1 files changed, 140 insertions, 0 deletions

diff --git a/src/core/Search/ReqExclScorer.cs b/src/core/Search/ReqExclScorer.cs
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+++ b/src/core/Search/ReqExclScorer.cs
@@ -0,0 +1,140 @@
+/* 
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * 
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+using System;
+
+namespace Lucene.Net.Search
+{
+	
+	
+	/// <summary>A Scorer for queries with a required subscorer
+	/// and an excluding (prohibited) sub DocIdSetIterator.
+	/// <br/>
+    /// This <c>Scorer</c> implements <see cref="DocIdSetIterator.Advance(int)" />,
+	/// and it uses the skipTo() on the given scorers.
+	/// </summary>
+	class ReqExclScorer:Scorer
+	{
+		private Scorer reqScorer;
+		private DocIdSetIterator exclDisi;
+		private int doc = - 1;
+		
+		/// <summary>Construct a <c>ReqExclScorer</c>.</summary>
+		/// <param name="reqScorer">The scorer that must match, except where
+		/// </param>
+		/// <param name="exclDisi">indicates exclusion.
+		/// </param>
+		public ReqExclScorer(Scorer reqScorer, DocIdSetIterator exclDisi):base(null)
+		{ // No similarity used.
+			this.reqScorer = reqScorer;
+			this.exclDisi = exclDisi;
+		}
+		
+		public override int NextDoc()
+		{
+			if (reqScorer == null)
+			{
+				return doc;
+			}
+			doc = reqScorer.NextDoc();
+			if (doc == NO_MORE_DOCS)
+			{
+				reqScorer = null; // exhausted, nothing left
+				return doc;
+			}
+			if (exclDisi == null)
+			{
+				return doc;
+			}
+			return doc = ToNonExcluded();
+		}
+		
+		/// <summary>Advance to non excluded doc.
+		/// <br/>On entry:
+		/// <list type="bullet">
+		/// <item>reqScorer != null, </item>
+		/// <item>exclScorer != null, </item>
+		/// <item>reqScorer was advanced once via next() or skipTo() 
+        /// and reqScorer.doc() may still be excluded.</item>
+		/// </list>
+		/// Advances reqScorer a non excluded required doc, if any.
+		/// </summary>
+		/// <returns> true iff there is a non excluded required doc.
+		/// </returns>
+		private int ToNonExcluded()
+		{
+			int exclDoc = exclDisi.DocID();
+			int reqDoc = reqScorer.DocID(); // may be excluded
+			do 
+			{
+				if (reqDoc < exclDoc)
+				{
+					return reqDoc; // reqScorer advanced to before exclScorer, ie. not excluded
+				}
+				else if (reqDoc > exclDoc)
+				{
+					exclDoc = exclDisi.Advance(reqDoc);
+					if (exclDoc == NO_MORE_DOCS)
+					{
+						exclDisi = null; // exhausted, no more exclusions
+						return reqDoc;
+					}
+					if (exclDoc > reqDoc)
+					{
+						return reqDoc; // not excluded
+					}
+				}
+			}
+			while ((reqDoc = reqScorer.NextDoc()) != NO_MORE_DOCS);
+			reqScorer = null; // exhausted, nothing left
+			return NO_MORE_DOCS;
+		}
+		
+		public override int DocID()
+		{
+			return doc;
+		}
+		
+		/// <summary>Returns the score of the current document matching the query.
+		/// Initially invalid, until <see cref="NextDoc()" /> is called the first time.
+		/// </summary>
+		/// <returns> The score of the required scorer.
+		/// </returns>
+		public override float Score()
+		{
+			return reqScorer.Score(); // reqScorer may be null when next() or skipTo() already return false
+		}
+		
+		public override int Advance(int target)
+		{
+			if (reqScorer == null)
+			{
+				return doc = NO_MORE_DOCS;
+			}
+			if (exclDisi == null)
+			{
+				return doc = reqScorer.Advance(target);
+			}
+			if (reqScorer.Advance(target) == NO_MORE_DOCS)
+			{
+				reqScorer = null;
+				return doc = NO_MORE_DOCS;
+			}
+			return doc = ToNonExcluded();
+		}
+	}
+}
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