/*
* Copyright 2004 The Apache Software Foundation
*
* Licensed 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;
using TermLucene.Net.Index.Term;
using TermEnumLucene.Net.Index.TermEnum;
namespace Lucene.Net.Search{
/// <summary>Abstract class for enumerating a subset of all terms.
/// <p>Term enumerations are always ordered by Term.compareTo(). Each term in
/// the enumeration is greater than all that precede it.
/// </summary>
public abstract class FilteredTermEnum:TermEnum
{
private Term currentTerm = null;
private TermEnum actualEnum = null;
public FilteredTermEnum()
{
}
/// <summary>Equality compare on the term </summary>
protected internal abstract bool TermCompare(Term term);
/// <summary>Equality measure on the term </summary>
public abstract float Difference();
/// <summary>Indiciates the end of the enumeration has been reached </summary>
public abstract bool EndEnum();
protected internal virtual void SetEnum(TermEnum actualEnum)
{
this.actualEnum = actualEnum;
// Find the first term that matches
Term term = actualEnum.Term();
if (term != null && TermCompare(term))
currentTerm = term;
else
Next();
}
/// <summary> Returns the docFreq of the current Term in the enumeration.
/// Returns -1 if no Term matches or all terms have been enumerated.
/// </summary>
public override int DocFreq()
{
if (actualEnum == null)
return - 1;
return actualEnum.DocFreq();
}
/// <summary>Increments the enumeration to the next element. True if one exists. </summary>
public override bool Next()
{
if (actualEnum == null)
return false; // the actual enumerator is not initialized!
currentTerm = null;
while (currentTerm == null)
{
if (EndEnum())
return false;
if (actualEnum.Next())
{
Term term = actualEnum.Term();
if (TermCompare(term))
{
currentTerm = term;
return true;
}
}
else
return false;
}
currentTerm = null;
return false;
}
/// <summary>Returns the current Term in the enumeration.
/// Returns null if no Term matches or all terms have been enumerated.
/// </summary>
public override Term Term()
{
return currentTerm;
}
/// <summary>Closes the enumeration to further activity, freeing resources. </summary>
public override void Close()
{
actualEnum.Close();
currentTerm = null;
actualEnum = null;
}
}
}
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