mcs/tools/monkeydoc/Lucene.Net/Lucene.Net/Search/FilteredTermEnum.cs

   1 /*
   2  * Licensed to the Apache Software Foundation (ASF) under one or more
   3  * contributor license agreements.  See the NOTICE file distributed with
   4  * this work for additional information regarding copyright ownership.
   5  * The ASF licenses this file to You under the Apache License, Version 2.0
   6  * (the "License"); you may not use this file except in compliance with
   7  * the License.  You may obtain a copy of the License at
   8  *
   9  * http://www.apache.org/licenses/LICENSE-2.0
  10  *
  11  * Unless required by applicable law or agreed to in writing, software
  12  * distributed under the License is distributed on an "AS IS" BASIS,
  13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14  * See the License for the specific language governing permissions and
  15  * limitations under the License.
  16  */
  17
  18 using System;
  19
  20 using Term = Mono.Lucene.Net.Index.Term;
  21 using TermEnum = Mono.Lucene.Net.Index.TermEnum;
  22
  23 namespace Mono.Lucene.Net.Search
  24 {
  25
  26         /// <summary>Abstract class for enumerating a subset of all terms.
  27         /// <p/>Term enumerations are always ordered by Term.compareTo().  Each term in
  28         /// the enumeration is greater than all that precede it.
  29         /// </summary>
  30         public abstract class FilteredTermEnum:TermEnum
  31         {
  32                 /// <summary>the current term </summary>
  33                 protected internal Term currentTerm = null;
  34
  35                 /// <summary>the delegate enum - to set this member use {@link #setEnum} </summary>
  36                 protected internal TermEnum actualEnum = null;
  37
  38                 public FilteredTermEnum()
  39                 {
  40                 }
  41
  42                 /// <summary>Equality compare on the term </summary>
  43                 public /*protected internal*/ abstract bool TermCompare(Term term);
  44
  45                 /// <summary>Equality measure on the term </summary>
  46                 public abstract float Difference();
  47
  48                 /// <summary>Indicates the end of the enumeration has been reached </summary>
  49                 public abstract bool EndEnum();
  50
  51                 /// <summary> use this method to set the actual TermEnum (e.g. in ctor),
  52                 /// it will be automatically positioned on the first matching term.
  53                 /// </summary>
  54                 protected internal virtual void  SetEnum(TermEnum actualEnum)
  55                 {
  56                         this.actualEnum = actualEnum;
  57                         // Find the first term that matches
  58                         Term term = actualEnum.Term();
  59                         if (term != null && TermCompare(term))
  60                                 currentTerm = term;
  61                         else
  62                                 Next();
  63                 }
  64
  65                 /// <summary> Returns the docFreq of the current Term in the enumeration.
  66                 /// Returns -1 if no Term matches or all terms have been enumerated.
  67                 /// </summary>
  68                 public override int DocFreq()
  69                 {
  70                         if (currentTerm == null)
  71                                 return - 1;
  72                         System.Diagnostics.Debug.Assert(actualEnum != null);
  73                         return actualEnum.DocFreq();
  74                 }
  75
  76                 /// <summary>Increments the enumeration to the next element.  True if one exists. </summary>
  77                 public override bool Next()
  78                 {
  79                         if (actualEnum == null)
  80                                 return false; // the actual enumerator is not initialized!
  81                         currentTerm = null;
  82                         while (currentTerm == null)
  83                         {
  84                                 if (EndEnum())
  85                                         return false;
  86                                 if (actualEnum.Next())
  87                                 {
  88                                         Term term = actualEnum.Term();
  89                                         if (TermCompare(term))
  90                                         {
  91                                                 currentTerm = term;
  92                                                 return true;
  93                                         }
  94                                 }
  95                                 else
  96                                         return false;
  97                         }
  98                         currentTerm = null;
  99                         return false;
 100                 }
 101
 102                 /// <summary>Returns the current Term in the enumeration.
 103                 /// Returns null if no Term matches or all terms have been enumerated.
 104                 /// </summary>
 105                 public override Term Term()
 106                 {
 107                         return currentTerm;
 108                 }
 109
 110                 /// <summary>Closes the enumeration to further activity, freeing resources.  </summary>
 111                 public override void  Close()
 112                 {
 113                         if (actualEnum != null)
 114                                 actualEnum.Close();
 115                         currentTerm = null;
 116                         actualEnum = null;
 117                 }
 118         }
 119 }