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