beagled/Lucene.Net/Search/Spans/SpanScorer.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 Explanation = Lucene.Net.Search.Explanation;
  19 using Scorer = Lucene.Net.Search.Scorer;
  20 using Similarity = Lucene.Net.Search.Similarity;
  21 using Weight = Lucene.Net.Search.Weight;
  22
  23 namespace Lucene.Net.Search.Spans
  24 {
  25
  26
  27         class SpanScorer : Scorer
  28         {
  29                 private Spans spans;
  30                 private Weight weight;
  31                 private byte[] norms;
  32                 private float value_Renamed;
  33
  34                 private bool firstTime = true;
  35                 private bool more = true;
  36
  37                 private int doc;
  38                 private float freq;
  39
  40                 internal SpanScorer(Spans spans, Weight weight, Similarity similarity, byte[] norms) : base(similarity)
  41                 {
  42                         this.spans = spans;
  43                         this.norms = norms;
  44                         this.weight = weight;
  45                         this.value_Renamed = weight.GetValue();
  46                 }
  47
  48                 public override bool Next()
  49                 {
  50                         if (firstTime)
  51                         {
  52                                 more = spans.Next();
  53                                 firstTime = false;
  54                         }
  55
  56                         if (!more)
  57                                 return false;
  58
  59                         freq = 0.0f;
  60                         doc = spans.Doc();
  61
  62                         while (more && doc == spans.Doc())
  63                         {
  64                                 int matchLength = spans.End() - spans.Start();
  65                                 freq += GetSimilarity().SloppyFreq(matchLength);
  66                                 more = spans.Next();
  67                         }
  68
  69                         return more || freq != 0.0f;
  70                 }
  71
  72                 public override int Doc()
  73                 {
  74                         return doc;
  75                 }
  76
  77                 public override float Score()
  78                 {
  79                         float raw = GetSimilarity().Tf(freq) * value_Renamed; // raw score
  80                         return raw * Similarity.DecodeNorm(norms[doc]); // normalize
  81                 }
  82
  83                 public override bool SkipTo(int target)
  84                 {
  85                         more = spans.SkipTo(target);
  86
  87                         if (!more)
  88                                 return false;
  89
  90                         freq = 0.0f;
  91                         doc = spans.Doc();
  92
  93                         while (more && spans.Doc() == target)
  94                         {
  95                                 freq += GetSimilarity().SloppyFreq(spans.End() - spans.Start());
  96                                 more = spans.Next();
  97                         }
  98
  99                         return more || freq != 0.0f;
 100                 }
 101
 102                 public override Explanation Explain(int doc)
 103                 {
 104                         Explanation tfExplanation = new Explanation();
 105
 106                         SkipTo(doc);
 107
 108                         float phraseFreq = (Doc() == doc)?freq:0.0f;
 109                         tfExplanation.SetValue(GetSimilarity().Tf(phraseFreq));
 110                         tfExplanation.SetDescription("tf(phraseFreq=" + phraseFreq + ")");
 111
 112                         return tfExplanation;
 113                 }
 114         }
 115 }