beagled/Lucene.Net/Search/CachingWrapperFilter.cs

   1 /*
   2  * Copyright 2004 The Apache Software Foundation
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  * http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 using System;
  18 using System.Runtime.InteropServices;
  19 using IndexReader = Lucene.Net.Index.IndexReader;
  20
  21 namespace Lucene.Net.Search
  22 {
  23
  24         /// <summary> Wraps another filter's result and caches it.  The caching
  25         /// behavior is like {@link QueryFilter}.  The purpose is to allow
  26         /// filters to simply filter, and then wrap with this class to add
  27         /// caching, keeping the two concerns decoupled yet composable.
  28         /// </summary>
  29         [Serializable]
  30         public class CachingWrapperFilter:Filter
  31         {
  32                 private Filter filter;
  33
  34                 /// <todo>  What about serialization in RemoteSearchable?  Caching won't work. </todo>
  35                 /// <summary>       Should transient be removed?
  36                 /// </summary>
  37                 [NonSerialized]
  38                 private System.Collections.IDictionary cache;
  39
  40                 /// <param name="filter">Filter to cache results of
  41                 /// </param>
  42                 public CachingWrapperFilter(Filter filter)
  43                 {
  44                         this.filter = filter;
  45                 }
  46
  47                 public override System.Collections.BitArray Bits(IndexReader reader)
  48                 {
  49                         if (cache == null)
  50                         {
  51                                 cache = new System.Collections.Hashtable();
  52                         }
  53
  54                         lock (cache.SyncRoot)
  55                         {
  56                                 // check cache
  57                                 System.Collections.BitArray cached = (System.Collections.BitArray) cache[reader];
  58                                 if (cached != null)
  59                                 {
  60                                         return cached;
  61                                 }
  62                         }
  63
  64                         System.Collections.BitArray bits = filter.Bits(reader);
  65
  66                         lock (cache.SyncRoot)
  67                         {
  68                                 // update cache
  69                                 cache[reader] = bits;
  70                         }
  71
  72                         return bits;
  73                 }
  74
  75                 public override System.String ToString()
  76                 {
  77                         return "CachingWrapperFilter(" + filter + ")";
  78                 }
  79
  80                 public  override bool Equals(System.Object o)
  81                 {
  82                         if (!(o is CachingWrapperFilter))
  83                                 return false;
  84                         return this.filter.Equals(((CachingWrapperFilter) o).filter);
  85                 }
  86
  87                 public override int GetHashCode()
  88                 {
  89                         return filter.GetHashCode() ^ 0x1117BF25;
  90                 }
  91         }
  92 }