) iterator.Current;
}
public override void Reset()
{
if (cache != null)
{
iterator = cache.GetEnumerator();
}
}
private void FillCache()
{
Token token;
while ((token = input.Next()) != null)
{
cache.Add(token);
}
}
}
}
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