beagled/Lucene.Net/Search/SloppyPhraseScorer.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 TermPositions = Lucene.Net.Index.TermPositions;
  18 namespace Lucene.Net.Search
  19 {
  20
  21         sealed class SloppyPhraseScorer:PhraseScorer
  22         {
  23                 private int slop;
  24
  25                 internal SloppyPhraseScorer(Weight weight, TermPositions[] tps, int[] positions, Similarity similarity, int slop, byte[] norms) : base(weight, tps, positions, similarity, norms)
  26                 {
  27                         this.slop = slop;
  28                 }
  29
  30                 protected internal override float PhraseFreq()
  31                 {
  32                         pq.Clear();
  33                         int end = 0;
  34                         for (PhrasePositions pp = first; pp != null; pp = pp.next)
  35                         {
  36                                 pp.FirstPosition();
  37                                 if (pp.position > end)
  38                                         end = pp.position;
  39                                 pq.Put(pp); // build pq from list
  40                         }
  41
  42                         float freq = 0.0f;
  43                         bool done = false;
  44                         do
  45                         {
  46                                 PhrasePositions pp = (PhrasePositions) pq.Pop();
  47                                 int start = pp.position;
  48                                 int next = ((PhrasePositions) pq.Top()).position;
  49                                 for (int pos = start; pos <= next; pos = pp.position)
  50                                 {
  51                                         start = pos; // advance pp to min window
  52                                         if (!pp.NextPosition())
  53                                         {
  54                                                 done = true; // ran out of a term -- done
  55                                                 break;
  56                                         }
  57                                 }
  58
  59                                 int matchLength = end - start;
  60                                 if (matchLength <= slop)
  61                                         freq += GetSimilarity().SloppyFreq(matchLength); // score match
  62
  63                                 if (pp.position > end)
  64                                         end = pp.position;
  65                                 pq.Put(pp); // restore pq
  66                         }
  67                         while (!done);
  68
  69                         return freq;
  70                 }
  71         }
  72 }