beagled/Lucene.Net/Index/TermEnum.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
  19 namespace Lucene.Net.Index
  20 {
  21
  22         /// <summary>Abstract class for enumerating terms.
  23         /// <p>Term enumerations are always ordered by Term.compareTo().  Each term in
  24         /// the enumeration is greater than all that precede it.
  25         /// </summary>
  26
  27         public abstract class TermEnum
  28         {
  29                 /// <summary>Increments the enumeration to the next element.  True if one exists.</summary>
  30                 public abstract bool Next();
  31
  32                 /// <summary>Returns the current Term in the enumeration.</summary>
  33                 public abstract Term Term();
  34
  35                 /// <summary>Returns the docFreq of the current Term in the enumeration.</summary>
  36                 public abstract int DocFreq();
  37
  38                 /// <summary>Closes the enumeration to further activity, freeing resources. </summary>
  39                 public abstract void  Close();
  40
  41                 // Term Vector support
  42
  43                 /// <summary>Skips terms to the first beyond the current whose value is
  44                 /// greater or equal to <i>target</i>. <p>Returns true iff there is such
  45                 /// an entry.  <p>Behaves as if written: <pre>
  46                 /// public boolean skipTo(Term target) {
  47                 /// do {
  48                 /// if (!next())
  49                 /// return false;
  50                 /// } while (target > term());
  51                 /// return true;
  52                 /// }
  53                 /// </pre>
  54                 /// Some implementations are considerably more efficient than that.
  55                 /// </summary>
  56                 public virtual bool SkipTo(Term target)
  57                 {
  58                         do
  59                         {
  60                                 if (!Next())
  61                                         return false;
  62                         }
  63                         while (target.CompareTo(Term()) > 0);
  64                         return true;
  65                 }
  66         }
  67 }