/*
* 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 System.Runtime.InteropServices;
using IndexReaderLucene.Net.Index.IndexReader;
namespace Lucene.Net.Search{
/// <summary> Wraps another filter's result and caches it. The caching
/// behavior is like {@link QueryFilter}. The purpose is to allow
/// filters to simply filter, and then wrap with this class to add
/// caching, keeping the two concerns decoupled yet composable.
/// </summary>
[Serializable]
public class CachingWrapperFilter:Filter
{
private Filter filter;
/// <todo> What about serialization in RemoteSearchable? Caching won't work. </todo>
/// <summary> Should transient be removed?
/// </summary>
[NonSerialized]
private System.Collections.IDictionary cache;
/// <param name="filter">Filter to cache results of
/// </param>
public CachingWrapperFilter(Filter filter)
{
this.filter = filter;
}
public override System.Collections.BitArray Bits(IndexReader reader)
{
if (cache == null)
{
cache = new System.Collections.Hashtable();
}
lock (cache.SyncRoot)
{
// check cache
System.Collections.BitArray cached = (System.Collections.BitArray) cache[reader];
if (cached != null)
{
return cached;
}
}
System.Collections.BitArray bits = filter.Bits(reader);
lock (cache.SyncRoot)
{
// update cache
cache[reader] = bits;
}
return bits;
}
public override System.String ToString()
{
return "CachingWrapperFilter(" + filter + ")";
}
public override bool Equals(System.Object o)
{
if (!(o is CachingWrapperFilter))
return false;
return this.filter.Equals(((CachingWrapperFilter) o).filter);
}
public override int GetHashCode()
{
return filter.GetHashCode() ^ 0x1117BF25;
}
}
}
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